Hygroscopic salt microcapsules and uses thereof

Abstract

The present invention relates to microencapsulation technology, in particular to microcapsules of nitrite salts, and the use of microencapsulated nitrite salts in the manufacture of animal pest lures and toxic feed mixtures, particularly in humane methods of controlling pig and rodent populations.

Description

Technical Field

[0001] This invention relates to microencapsulation technology, particularly nitrite microcapsules, and the use of microencapsulated nitrites in the manufacture of animal pest baits and toxic feed mixtures, especially in humane methods for controlling pig and opossum populations. Background Technology

[0002] Feral pigs cause damage to the environment, biodiversity, and agriculture, and pose a risk of disease transmission over large geographic areas. Therefore, feral pigs have a direct impact on the environment, agricultural production, rural industry, and semi-urban infrastructure.

[0003] In Australia, the wild boar population is estimated at over 4 million, with some estimates reaching as high as 25 million. Wild boars inhabit approximately 40% of Australia's land area and can reproduce rapidly under favorable conditions. These population estimates mean that at their peak, Australia may have had more wild boars than grazing cattle. Wild boars inhabit and are well-adapted to a wide range of habitats, including subalpine, temperate, subtropical, tropical, and arid regions, and they are present in most states and territories of Australia.

[0004] Furthermore, in the United States, it is reported that approximately 8 million wild boars (also known as hogs, boars, or swine) exist in about 34 states, from California to Virginia, with the majority living in Texas and other southern states, including Louisiana, Mississippi, and Florida. Wild boars are the most numerous introduced ungulates in the United States, and their density and range area are rapidly expanding.

[0005] Wild boars are highly prolific, with each breeding sow typically producing more than six piglets. Therefore, wild boar populations are highly responsive to control measures or capable of fully utilizing food supplies, necessitating large-scale and sustained control measures to reduce population numbers.

[0006] Wild boars have adverse effects on agricultural production, the environment, and ecosystems. Numerous studies have identified a range of environmental and agricultural problems caused by wild boar encroachment (Alexiou (1984) Effects of feral pigs (Sus scrofa) on sub-alpine vegetation at Smokers Gap, ACT, Proceedings of Ecological Society of Australia, 12:135-142; Tisdell, CA, (1982) Wild Pigs: Environmental Pest or Economic Resource? Pergamon Press, Sydney; Miller, B. and Mullette, K., (1985) Rehabilitation of an endangered Australian bird: the Lord Howe Island Woodhen, Tricholimnas sybvestris, Biological Conservation, 34:55-95; Mitchell, J. and Mayer, R., (1997) Digging by feral pigs in the wet tropics world heritage area of ​​north Queensland, Wildlife Research, 24:591-601; Choquenot, D., McIlroy, J. and Korn, T., (1996) Managing Vertebrate Pests: Feral Pigs (Ed.M.Bomford) Bureau of ResourceSciences, Australian Government Publishing Service, Canberra, p. 163; Mitchell, J., (2000) Ecology and management of feral pigs in tropical rainforest,Unpublished PhD Thesis,James Cook University of North Queensland,Townsville;Hone,J.(2002) Feral pigs in Namadgi National Park: dynamics, impacts and management, Biological Conservation 105:231-242); Singer, FJ, Swank, WT, and Clebsch, EEC, Effects of wild pig rooting in a deciduous forest, Wildlife Management 48:464-473; Lacki, MJ, and Lancin, RA, (1986) Effects of wild pigs onbeech growth in Great Smoky Mountains National Park, Journal of Wildlife Management 50:655-659). The key points of these different studies are summarized below.

[0007] Wild boar predation causes significant economic losses to livestock production across vast areas. The damage is so severe that some areas are unable to sustain productive grazing of livestock such as sheep simply due to the widespread presence of wild boars. Conservative estimates suggest that the species impacts Australian agricultural production by more than AU$100 million annually.

[0008] Wild boars also cause significant environmental damage due to their destructive foraging habits, including digging up plant roots or soil fauna (including worms (rooting)) and consuming plants and plant roots. This destructive behavior, coupled with their need to access food resource areas or waterways, can damage infrastructure, including fences, dams, and riverbanks, and destroy large areas of vulnerable riparian habitat. Wild boar dung pollution of waterways and reservoirs is also a problem. Their impact on native animal species is unclear, but given their predatory behavior and competition for food resources, the impact could be severe. Wild boars are known to aggressively prey on newborn lambs, to the point that profitable sheep farming has ceased in large areas due to their invasion. Wild boars may also have adverse effects on native wildlife species, although these impacts are not well quantified.

[0009] Besides causing direct damage to grazing businesses and the environment, wild boars also carry a variety of serious human and animal diseases. Many of these diseases are zoonotic, and pigs are ideal amplification hosts. Japanese encephalitis virus, leptospirosis, brucellosis, and melioidosis have been detected in wild boars in Australia. However, the risk is even greater if foot and mouth disease (FMD) virus invades wild boar populations, as cloven-hoofed pigs are widely distributed and highly mobile amplification hosts and virus carriers.

[0010] In the United States, pseudorabies virus (PRV) has been eradicated from domestic pigs, but it continues to circulate in wild boar and raccoon populations. Therefore, wild omnivorous populations could also serve as reservoir hosts, potentially leading to new PRV outbreaks.

[0011] Recent findings under experimental conditions have linked the potential spread of Ebola virus in non-human primates to contact with caged pigs, which reportedly carried the virus in lung lesions during laboratory trials, but without causing fatal consequences for the pigs.

[0012] The book “Managing Vertebrate Pests: Feral Pigs” (Choquenot, D., McIlroy, J., and Korn, T., (1996) *Managing Vertebrate Pests: Feral Pigs* (Ed. M. Bomford), Bureau of Resource Sciences, Australian Government Publishing Service, Canberra, 163 pages) provides detailed information on the environmental, human health, animal health, and agricultural production problems that the uncontrolled expansion of wild boar populations has caused or may cause. Infections of other omnivorous species (such as raccoons, collared peccaries, opossums, and rodents) with viruses or other pathogens known to affect pigs cause similar adverse agricultural, environmental, financial, and health problems in various countries. The recent spread of African swine fever (ASF) virus in wild boar populations now also poses a considerable threat to farmed pig populations globally. This highly deadly and untreatable disease has caused the acute deaths of approximately 250 million farmed pigs in China alone.

[0013] Therefore, considerable efforts have been made to reduce the risks posed by wild omnivorous species in Australia, the United States, New Zealand, Europe, South America, and other parts of the world where the populations of such species are out of control.

[0014] Despite their impact, the control of omnivores such as wild boar is often time-consuming, temporary, and passive rather than proactive. Many techniques are currently used primarily for localized control. These methods include poison baiting, shooting (using ground teams or via helicopters or fixed-wing shooters), trapping (for destruction or hunting), and fencing (attempting to exclude pigs from a particular area). It has been recognized that while no single technique can be expected to be 100% effective in all situations, large-scale and integrated baiting campaigns are the most cost-effective for reducing and maintaining large-area, low-to-medium density wild omnivorous populations. Typical baiting campaigns involve placing bait on the ground after pigs have gathered at their habitual feeding sites, or launching bait from the air, where bait is dropped from an aircraft onto the location of the target omnivorous population to be controlled.

[0015] Deadly baiting activities involve the use of various poisons, such as placing or depositing sodium fluoroacetate (1080) in or on grains, fermented grains, compressed bran / cornmeal pellets, fresh or dried meat, offal, carcasses, lupin seeds, fruits and vegetables, and prepared baits. The use of soaked or dried grains or fresh meat as bait is the most common. Warfarin soaked in grains is also used as bait for wild boars, or yellow phosphorus suspended in carbon disulfide is applied to the carcasses and offal consumed by wild boars. The use of yellow phosphorus as a poison is permitted only in one state of Australia and is prohibited in other jurisdictions because it is neither targeted nor humane. The use of sodium fluoroacetate is effective but requires high doses of the toxin because pigs are relatively less sensitive than some other harmful species such as foxes, rabbits, and wildcats. Because a large amount of sodium fluoroacetate poison is required to kill pigs (more sensitive species such as wild dogs, foxes, and rabbits require the same amount), this high intensity poses a risk to other species that may consume bait materials that are attractive to them, such as meat and grains. Prepared pig baits have a lower risk of non-target ingestion because they have been shown to be target-specific and unattractive to certain non-target species.

