For livestock and poultry, there will be insufficient secretion of endogenous digestive enzymes under some special growth and development stages and feeding and management conditions. For example, the development of digestive enzymes in young animals is incomplete, the secretion capacity of digestive enzymes in old animals is reduced, and the secretion of digestive enzymes in animals is disordered after stress or disease infection. Exogenous digestive enzymes can supplement the deficiencies of endogenous enzymes and enhance the ability of animals to digest and absorb feed nutrients, thereby improving livestock productivity and feed conversion efficiency. Selecting appropriate digestive enzyme preparations to make up for the lack of endogenous enzymes can increase livestock productivity and improve feed utilization efficiency. Broiler chickens eat much more than egg chicks, but the secretion of pancreatic digestive enzymes is similar. Broilers need to process more chyme at the same level of digestive enzymes, and it is more important to supplement the diet with exogenous digestive enzymes, and the feeding effect is significant.
Temperature and pH are the two major environmental factors that affect the effect of enzymes. Each enzyme has its own optimum environment temperature and pH to maintain the stability of its structure and properties. The pH and temperature of the intestines of poultry and pigs are quite different, so the type of enzyme preparation or the amount of enzyme activity suitable for pigs may not be suitable for poultry. The same type of enzymes may have different sources and properties, such as plant, bacterial and fungal sources, and the same type of enzymes from different sources may also have different environmental adaptations. Therefore, attention should be paid to different acidity and alkalinity when selecting livestock and poultry enzyme preparations.
Due to the substrate specificity of the enzyme action, in order to make the feed enzyme preparation play a good role, the characteristics of the feed material must be considered in the application. The composition and chemical structure of different feed ingredients are specific. The main non-starch polysaccharide in wheat and rye is arabinoxylan; in barley and oat, in addition to arabinoxylan, it is mainly β-glucan; in legume seeds, it is mainly pectin. It can be seen that the enzymes used for wheat-soybean meal feed should be mainly xylanase, pectinase and cellulase, while those used for barley-soybean meal feed are mainly β-glucanase, pectinase, xylanase Carbohydrase and cellulase. Phytic acid in plant feed ingredients is relatively simple compared to the above carbohydrates, it has a fixed chemical structure and properties, and the factors to be considered in the use of phytase are much simpler.
The purpose of using non-digestive enzymes in the diet is to improve the utilization rate or eliminate the anti-nutritional effect of the substances in the feed that livestock and poultry cannot digest by relying on endogenous enzymes. If the substrate is too small, the addition of enzyme will not produce obvious improvement effect; if the amount of substrate is too much, the amount of added enzyme or enzyme activity is not sufficient, the amount of substrate that can be degraded is limited and the effect is not good. This requires that there should be an appropriate proportional relationship between the substrate and feed enzyme dosage, and the dosage of the added enzyme preparation should be determined according to the target substrate content.
There is no uniform standard for measuring the activity of most enzymes in feed enzymes. Since the pH, temperature and substrate selected for the determination have a great influence on the results of the enzyme activity determination, it is difficult to judge the quality of the enzyme preparation from the enzyme activity index, and the use effects of products with the same enzyme activity are quite different.
Enzymes are proteins. Except for very few enzymes, which can maintain the stability of structure and function at a high temperature of around 90 °C, most of them do not have the property of resisting high heat above 70 °C. Enzyme preparations that have not undergone special stabilization treatment are difficult to withstand the granulation process and still maintain a high vitality, and they cannot adapt to the puffing process. For feeds that must be pelleted or extruded, post-spray technology should be used to evenly add feed enzymes (liquid) to the compound feed.
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