The difficulty of silage is different because of different plant species, growth stage and chemical composition. For plant raw materials that are difficult to silage (low carbohydrate content, high water content, high buffering), semi-dry silage, mixed silage or additive silage can generally be used.
The addition of methyl (ant) acid silage is a widely used method of acid silage abroad. Norway’s nearly 70 silage added formic acid, the United Kingdom since 1968 has also been widely used, its dosage is 2.85 kg per ton of silage raw material added 85 formic acid, the United States per ton of silage raw material added 90 formic acid 4.53 kg. Of course, the amount of formic acid varies with its concentration, the difficulty of silage and the purpose of silage, and the addition amount is generally 0.3 to 0.5 of the weight of the silage raw material, or 2 to 4ml/kg.
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Formic acid is a strong acid in organic acids, and has a strong reducing ability, is a by-product of coking. The addition of formic acid is better than the addition of inorganic acids such as H2SO4 and HCl, because inorganic acids have only acidifying effects, and formic acid can not only reduce the pH value of silage, but also inhibit plant respiration and bad microorganisms (Clostridium, bacillus and some gram-negative bacteria) fermentation. In addition, formic acid can be decomposed into non-toxic CO2 and CH4 in livestock during silage and rumen digestion, and formic acid itself can also be absorbed and utilized. The silage made of formic acid has bright green color, fragrance and high quality, and the loss of protein decomposition is only 0.3~0.5, while in general silage it is up to 1.1~1.3. As a result of adding formic acid to alfalfa and clover silage, the crude fiber was reduced by 5.2~6.4, and the reduced crude fiber was hydrolyzed into oligosaccharides, which could be absorbed and utilized by animals, while the general crude fiber was only reduced by 1.1~1.3. In addition, adding formic acid to silage can make the loss of carotene, vitamin C, calcium, phosphorus and other nutrients less than ordinary silage.
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2.1 Effect of formic acid on pH
Although formic acid is the most acidic of the fatty acid family, it is much weaker than the inorganic acids used in the AIV process. To reduce the pH of crops to below 4.0, formic acid is generally not used in large quantities. The addition of formic acid can decrease the pH value rapidly at the initial stage of silage, but has different effects on the final pH value of silage. The degree to which formic acid changes pH is also affected by many factors. The amount of lactic acid bacteria (LAB) decreased by half and the pH of the silage increased slightly by adding 85 formic acid 4ml/kg to forage silage. When formic acid (5ml/kg) was added to forage silage, LAB decreased by 55 and pH increased from 3.70 to 3.91. Typical effect of formic acid on silage raw materials with low water soluble carbohydrates (WSC) content. In this study, they treated alfalfa silage with low (1.5ml/kg), medium (3.0ml/kg), and high (6.0ml/kg) levels of 85 formic acid. Results The pH was lower than that of the control group, but with the increase of formic acid concentration, the pH decreased from 5.35 to 4.20. For more buffered crops, such as leguminous grasses, more acid is needed to bring pH down to the desired level. It is suggested that the appropriate use level of alfalfa is 5~6ml/kg.