[0016] Of the various control methods discussed above, poison baiting of wild boar and other omnivorous populations is considered one of the most effective means of controlling such populations and reducing the damage they cause. However, unfortunately, two major problems with many types of bait made from grains or meat and animal offal or pellets are that they require high doses of the toxic substance and they exhibit poor target specificity. Therefore, while commonly employed baiting activities may prove effective in controlling wild omnivorous populations (e.g., pigs) in a particular area, such activities may also pose risks or adverse effects on individuals of other animal species, whether desired or native.

[0017] Other drawbacks of current baiting methods can be directly attributed to the specific poisons used. For example, one disadvantage of 1080 is that wild boars appear to have relatively high resistance to its effects compared to rabbits, foxes, and wild dogs, making it a more desirable poison for them. For instance, during captive trials using baits delivered with 1080 (McIlroy et al., Australian Wildlife Research 16:195-202), wild dogs required 0.11 mg / kg to reach the LD50. 50 The dosage is reportedly at least 1 mg / kg for wild boars, and some even as high as 4.11 mg / kg (O'Brien et al., Australian Wildlife Research 15:285-291), which is up to 40 times the dosage used for canine pests.

[0018] Furthermore, although late-stage toxic events associated with 1080 poisoning are not thought to be accompanied by conscious pain, the blockade of energy-producing enzymes can increase blood citrate levels and reduce free calcium necessary for muscle coordination. Therefore, it is believed that the accumulation of citrate in the blood and its ability to chelate and remove extracellular calcium ions (hypocalcemia) disrupts the neural control of muscle function, thus affecting behavior that may appear unpleasant to an untrained observer. Individuals recovering from near-fatal 1080 exposure do not recall pain after the event, but the final stages of poisoning have been likened to hypoglycemia or a seizure. Similarly, accidental exposure to excessive amounts of citrate as an anticoagulant during blood transfusions can manifest as similar painless spasms associated with induced hypocalcemia. In addition to the need for high-dose restrictions, sodium fluoroacetate is a naturally occurring phytotoxin in certain Australian plant species, leading to partial evolutionary tolerance in many native Australian herbivore species. For this and other reasons, 1080 remains one of the best toxin options for Australian wild boar management, but this chemical is unavailable for pig control in the US or elsewhere in the world. However, reliable lethal control of wild boar requires high doses of sodium fluoroacetate, meaning it is not a completely suitable toxin for pig management, especially since such high doses can endanger potential non-target species. This toxin can take up to 12 hours to kill a pig, so carcasses are often located some distance from bait placement sites and scattered. This is an obstacle to using this toxin in disease control situations where carcass retrieval is required to prevent the spread of infection. This risk to non-target species is particularly high when substrates such as grains and fresh animal carcass meat are used as bait carriers, as some non-target animals exhibit a preference for these substrates, and the clearing of bait by non-target species reduces the available bait for wild boar target animals, making some bait placement programs more expensive and less effective.

[0019] People who have experienced poisoning by other toxins such as CSSP or strychnine have reported suffering immense pain and agony, making these poisons likely too inhumane to use in controlling wild animals such as pigs. Similarly, while warfarin is used in low doses to treat people with clotting disorders, and this use is painless, it is contingent on not inducing uncontrolled bleeding. However, its use in large animals sensitive to this anticoagulant (such as wild boars) can lead to delayed action, painful bleeding and swelling of sensitive tissues, and prolonged suffering in some animals, making it also not the preferred poison for this application.

[0020] This indicates that neither these poisons nor the commonly used food-based baits are entirely suitable or represent a completely humane alternative for eradicating or controlling this pest species.

[0021] Besides wild boar species, humane euthanasia of domestic pig populations is sometimes necessary, for example, in the event of a disease outbreak in pigsties. African swine fever (ASF), for instance, is a contagious viral disease affecting both domestic and wild (outdoor) pigs. Currently, there is no vaccine. ASF kills approximately 80% of the pigs it infects. The acute form of the disease is caused by a highly virulent strain, causing pigs to develop a high fever, but without other obvious symptoms for the first few days. They then gradually lose their appetite and become depressed. In pigs with white skin, the limbs turn bluish-purple, and there is noticeable bleeding from the ears and abdomen. Groups of infected pigs huddle together, tremble, breathe abnormally, and sometimes cough. If forced to stand, their legs become unsteady. Within days of infection, they experience massive bleeding, enter a coma, and then die. In pregnant sows, spontaneous abortion occurs.

[0022] In milder infections, infected pigs lose weight, become emaciated, and exhibit signs of pneumonia, skin ulcers, and swollen joints.

[0023] The clinical symptoms of ASFV infection are very similar to those of classical swine fever, and the two diseases usually must be distinguished by laboratory diagnosis.

[0024] The virus can be transmitted through ticks and other potentially biting insects, as well as by pigs consuming contaminated pork products or through exposure to contaminated areas such as pigpens. The UK industry body, the National Swine Federation, states that the virus can also be transmitted through direct or indirect contact with infected pigs, their feces, or bodily fluids. Because the virus can survive in pig feces for up to 11 days and in pork products for months or years, the federation recommends strict biosecurity measures for pig farms, including a three-day quarantine upon entry into the UK and avoiding areas where pigs and wild boars are found.

[0025] One of the most common methods of euthanizing infected pigs is using a tranquilizer gun. While quick and effective, it does cause pain to both the pigs and the operator, creates problems with carcass removal, and the blood produced during the process can exacerbate contamination of the pigsty and increase the spread of infection.

[0026] Recent reports suggest that nitrites may be useful for controlling pig populations in New Zealand (wild boars (sus scrofa)) and other omnivores, such as the brush-tailed possum (Trichosurus vulpecula). Specifically, sodium nitrite is generally approved for use in very low doses to preserve many foods, reducing the risk of bacterial contamination and improving the color of certain meat products. While the risks are low when used as a food preservative in low doses, at high doses, it directly oxidizes iron molecules in heme proteins, causing normal hemoglobin to convert to methemoglobin. Because methemoglobin cannot efficiently transport oxygen to the brain and other tissues, when the level of methemoglobin in an animal's blood reaches approximately 70% or more of all hemoglobin, it can lead to acute metabolic hypoxia, resulting in unconsciousness and death. The clinical effects of methemoglobinemia are similar to those of carbon monoxide, which binds strongly to normal hemoglobin and also prevents oxygen delivery to vital organs and the brain. Therefore, nitrite-induced methemoglobinemia is more humane and faster in blocking oxygen transport than most (if not all) other toxins. Furthermore, pigs (also known as swine or hog) lack methemoglobin reductase, an enzyme that converts methemoglobin into normal hemoglobin, at higher levels in many other animals. This enzyme protects most animals from the accumulation of low to moderate levels of methemoglobin, which can occur naturally due to exposure to any oxidizing compound, such as nitrites present in some foods and water. Therefore, pigs are particularly vulnerable to such toxins because they lack the means to reverse the toxic process of methemoglobin formation.

[0027] Although sodium nitrite is effective as a poison, it is an unstable molecule that can be oxidized and react with other chemicals present in food. Sodium nitrite is highly hygroscopic, readily soluble in water, and then undergoes a series of decomposition reactions after dissolving in water to form carbonic acid from atmospheric carbon dioxide. Nitrites are highly polar and can even acquire acid (H+) through the deprotonation of water molecules, resulting in a highly alkaline initial solution. Numerous potential degradation pathways exist that interact with other components of a bait containing sodium nitrite, but one decomposition product is nitric oxide (NO), which is unstable on its own but can act as a corrosive agent, chemical messenger, and vasodilator, and can be exothermally oxidized in air to nitrogen dioxide (NO2). Nitrogen dioxide can be converted to nitrite (HNO2), which can then combine with itself to generate more nitrite and water, ultimately forming nitrate (HNO3). These reactions, including the natural formation of nitrates as part of the soil nitrogen cycle, lead to the eventual degradation of nitrites in the environment. From an environmental perspective, this lack of persistence and complete degradation is a valuable characteristic, but this instability is problematic when seeking to use nitrites in bait formulations. Not only do degradation products trigger chemical reactions within the bait, but direct decomposition products are also harmful to mucous membranes (e.g., sensitive pig snouts). Sodium nitrite also has a salty taste, and pigs generally dislike high-salt diets. Therefore, the use of large amounts of sodium nitrite or other nitrites as toxins in bait products presents a challenge to formulation, requiring baits that are stable during storage and use, yet simultaneously capable of delivering significant amounts of toxins to pigs while maintaining palatability.

