Rodenticidal formulation

Abstract

Described herein is a rodenticidal bait formulation comprising a rodenticide, water, and at least one gelling agent.

Description

[0001]RODENTICIDAL FORMULATION The present invention relates to a formulation including a rodenticide that is stable in a variably wet and dry environment and is highly palatable to rodents. 5 Rats and mice forage or scavenge for food and, typically, take a small amount of food from a food source and then look for something different to eat. As a result, it is common to use a rodenticide which takes effect within a short time after consumption. However, if the rodenticide is too fast acting and a rat experiences feeling unwell, it associates the feeling 10 with the food consumed and subsequently avoids that source. Unwell or deceased rodents close to a food source will also deter other rodents from eating the food. As a result, the bait must be made very palatable to ensure the rodent will eat a sufficient amount to deliver enough rodenticide in one go before the rodent becomes bait-shy. The availability of water is also essential to rodents and food materials with high water content are highly attractive. 15 Rodenticides are formulated in varying bait matrices, typically with the active ingredient making up a very small percentage of the ingredient (typically for second generation anticoagulant in an amount of 25 or 50 mg / kg). As much as possible of the remaining bait is made of food stuffs meant to attract the rodents to eat the bait, and therefore succumb to the 20 active. Many baits are made with a majority of food stuffs like grain, carbohydrate, and fats, making them highly attractive. There is a requirement for a more weatherproof formulation block, typically for use in areas such as sewers where even dry areas have a very high moisture content in the atmosphere. These products are often formulated as blocks which are typically made by fusing bait materials with paraffin wax. Paraffin waxes are edible but, 25 at best, have an inert taste and are not attractive in themselves. Levels of paraffin are typically in the region of 30-40% to provide sufficient protection against wet environments. A drawback of fats is that they melt in warm temperatures and dessicate in dry conditions, which results in degradation of these baits. Wax, in particular, lacks stability at elevated 30 temperatures. Fats in general oxidise over time due to exposure to heat, light and or oxygen which turns the bait rancid and substantially decreases the palatability of such formulations. The use of fats as a base also means that only lipophilic or fat-soluble rodenticides may be used. 35 Another drawback with using fats, such as wax, as a base for a rodenticidal formulation or preparation is that rodents have continuously growing incisors and have a natural tendency to gnaw hard material to keep the teeth short. Conventional wax-based bait does not have sufficient hardness to satisfy the rodents’ natural desire to gnaw. GB 2115698 addresses a rodent’s need to gnaw and describes a brittle, hard bait 5 preparation which uses polyvinyl acetate or a co-polymer of vinyl acetate and acrylic acid ester as its base. Foodstuffs treated with poison are incorporated into this base. An advantage of such a preparation is that it is water resistant and is able to swell without the firmness or integrity of the bait being impaired. 10 WO 2014 / 064272 desribes a wax-free bait block that is made palatable by the inclusion of a large amount of edible seed or food. The block has 50-99% seed or cereal which is bound together with a polymeric binder based on a co-polymer of actylic ester and acryonitrile. The block is also suitably hard to satisfy the gnawing requirement. 15 WO 96 / 03037 describes a bait with an open-textured agglomerated granules being made up of a cereal base comprising a ground cereal and a rodenticide which are agglomerated using a water-soluble film-forming binder. Such an open structure is believed to be attractive to rodents because small portions may be detached more easily than from a solid block or pellet. 20 In summary, many commercially available bait formulations are simply not sufficiently palatable to rodents to ensure that they retain an on-going interest in the bait, and it is against this background that the present invention has been derived. 25 Specifically, the present invention resides in a rodenticidal bait formulation comprising i) a rodenticide, ii) water; and iii) at least one gelling agent. In other words, the formulation of the present invention replaces paraffin wax as a binder in rodenticidal bait formulations with a water-based gelling agents. The gel acts as both a carrier for the rodenticide and a binding agent for any additional ingredients. 