Crushing is a necessary part of the processing of all compound feed products and one of the most energy-intensive sections. Feed crushing technology has significant research and development value for improving the nutritional value of feed ingredients, animal production performance and controlling processing costs. Basic concept of smash 1. Crushing Material particles are made smaller by impact, shearing, grinding or other methods. 2. Fine pulverization The material was pulverized to a pulverization which was passed through a 0.42 mm sieve (40 mesh sieve). Mainly used for processing aquatic feed and feed additives. 3. Ultrafine pulverization The material was pulverized to 95% and pulverized through a 0.15 mm mesh (100 mesh sieve). Mainly used for processing special aquatic feeds and feed additives. 4. Feed pulverization particle size refers to the particle size of the powdery feed product: or the particle size of the mixed powder after mixing, granulation, puffing, or the pulverized feed material. 5. Weight geometric mean particle size This method uses a 14-layer standard sieve with sieve numbers of 4, 6, 8, 12, 20, 30, 40, 50, 70, 100, 140, 200, 270 to screen 100 grams of sample. Then, the mass of each layer of the sieve and the bottom sieve are respectively referred to, and the geometric mean particle diameter and the geometric standard deviation of the weight are calculated accordingly. The advantage of this method is that it can accurately reflect the feed particle size and reflect the variation of feed particle size. 6. The pulverized feed optimum particle size refers to feed domestic animals with a maximum efficiency or performance without affecting the optimum animal health, economic and cost-effective weight geometric mean particle size. Effect of feed crushing particle size on nutritional value of feed and animal performance 1 . The crushing size of feed will significantly affect the solubility of feed nutrients in the digestive juice. The authors and others studied the relationship between the pulverization size of the six feed ingredients and the solubility of the protein. The protein solubility of the six raw materials determined by the test increased with the decrease of the pulverization particle size. After analysis of variance, the correlation between the protein solubility of the six raw materials and the logarithmic geometric mean particle size after pulverization was extremely significant (P<0.01), that is, reducing the pulverized particle size significantly improved the protein solubility of five raw materials such as corn. The effective digestion of digestive enzymes in the digestive tract of animals provides the basis. Among them, the difference in protein solubility between the peeled soybean meal (Donghai), the skinned soybean meal (Donghai) and the skinned soybean meal (local) reached a very significant level. It is indicated that the pulverization can continue to significantly increase the protein solubility of the peeled soybean meal and the preserved soybean meal. Using SPSS statistical analysis software, regression analysis was carried out on the five different logarithmic geometric mean particle size and protein solubility data of the six raw materials after pulverization, and the linear regression equation was obtained. The correlation was tested by significant test to reach a very significant level. 2 . The pulverization particle size will significantly affect the in vitro digestibility of the feed protein The authors and others conducted five kinds of in vitro pepsin and trypsin digestibility experiments on seven kinds of feed materials. In terms of pepsin digestibility, it can be seen from the comparison between different raw materials, under the same meshing conditions, The protein digestibility of the nutmeg is the highest, followed by the skinned soybean meal (local), bran, and skinned soybean meal (East Sea). Cotton aphid and rapeseed have the lowest digestibility. This is basically consistent with the results of another study by Wang Weiguo et al. (2000). The pepsin digestibility of corn is the most sensitive to the pulverized particle size, followed by cotton aphid, peeled soybean meal and local soybean meal, while the digestibility of the other three raw materials is less sensitive to the change of pulverization size. Analysis of the variance of pepsin digestibility under different pulverized particle sizes of each raw material showed that there was significant difference between the digested soybean meal (Donghai), the skinned soybean meal (Donghai), the soybean meal (local), and the corn. Differences indicate that comminution can significantly increase their digestibility. The difference between the digestive data of rapeseed meal and bran was not significant. From the pulverized particle size and the total pepsin-trypsin digestibility, the peeled soybean meal (Donghai) has the highest digestibility, followed by the skinned soybean meal (local), bran, and preserved soybean meal (East Sea). The total digestibility of cotton aphid and rapeseed meal is low. The reason for the low digestibility of cotton aphid and rapeseed meal may be due to the high crude fiber content and the presence of anti-nutritional factors such as antitrypsin, phytic acid, gossypol, etc., which affect the enzyme activity and affect the protein digestibility. . In addition, the process conditions of oil processing are also important factors affecting protein digestibility. Advanced processing conditions for peeled soybean meal are an important guarantee for obtaining high digestibility, so advanced oil-making processes should be promoted. 3 . Study on the best pulverization particle size of pig feed 1) Study on the pulverization particle size of piglets. The results of research on the pulverization particle size of foreign piglets are mainly concentrated in cereals. According to the results of various studies, the crushing size of piglet grain is most suitable from 300-500gm. Among them, weaned piglets are suitable for 300gm after 0-1-4 days after weaning, and 500gm after 15 days of weaning. The suitable particle size of piglet feed varies with the type of grain (Ohh, 1999). Goodband et al reported that barley needs to be pulverized to a larger particle size (600-700 gm). Hale et al. (1979) reported that wheat pulverization is better than fine pulverization for feed efficiency and animal performance, while corn has better feed efficiency and animal performance during fine pulverization (Reiman, 1968; Hedde, 1985). Wang Weiguo et al. (2000) studied the effects of three kinds of pulverized size of corn and soybean meal on the performance and feed utilization efficiency of piglets in piglet feed. The diameter of the sieve used by the pulverizer is 2.5mm, 3.0mm and 4.5mm. The geometric average particle size of the pulverized material is 261, 352, 432gm for corn, the grain size of soybean meal is 388, 414, 498gm, and the particle size of the compound feed is 282, 323, 345 gmo. The production performance and feed utilization of the three-grain feed products for pigs are shown in Table 5. It can be seen from Table 5 that in terms of weight gain level, the test group C and D using 3mE mesh processing have the highest weight gain, with an average of 56.75kg, and the test group with 2.5mm mesh hole gains the second. The average was 55 kg, and the test group with a 4.5 mm mesh had the worst weight gain. From the ratio of meat to meat, to 3. Piglets in the Omm sieve test group performed best, with an average of 2.22. The digestibility of feed dry matter and crude protein was highest in the medium-grain group, followed by the fine-grained group, and the coarse-grained group was the worst. 