[0028] MacMorran and Eason's WO 2010 / 151150 discloses a nitrite bait formulation in which the nitrite in the bait is encapsulated with corn protein at a nitrite content of approximately 80% wt. The results shown in the examples were obtained using freshly prepared bait. According to the inventors' knowledge, while these baits are effective when fresh, they degrade very slowly over time during storage, reducing their effectiveness and palatability over time. It is presumed that this degradation occurs based on a cascade of nitrite decomposition conditions discussed above. Furthermore, protein coating requires the application of a binary solvent system containing some water, which may be absorbed by the nitrite before an effective seal can be achieved.

[0029] Therefore, an improved method is needed to protect sodium nitrite in bait carrier systems by partially reducing the generation of harmful or undesirable decomposition products, thereby achieving formulation stability over an extended shelf life. These decomposition products are believed to reduce bait effectiveness. If such stability can be achieved, this would, in turn, reduce the likelihood of target pigs detecting nitrite and lead to increased voluntary ingestion.

[0030] Any new variant of the bait formulation still needs to provide animals with an effective release of nitrite to induce high levels of methemoglobinemia, thereby causing a rapid, painless death without suffering.

[0031] This invention addresses these long-term stability shortcomings currently existing in the field, and provides an effective bait formulation for the humane control of wild omnivorous pest populations.

[0032] If pig farms need to reduce their herd size immediately, such as during an outbreak, they also need to provide humane means to quickly euthanize their domestic pig populations.

[0033] Therefore, this invention also solves this existing drawback. Summary of the Invention

[0034] This invention is driven by the need to improve the delivery form of sodium nitrite as a poison in animal bait formulations. The inventors have discovered that the combined use of specific encapsulating components with specific plasticizers provides unexpectedly significant improvements in stability compared to various other combinations of encapsulating ingredients (e.g., waxes, lipids, acrylic polymers, glycerides, fatty acids and fatty alcohols, shellac, PVP / corn gluten, and paraffin) tested in process scale-up and for better encapsulation coverage, thereby greatly reducing nitrite leaching due to edge effects in the final bait formulation. This yields an improved formulation that is superior in terms of moisture resistance and long-term storage stability, while also delivering an effective physiological amount of nitrite in vivo.

[0035] The present invention is based on the discovery that using ethyl cellulose (EC) and linoleic acid (LA) as plasticizers in an amount of about 99:1 to about 99.99:0.01% by weight (EC:LA) can achieve unexpected improvements in nitrite-coated materials.

[0036] Therefore, in one aspect, the present invention provides ethyl cellulose / linoleic acid (EC / LA) microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from about 99:1 to about 99.99:0.01 by weight.

[0037] The present invention also provides a bait composition for omnivorous wild animals comprising a carrier material and sodium nitrite, wherein the carrier material is a lipophilic carrier, and the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from about 99:1 to about 99.99:0.01 by weight.

[0038] In another aspect, the present invention also provides a toxic feed composition for euthanizing a pig herd comprising a carrier material and sodium nitrite, wherein the carrier material is a pig feed ingredient or a combination thereof, and the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from about 99:1 to about 99.99:0.01 by weight.

[0039] In one embodiment and with reference to the foregoing, the method can be applied to pig herds that have been exposed to or infected with pathogens that pose a clinically serious or fatal risk to the pig herd or can be transmitted from pigs to humans. For example, in one embodiment, a toxic feed composition can be used to euthanize pig herds that have been exposed to or infected with African swine fever (ASF).

[0040] In one embodiment, based on the weight / weight ratio of ethyl cellulose / linoleic acid to nitrite, the ethyl cellulose / linoleic acid coating material is added to the nitrite at about 2.5% to 30% to form microspheres. Preferably, the nitrite is in particulate form.

[0041] Therefore, the present invention also provides a bait composition for omnivorous wild animals comprising a carrier material and sodium nitrite, wherein the carrier material is a lipophilic carrier, and the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from about 99:1 to about 99.99:0.01 by weight, and the ethyl cellulose / linoleic acid coating material is added to the nitrite at about 2.5 to 30% by weight to form microspheres based on the weight / weight ratio of ethyl cellulose / linoleic acid to nitrite.

[0042] In some embodiments, the inventors have demonstrated that additional stability can be achieved by incorporating a pH stabilizer into the carrier material to provide the bait with a pH greater than 7. In one embodiment, calcium carbonate can be added to the carrier material to make the pH > 7, since sodium nitrite in the bait composition has been found to be unstable at pH < 7. Lime can also be used as a pH adjuster, as can certain buffer solutions.

[0043] This invention also provides a bait composition for omnivorous wild animals comprising a carrier material and sodium nitrite, wherein the carrier material is a lipophilic carrier, and the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from about 99:1 to about 99.99:0.01 by weight. Based on the weight / weight ratio of ethyl cellulose / linoleic acid to nitrite, the ethyl cellulose / linoleic acid coating material is added to the nitrite at about 2.5 to 30% to form microspheres. The carrier material contains a pH stabilizer, thereby maintaining the bait at a pH greater than 7. Notably, this is accomplished using only ethanol as a solvent, thus eliminating the risk of water loss that occurs when using aqueous binary solvents.

[0044] The present invention also provides a toxic feed composition for euthanizing pig herds comprising a carrier material and sodium nitrite, wherein the carrier material is a pig feed ingredient or a combination thereof, and the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from about 99:1 to about 99.99:0.01 by weight, and based on the weight / weight of ethyl cellulose / linoleic acid and nitrite, the ethyl cellulose / linoleic acid coating material is added to the nitrite at about 2.5 to 30% to form microspheres.

[0045] The present invention also provides a method for humanely controlling omnivorous wild animals, particularly wild boars and opossums, comprising the step of dispersing the bait composition disclosed herein within the foraging areas of the omnivorous wild animals.

[0046] The present invention also provides a method for humanely controlling pig populations, particularly farmed pig populations, comprising the step of distributing the toxic feed composition disclosed herein within the pigs' foraging area.

[0047] The present invention further provides a method for preparing a bait composition for omnivorous wild animals comprising a lipophilic carrier material and sodium nitrite, wherein the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from about 99:1 to about 99.99:0.01 by weight, and the method comprises:

[0048] (a) Optionally, the granular sodium nitrite is dried to constant weight, thereby substantially reducing all moisture content;

[0049] (b) Encapsulating the granular sodium nitrite from step (a) using a mixture of ethyl cellulose and linoleic acid with a volatile organic solvent via pan coating or fluidized bed coating technology; and

[0050] (c) Mixing the encapsulated material with the carrier material to form a bait composition.

[0051] The present invention further provides a method for preparing a bait composition for omnivorous wild animals comprising a lipophilic carrier material and sodium nitrite, wherein the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from about 99:1 to about 99.99:0.01 by weight, the carrier material comprises a pH stabilizer such that the bait maintains a pH of about 7 to 8, and the amount of ethyl cellulose / linoleic acid is about 3.5 to 20% by weight relative to the amount of sodium nitrite, the method comprising:

[0052] (a) Optionally, the granular sodium nitrite is dried to constant weight, thereby substantially removing all moisture;

[0053] (b) Encapsulating the granular sodium nitrite from step (a) using a mixture of ethyl cellulose and linoleic acid with a volatile organic solvent via pan coating or fluidized bed coating technology; and

[0054] (c) The encapsulated material is mixed with a carrier material containing a pH stabilizer to form a bait composition.

[0055] The present invention further provides a method for preparing a toxic feed composition for pig herds comprising a carrier material and sodium nitrite, wherein the carrier material is a pig feed ingredient or a combination thereof, wherein the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from about 99:1 to about 99.99:0.01 by weight, and the method comprises:

[0056] (d) Optionally, the granular sodium nitrite is dried to constant weight, thereby substantially reducing all moisture content;

[0057] (e) Encapsulating the granular sodium nitrite from step (a) using a mixture of ethyl cellulose and linoleic acid via a volatile organic solvent through a pan coating or fluidized bed coating technique; and

[0058] (f) Mixing the encapsulated material with the carrier material to form a toxic feed composition.