30 It will be appreciated that the present invention is directed to the formulation of bait and so any suitable and known rodenticide may be used. An advantage of a water-based formulation is that water-soluble (hydrophilic) rodenticides may be used where their use may previously have been precluded due to the high wax / fat content in bait. 35 In one embodiment, the water may be present in an amount of between about 10% and 60%, optionally between about 33% and about 45%. The water is added to the formulation and is in addition to water contained in other ingredients and components. The water may simply be potable mains water. The inclusion of water is in marked contrast to currently available baits which cannot contain water due to the wax / fat content. 5 In another embodiment, the at least one gelling agent may be present in an amount of between about 0.2% and 3.3%. While it will be appreciated that any suitable gelling agent may be used, it should ideally be edible. Examples of suitable agents include natural gums, gelatine, gellan gum, acacia gum, starches, pectin, agar, tragacanth, carbomer, alginic acid and alginates, cellulose derivatives, locust bean gum, carrageenan, and glucomannan 10 polysaccharide gum. The formulation may comprise a single gelling agent or a combination of two or more. For example, the formulation may comprise a combination of gelatine, gellan gum and / or acacia gum. Gellan gum is a water-soluble anionic polysaccharide produced by the bacterium 15 Sphingomonas elodea and is able to withstand 120°C heat. It was initially identified as a gelling agent to replace agar at significantly lower concentrations in solid culture media for the growth of various microorganisms. Gellan gum has been approved for use as a food additive since 1988 and is now also approved for non-food, cosmetic and pharmaceutical uses by many countries. It is widely used as a thickener, emulsifier, and stabiliser. It has the 20 E number E418 and is used as the gelling agent, as an alternative to gelatine, in the manufacture of vegan varieties of “gum” confectionary. It will be appreciated that the amount of water in the formulation will be balanced with the amount of gelling agent(s) to ensure that a gel of desired consistency is formed. Specific 25 examples include about 38% water and about 1% gelling agent, about 41% water with about 0.95% gelling agent, and about 38% water with about 2.95% gelling agent. In a particular embodiment, the formulation may further comprise one or more preservative, preferably a food preservative such as potassium sorbate, sodium benzoate, citric acid, 30 benzoic acid, and / or calcium sorbate, for example. A combination of both potassium sorbate and sodium benzoate has been found to be effective against a wide variety of bacteria and moulds. Citric acid adds palatability to the formulation, as well as neutralising the calcium content of hard mains water: calcium inhibits the process of gelling and so the inclusion of citric acid also speeds up preparation of the formulation. The inclusion of a preservative per 35 se protects the formulation against spoilage in general and, specifically, mould in wet or humid atmospheres. In a particular example, the one or more preservative may be present in the formulation in an amount of between about 0.1% and 1.0%. A potential drawback of using a water-based formulation is dehydration of the formulation over time which may adversely affect the palatability and effectiveness of a bait. Therefore, in some embodiments, it may be desirable to include a component that retains or preserves 5 moisture in the formulation, i.e. a humectant. A humectant is a hygroscopic (water- absorbing) substance used to keep things moist. A humectant attracts and retains moisture in the air nearby via absorption, drawing the water vapour into or beneath an object's surface. Ideally the humectant is suitable for use in food, such as sugar, glucose syrup, salt, glycerine, aloe vera, egg yolk and egg white, honey, molasses, castor oil, sugar alcohols 10 (sugar polyols) such as glycerol, sorbitol, xylitol, and maltitol, and alpha hydroxy acids such as lactic acid. The presence of a humectant, such as glycerine, in an amount of between about 1.0% and 15%, preferably between about 4% and 13%, has been found to be effective. 15 In another embodiment, the formulation of the present invention may further comprise one or more sugars, such as sugar, sucrose and glucose syrup either alone or in any combination thereof. Rodents are attracted to the sweetness of sugar and so addition to the formulations of the present invention increases the palatability for rodents and acts as an attractant to the bait. The inclusion of between about 2% and 30% of one or more sugars, preferably 20 between about 8% and about 25%, for example around 18%, has been found to be appropriate. In a particular embodiment, the formulation of the present invention may further comprise a mixture of (dry) food ingredients palatable to rodents that includes cereals, flours and / or 25 sugars. It will be appreciated that the mixture may be varied and that any suitable cereals, flours and / or sugars may be used. As an example, the cereals may be whole and / or cut wheat, rice, millet, maize, barley, sorghum and / or (rolled) oats, the flour may be wheat flour, rice flour, millet flour, barley flour, maize flour, sorghum flour and / or oat flour, and the sugars may be sucrose, galactose, lactose or maltose. An amount of between about 20% and about 30 30%, optionally around 25%, of dry food ingredients has been found to be particularly suitable. The inclusion of a mixture of dry food ingredients acts as an attractant and adds palatability to the formulation. For example, unlike rats, mice have not been found to eat bait formulations unless a dry food ingredient is included. 