Method for producing silage

Abstract

To provide novel means for reducing nitrate nitrogen in silage.SOLUTION: A method for producing silage comprises the following steps (1) and (2) of: (1) adding ascorbic acid or a salt of ascorbic acid to a raw material of silage; and (2) subjecting the raw material of silage to fermentation after step (1).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing silage. The method for producing silage of the present invention makes it possible to produce silage with a reduced nitrate nitrogen content and silage with a stably reduced pH. [Background technology]

[0002] A high-quality feed supply is essential for stable production of milk and beef. In order to build a sustainable livestock industry in the future, it is necessary to steadily produce high-quality feed.

[0003] The application of compost and chemical fertilizers during the cultivation of forage crops can increase the dry matter yield and crude protein content. The increased yield and improved nutritional value of forage crops are expected to contribute to increased profits for producers, but the nitrate nitrogen content may increase depending on the fertility of the field, the grass species, and the harvest time. High levels of nitrate nitrogen in feed are harmful to ruminant livestock, so care must be taken when feeding them. In particular, pregnant cows may suffer from the risk of miscarriage, so care must be taken when feeding them to breeding cows. Technology that can reduce the nitrate nitrogen in roughage after harvest would make it possible to feed high-yield, high-crude protein roughage produced with the application of compost, etc. to a variety of livestock, broadening the scope of use of the produced roughage.

[0004] As basic knowledge regarding the reduction of nitrate nitrogen, it is generally well known that nitrate ions and nitrite ions are decomposed into nitric oxide by reducing agents (Non-Patent Document 1), and the reducing property of ascorbic acid is also well known (Non-Patent Document 2). As knowledge in the field of feed production, it is known that Italian ryegrass varieties that do not easily accumulate nitrate nitrogen have already been bred (Non-Patent Document 3), that the nitrate nitrogen concentration of corn decreases significantly as the growth stage progresses (Non-Patent Document 4), and that the nitrate nitrogen concentration of oats decreases with time after heading, but there is no significant change in sorghum (Non-Patent Document 5). As knowledge in the field of feed preparation, it is known that nitrate nitrogen can be reduced by fermentation by adding glucose and a buffer agent during silage preparation (Non-Patent Document 6). As knowledge outside the field of feed, in the food field, ascorbic acid is generally added to processed meat for coloring purposes in order to reduce nitrosamines, which are suspected to be carcinogenic and are synthesized from nitrate and nitrite ions (Non-Patent Document 7). However, there is a report that adding ascorbic acid to the rice bran bed when pickling cucumbers did not reduce the levels of nitrate and nitrite (Non-Patent Document 8). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Fox and Nicholas, 1974, J. Agr. Food Chem., vol.22, no.2 [Non-Patent Document 2] Hayashi, 1986, Journal of the Japanese Society of Food Technology, vol.33, no.6, 456-462 "Chemistry of ascorbic acid and its use in food" [Non-Patent Document 3] Ministry of Agriculture, Forestry and Fisheries Variety Registration No. 25366, SI-14 (product name Tachiyuka) [Non-Patent Document 4] Harada et al., (1996), Journal of the Japanese Society of Grassland Science 41 [Non-Patent Document 5] Harada et al., (2002), Journal of the Japanese Society of Grassland Science 48 [Non-Patent Document 6] Okada, (1994), Pasture and Horticulture 42 [Non-Patent Document 7] Yamamoto, 2015, 7.1 Principles of meat processing, functions and science of meat [Non-Patent Document 8] Hata and Ogata, 1979, Journal of the Japanese Society of Food Technology, vol. 26, no. 1, "On the nitrate and nitrite contents of pickled vegetables" Summary of the Invention [Problem to be solved by the invention]

[0006] When it comes to reducing nitrate nitrogen by harvesting time, external factors such as weather can make it difficult to carry out harvesting work as originally planned, making it difficult to apply the technology. In addition, when it comes to reducing nitrate nitrogen by selecting grass species, if it is considered as part of a cropping system, it may be difficult to change to another grass species due to restrictions such as the harvest time of the previous crop and the sowing time of the subsequent crop. Only some varieties such as Italian ryegrass that do not accumulate nitrate nitrogen are available, and depending on the fertility of the cultivated field and the harvesting conditions, the effect of reducing nitrate nitrogen may be insufficient, so there is a lack of certainty. In order to confirm the fertility of a field, it is necessary to collect and analyze soil, but when there are many small fields, the number of analysis points will be large, and fertility may be non-uniform even within the same field, so it may be difficult to determine the appropriate amount of fertilizer from the results of soil analysis.