[0059] In some implementations, the volatile organic solvent is anhydrous or substantially anhydrous. Invention Details

[0061] As used herein, the term "microsphere" refers to substantially spherical discrete particles with a size of about 100 nm to about 1 mm. Furthermore, the microspheres of the present invention, referred to as "microcapsules," are characterized by using sodium nitrite as a core material and a mixture of ethyl cellulose (EC) and linoleic acid (LA) plasticizers as a coating or encapsulation material on said core material. The microspheres of the present invention are approximately spherical in shape, but not perfectly regular, with some individual particles showing small particles adhering to the surface of larger particles. At 100x magnification, the surface of the sodium nitrite microspheres is rough, with nodular small particles adhering to large nitrite particles. It has been shown that after the coating process, these particle assemblies are not easily broken or destroyed by physical forces and are generally coated as a single particle. Time-of-flight microscopy studies show almost complete coverage / encapsulation with the encapsulated material disclosed herein.

[0062] In one embodiment, the ethyl cellulose / linoleic acid coating material is added to sodium nitrite at a weight ratio of about 3.5 to 20%, for example, at about 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.4, 6.6, 6.8, 7.0, 7.2, 7.4, 7.6, 7.8, 8.0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8, 10, 10.2, 10.4, 10.6, 10.8, 11.0, 11.2, 11.4, 11.6 11.8, 12.0, 12.2, 12.4, 12.6, 12.8, 13.0, 13.2, 13.4, 13.6, 13.8, 14.0, 14.2, 14.4, 14.6, 14.8, 15.0, 15.2, 15.4, 15.6, 15.8, 16.0, 16.2, 16.4, 16.6, 16.8, 17.0, 17.2, 17.4, 17.6, 17.8, 18.0, 18.2, 18.4, 18.6, 18.8, 19.0, 19.2, 19.4, 19.6 to about 19.8% by weight / weight added to sodium nitrite.

[0063] In one embodiment, the amount of ethyl cellulose / linoleic acid is about 5 to 10% by weight relative to the amount of sodium nitrite.

[0064] In one embodiment, the amount of ethyl cellulose / linoleic acid is about 5% by weight relative to the amount of sodium nitrite.

[0065] In one embodiment, the microspheres of the present invention have an average size of about 100 to 1000 micrometers. In another embodiment, the microspheres have an average size of about 200 to 750 micrometers, for example 210, 220, 230, 250, 270, 290, 310, 330, 350, 370, 380, 390, 410, 430, 450, 470, 490, 500, 510, 530, 550, 570, 590, 600, 610, 620, 630, 640, 660, 680, 690, 700, 710, 720, 730, or 740 micrometers, or within the range of any two of the above values. It should be understood that the average size of the microspheres will depend on their manufacturing method. In one embodiment, the microspheres are prepared by pan coating or fluidized bed coating technology.

[0066] As used herein, the term "bait" refers to a combination of carrier materials and active agents deliberately selected for the specific purpose of preparing a livestock pest control agent, wherein the carrier materials and the bait as a whole are palatable and can be at least partially consumed by the target livestock. Therefore, the "bait" of this invention is a deliberately manufactured livestock pest control agent that contrasts with, for example, naturally occurring materials (e.g., plant materials that may contain natural amounts of sodium nitrite) and is distinct from, for example, meat sausages that may contain large amounts of active agents, or in which the active agents are added in an unprotected form and at very low doses for the purpose of enhancing flavor or preventing certain bacteria (such as Clostridium botulinum or Salmonella).

[0067] As used herein, the term "toxic feed composition" refers to a combination of a carrier material and an active agent, used as an ingredient or combination thereof in pig feed, for the explicit purpose of euthanizing a pig herd, wherein the carrier material and the active agent (in this case, encapsulated sodium nitrite) are palatable in combination and can be at least partially consumed by farmed / domesticated pigs. Suitable pig feed ingredients may include grains, nuts, and sugars; suitable plant-derived components include milled grains, cornmeal, bran, corn, plant fiber, flour, fruits, vegetables, seeds, sugars (e.g., molasses), grains, and straw, and mixtures thereof. Therefore, the present invention contemplates the incorporation of microencapsulated sodium nitrite into the normal feed of a pig herd in an amount that provides a lethal dose.

[0068] In one embodiment, the toxic feed composition is a mixture of microencapsulated sodium nitrite and dry pig feed ingredients.

[0069] This invention relates to the humane control of omnivorous wild animals, particularly wild boar and wild opossum, as well as domestic pigs in pig farms. Therefore, the terms "humane" and "humanely" as used herein refer to methods that do not cause excessive suffering to the target animal species. Signs of suffering avoided or minimized by this invention include bleeding, excessive vomiting, vocalization, severe central nervous system damage (including hyperexcitability, convulsions, ataxia, leg tremors, and leg paddling while prone), and prolonged death. Preferably, death occurs within 1 to 3 hours after ingestion of the bait of this invention, with few other symptoms besides progressive recumbency, loss of consciousness, weak breathing, and death caused by the conversion of normal hemoglobin to methemoglobin, which does not transport oxygen in the blood, due to nitrites.

[0070] For the purposes of this invention, when the target pests are omnivorous wild animals, these are preferably wild boars and opossums. In this embodiment, the invention considers using the stable bait of this invention to control wild boar populations. In another embodiment, the bait of this invention is designed to control wild opossum populations. These specially formulated baits remain stable even after exposure to outdoor weather conditions for weeks or months.

[0071] For the present invention, when the target pests are domestic pigs kept in pigsties, the present invention considers using a combination of pig feed ingredients and the readily prepared microencapsulated sodium nitrite of the present invention (i.e., a toxic feed composition) to control the pig herd. Preferably, the combination is a dry feed combination with the microencapsulated sodium nitrite of the present invention.

[0072] It should be understood that the term "wild" as used in this article refers to target pest species (i.e., omnivorous animals) living in the wild whose populations or numbers are difficult to control. For example, in Australia, many wild animals, such as dogs, goats, cats, and pigs, were originally introduced during the British colonial period as domesticated species, suitable for hunting, or to potentially control other pests. After escaping into the wild, these animals became wild, settling and reproducing without human intervention. Many wild animals are introduced species whose presence in the wild is undesirable because they can negatively impact agricultural activities such as crop production and grazing. An example in New Zealand is the introduction of the opossum, particularly the common brushtail opossum (brushtail possum). Wild animals introduced as species differ from native or domesticated species. These wild animals also frequently have adverse environmental impacts, especially as their numbers increase. Increased wild animal numbers are due to their vitality and survival rates, lack of natural predators and high reproductive rates, and their ability to adapt to a wide range of food sources. Therefore, these wild animals have been classified as pests, and the aim is to keep their numbers to a minimum, or, where possible, to eradicate them entirely from the wild or from areas of high agricultural or conservation value. It should be understood that while the bait of this invention cannot distinguish between wild animals and domesticated animals, it is intended solely for controlling wild animal populations, and therefore appropriate measures should be taken to ensure that the bait does not spread to domesticated populations.

[0073] The term "activator" mentioned above refers to an agent that affects the physiology of a target wild animal in a desired manner. The activator of this invention is sodium nitrite, but it should be recognized that other forms of nitrite have similar effects and can also be used, such as potassium nitrite.

[0074] The present invention is based on the discovery that the integrity of baits containing nitrites may be severely compromised due to (i) insufficient coating of nitrite particles and / or (ii) water / moisture in the bait composition due to pH incompatibility.

[0075] The inventors have derived the following solution to explain the degradation of sodium nitrite in bait products:

[0076] NaNO2 + HCl → HNO2 + NaCl

[0077] Then, nitrous acid decomposes on its own:

[0078] 2HNO2→NO2+H2O

[0079] (Therefore, it is possible for it to generate water itself.)

[0080] Nitric oxide (NO) can also spontaneously and exothermically oxidize to NO2 in the air, and then nitrogen dioxide (NO2) can react with water to produce nitric acid and more nitrite.

[0081] 2NO2 + H2O → HNO3 + HNO2

[0082] • NaNO2 can also be slowly oxidized to NaNO3 in air, and can react with amine groups to form nitrosamines.

[0083] • NaNO2 can also deprotonate water, thus providing itself with acid to react with itself.