2.2 Effects of formic acid on microflora
Like other fatty acids, the antibacterial effect of formic acid is due to two effects, one is the effect of hydrogen ion concentration, and the other is the selection of non-free acids to bacteria. In the same fatty acid series, the hydrogen ion concentration decreases with the increase of molecular weight, but the antibacterial effect increases, and this property can rise at least to C12 acid. It was determined that formic acid had the best effect on inhibiting bacterial growth when pH value was 4. The slope plate technique measured the antimicrobial activity of formic acid, and he found that selected strains of Pediococcus and Streptococcus were all inhibited at a formic acid level of 4.5ml/kg. However, lactobacilli (L. Buchneri L. Cesei and L. platarum) were not completely inhibited. In addition, strains of Bacillus subtilis, Bacillus pumilis, and B. Brevis were able to grow in 4.5ml/kg of formic acid. The addition of 85 formic acid (4ml/kg) and 50 sulfuric acid (3ml/kg), respectively, reduced the pH of silage to similar levels, and found that formic acid significantly prevented the activity of LAB (66g/kgDM in formic acid group, 122 in control group, 102 in sulfuric acid group), thus preserving a large amount of WSC (211g/kg in formic acid group, 12 in control group, 12 in acid group). The sulfuric acid group is 64), which can provide some more energy sources for the growth of rumen microorganisms. Yeasts have a special tolerance for formic acid, and large numbers of these organisms were found in silage raw materials treated with recommended levels of formic acid. The presence and activity of yeast in silage is undesirable. Under anaerobic conditions, yeast ferments sugars to obtain energy, produce ethanol and reduce dry matter. Formic acid has a significant inhibitory effect on Clostridium difficile and intestinal bacteria, but the strength of the effect depends on the concentration of acid used, and low concentrations of formic acid actually promote the growth of some heterobacteria. In terms of inhibiting enterobacter, the addition of formic acid reduced pH, but the number of enterobacter could not be reduced, but the rapid growth of lactic acid bacteria inhibited enterobacter, because the effect of formic acid on enterobacter was less than that of lactic acid bacteria. They noted that moderate levels (3 to 4ml/kg) of formic acid may inhibit lactic acid bacteria more than enterobacter, leading to adverse effects on fermentation; Slightly higher formic acid levels inhibited both Lactobacillus and enterobacter. Through the study of perennial ryegrass with 360g/kg DM content, it was found that formic acid (3.5g/kg) can reduce the total number of microorganisms, but has little effect on the activity of lactic acid bacteria. Large bundles of alfalfa (DM 25, DM 35, DM 40) silage were treated with formic acid (4.0 ml/kg, 8.0ml/kg). The silage was inoculated with clostridium and Aspergillus flavus. After 120 days, formic acid had no effect on the number of clostridium, but had complete inhibition on the latter. Formic acid also encourages the growth of Fusarium bacteria.
2.3 Effects of Formic acid on silage composition The effects of formic acid on silage chemical composition vary with the application level, plant species, growth stage, DM and WSC content, and silage process.
In materials harvested with the chain flail, low formic acid treatment is substantially ineffective against Clostridium, which prevents the breakdown of proteins, and only high levels of formic acid can be effectively preserved. With finely chopped materials, all formic acid treated silage is well preserved. The contents of DM, protein nitrogen and lactic acid in formic acid group were increased, while the contents of acetic acid and ammonia nitrogen were decreased. With the increase of formic acid concentration, acetic acid and lactic acid decreased, WSC and protein nitrogen increased. When formic acid (4.5ml/kg) was added to alfalfa silage, compared with the control group, the content of lactic acid decreased slightly, soluble sugar increased, and other components did not change much. When formic acid was added to crops rich in WSC, lactic acid fermentation was dominant and the silage was well stored. Formic acid limited the production of acetic acid and lactic acid and preserved WSC. Use 6 levels (0, 0.4, 1.0,. Ryegrass-clover silage with DM content of 203g/kg was treated with formic acid (85) of 2.0, 4.1, 7.7ml/kg. The results showed that WSC increased with the increase of formic acid level, ammonia nitrogen and acetic acid on the contrary, and the content of lactic acid increased first and then decreased. In addition, the study also found that when high levels (4.1 and 7.7ml/kg) of formic acid were used, the WSC content in silage was 211 and 250g/kgDM, respectively, which exceeded the initial WSC of silage raw materials (199g/kgDM). It is speculated that the cause may be the hydrolysis of polysaccharides during storage. Results The lactic acid, acetic acid and ammonia nitrogen of silage in formic acid group were slightly lower than those in control group, but had little effect on other components. Whole barley and maize harvested in wax ripening stage were treated with 85 formic acid (0, 2.5, 4.0, 5.5mlkg-1), and the soluble sugar content of maize silage was increased significantly, while the contents of lactic acid, acetic acid and ammonia nitrogen were decreased. The content of lactic acid in barley silage decreased significantly, ammonia nitrogen and acetic acid also decreased, but not obviously, and soluble sugar increased.
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The experiment fully confirmed that the addition of formic acid silage was beneficial to improve the voluntary feed intake of silage dry matter and livestock performance. Adding formic acid silage directly after harvest can increase the apparent digestibility of organic matter 7, while wilting silage only increases 2. When energy digestibility is taken into account, formic acid treatment improves by less than 2. After a lot of experiments, it is believed that the data of organic digestibility is biased due to the loss of fermentation. The feeding experiment also showed that the average weight gain of livestock was 71 and that of wilting silage was 27. In addition, formic acid silage improves milk production2. Feeding experiments with hay and formic acid prepared with the same raw materials showed that silage could increase milk yield of dairy cattle. The percentage increase of performance in formic acid treatment was lower in milk production than in weight gain. Adding sufficient amount of formic acid to difficult plants (such as chicken foot grass, alfalfa) has a very obvious effect on livestock performance. The results of formic acid treatment of alfalfa silage (3.63~4.8ml/kg) showed that the organic digestibility, dry matter intake and daily gain of formic acid silage in cattle and sheep were significantly higher than those in control group.