[0007] Although there have been many reports on the preparation and feeding of silage using food waste that is thought to contain a lot of ascorbic acid, no studies have been conducted on the nitrate nitrogen content, and it is unclear whether adding these substances reduces nitrate nitrogen. In addition, since the reduction of nitrate nitrogen using silage fermentation is closely related to microbial activity, it is difficult to control fermentation by adjusting temperature, etc., in the case of silage that is often stored in outdoor environments.

[0008] The reduction of nitrate nitrogen by adding ascorbic acid to processed meats and other foods requires significantly different conditions than silage, so it is not clear whether this method is effective in reducing nitrate nitrogen.

[0009] As described above, although there are techniques for reducing nitrate nitrogen in silage, each technique has some problems. The present invention has been made under such a background, and aims to provide a novel means for reducing nitrate nitrogen in silage. [Means for solving the problem]

[0010] As a result of intensive research to solve the above problems, the present inventors discovered that the nitrate nitrogen in silage can be reduced and the pH can be stably lowered by adding ascorbic acid to the raw material of silage, and thus completed the present invention. That is, the present invention provides the following [1] to [6].

[0011] [1] A method for producing silage, comprising the following steps (1) and (2): (1) adding ascorbic acid or a salt of ascorbic acid to a silage raw material; (2) After step (1), a step of fermenting the silage raw material.

[0012] [2] A method for producing silage according to [1], characterized in that the ascorbic acid or a salt of ascorbic acid is purified ascorbic acid or a salt of purified ascorbic acid.

[0013] [3] The method for producing silage according to [1], characterized in that the amount of ascorbic acid or a salt of ascorbic acid added is 0.3 to 10% by weight, calculated as ascorbic acid, based on the weight of the silage raw material.

[0014] [4] The method for producing silage according to [1], characterized in that the fermentation period of the silage raw materials is 1 to 24 months.

[0015] [5] A method for producing silage according to [1], characterized in that the salt of ascorbic acid is sodium ascorbate.

[0016] [6] A method for producing silage according to [1], characterized in that the raw material for the silage is pasture grass. Effect of the Invention

[0017] The present invention provides a novel method for producing silage. The method of the present invention makes it possible to produce silage with a reduced nitrate nitrogen content and a stably reduced pH. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 shows the nitrate nitrogen content in each treatment plot after storage for 1 month and 6 months. [Diagram 2] FIG. 1 shows the nitrate nitrogen content in each treatment area. [Diagram 3] FIG. 1 shows the pH in each treatment area. [Figure 4] FIG. 1 shows the nitrate nitrogen content in the chilled and RT groups. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention will be described in detail below. The method for producing silage of the present invention is characterized by comprising the following steps (1) and (2).

[0020] In step (1), ascorbic acid or a salt of ascorbic acid is added to the silage raw material.

[0021] Ascorbic acid is usually L-ascorbic acid. Ascorbic acid is commercially available as a feed additive, etc., and such commercially available feed additives can be used in the present invention.

[0022] Examples of the salts of ascorbic acid include alkali metal salts of ascorbic acid and alkaline earth metal salts of ascorbic acid. Examples of the alkali metal salts of ascorbic acid include sodium ascorbate and potassium ascorbate, and examples of the alkaline earth metal salts of ascorbic acid include calcium ascorbate and magnesium ascorbate.

[0023] Ascorbic acid and salts of ascorbic acid are preferably in a purified form such as a feed additive, but may be unpurified.

[0024] The raw material for silage may be any one used in general silage manufacturing methods, such as pasture grass, including Italian ryegrass, orchard grass, timothy, perennial ryegrass, Kentucky bluegrass, tall fescue, teff grass, guinea grass, sudan grass, corn, white clover, red clover, and alfalfa.