[0084] For the reaction scheme described above, the acid (HCl) shown can be any acid (H+). + Many bait carrier materials are characterized by their acidic components. Since other bait components (e.g., wheat) have a pH < 7, it is necessary to overcome this potential source of H+ ions. The inventors have also discovered that the stability of the bait product can be further improved by maintaining the pH of the bait product above 7. Therefore, in some embodiments, the bait compositions disclosed herein further comprise a pH stabilizer. The pH stabilizer can be any compound capable of maintaining the pH of the bait above pH 7, preferably around 7 to 8. Suitable stabilizers include non-hygroscopic agents such as sodium carbonate (soda ash), sodium citrate, sodium acetate, sodium silicate, sodium sulfide, calcium carbonate, sodium bicarbonate, known phosphate buffers, or sodium hydroxide / calcium hydroxide.

[0085] In one embodiment, a pH stabilizer is added at a ratio of about 50 to 110 grams per 60 kg of whole bait composition, for example, about 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, or about 109 grams per 60 kg of whole bait composition.

[0086] In one embodiment, the water content of the bait composition is less than about 10% (w / w), for example less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, or less than 2% wt / wt, or less than 1% wt / wt.

[0087] By pre-drying the components of the bait composition while formulating the final composition, the water content of the bait can be substantially minimized.

[0088] The inventors have discovered that the presence of trace amounts of water in nitrite-based compositions can lead to the accumulation of hydroxyl ions, which can interact with certain types of coatings that are sensitive to high pH, ​​and can also lead to the release of nitric oxide or other decomposition products. These nitric oxide or decomposition products are produced by the reaction of nitrite with itself or with other chemicals and / or bait components, and these reactions can produce decomposition products that wild boars can detect, including nitric oxide, nitrogen dioxide, nitrite, and nitrate, leading to aversion to voluntary ingestion. It has also been found that the saltiness of nitrite bait provides an aversion signal that limits voluntary ingestion of the bait by wild boars, thereby exacerbating this problem.

[0089] To improve upon known baits, the inventors developed a bait system to prevent nitrite degradation (i.e., increase stability) and enhance the palatability of the target species. In particular, the inventors have investigated numerous encapsulated ingredients and found that many fail to satisfactorily coat nitrites to prevent / minimize nitrite leaching, which in turn compromises the effectiveness of the final bait product. The inventors have devised a special coating technology, such as pan coating, especially fluidized bed coating, which forms a more complete coating of nitrite particles. Specifically, it uses ethyl cellulose and linoleic acid in a ratio ranging from 99:1 to 99.99:0.01 in %wt / wt, for example, ethyl cellulose:linoleic acid ratios of about 99.1:0.9, 99.2:0.8, 99.3:0.7, 99.4:0.6, 99.5:0.5, 99.6:0.6, 99.7:0.3, 99.8:0.2 and about 99.9:0.1, and ratios between these figures.

[0090] The nitrites in the bait work by preventing oxygen transport through the formation of methemoglobin (Met Hb) in red blood cells, and at certain doses, cause rapid death through methemoglobinemia. There have been reports of livestock (e.g., pigs) dying accidentally from nitrite poisoning (see, for example, Vyt, P et al., Viaams DiergeneeskundigTijdschrift, 2005, 74, 359-363; Gibson, R., The Veterinary Record, March 22, 1975, p. 270; McParland, PJ et al., The Veterinary Record, March 1, 1980, p. 201; Counters, DE et al., The Veterinary Record, May 3, 1975, p. 412; Winks, WR., The Queensland Journal of Agricultural Science, Vol. 7, Nos. 1 and 2, March and June 1950, pp. 1-14; and London, WT et al., JAVMA, Vol. 150, No. 4, pp. 398-402).

[0091] According to a study on the formation and reduction of methemoglobin in various animals (see Smith and Butler, Am. J. Physiology. 210(2): 347-350, 1966), susceptibility to MetHb formation appears to be related to the MetHb reduction rate, in that the rapid oxidation of hemoglobin to methemoglobin is offset by a rapid MetHb reduction rate. In this study, pigs were observed to be particularly susceptible to methemoglobinosis because they were unable to effectively reduce MetHb. This is because pigs have relatively low levels of methemoglobin reductase, making them highly sensitive to compounds that form methemoglobin.

[0092] Furthermore, nitrite poisoning, as an effective toxin, causes rapid and relatively painless, or even completely painless, poisoning and death. Due to the low oxygen-carrying capacity of nitrite-induced methemoglobin, its mechanism of action leads to the rapid development of cerebral hypoxia. Therefore, one of the primary symptoms of poisoning is loss of consciousness, very similar to the mechanism of action of carbon monoxide. Carbon monoxide causes the formation of carboxyhemoglobin, which, like methemoglobin, cannot effectively transport oxygen to tissues. Carbon monoxide has been used as a method of humane disposal of unwanted animals and is considered one of the most humane techniques available for this process. This contrasts sharply with the severe clinical symptoms caused by warfarin (bleeding in various organs leading to pain, such as lameness) and phosphorus (e.g., liver failure and severe tissue damage leading to slow death, resulting in prolonged malaise). Moreover, the death rate from nitrite is extremely rapid, so any symptoms will only be experienced within a short period. Therefore, the advantages of the baits of this invention are that they provide a more humane alternative to existing wild omnivorous baits, and the carcasses of poisoned animals typically accumulate near the bait placement site, allowing for carcass retrieval or impact assessment. However, this advantage is only realized when sufficient bait is ingested and the toxic component (i.e., nitrite) has physiological bioavailability over a short period. Gradual bait ingestion will result in insufficient methemoglobin to achieve the desired rapid lethal effect and may reduce the animal's mobility, thus interrupting further bait ingestion. Therefore, there is a balance between the stability of nitrite and the ability of encapsulated nitrite to release nitrite for effective control of pests. The inventors have developed baits that address this balance by using a specific concentration of a combination of EC and LA.

[0093] In one embodiment, sodium nitrite, which serves as an active agent or core material in the decoy of the present invention, is present in the form of free-flowing particles. It should also be understood that "particles" refers to discrete solids, aggregates of macroscopic particles. This should be contrasted with non-particulate forms (such as powders, liquids, or flakes). Preferably, the particle size of sodium nitrite is from 200 μm to 1 mm.

[0094] Larger particles, such as those greater than 1 mm, can be detected and eliminated by pigs during consumption after coating, and may have lower resistance to mechanical damage during processing (e.g., mixing, extrusion, and packaging). Smaller particles have a higher coating-to-encapsulated active ingredient ratio, making them less suitable for applications requiring the delivery of large amounts of active ingredient to influence lethal doses. The particle shape is typically irregular, but can also be spherical. Preferably, the particle form is granular sodium nitrite. This granular salt is commercially available and is formed from molten liquid. However, the inventors recognize that extruded formulations of sodium nitrite combined with a suitable binder and cut into short lengths also provide a suitable form of sodium nitrite for coating via fluidized bed or pan coating processes.

[0095] In one embodiment, prior to microencapsulation, the sodium nitrite particles have a moisture content of less than 2% wt / wt, for example less than 1.5% wt / wt, 1.0% wt / wt, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1% wt / wt.

[0096] In a preferred embodiment, sodium nitrite comprises about 5 to 15 wt / wt% of the total bait composition, for example, about 5 wt / wt%, 5.5 wt / wt%, 6 wt / wt%, 6.5 wt / wt%, 7 wt / wt%, 7.5 wt / wt%, 8.0 wt / wt%, 8.5 wt / wt%, 9.0 wt / wt%, 9.5 wt / wt%, 10 wt / wt%, 10.5 wt / wt%, 11 wt / wt%, 11.5 wt / wt%, 12 wt / wt%, 12.5 wt / wt%, 13 wt / wt%, 13.5 wt / wt%, 14 wt / wt%, 14.5 wt / wt%, or about 15 wt / wt%, or within the range of any two of the foregoing values.

[0097] The inventors have discovered that by preparing microspheres according to the invention and delivering these microspheres into a bait composition such that sodium nitrite comprises about 5 to 15 wt%, it is possible to balance the need for sufficient sodium nitrite to provide a lethal humane dose without the risk of excessive toxicity, such that, for example, pigs will still be attracted to the bait and find it palatable.