The daily gain of sheep in the control group even showed a negative increase. The addition of formic acid to WSC rich plants with medium DM content (190-220g /kg) usually has little effect on livestock performance. Ryegrass silage with formic acid (2.6ml/kg) was carried out in feeding experiment. Although formic acid silage increased weight gain 11 compared with control, the difference was not significant. The digestibility of the two silages measured in sheep was substantially the same. Feeding corn silage to dairy cattle showed that formic acid slightly increased silage dry matter intake, but had no effect on milk production. There is little information on the energy utilization of formic acid silage. In the experiment of sheep, the metabolizable energy concentration of dry matter and maintenance efficiency of silage were higher than that of hay and hay harvested in three growing periods. Energy value comparison experiments with hay and formic acid silage showed no difference in the efficiency of converting metabolic energy into net energy. The addition of formic acid to forage grass can help protect its protein.
The results showed that formic acid treatment of grass and alfalfa could improve the utilization of nitrogen in silage, but had no significant effect on digestibility. The degradation rate of ensilage nitrogen treated with formic acid in rumen accounted for about 50 ~ 60 % of the total nitrogen.
It can be seen that the strength and efficiency of formic acid silage in rumen synthesis of thallus proteins are reduced. The dynamic degradation rate of dry matter in rumen was significantly improved with formic acid silage. Although formic acid silage can reduce ammonia production, it can also reduce the digestibility of proteins in the rumen and intestines.
4. Mixing effect of formic acid with other products
4.1 Formic acid and formaldehyde are mixed in production, and formic acid alone is used to treat silage, which is expensive and corrosive; The digestibility and dry matter intake of livestock were decreased when the silage was treated with high concentration formic acid. Low concentrations of formic acid encourage the growth of clostridium. It is generally believed that the combination of formic acid and formaldehyde with low concentration has a better effect. Formic acid mainly acts as a fermentation inhibitor, while formaldehyde protects proteins from over-decomposition in the rumen.
Compared with the control group, the daily gain was increased by 67 and the milk yield was increased by adding formic acid and formaldehyde. Hinks et al. (1980) conducted a mixture of rygrass formic acid silage (3.14g/kg) and formic acid (2.86g/kg) -formaldehyde (1.44g/kg), and measured the digestibility of the silage with sheep, and conducted feeding experiments with growing cattle. Results There was little difference in digestibility between the two types of silage, but the metabolizable energy of formic-formaldehyde silage was significantly higher than formic acid silage alone. The metabolizable energy intake and daily gain of formic-formaldehyde silage were significantly higher than formic acid silage alone when cattle were fed silage and barley was supplemented with 1.5 kg per day. A mixed additive containing about 2.8ml/kg of formic acid and a low level of formaldehyde (about 19g/kg of protein) may be the best combination in pasture crops.
4.2 Formic acid mixed with biological agents The combination of formic acid and biological additives can significantly improve the nutritional composition of silage. Cattail grass (DM 17.2) was used as raw material, formic acid and lactobacillus were added for silage. The results showed that lactic acid bacteria produced more in the early stage of silage, which had a good effect on inhibiting the fermentation of bad microorganisms. At the same time, the final lactic acid content of silage was significantly higher than that of ordinary silage and formic acid silage, the lactic acid level was increased by 50 ~ 90, while the contents of propyl, butyric acid and ammonia nitrogen were significantly decreased. The ratio of lactic acid to acetic acid (L/A) was significantly increased, indicating that lactic acid bacteria increased the degree of homogeneous fermentation during silage.
5 Summary
It can be seen from the above that the appropriate amount of formic acid in silage is related to the types of crops and different harvesting periods. The addition of formic acid does reduce pH, ammonia nitrogen content, and retain more soluble sugars. However, the effect of adding formic acid on the digestibility of organic matter and the production performance of livestock remains to be further studied.
Post time: Jun-06-2024