35 In a yet further embodiment, the formulation may further comprise one or more oils and / or fats. Oils and / or fats are an attractant for rodents and also assist with the solubility of any hydrophobic active ingredients. In this way, the rodenticide may be hydrophilic (polar), hydrophobic (non-polar), or more than one rodenticide having different solubility profiles may be included in the formulation. In a particular embodiment, the oils and / or fats may be selected from one or more of an animal fat or lard, a vegetable fat or lard and / or a vegetable or sunflower oil. The presence of an amount of up to around 10% oils and / or fats in the 5 formulation has been found to be advantageous. A suitable range may be about 3% to about 10% oils and / or fats in the formulation. A specific example of a formulation of the present invention consists of the following ingredients: a rodenticide, water, gelatine, gellan gum, potassium sorbate, sodium benzoate, 10 acacia gum, sugar, glucose syrup, glycerine, citric acid, cereal mix, lard and vegetable oil. Another specific example of a formulation of the present invention has the following composition: Water 33.0% w / w 15 Gelling agents 3.3% w / w Food preservatives 0.7% w / w Sugars 18.0% w / w Humectant 10.0% w / w cereal mix 25.0% w / w 20 Oil / fats 10.0% w / w In a yet further specific example, the formulation ingredients listed above (excluding the rodenticide) may be present in the following amounts: Ingredient (% w / w) Min (% w / w) Max (% w / w) Water 33.35 33.4 43.4 Gelatine 2.00 0.0 2.0 Gellan gum 0.75 0.8 1.0 Potassium sorbate 0.10 0.1 0.1 Sodium benzoate 0.10 0.1 0.2 Acacia gum 0.20 0.0 0.2 Sugar 8.00 8.0 10.0 Glucose syrup 10.00 0.0 20.0 Glycerine 10.00 10.0 10.0 Citric acid 0.50 0.3 0.5 Cereal mix 25.00 20.0 30.0 Lard 6.15 5.8 6.2 Vegetable oil 3.85 3.6 3.9 The formulations of the present invention have been found to be highly palatable to rodents, are made of food-grade components or components designed for use in food products, and there is an absence of hydrocarbons derived from fossil fuel. All the ingredients are either 5 food stuffs or food additives readily available from public sources. While attractants and / or aromas may be added to the formulation, the formulation has been found to be highly palatable without such additions. However, it will be appreciated that any active ingredient, solid or liquid, and / or any attractant may be added to the formulation. 10 Another advantage of the formulations described herein is the presence of both an aqueous and an oil phase. Trials have shown that both water soluble and oil soluble active ingredients can be included in the formulation and are stable without the addition of emulsifiers and the like. 15 The formulations described herein may be formed as a soft block that can be cast, and the 30-40% wax component commonly found in existing block baits has been replaced by water. This increases palatability for both mice and rats and reduces costs. The blocks are soft but firm to the touch. The blocks may be immersed in water (up to at least 4 weeks) and, when taken out of the water and dried, the form and structure is unaffected such that the 20 weatherability properties are excellent. The block does lose water in hot conditions and becomes hard but re-absorbs water if sprayed and returns to its original form. The present invention will now be further described with reference to the following non- limiting examples. 25 The following experiments investigated the replacement of paraffin wax in rodenticidal bait formulations with food-grade binding agents and water. Specifically, consideration was given to developing a formulation with a texture similar to wine gums, which are gelatine based. However, the use of gelatine as a gellant needs to be with care because of the need for the 30 formulation to be temperature stable to >50°C. The first trials were performed using a number of different gelling agents including gellan, agar, gum arabic, guar gum. Gellan, gelatine, and gum arabic gave the most likely best outcome, and a further series of formulations was developed to include a range of percentages, adding components to prevent water loss, increase oil content for palatability, and test possible coatings. EXPERIMENT 1 5 The formulations described herein were prepared using the following process: Phase A Gelatine was added to water and allowed to hydrate for approx.30 minutes. This time varied depending on ambient air and water temperature. After 30 minutes, gelling agent and any 10 preservatives were added to the solution. The mixture was heated and stirred using an overhead stirrer turning at approx.400 rpm. Acacia gum was added to granulated sugar and set aside. Glucose syrup was added to glycerine and set aside. Glucose syrup was warmed as necessary to improve flowability. 