2) Study on the pulverization particle size of sow feeds There are few reports on the pulverization particle size of sow feed. However, the appropriate pulverization particle size can also increase the feed intake and nutrient digestibility of the sow and reduce the discharge of the sow feces. Wandra et al. (1995) pulverized corn into four sizes (1200 μm, 900 μm, 600 μm, 400 μm) and prepared 100 diets for primiparous sows. The results showed that the grain size decreased from 1200 μm to 400 μm, and the average daily feed intake. From 4.19 to 4.43kS/d, the energy digestibility increased from 83.8% to 90%, and the digestible energy intake was 13. TMcal/d increased to 15.6 Mcal/D and litter weight gain increased from 34.9 kg to 38.6 kg. Since reducing the particle size increases the nutrient digestibility, the dry matter discharge of the manure is reduced by 21%, and the nitrogen excretion in the manure is reduced by 31%, which has a significant effect on reducing the burden of manure treatment. The pulverized particle size of the sow feed is most suitable from 400 to 500 mm. 3) Growth and fattening pig feed pulverization particle size The grain pulverization particle size is shown in Table 6 for the growth and fattening pigs. Mahan et al. (1966) and Lawrence (1983) have reported that grain size reduction improves body weight gain and feed conversion. Giesemann et al. (1990) also reported that reducing corn kernel size would increase body weight gain by 5% and feed conversion ratio by 9%. Wandra et al. (1995) used a diet of 1000-400 gm corn size to prepare a diet for feeding pigs. The results showed that for every 100 μm reduction in grain size, 1.3% feed efficiency was improved and N excretion was reduced. However, at the minimum particle size, porcine gastrointestinal damage and keratinization occur. Tests have shown that the optimum pulverization size of corn is 600-500 μm. Philips (1995) used a small-grain feed for granulation and then fed the finishing pigs with a 27% reduction in dry matter in the faeces. 4) Effect of feed size on pig digestive organs The particle size of the feed has an effect on the gastrointestinal morphology of pigs. Excessive mashing of the feed can cause adverse reactions in the stomach of the pig, leading to gastrointestinal keratinization and damage (Maxwell et al, 1970, 1972; Cabrera et al, 1993; Healv et al 1994; Phillips, 1995: Wondra et al, 1995). Excessive comminution results in increased fluidity of the gastrointestinal contents, increases the mixing of the contents, causes an increase in acid secretion and pepsin activity, and ultimately leads to an increase in ulceration of the esophagus and stomach (Maxwell et al., 1972). 4 . Study on the best crushing particle size of chicken feed 1) Study on granulation size of broiler feed Douglas et al. (1990) added corn, low tannin sorghum and high tannin sorghum processed by hammer mill and roller mill to the diet to feed 21-day-old broilers. The logarithmic geometric average particle size of the feed processed by the hammer mill was 874 μm, and the log geometric mean particle diameter of the feed processed by the roller mill was 1681 μm. The results showed that the weight gain of chickens fed a feed with a small particle size was significantly higher than that of a chicken fed a large grain size feed. Nir et al. (1990) used a hammer mill and a roller mill to pulverize three different particle sizes, namely 555an (fine), 702 μm (middle), and 888an (coarse). In the 10-day selection trial, chicks prefer to feed larger sized feeds. The larger the grain size, the higher the feed intake of the chicken. Adding the same grain to the diet to feed broilers aged 7-21 days, the thicker the feed, the more obvious the increase in feed intake. This led to a significant increase in chicken body weight. In a series of four trials (2,400 broilers per group), Reece et al. (1986) smashed feed using sieves of different pore sizes (4.76 mm, 6.35 mm) and fed broilers with two granulated feeds of different sizes. The results showed that there was no difference in weight gain and feed conversion ratio between the groups at 21 days of age or 42 days of age. Lot et al. (1992) used a hammer mill to pulverize corn into different particle sizes, dispensed into feed, and used it to make a pellet feed. In the first test, the pulverized sieve apertures were 3.18 mm and 9.59 mm, and the resulting pulverized material had a logarithmic geometric mean particle size of 7161 an and 1196 μm. The feeding results showed that the individual weight gain and feed conversion rate of the chickens fed the 716 μm grain feed were significantly improved. However, in the second experiment, the corn was pulverized to a particle size of 690-974 μm and was fed into the broiler as a pellet feed. As a result, there was no difference in body weight gain and feed utilization. The uniformity of the particle size of the feed pulverized material affects the performance of the broiler. Nir et al. (1994) screened the same grain crushed sample into different sections. The different parts are then added to the feed for feeding broilers. Broilers fed medium-grain corn obtained the best performance. The other two groups of feeds mixed with corn with a particle size of 1102 μmn and 525 Pm did not reach the level of the former. Depending on the particle size, the comminuted grain sieve is divided into different parts and has no effect on its nutritional composition. Nir et al. (1994) used a sieve to divide the crushed corn into several parts and found that there was no difference in the nutrient content of different parts. Martin (1983) pulverized corn and sorghum into different particle sizes. As a result, the pulverization fineness or the processing mode of the two grains during mixing and granulation had no effect on the variation of nutrients. Based on the above research results, the crushed grain size of the feed grains of broilers is preferably 700-900 Pm. 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