[0098] Ethyl cellulose (EC) is a derivative of cellulose in which some of the hydroxyl groups on the repeating glucose are present in the form of diethyl ether groups. The amount of ether groups can vary, for example, from about 40 to 54% w / w ethoxy.

[0099] Description of ethyl cellulose types

[0100] type Ethoxy group content (%) Degree of substituent groups per dehydrated glucose unit K type 45.0-47.2 2.22–2.41 N-type 48.0–49.5 2.46–2.58 T-shaped 49.6–51.5 2.58–2.73 X type 50.5–52.5 2.65–2.81

[0101] However, it is largely insoluble in water, but very stable in mixtures of tetrahydrofuran, methyl acetate, chloroform, and aromatic ethanol.

[0102] Surprisingly, however, no nitrite degradation or water adsorption of the coating solution occurred when coating experiments were performed under these conditions. Not wanting to be bound by theory, the inventors hypothesize that ethyl cellulose acts as a chelating agent to lock in available water, ensuring that nitrite is not exposed (to any significant extent) to free water during the encapsulation process. 96 to 99% pure ethanol is economical, and the inventors' knowledge has shown that there is no significant increase in water content of ethyl cellulose microspheres using EC / LA / EtOH in a fluidized bed process at a coating air temperature of 40°C or a hotter dehumidified airflow. Flexible flow or Wurster-type fluidized bed coating processes can be used, but the inventors prefer the flexible flow process because it allows for scaling up production. The size of the EC / LA microspheres, as described herein, is also considered a factor contributing to the stability of the encapsulated nitrite. If the microspheres are too large (e.g., greater than 1 mm), osmosis effects may lead to swelling and self-destruction. Too small a size (less than 100 nm) results in a more robust coating wall, which in turn may lead to insufficient release of nitrite under physiological conditions, hindering the delivery of humane and lethal doses, and also causing some small spheres to be lost from the coating machine via the police filter of the outlet airflow.

[0103] Linoleic acid, also known as LA, has the molecular formula C2. 18 H 32 O2 is a fatty acid. It is usually abbreviated as 18:2(n-6) or 18:2cis-9,12.

[0104] Standard methods such as fluidized bed coating or pan coating techniques can be used to apply encapsulated materials by spraying a coating material solution from a volatile solvent system onto nitrite core particles. In some embodiments, the solvent is ethanol, particularly absolute ethanol.

[0105] In one embodiment, the encapsulated nitrite comprises about 2-15% wt / wt of the final bait composition, for example, about 2.5% wt / wt, 3.5% wt / wt, about 4% wt / wt, about 4.5% wt / wt, about 5% wt / wt, about 5.5% wt / wt, about 6% wt / wt, about 6.5% wt / wt, about 7% wt / wt, about 7.5% wt / wt, about 8% wt / wt, about 8.5% wt / wt, about 9% wt / wt, about 9.5% wt / wt, about 10% wt / wt, about 11% wt / wt, about 12% wt / wt, about 13% wt / wt, about 14% wt / wt, or about 15% wt / wt, or any two of the foregoing values.

[0106] In one embodiment, the encapsulated nitrite composition comprises about 2 to 10% wt / wt of the final bait composition (i.e., the carrier material and microencapsulated sodium nitrite).

[0107] In one embodiment, the encapsulated nitrite composition comprises about 2 to 20% wt / wt of the final toxic feed composition (i.e., the carrier material and microencapsulated sodium nitrite).

[0108] According to the present invention, the encapsulated nitrite particles of the bait can be mixed with a lipophilic carrier. The lipophilic carrier can be selected from lipophilic surfactants, vegetable oils, fatty acids and esters, fatty alcohols, glycerides, waxes, etc.

[0109] However, it should be understood that the lipophilic carrier needs to be palatable to the target species, and preferably palatable and attractive. In this regard, preferred lipophilic carriers are selected from vegetable oils and lipid-based materials. In one embodiment, castor oil, peanut oil, corn oil, flaxseed oil, and sesame oil are selected.

[0110] In one embodiment, the carrier is peanut oil paste (or simply "peanut paste"), thus the bait can be in paste form. Peanut paste, used in the food industry as a base for peanut butter, is formed by roasting, blanching, and grinding raw peanuts; therefore, the paste contains peanut endosperm and peanut oil. Combined with the encapsulated microspheres of this invention, the inventors have found that the stability of nitrites in the bait and the stability of the bait itself are greatly improved.

[0111] In one embodiment, the encapsulated nitrite comprises about 2-15% wt / wt of the final bait composition, for example, about 2.5% wt / wt, 3.5% wt / wt, about 4% wt / wt, about 4.5% wt / wt, about 5% wt / wt, about 5.5% wt / wt, about 6% wt / wt, about 6.5% wt / wt, about 7% wt / wt, about 7.5% wt / wt, about 8% wt / wt, about 8.5% wt / wt, about 9% wt / wt, about 9.5% wt / wt, about 10% wt / wt, about 11% wt / wt, about 12% wt / wt, about 13% wt / wt, about 14% wt / wt, or about 15% wt / wt, or any two of the foregoing values.

[0112] In one embodiment, the encapsulated nitrite composition comprises about 2 to 10% wt / wt of the final bait composition (i.e., the carrier material and microencapsulated sodium nitrite).

[0113] The desired outcome is a final bait product that offers a usable shelf life at room or field temperatures, but is not fully coated and protected so that the coating does not impede the rapid release of the active ingredient into the pig's stomach shortly after ingestion. This is because sodium nitrite is a mass active agent that only induces lethal levels of methemoglobinemia when rapidly injected into the target animal system. Gradual delivery of the theoretically lethal acute dose may not necessarily achieve the level of methemoglobinemia required for death. Therefore, when designing a protective coating, a balance must be struck between protecting nitrite from degradation or interaction with the bait components and simultaneously allowing for rapid bioavailability of the toxins after the bait is ingested.

[0114] In one embodiment, the bait composition is a semi-solid, such as a paste.

[0115] In another embodiment, the bait composition is substantially solid.

[0116] In another embodiment, the toxic feed composition is a loose combination of a carrier (pig feed component) and encapsulated sodium nitrite.

[0117] It should be understood that during typical baiting operations, multiple baits are dispersed within the foraging area of ​​the target animal species. Even if a single bait is completely consumed, it may not provide a lethal dose to a single target animal. However, preferably, the amount of nitrite provides a lethal dose after the target wild animal has consumed a small amount of the bait material. That is, the amount of nitrite in a single edible portion of a single bait, or even a larger bait, is sufficient to effectively kill a wild omnivore. Ideally, the target animal will not eat too much bait or monopolize it, but only the amount necessary to kill the animal. This allows many animals to be killed with a single baiting session and also minimizes the excessive toxic load in the carcass.

[0118] It should be understood that when humanely euthanizing farmed / domesticated pig herds, toxic compositions can be administered in the manner the pigs are normally fed. Preferably, the feed provides a lethal dose. However, more preferably, the amount of nitrite provides a lethal dose after the target wild animal has consumed a small amount of bait material. That is, the amount of nitrite in a single feed or a single edible portion is sufficient to effectively kill one or more pigs in the herd.

[0119] It should be understood that the lethal dose of nitrite for killing pigs generally depends on the species' physiology and body weight. For pigs, the lethal dose is preferably at least 135 mg nitrite / kg body weight. Therefore, for a pig weighing 60 kg, a single bait needs to contain at least 5 g of nitrite to provide a lethal dose. Thus, since most adult pigs typically weigh between about 10 and 200 kg, the preferred nitrite content in a single bait portion is 1.35 g to 270 g. More preferably, the preferred amount of nitrite in a single bait or bait portion consumed is less than 30 g, even more preferably less than 20 g, for example, less than 15 g.

[0120] For the present invention, which is intended to control wild omnivores such as wild boars, the bait may also contain additional food sources that are attractive, palatable and edible to the target omnivores.

[0121] Examples of suitable plant-based components include corn flour, bran, corn (corn), plant fiber, flour, fruits, vegetables, seeds, grains, and straw.

[0122] In another embodiment, the compositional ingredients are selected with non-target species in mind to reduce the likelihood of ingestion of the bait by these species. Therefore, the specific types and amounts of components constituting the bait composition can be varied depending on the non-target species to be avoided. For example, when the non-target species are herbivores (e.g., specific non-carnivorous birds, marsupials, etc.), the carrier material can be chosen to consist primarily of animal-derived components. This is particularly preferred when targeting Australian wild boars, as most non-target native species have limited dietary ranges, and many are obligate herbivores or grain-eating birds that are less interested in omnivorous baits.