15 Once the water / gelling agent mixture reached at least 80°C, the temperature was held for 2 minutes to activate the gelling agent. The acacia gum / sugar mix and glucose / glycerine mix were then added to the water / gelling agent mixture and the resulting mixture stirred until fully mixed. The time to achieve full mixture was typically less than about 2 minutes. 20 Finally, citric acid was added and the mixing speed was increased to 800 - 1000 rpm to complete the A-phase. Phase B 25 Lard and oil were gently heated, the dry food (cereal) mix was added and combined to form the B-phase of the formulation. This was kept warm during the experiment to prevent the lard from setting. The B-phase was added to the A-phase straight after the addition of citric acid to the A- 30 Phase, to complete the A-phase, and the two phases were mixed until a consistent, thick, but still fluid mixture was achieved. It was found that maintaining a temperature of at least 70°C kept the mixture sufficiently fluid. When ready, the final mixture was poured into casting trays. 35 The key component to the process is heating the hydrated gelatin and water to 80°C which causes a reaction in the gelling agent so that, when cooled, the formulation forms a gel. EXPERIMENT 2 The following formulations were created with the aim to reduce the evaporation of water from the formulation over time so that the formulation retains a gel-like texture and does not 5 become too hard. Thus, the effect of the addition of humectants, such as glycol, glycerine and sugar, was investigated. Additionally, the oil phase of the formulation was increased so oils and fat were added to the dry mix. As a result, the coconut oil / grapeseed oil blend in some formulations was replaced with lard / rapeseed oil. The effect of different moisture- resistant, edible coatings was also tested. 10 Table 1: Formulations Formulation (amount in %) Ingredient #1 #2 #3 #4 #5 #6 Phase A Water 58.00 33.30 46.00 38.40 42.80 48.40 Gellan gum 1.40 1.40 1.00 1.00 1.00 1.00 Acacia gum - - - - - - Potassium sorbate 0.30 0.10 0.10 0.10 0.10 0.10 Sodium benzoate 0.30 0.20 0.20 0.20 0.20 0.20 Sugar - 25.00 - 10.00 - - Glucose syrup - - - - - 10.00 Glycerine - - 12.50 10.00 - 10.00 Citric acid 25% - - 0.20 0.30 0.30 0.30 Phase B Dry food mix 30.00 30.00 30.00 30.00 30.00 20.00 Coconut & grapeseed oil 10.00 10.00 10.00 10.00 25.00 10.00 blend Span-83 - - - - 0.60 - Lard (pork) - - - - - - Vegetable oil - - - - - - TOTAL 100.00 100.00 100.00 100.00 100.00 100.00 Table 1 continued: Formulation (amount in %) Ingredient #7 #8 #9 #10 #11 Phase A Water 34.40 48.32 41.00 42.20 41.00 Gellan gum 0.70 0.70 0.75 1.00 0.75 Acacia gum - 0.50 0.75 0.50 0.20 Potassium sorbate 0.10 0.10 0.10 0.10 0.10 Sodium benzoate 0.10 0.10 0.10 0.10 0.10 Sugar - - - - 8.00 Glucose syrup 28.00 12.50 18.00 20.00 20.00 Glycerine 6.00 - 4.00 8.00 - Citric acid 25% 0.30 0.30 0.30 0.45 0.50 Phase B Dry food mix 20.00 25.00 22.50 20.00 20.00 Coconut & grapeseed oil - - - - - blend Span-83 - - - - - lard 6.40 7.68 7.70 4.80 5.75 Vegetable oil 4.00 4.80 4.80 3.00 3.60 TOTAL 100.00 100.00 100.00 100.00 100.00 Phase A Acacia gum was added to emulsify oil and reduce evaporation. Potassium sorbate and sodium benzoate are preservatives and were added to the formulations to protect against 5 spoilage and mould. Sugar and glucose syrup are attractants and impart palatability to the formulation. Glycerine is another humectant and was included to test its ability to retard the loss (evaporation) of water. Citric acid was added both to improve flavour and increase the firmness of gellan. 10 Phase B The dry mix component was a mixture of food ingredients including cereals (wheat or oats) and sugar (normally sucrose) that can vary in composition. A blend of coconut and grapeseed oil was included to act as a solvent and add palatability. Span-83 is a liquid sorbitan sesquioleate which acts as an emulsifier and emulsion stabiliser. Lard and 15 vegetable oil are attractants and aid solubility of oil-soluble active ingredients. Blocks were prepared according to the formulation protocol described in Experiment 1, poured into moulds and stored overnight. Blocks were removed from the moulds and weighed immediately before being stored under various conditions. Blocks were re-weighed after 24 hours and at daily intervals for 7 days. Selected