[0025] The amount of ascorbic acid or an ascorbic acid salt to be added is not particularly limited as long as it is an amount that can obtain the effect of reducing nitrate nitrogen and the effect of stably lowering pH, and can be, for example, 0.3 to 10% by weight, preferably 0.5 to 8% by weight, and more preferably 1 to 5% by weight, calculated as ascorbic acid relative to the weight of the silage raw material. Note that "ascorbic acid equivalent" means that the amount of ascorbic acid salt to be added is calculated as the weight of the same substance amount of ascorbic acid. Specifically, the amount of ascorbic acid salt to be added is calculated by dividing the amount of ascorbic acid salt to be added by the molecular weight of the ascorbic acid salt, and multiplying the result by the molecular weight of ascorbic acid (176.12).

[0026] Silage raw materials may contain other substances than ascorbic acid or salts of ascorbic acid, for example, basic substances. Ascorbic acid is reduced by ascorbic acid ions (Hayashi, 1986, Journal of the Japanese Society of Food Engineering, vol. 33, no. 6, 456-462, "Chemistry of Ascorbic Acid and Its Use in Foods"), so it is considered that the addition of basic substances increases the amount of ascorbic acid ions, speeds up the reduction reaction, and enables efficient reduction of nitrate nitrogen. The basic substances used are not particularly limited, and examples include sodium bicarbonate, potassium bicarbonate, sodium carbonate, and potassium carbonate. In addition, substances that promote the growth of microorganisms in silage, such as sugars, may be added to the silage raw materials. In addition, lactic acid bacteria, for example, may be added to the silage raw materials to stabilize the fermentation quality.

[0027] In step (2), after step (1), the silage raw material is fermented.

[0028] Fermentation of the raw material for silage can be carried out in the same manner as in general silage production methods.

[0029] The fermentation period is not particularly limited, but since nitrate nitrogen can be significantly reduced when fermented for about 6 months, the fermentation period may be about 6 months or more. Specifically, the fermentation period may be, for example, 1 to 24 months, preferably 2 to 12 months, and more preferably 3 to 6 months.

[0030] The fermentation temperature is not particularly limited, and fermentation may be carried out at refrigeration temperatures, but fermentation at room temperature (20 to 30° C.) is preferable since this allows for a greater reduction in nitrate nitrogen. EXAMPLES

[0031] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0032] Example 1 Italian ryegrass (variety: Kyusyu 1) to which nitrogen was applied as chemical fertilizer at 10 kg / 10 a before sowing and during cultivation was harvested before heading, when the nitrate nitrogen ratio is expected to be high (harvest date: 2022 / 12 / 19), and cut with a cutter at a cutting length of 38 mm. After mixing the cut Italian ryegrass, three treatments were set: a control area without added ascorbic acid, an AcH area in which L(+)-ascorbic acid was added at 3% of the material grass weight, and a Na area in which sodium L-ascorbate was added in an amount equivalent to the amount of ascorbic acid added in the AcH area. Approximately 100 g of each was placed in a vacuum packing plastic bag and sealed while degassing using a vacuum packaging machine. The material grass was collected from the control area (without addition) before sealing. After storage in the laboratory for one or six months, the bags were opened and silage samples were obtained. The grass and silage were dried at 70°C, and the dry matter (DM) content, which is the percentage of the sample other than moisture, was calculated from the difference in weight before and after drying. After drying, the samples were crushed using a cutting mill so that they passed through a 0.5 mm screen, and the nitrate nitrogen content was measured by quantifying the concentration in the aqueous solution extracted from the crushed sample with an extraction reagent using the alkali reduction-diazo dye method. For samples stored for 6 months, 25 g was weighed out, 100 mL of pure water was added, and extraction was performed for more than 24 hours at 4°C. The extract was filtered through 5A filter paper, and the pH of the filtrate was measured using a pH meter equipped with a general-purpose glass body pH combination electrode.

[0033] The nitrate nitrogen content in each treatment area after 1 month and 6 months of storage is shown in Figure 1. The nitrate nitrogen was lower after 6 months of storage (6:Control, 6:AcH, 6:Na) than the material grass (0:Material) and after 1 month of storage (1:Control, 1:AcH, 1:Na) (Figure 1). In addition, after 1 month of storage, no clear difference in nitrate nitrogen was observed among the treatment areas, whereas after 6 months of storage, the nitrate nitrogen content in the Na area (6:Na) to which sodium ascorbate was added was lower than the other areas (6:Control, 6:AcH) (Figure 1). It was not possible to determine from the results of this experiment whether the decomposition of nitrate nitrogen was due to fermentation (microorganisms) or chemical reaction.