[0123] The selection of bait matrix components must also take into account the moisture content of the carrier material or attractant. In one embodiment, the carrier is a mixture of corn and wheat, as well as wheat flour, which is pre-dried to minimize the moisture content to below levels naturally present in such grains.

[0124] The bait may also contain specific chemical attractants, such as spices or flavoring substances (odorants). Chemical attractants can be natural or artificial flavorings, such as banana, honey, fennel, molasses, cinnamon oil, and chocolate. The carrier material may also contain other additives known in the art, such as colorants, preservatives, binders, fillers, etc. The choice of colorant is important because nitrites can react with reagents containing amide groups, and upon contact with water, nitrites produce an alkaline solution that can alter the color of some dyes. Inert and stable dyes are preferred. For example, in a preferred embodiment, the carrier material contains a colorant (dye) that makes the bait black to mask it for non-target species (e.g., birds) that typically prefer to eat yellow and red foods consistent with ripe fruit. For example, in one embodiment, the composition contains a certain amount of iron oxide (ferric iron) to turn the composition gray or black. The choice of dye must also take into account cost and the possibility of reaction between the active ingredient sodium nitrite and the colorant. Ferric oxide is a suitable inert colorant for this purpose, while dyes containing amide groups are less suitable because they may react with the active ingredient. Water-soluble dyes are not easy to use. In addition, preservatives, antioxidants, and binders can be added to provide mechanical strength to the finished bait and reduce the risk of premature degradation during storage.

[0125] To further ensure stability, the composition can also be packaged in a barrier laminated tray with a plastic seal, and the tray is designed to be purged with nitrogen before sealing to remove oxygen from the top space as a further method to reduce nitrite oxidation levels.

[0126] In addition, to increase target specificity, the bait may also contain repellents for other non-target species, such as methyl anthranilate, which is a known bird repellent.

[0127] References to any prior publications (or information derived therefrom) or any known matters in this specification are not, and should not be construed as, an acknowledgment or endorsement, or an indication in any form that such prior publications (or information derived therefrom) or known matters constitute part of the general knowledge in the field covered by this specification.

[0128] In this specification and the following claims, unless the context otherwise requires, the word “comprising” and variations such as “including” and “containing” will be understood to imply the inclusion of the specified integer or step or a set of integers or steps, but not to exclude any other integer or step or a set of integers or steps.

[0129] Some embodiments of the invention will now be described with reference to the following examples, which are for illustrative purposes only and are not intended to limit the general scope of the above description. Detailed Implementation

[0130] Example

[0131] Example 1 - Preparation of encapsulated NaNO2 using a corn gluten / plasticizer mixture.

[0132] method

[0133] Encapsulation of granules

[0134] NaNO2 (SN) particles (food grade E250, BASF) of approximately 0.2 to 1.0 mm and EC were used as is. BASF SN is free-flowing and contains an anti-caking agent (approximately 0.1% w / w of amorphous silica). We also pre-sieved the SN to obtain a more uniform particle size range (100 to 1000 micrometers in diameter) by removing fine powder (<100 micrometers). Optionally, the NaNO2 particles were dried in a commercial oven at 60°C for 12 hours to remove any residual moisture. The NaNO2 particles (500 g) were coated using a pan coating process; EC (9.975%, or 9.95%, or 9.90%) was dissolved in 95 to 96% ethanol (90%), and 0.025%, or 0.05%, or 0.10% LA was added to prepare a mixture containing EC and LA. To coat NaNO2, 500g of granules are placed in a spherical disc, which is rotated at 20 revolutions per minute. A liquid encapsulating agent solution is sprayed onto the granules at a rate of one liter per hour, while the entire mixture is heated to 40°C by pre-drying hot air directed onto the granule bed to gradually evaporate the solvent. Once all coating material has been applied, the granules are continued to be rotated to ensure dryness.

[0135] Scanning electron microscopy examination of encapsulated particles

[0136] Visual evaluation of NaNO2 particles coated with four different solutions and uncoated NaNO2 particles was performed using a scanning electron microscope (SEM) (Philips XL30S FEG, Netherlands). Samples were sputter-coated with gold for 2 minutes (Quorum Technologies Polaron SC 7640 sputtering system, UK) and observed at an accelerating voltage of 5 kV. Samples were observed and photographed at 54× or 55× magnification, then at 250× and 1000× magnification. Potential particle aggregation and cracks on the surface of the coated formulations were observed.

[0137] Cast film and mechanical properties

[0138] The EC / LA coating formulation was cast into a film, and the mechanical properties were evaluated using a texture analyzer (TA-XT2i instrument, Stable Micro-system, UK).

[0139] The solution was poured into plastic petri dishes (10cm × 10cm) and placed in a fume hood at room temperature for 24 hours. The films were then removed from the petri dishes and fixed between two plates with aligned 10mm openings. The fracture strength of each film was assessed using a probe (1 / 4” spherical probe, 1mm / s), with six new film sections tested each time. The maximum force required for the probe to break the test sample was recorded.

[0140] Casting permeability and water absorption

[0141] As described above, the membrane was cast using an ethanol (80% w / w) solution. Four small circular portions (approximately 12 mm in diameter) of the membrane were cut from the cast membrane. Each circular portion of the membrane was placed inside the screw cap of a separate Hungate anaerobic culture tube. The cap had holes approximately 9 mm in diameter, which were covered by the circular pieces of the membrane. The cap was screwed onto the test tube, allowing the membrane to provide a barrier. Approximately 5 g of CaCl2 was placed in each test tube. Twelve test tubes (four for each membrane tested) were placed in beakers within a sealed plastic container, next to a beaker containing NaCl2, which was moistened with water until visibly wetted. The saturated solution of NaCl2 and water within the sealed container provided a stable, constant environment and humidity. The water gain in each tube was measured by weighing each assembled tube before the test, then weighing each assembled tube at set time points of 1, 2, 3, and 4 hours later, and then weighing each assembled tube daily until the seventh day.

[0142] Example 2 - Preparation of encapsulated bait composition

[0143] a) Formulation components

[0144] The proportions of these components are:

[0145]

[0146]

[0147] b) Preparation process (coating pan)

[0148] Industrial-grade particulate sodium nitrite (200 to 800 μm) was obtained from BASF.

[0149] Sodium nitrite is heated in a coating pan at 45°C for 30 minutes, with the pan gently agitated during the process. At the end of the process, the moisture content should be <0.1% w / w.

[0150] The encapsulating agent containing EC / LA is mixed / dissolved in 96% ethanol.

[0151] The coated nitrite was then formulated with a palatable carrier that further protected the nitrite from degradation and provided the mixture in a palatable form for wild boar consumption. In this carrier, the bait consisted of peanut paste and peanut oil mixed with dried, ground grains (including wheat, corn, and wheat flour) to form a robust paste. The final concentration of nitrite in the paste was approximately 10% wt / wt, meaning that a boar would be killed if it ingested 15 to 200 grams of the bait paste. This paste was packaged in trays so that boars could consume it at any time. Experiments showed that wild boars tended not to overeat the paste; therefore, in areas with a high local boar population, a small amount of the paste could kill a large number of boars foraging together.

[0152] Field test

[0153] In one example, a group of pigs is gathered to a foraging area or bait station by first identifying points where they seek food or water. Such points can be easily identified by observing pig tracks on the ground, by signs of pigs rubbing against trees or defecating, or by using remotely triggered cameras well known in the art. The pigs are then encouraged to forage at the selected location by providing typical food (e.g., grains such as wheat or corn). When pigs are observed to regularly visit and forage at the location, toxic bait material is provided, or the bait material is initially provided in a non-toxic form to further acclimate the pigs to the feed at the location, followed by a toxic version the following evening.

[0154] The pigs then consumed the poisoned bait and were quickly killed; numerous carcasses were found near the baiting area the following morning. The rapid killing of affected animals facilitated an assessment of the bait's effectiveness, and the carcasses could be easily recovered and disposed of if necessary.

[0155] The paste was stored under standard field conditions for three months (without temperature control) before testing to confirm that the formulation retained its lethality and palatability in pigs even after long-term storage after production.