formulas were re-made and coated with various coatings, weighed and stored at 5 ambient temperature, uncovered. Blocks were re-weighed after 1 day, 3 days and 7 days. Uncoated blocks were stored in water to see whether they would swell or dissolve as a result of the high sugar and starch content. Table 2: Uncoated formulations: % Weight-loss: Day 1 Day 7 Formulation Ambient* 40°C Ambient 40°C #1 9.93 36.07 38.33 53.86 #4 5.45 19.26 21.41 31.86 #7 7.64 14.33 17.73 25.50 #10 8.01 23.16 27.45 38.14 #11 7.45 19.33 23.84 31.71 10 * Ambient temperature was the temperature of the laboratory in which the experiment was conducted. Table 3: Coated formulations - % weight loss after 24 hours: Formul- Submerged in Dry Sugar Starch Wax Acacia gum ation water uncoated coated coated coated coating #7 Disintegrated 9.22 6.49 7.22 3.02 12.61 #10 Disintegrated 9.68 6.26 11.01 4.96 8.01 #11 Gained ~4% 1.03 7.45 10.94 5.02 10.66 15 Table 4: Coated formulations - % weight loss after 7 days: Formul- Submerged in Dry Sugar Starch Wax Acacia gum ation water uncoated coated coated coated coating #7 Disintegrated 20.86 16.03 17.33 10.92 22.68 #10 Disintegrated 25.44 18.30 25.40 17.43 21.99 #11 Gained ~2% 17.82 20.60 24.24 18.69 25.08 Formulations #7 and #11 had the lowest weight loss combined with good texture, while Formulations #4 and #10 had low weight loss and good texture. Storing blocks at 40°C overnight appeared to correlate with storing for 7 days at ambient temperature and could be an option in manufacturing to speed up drying times for the blocks. 5 Coating with wax, sugar or gum acacia provided some reduction in moisture loss. EXPERIMENT 3 In this experiment, hot- and cold-processed gellan gum formulations were compared for palatability. 10 Sodium alginate was used to make a firm gel using a cold process but was slightly more complicated to prepare because of the need to control the rate of Ca2+ion release to prevent instant gelling. 15 The inclusion of water made it necessary to include a suitable preservative to prevent spoiling. After several trials, a mix of potassium sorbate and sodium benzoate was chosen because both are water-soluble and food-approved globally. Formulations were prepared using tap-water rather than deionised water to exploit the 20 relatively high concentration of Ca2+ions in the water which increase the gel-strength of the gums selected. A printout of the local water quality for the UK postcode GU34 provided the following analysis: 25 Table 5: Water Quality Mg / L Average total Hardness Calcium 112.75 mg / L Ca 115.45 Magnesium 2.6 Mg / L CaCO3288.63 Sodium 11.79 Clark degrees 20.2 Sulphates 24.03 French degrees 28.86 Hardness 115.45 German Degrees 16.16 Alkalinity 329.5 Conductivity 550.3 pH 7.3 Hot Process Blocks prepared with Gellan Gum Table 6: Formulation Ingredients Phase Ingredient % w / w Function A Tap Water 58.00 Carrier Kelcogel CG-LA (Gellan Gum) 1.40 Gelling agent – low-acyl grade to give a strong gel Potassium Sorbate 0.30 Preservative Sodium Benzoate 0.30 Preservative B Dry Food Mix 30.00 Lure coconut & grapeseed oil blend 10.00 Carrier, prevents starches in the dry mix from dissolving too quickly Total 100.00 5 The gellan gum and preservative were added to cold water while being continuously mixed and heated until the gellan gum had completely dissolved. In a separate vessel, the dry food mix and oil were combined with careful mixing so that the powders were completely coated in oil. Without this step, the starches in the dry food mix dissolve quickly in the hot water making the mixture very viscous and sticky. 10 Phase B was added to Phase A with thorough mixing, poured into moulds and cooled to ambient temperature. Cold Process Blocks with Sodium Alginate 15 Table 7: Formulation Ingredients Phase Ingredients %w / w Function A Tap Water 58.30 Carrier Potassium Sorbate 0.30 Preservative Sodium Benzoate 0.30 Preservative Potassium Triphosphate 0.30 Sequestrant for Ca2+to prevent instant gelation Sugar 2.00 Flavour enhancer B Vivapur Alginate FDG153 2.50 Thickener / Gelling agent, ‘High G’, low viscosity grade vegetable oil 3.00 Carrier C Dry Food Mix 26.00 Lure Arbocel BE 600 / 30 4.00 Inert filler to improve firmness can be Cellulose fibres replaced with clay citric acid powder 0.60 To adjust pH and flavour enhancer Calcium Carbonate 2.70 Acid-soluble Ca2+source (for slow release) Total 100.00 The phase A ingredients were dissolved in the water while being stirred. Alginate was mixed in the oil to form a slurry to help prevent lumping when adding to the 5 water-phase. A relatively fast mixing was used to ensure good distribution of the alginate before it started to swell and thicken. The phase C ingredients were then added to the phase A mix and the alginate slurry (phase B) with thorough mixing until all the dry ingredients were fully dispersed through the gel. 10 The resulting mixture was poured into moulds and left to set for about 50 minutes. The Alginate gel