[0034] Example 2 Italian ryegrass cultivated under the same conditions as in Example 1 was harvested at the heading stage (harvest date: 2023 / 5 / 2), cut and mixed under the same conditions as in Example 1. Four treatments were set for the cut Italian ryegrass: A+S+, in which ascorbic acid and sodium bicarbonate were added at 3% and 1% of the material grass weight, respectively; A+S-, in which only ascorbic acid was added at 3%, AS-, in which only sodium bicarbonate was added at 1%, and AS-, in which neither was added. Samples of the material grass were collected from each area after the addition of ascorbic acid or sodium bicarbonate and before sealing. After sealing under the same conditions as in Example 1, the silage samples were opened after storing in a dark place in the laboratory for one month. The air drying, crushing, measurement of nitrate nitrogen content, extraction with pure water, and measurement of nitrate nitrogen content were performed under the same conditions as in Example 1.

[0035] The nitrate nitrogen content and pH in each treatment area are shown in Figures 2 and 3, respectively. At the time of the material grass (storage period (month) 0), the nitrate nitrogen was low in the areas where ascorbic acid was added (A+S+ area, A+S- area), suggesting a reduction in nitrate nitrogen that was not due to fermentation (Figure 2). In all areas, the nitrate nitrogen content after one month of storage (storage period (month) 1) was lower than that of the material grass without addition (storage period (month) 0, AS- area), and the A-S+ area (sodium bicarbonate only added) showed a particularly large decrease (Figure 2). There was also little variation in the nitrate nitrogen content in the A+S- area (Figure 2).

[0036] After a storage period of one month, the A-S+ group (with only sodium bicarbonate added) had a high pH (Figure 3), and it is thought that adding only sodium bicarbonate would not produce good silage. On the other hand, the A+S- group (with only ascorbic acid added) had a low pH and little variation (Figure 3). The AS- group (no additions) and the A+S+ group (both added) sometimes had a high pH (Figure 3). A high pH can be said to indicate poor fermentation, but for those with a low pH, it is necessary to measure the concentration of organic acids (such as lactic acid) to confirm the fermentation quality, and it is not possible to immediately determine whether the fermentation is good.

[0037] Example 3 In carrying out Example 2, a treatment group (Chilled group) was set up in which silage made under the same conditions as the A+S- group was stored in a refrigerator at 4°C for one month. The RT group and the material grass were the same as the silage after one month of storage in the A+S- group in Example 2 and the material grass before sealing, respectively. Air drying, crushing, measurement of nitrate nitrogen content, extraction with pure water, and measurement of pH of the samples were carried out under the same conditions as in Example 1.

[0038] The nitrate nitrogen content in the chilled and RT groups is shown in Figure 4. As shown in Figure 4, the nitrate nitrogen content was slightly higher in the chilled group than in the room temperature group (RT group). [Industrial Applicability]

[0039] The present invention can be used in the fields of feed production and feed preparation, etc.

Claims

1. A method for producing silage, comprising the following steps (1) and (2): (1) adding ascorbic acid or a salt of ascorbic acid to a silage raw material; (2) After step (1), a step of fermenting the silage raw material.

2. 2. The method for producing silage according to claim 1, wherein the ascorbic acid or a salt of ascorbic acid is purified ascorbic acid or a salt of purified ascorbic acid.

3. 2. The method for producing silage according to claim 1, wherein the amount of ascorbic acid or a salt of ascorbic acid added is 0.3 to 10% by weight, calculated as ascorbic acid, based on the weight of the silage raw material.

4. 2. The method for producing silage according to claim 1, wherein the fermentation period of the silage raw materials is 1 to 24 months.

5. 2. The method for producing silage according to claim 1, wherein the salt of ascorbic acid is sodium ascorbate.

6. 2. The method for producing silage according to claim 1, wherein the raw material for the silage is grass.

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