It is understood that corn protein meal contains up to 40% to 60% protein, with a protein content 21% and 3.7% higher than soybean cake and fish meal, respectively. It is a feed material with high protein content, and the crude fiber content is 3.9% lower than soybean cake; Rich in amino acids, it can be used to replace protein feed such as soybean cakes and fish meal in the feed market where there is a shortage of soybean cakes and fish meal; Therefore, the following editor will provide a detailed introduction to the role of corn protein powder in feed.
1. Classification and structural composition of corn protein
Corn protein can be divided into: water-soluble albumin; Globulin insoluble in water but soluble in salt; Alcohol soluble protein that is insoluble in water but soluble in ethanol; Glutenin insoluble in water and alcohol, but soluble in dilute acids or alkalis. These four proteins are unevenly distributed in various parts of corn kernels, with gliadin (40%) and glutenin (37%) mainly distributed in the embryo; Albumin and globulin are mainly distributed in the embryo, and their content is relatively low. The protein content in corn gluten powder is as high as 40% to 70%. Corn gluten powder is mainly composed of zein and glutelin, with zein accounting for about 68% and glutelin accounting for about 28%. Due to the large amount of non-polar amino acids in zein, it has poor solubility in aqueous solutions, while it has high solubility in 60% to 95% alcohol aqueous solutions, The insolubility and acid resistance of zein in water have led to unsatisfactory digestion and utilization of corn protein powder by animal bodies. In recent years, with the continuous deepening of research on zein, hydrolyzing zein to improve the utilization rate of corn protein powder has gradually attracted people's attention. There are reports in domestic and foreign literature that adding a certain amount of exogenous protease preparations can improve the digestion and utilization rate of corn protein powder in animal bodies.
2. Nutrient composition of corn protein powder
The nutritional composition of corn protein powder produced by different uses and production processes varies greatly, which directly affects the effective utilization rate of feed raw materials and the economic benefits of feed formulas. From Table 1, it can be seen that the protein content in corn protein meal is 21% and 3.7% higher than that in soybean cake and fish meal, respectively. The difference between corn protein meal and soybean cake is significant, and it is a high protein substance. At the same time, the crude fiber content is 3.9% lower than that in soybean cake, which can be classified as refined feed. In addition, the fat content in corn protein powder is higher than that in soybean cakes and corn seeds. According to domestic and foreign research, adding fat to the diet can increase the weight gain of livestock and poultry by 15%~20%, and reduce the feed consumption per kilogram of weight gain by 10%~15%. It can reduce the oxidation of amino acids and convert more amino acids into body protein, improving the digestibility of amino acids; It can inhibit the conversion of glucose and other precursor substances into fat; Under high temperature conditions, it is also beneficial to increase energy intake, reduce the body heat consumption of livestock and poultry, and slow down heat stress. In addition, high fat content can effectively improve the palatability of feed. From this, it can be seen that corn protein powder, as an important protein source for formula feed, can be comparable to soybean cakes and fish meal.
3. The role of corn protein powder in feed
Nowadays, corn protein powder is mainly used in the feed industry in China. However, the use of corn protein powder can extract natural food pigments, zein, and glutamic acid, as well as prepare corn active peptides with various physiological functions, such as glutamine peptides, high F-value oligopeptides, antihypertensive peptides, and corn protein peptides, greatly improving their economic value.
3.1 Corn protein powder as a feed protein source
Corn protein powder has a high protein content and abundant amino acids, but its amino acid composition is unbalanced. It contains abundant branched chain amino acids (leucine, isoleucine, valine), sulfur-containing amino acids, proline, and phenylalanine, especially glutamic acid, but lacks basic and acidic amino acids, such as tryptophan and lysine, which are very low in content.Corn gluten meal is mainly composed of gliadin, which limits the digestion and utilization of animals due to its unique structure and strong hydrophobicity. Although microorganisms in the animal digestive tract and digestive enzymes in the intestine can digest and degrade a portion of corn gluten meal to a certain extent, its digestion effect is very limited. There are literature reports that adding exogenous proteases can promote the digestion and absorption of corn protein powder by animal bodies. Corn protein powder is a highly F value oligopeptide molecule produced by digestion enzymes or biodegradation, which has significant biological activity. Corn active peptides not only have the ability to be easily digested and absorbed by animal bodies, but also have physiological activities such as antioxidant, fatigue elimination, and blood pressure lowering; High F-value oligopeptide molecules can improve the liver, kidney, intestine, and stomach functions of animal bodies.Corn protein meal can be used to replace some protein feed such as soybean cakes and fish meal in the feed market where soybean cakes and fish meal are very scarce. In addition, soybean protein contains abundant lysine and tryptophan, but lacks sulfur-containing amino acids. Therefore, combining soybean protein with corn protein powder in a certain proportion for enzymatic hydrolysis can play a complementary role in further improving the nutritional value and quality of grain protein powder, which is conducive to improving the digestion and absorption of livestock and poultry, and meeting their nutritional needs. Corn protein powder based formula feed for laying hens can improve egg production rate, prevent and treat chicken cartilage disease and other diseases, promote growth, and also help improve egg protein quality. In the field of cattle farming, using corn protein powder as a concentrate feed can better digest and absorb the protein that cannot be digested by the rumen in the small intestine. Corn protein meal contains linoleic acid, which can promote fat metabolism in chickens and promote the aggregation of essential amino acids.