is based on dental impression powders which work by a process called internal gelation, or ‘acid setting’. Alginate will gel instantly when it comes into contact with 15 available calcium ions. Alginate beads can be prepared by dropping a solution of alginate into a water-bath containing about 1% w / w calcium chloride. A skin forms on the outside of the drops which become very hard if left in the water for more than a minute. This method would be suitable for making ‘pearls’ or ‘drops’ of bait up to about the size of a blueberry but is not appropriate for larger gels. 20 For larger gels, simply add the dry mix to a 1-2% solution of sodium alginate and then let drops of mixture fall into the calcium bath, wait for approx.60 seconds and scoop out into a container of deionised water to rinse and drain. 25 The hot-process gellan gum formulations were preferred by rats over cold-process alginate formulations but the formulations suffered from evaporation and hardening. EXPERIMENT 4 Formulations #4 and #11 were identified as having the best potential to give blocks of the required texture and the following experiment investigated modifications to those formulas to optimise the level of dry mix and oil using combinations of gellan gum, gellan gum / acacia gum, and gellan gum / gelatine / acacia gum. 5 Gellan gum gives hard brittle formulations. Acacia is not a gelling agent but is a binder that traps moisture and also improved the texture and appearance of the blocks prepared with gellan gum. 10 Gelatine is not appropriate to use alone because it has too low a melting point, but it can potentially increase the elasticity of gellan gum / acacia gum blends and further reduce moisture loss. Acacia gum was tested as a moisture-resistant coating using two different methods of 15 application: i) Applied as a powder that dissolved in the water evaporating from the formulations. ii) Applied a 25% active solution and allowed to dry out to give a very glossy coating to the formulations. 20 Table 8: Formulations Formulations Ingredient #4 #11 #12 #4x #11x #12x Phase A Tap water 38.40 41.00 38.85 43.40 35.35 33.35 Gelatine - - 2.00 - - 2.00 Gellan Gum 1.00 0.75 0.75 1.00 0.75 0.75 (low acyl grade) Potassium sorbate 0.10 0.10 0.10 0.10 0.10 0.10 Sodium benzoate 0.20 0.10 0.10 0.20 0.10 0.10 Acacia Gum - 0.20 0.20 - 0.20 0.20 Sugar 10.00 8.00 8.00 10.00 8.00 8.00 Glucose syrup - 20.00 10.00 - 20.00 10.00 Glycerine 10.00 - 10.00 10.00 - 10.00 Citric Acid 25% 0.30 0.50 0.50 0.30 0.50 0.50 Phase B Dry Mix 30.00 20.00 20.00 25.00 25.00 25.00 Lard 6.15 5.75 6.15 6.15 6.15 6.15 Vegetable Oil 3.85 3.60 3.85 3.85 3.85 3.85 TOTAL 100.00 100.00 100.00 100.00 100.00 100.00 X versions of the formulations (#4x, #11x, #12x) used the same gum-blends and humectants as the formulations in Experiment 2 but were optimised for dry mix and oil content. The higher the water content, the greater the weight loss was seen. Also, the higher the dry mix 5 content, the harder the blocks were after drying. Blocks were prepared according to the protocol set out in Experiment 1, poured into moulds and stored for two hours. If gelatin was used, it was soaked in cold water for 30 minutes before being processed further. Gellan gum and the preservatives were added to rapidly 10 stirred cold water while being heated to about 80°C with continued stirring until the mixture was clear. For the phase B mixture, acacia, sugar, syrup and glycerine were combined with continuous mixing and heating. In a separate vessel, the dry food mix was combined with lard and vegetable oil and mix until uniform. Citric acid was added to the phase A mixture before the phase B mixture was added. The resulting combination was mixed until uniform (a15 few minutes), poured into moulds and left to set for a minimum of 2 hours before de- moulding. Blocks were removed from the moulds and weighed immediately before being stored overnight (approximately 18 hours) at ambient temperature (approximately 8°C - 12°C). 20 Blocks were re-weighed after 24 hours and then either left uncoated or were coated with acacia powder or solution. Blocks were reweighed immediately after coating and again after 1 day, 3 days, 7 days and 14 days stored at ambient and at 40°C. Control blocks were stored in the refrigerator to minimise weight loss and were used as a comparison for the texture of the blocks at the end of storage time. 25 Table 9: % weight loss for uncoated and coated formulations: % weight loss over time Conditions # % increase 24 hours 4 days 7 days 14 days with coating Uncoated, ambient 4a 0.00 4.39 10.75 14.39 14.62 Dry coated, ambient 4b 2.19 1.76 8.29 12.48 13.02 Wet glazed, ambient 4c 8.71 -4.16 2.93 7.62 9.23 Uncoated, 40°C 4d 0.00 16.57 24.96 26.69 27.96 Dry coated, 40°C 4e 1.96 10.59 20.21 22.54 24.50 Wet glazed, 40°C 4f 9.33 7.01 18.35 20.31 22.05 ’fridge control at 3°C 4g 0.00 0.31 0.25 0.41 1.02 ’fridge control at 4h 0.98 -1.45 -0.94 -1.50 -0.98 3°C, wrapped* Uncoated, ambient 