[0156] Therefore, these field tests confirmed that the bait was palatable to untamed wild boars and was consumed by them, and that the amount of toxin released or the bioavailability were sufficient to kill most of the animals visiting the foraging site. Furthermore, large numbers of animals weighing 10 to 90 kg were killed by a bucket containing 10 kg of bait (first embodiment) or a plastic tray containing 5 kg of bait (exemplary 2), thus no individual monopolized a large quantity of bait.

[0157] Example 3 - Preparation of encapsulated microspheres (based on EC / LA).

[0158] Methods for producing spheres:

[0159] Particulate sodium nitrite with a moisture content of less than 1% (typically about 0.2 to 0.3%) and a particle size distribution of 180 to 800 micrometers is suspended in an air stream in the form of a fluidized bed. This air stream is drawn into a coating apparatus at a relative humidity of 80%, a temperature of 12°C, and preheated to 40 to 45°C. EC coating materials are prepared by completely dissolving 9.95% w / w EC in 96% ethanol and containing 0.05% LA as a plasticizer to form a coating solution.

[0160] The coating solution is initially sprayed at a low rate onto a fluidized bed of sodium nitrite particles, then a uniform coating layer is provided at a gradually increasing rate until 2.5% to 25% EC / LA coating is achieved on the particles, typically 5% w / w for the final product. In this embodiment, the final coated microsphere product consists of 95% sodium nitrite and 5% EC / LA, and is further dried by a stream of hot air prior to packaging to remove all solvents. Variants of the EC / LA microencapsulated sodium nitrite microspheres produced above have different percentages of corn gluten coating.

[0161] Example 4 - Producing decoys using the microspheres from Example 3.

[0162] Crushed wheat, finely crushed corn, white wheat flour, sugar, iron oxide (colorant), and sodium carbonate (as a pH adjuster) are mixed in a ribbon mixer until the color is uniform, thus preparing a palatable attractant containing sodium nitrite. Then, the desired amount of microencapsulated sodium nitrite microspheres are added and thoroughly mixed with the dried ingredients. The entire mixture is then bound together with a certain amount of ground peanut butter to obtain a semi-solid paste consistency at room temperature.

[0163] Example 5 - Palatability, Lethality and Stability

[0164] Palatability, lethality, and stability of the bait (i.e., fresh bait compared to bait stored for 8 months) were examined in captive populations of invasive wild boars. Over two treatment nights, bait consumption resulted in a 95% mortality rate in the treatment group (53 out of 56 cases). The majority of deaths (98%) occurred on the first night the poisoned bait was provided. Camera evidence indicated that deaths occurred within 3 hours of provision. The poisoned bait remained stable and effective for 10 months post-production.

[0165] The toxic bait remained palatable after 10 months of storage at room temperature and humidity. This indicates that the microencapsulation remained intact during this period to conceal the salty sodium nitrite and protect the bait matrix from unpleasant decomposition products resulting from adverse interactions with sodium nitrite.

[0166] Example 6 - Fertilization Study Using Toxic Feed Compositions (Topdress)

[0167] The toxic feed composition contains microencapsulated sodium nitrite and ground grains.

[0168] Table 1 - Average time (minutes) for domestic pigs to develop significant clinical symptoms of SN poisoning

[0169]

[0170]

[0171] Example 7 - Fertilization Study Using Toxic Feed Composition

[0172] Table 2 - Toxic feed compositions: (1) Microencapsulated sodium nitrite and ground grains and (2) Microencapsulated sodium nitrite and ground grains, peanut butter toxic paste.

[0173] Circle 1 (male) - 3 x 625g trays, give less than 200g; scrape off 363gm

[0174] Circle 2 (female) - given 3 x 625g trays; scraped off 116gm; no water (their choice).

[0175] Circle 3 (male) - given 3 x 625g trays; scraped off 370gm

[0176] Circle 4 (female) - 4x40 gm above 4x400 gm particles

[0177] Circle 5 (male) - 4x40 gm above 4x400 gm particles

[0178] Circle 6 (Female) - 4x40 gm above 4x400 gm particles; *Extra gain of pure toxins through "blank".

[0179]

[0180]

Claims

1. An ethyl cellulose / linoleic acid (EC / LA) microencapsulated sodium nitrite microsphere, wherein the ratio of ethyl cellulose to linoleic acid ranges from 99:1 to 99.99:0.01 by weight, and the ethyl cellulose / linoleic acid coating material is added to the nitrite at 2.5% to 30% based on the weight / weight of ethyl cellulose / linoleic acid and nitrite to form microspheres.

2. The microspheres according to claim 1, wherein the amount of ethyl cellulose / linoleic acid is 5% by weight relative to the amount of sodium nitrite.

3. A bait composition comprising a carrier material and sodium nitrite, wherein the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from 99:1 to 99.99:0.01 by weight, and the ethyl cellulose / linoleic acid coating material is added to the nitrite at 2.5% to 30% based on the weight / weight of ethyl cellulose / linoleic acid and nitrite to form microspheres.

4. The bait composition according to claim 3, wherein the carrier material is pig feed.

5. A bait composition for omnivorous wild animals, the bait composition comprising a carrier material and sodium nitrite, wherein the carrier material is a lipophilic carrier, and the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from 99:1 to 99.99:0.01 by weight, and based on the weight / weight ratio of ethyl cellulose / linoleic acid to nitrite, the ethyl cellulose / linoleic acid coating material is added to the nitrite at 2.5% to 30% to form microspheres.

6. A bait composition for omnivorous wild animals, the bait composition comprising a carrier material and sodium nitrite, wherein the carrier material is a lipophilic carrier, the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from 99:1 to 99.99:0.01 by weight, and based on the weight / weight ratio of ethyl cellulose / linoleic acid to nitrite, the ethyl cellulose / linoleic acid coating material is added to the nitrite at 2.5% to 30% to form microspheres, the carrier material comprising a pH stabilizer such that the bait maintains a pH greater than 7.

7. A method for humanely controlling omnivorous wild animals, comprising the step of dispersing the bait composition according to claim 5 or 6 within the foraging area of ​​the omnivorous wild animals.

8. A method for humanely controlling a penned pig population, comprising the step of dispersing a bait composition within the pigpen, said bait composition comprising ethyl cellulose / linoleic acid (EC / LA) microencapsulated sodium nitrite microspheres according to any one of claims 1 to 2 and pig feed.

9. The method of claim 8, wherein the pig herd is infected with African swine fever (ASF).

10. A method for preparing a bait composition for omnivorous wild animals, the bait composition comprising a lipophilic carrier material and a sodium nitrite salt, wherein the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from 99:1 to 99.99:0.01 by weight, and the amount of ethyl cellulose / linoleic acid is 3.5 to 20% by weight relative to the amount of sodium nitrite, the method comprising: (a) Optionally, the granular sodium nitrite is dried to constant weight, thereby substantially reducing all moisture content; (b) Encapsulating the granular sodium nitrite from step (a) using a mixture of ethyl cellulose and linoleic acid with a volatile organic solvent via pan coating or fluidized bed coating technology; and (c) Mixing the encapsulated material with the carrier material to form a bait composition.

11. A method for preparing a bait composition for omnivorous wild animals, the bait composition comprising a lipophilic carrier material and a sodium nitrite salt, wherein the sodium nitrite is present in the form of ethyl cellulose / linoleic acid microencapsulated sodium nitrite microspheres, wherein the ratio of ethyl cellulose to linoleic acid ranges from 99:1 to 99.99:0.01 by weight, the carrier material comprising a pH stabilizer such that the bait maintains a pH of 7 to 8, and the amount of ethyl cellulose / linoleic acid is 3.5 to 20% by weight relative to the amount of sodium nitrite, the method comprising: (a) Optionally, the granular sodium nitrite is dried to constant weight, thereby substantially removing all moisture; (b) Encapsulating the granular sodium nitrite from step (a) using a mixture of ethyl cellulose and linoleic acid with a volatile organic solvent via pan coating or fluidized bed coating technology; and (c) The encapsulated material is mixed with a carrier material containing a pH stabilizer to form a bait composition.

12. The method according to claim 10 or 11, wherein the volatile organic solvent is anhydrous or substantially anhydrous.

13. The method of claim 12, wherein the volatile organic solvent is absolute ethanol.

14. The method according to claim 12, wherein the pH stabilizer is sodium carbonate.

Images