3.2 Corn protein powder improves the color fastness of broiler chickens
Although the pigmentation of the skin of broilers is not related to their nutritional value, influenced by traditional culture, consumers and breeders still consider the pigmentation of broilers as one of the indicators to measure their quality, directly affecting the price and demand of the broiler market. Broilers cannot synthesize lutein themselves and can only obtain it from feed. The pigmentation of their epidermis depends on the effective supply of lutein in the feed and the total amount of lutein deposition in the chicken body. Broilers fed with diets such as corn and soybean cakes can only obtain normal skin color. To achieve ideal skin color, it is generally necessary to add chemical synthetic colorants such as Garrison Red and Garrison Yellow to broiler feed. These colorants have a higher selling price, increase feed costs after addition, and remain in poultry bodies, which is harmful to consumer health.Corn protein powder has a high content of lutein, which can be effectively absorbed, making eggs golden and chicken skin yellow, increasing nutritional value and selling price. The content of lutein in corn protein powder is 90-180 mg · kg -1, which is more than 5 times that of yellow corn, but the price is close to that of soybean cakes. In view of this, corn protein powder cabe used instead of chemical synthetic colorants to improve the color fastness of egg yolk and chicken.
3.3 Corn protein powder can partially replace antibiotics
Chen Shipei et al. reported that corn protein feed made from by-products of corn starch extracted from corn syrup contains 13% to 16% protein and 7% to 8% citric acid, which has a sour, fragrant, sweet taste, good palatability, and high digestibility. The citric acid contained in corn protein feed has special significance. By using acidifiers such as citric acid instead of drug-based growth promoters, there will be no residual harmful substances in livestock and poultry products, and there will be no discontinuation period like many antibiotics, which meets the requirements of the Health Organization. At the same time, it can also improve the feed intake and digestion rate of livestock and poultry.
3.4 Reduce nitrogen emission rate and reduce environmental pollution caused by livestock and poultry excreta
Through experiments on the effects of different types of corn protein meal dietary fiber and energy on nitrogen metabolism in growing pigs, this study further explores the laws of nitrogen digestion, absorption, utilization, and excretion in growing pigs, in order to more effectively study low pollution dietary technology. The results showed that the nitrogen deposition, nitrogen digestibility, and total nitrogen utilization rate of corn protein meal diet were positively correlated with the digestibility of neutral washing fiber, acidic washing fiber, and crude fiber in the diet; The ratio of fecal nitrogen to dietary nitrogen in the diet shows a linear negative correlation with the digestibility of neutral washing fiber, acidic washing fiber, and crude fiber in the diet, and a linear positive correlation with the content of neutral washing fiber or crude fiber. The increase in neutral washing fiber or crude fiber content in the diet leads to an increase in the ratio of fecal nitrogen to dietary nitrogen, resulting in an increase in nitrogen emissions and a decrease in total nitrogen utilization efficiency, which is beneficial for environmental protection.In short, corn protein powder has a high protein content, and its degradation product - bioactive peptides - not only facilitate digestion and absorption by animal bodies, but also have physiological functions such as antioxidant and immune enhancement. In addition, corn protein powder is rich in lutein content and has high feeding value. However, the content of gliadin in corn protein powder is relatively high, and the digestion and utilization of it by digestive enzymes and microorganisms in animal bodies are very limited, which cannot achieve the expected ideal effect. Adding exogenous protease preparations can improve the digestibility and utilization of corn protein powder in animals. Corn protein powder has a wide range of sources and will be widely used in the feed industry, especially its coloring effect. Its application prospects in poultry feed will be very broad.