11a 0.00 5.44 13.63 17.70 22.10 Dry coated, ambient 11b 1.62 3.06 10.52 14.42 18.22 Wet glazed, ambient 11c 6.65 0.64 10.16 14.76 18.85 Uncoated, 40°C 11d 0.00 15.76 26.41 28.85 31.14 Dry coated, 40°C 11e 2.01 12.33 22.36 25.25 27.43 Wet glazed, 40°C 11f 7.18 10.69 22.14 24.55 26.51 ’fridge control at 3°C 11g 0.00 1.49 4.48 7.47 12.06 ’fridge control at 11h 0.73 -0.69 -0.53 12.29 12.23 3°C, wrapped* Uncoated, ambient 12a 0.00 4.86 12.51 17.02 19.25 Dry coated, ambient 12b 1.69 2.69 9.84 14.12 19.58 Wet glazed, ambient 12c 8.49 -2.15 7.05 12.83 15.17 Uncoated, 40°C 12d 0.00 18.01 26.15 28.82 31.19 Dry coated, 40°C 12e 1.74 12.26 20.96 23.95 27.52 Wet glazed, 40°C 12f 6.68 10.84 20.44 23.63 26.99 ’fridge control at 3°C 12g 0.00 1.21 2.11 3.37 6.02 ’fridge control at 12h 0.83 -0.83 -0.72 -0.64 -0.49 3°C, wrapped* * wrapped in clingfilm. Table 9 continued: % weight loss for uncoated and coated formulations % weight loss over time Conditions # % increase 24 hours 4 days 7 days with coating Uncoated, ambient 4xa 0.00 6.62 13.94 17.64 Dry coated, ambient 4xb 1.93 4.31 11.22 15.03 Wet glazed, ambient 4xc 4.85 2.11 9.81 14.23 Uncoated, 40°C 4xd 0.00 20.56 30.43 32.62 Dry coated, 40°C 4xe 2.18 16.23 26.16 28.71 Wet glazed, 40°C 4xf 6.07 16.53 27.69 30.04 ’fridge control at 3°C 4xg 0.00 0.67 2.98 7.43 ’fridge control at 4xh 1.17 -1.08 -0.99 -0.68 3°C, wrapped* Uncoated, ambient 11xa 0.00 4.82 10.48 14.29 Dry coated, ambient 11xb 2.05 1.84 6.14 9.28 Wet glazed, ambient 11xc 7.06 -2.07 3.44 7.36 Uncoated, 40°C 11xd 0.00 13.78 22.43 24.73 Dry coated, 40°C 11xe 1.95 10.32 19.08 22.04 Wet glazed, 40°C 11xf 10.33 6.76 15.13 18.15 ’fridge control at 3°C 11xg 0.00 1.23 3.70 8.18 ’fridge control at 11xh 1.12 -0.81 -0.61 -0.31 3°C, wrapped* Uncoated, ambient 12xa 0.00 3.31 7.12 9.16 Dry coated, ambient 12xb 1.72 1.22 4.88 6.56 Wet glazed, ambient 12xc 7.19 -3.26 1.38 3.93 Uncoated, 40°C 12xd 0.00 11.22 19.26 21.87 Dry coated, 40°C 12xe 1.71 9.03 16.57 19.40 Wet glazed, 40°C 12xf 5.78 6.33 14.17 17.10 ’fridge control at 3°C 12xg 0.00 0.00 0.44 2.83 ’fridge control at 12xh 0.95 -0.95 -0.95 -0.78 3°C, wrapped* * wrapped in clingfilm. Table 10: % weight loss after 28 days: Formulations Conditions #4 #11 #12 #4x #11x #12x Uncoated, ambient 16.08 24.08 17.94 23.47 10.13 12.48 Dry coated, ambient 14.24 20.54 15.77 20.95 15.67 10.35 Wet glazed, ambient 9.28 20.19 13.77 21.74 15.19 9.38 Uncoated, 40°C 28.62 32.49 32.58 35.99 28.49 26.40 Dry coated, 40°C 26.22 28.97 29.41 32.61 25.69 24.11 Wet glazed, 40°C 23.21 27.86 30.00 33.10 22.40 21.73 ’fridge control at 3°C 5.45 16.99 9.52 19.44 15.59 1.84 ’fridge control at 3°C, -0.51 1.26 0.04 1.17 1.42 -0.04 wrapped Adding acacia gum to the formulation helped to reduce moisture loss but it needed to be added before the temperature of the water increased. In addition, amounts of more than 0.5% resulted in a formulation that did not gel, and the acacia gum appeared to interfere with 5 the gelling action of the other gelling components. An optimum formulation was seen with a 25% dry mix and 9-10% additional oil phase. More than 10% oil produced a formulation in which the oil was not suspended, and more than 25% dry mix gave a lumpy texture which was difficult to handle. 10 The addition of gelatine improved elasticity but there might have been oil leakage on storing at 40°C, which could have been melted gelatine. A humectant amount of 20% humectant was deemed to be not quite enough for the test and 15 an amount of between 25% and 35% seems to be optimum. A reduction in evaporation was seen with an acacia gum coating. From the above experiments, Formulation #12 had the most “chewy” texture and the lowest 20 moisture loss. All samples stored at 40°C eventually became hardened as the moisture was lost and the starches were ‘cooked’. However, the formulations re-absorbed moisture and softened when stored under water or in high humidity conditions. They did not disintegrate when submerged 25 in water. EXAMPLE 5 Palatability in rats was tested using formulations without active ingredients. These tests compared formulation #12 to a commercially available bait sold by Pelgar International Ltd 30 under the brand name Roban GoldTM. Roban Gold is a bait formulated using culinary grade wheat flour, blended with chopped wheat, other cereals and proteins which are bound together by edible waxes. The bait also contains an aroma, giving a unique chocolatey smell. 5 Table 11: % eaten out of daily intake Day Replicate 1 2 3 4 5 Formulation #12 1 91.90 86.36 92.26 87.88 74.07 2 77.42 100.00 77.39 71.43 82.35 3 100.00 100.00 87.94 82.50 70.45 4 93.73 75.93 73.84 62.50 54.35 Mean 90.76 90.57 82.86 76.08 70.31 Roban Gold 1 8.10 13.64 7.74 12.12 25.93 2 22.58 0.00 22.61 28.57 17.65 3 0.00 0.00 12.06 17.50 29.55 4 6.27 24.07 26.16 37.50 45.65 Mean 9.24 9.43 17.14 23.92 29.69 The preference for Test Formulation #12 compared to Roban Gold was approximately 5:1 across four replicates for each block. 10

Claims

CLAIMS 1. A rodenticidal bait formulation comprising: i) a rodenticide, 5 ii) water; and iii) at least one gelling agent.

2. The formulation of claim 1, wherein water is present in an amount of between about 10% and about 60%, optionally in an amount of between about 33% and about 45%.

3. The formulation of claim 1 or claim 2, wherein the at least one gelling agent is present in an amount of between about 0.2% and about 3.3%.

4. The formulation of any one of claims 1 to 3, wherein the gelling agent is selected from one or more of natural gums, gelatine, gellan gum, acacia gum, starches, pectin, agar, tragacanth, carbomer, alginic acid and alginates, cellulose derivatives, locust bean gum, carrageenan, and glucomannan polysaccharide gum.

5. The formulation of any one of claims 1 to 4, wherein the at least one gelling agent is a combination of gelatine, gellan gum and / or acacia gum.

6. The formulation of any one of claims 1 to 5, wherein the formulation further comprises one or more preservative.

7. The formulation of claim 6, wherein the one or more preservative is present in the formulation in an amount of between about 0.1% and 1.0%.

8. The formulation of claim 6 or claims 7, wherein the one or more preservative is selected from one or a combination of potassium sorbate, sodium benzoate, and citric acid.

9. The formulation of any one of claims 1 to 8, wherein the formulation further comprises a humectant.

10. The formulation of claim 9, wherein the humectant is present in an amount of between about 1.0% and 15%, optionally in an amount of between about 4% and about 13%.

11. The formulation of claim 9 or claim 10, wherein the humectant is selected from one or more of: sugar, glucose syrup, salt, glycerine, aloe vera, egg yolk and egg white, honey, molasses, castor oil, sugar alcohols (sugar polyols) such as glycerol, sorbitol, xylitol, and maltitol, and alpha hydroxy acids such as lactic acid. 5 12. The formulation of any one of claims 1 to 11, wherein the formulation further comprises one or more sugars.

13. The formulation of claim 12, wherein the one or more sugars are present in the formulation in an amount of between about 2% and about 30%, optionally, between about 8% and about 25%, optionally about 18%.

14. The formulation of claim 12 or claim 13, where in the one or more sugars is a combination of sugar, sucrose and / or glucose syrup.

15. The formulation of any one of claims 1 to 14, wherein the formulation further comprises a mixture of food ingredients palatable to rodents that includes cereals, flours and / or sugars.

16. The formulation of claim 15, wherein the cereals are wheat, rice, millet, maize, barley, sorghum or oats, and / or the flour is wheat flour, rice flour, millet flour, barley flour, maize flour, sorghum flour or oat flour, and / or the sugar is sucrose, galactose, lactose or maltose.

17. The formulation of claim 15 or claim 16, wherein the food mixture is present in the formulation in an amount of between about 20% and about 30%, optionally about 25%.

18. The formulation of any one of claims 1 to 17, wherein the formulation further comprises one or more oils and / or fats.

19. The formulation of claim 18, wherein the oils and / or fats are present in the formulation in an amount of up to about 10%, optionally between about 3% and about 10%.

20. The formulation of claim 18 or claim 19, wherein the oils and / or fats are selected from one or more of an animal fat, a vegetable fat and / or a vegetable oil.