eChapter Name: Natural Toxicants of Plant and Their Detoxificaion For Improving Livestock Feeding
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eBook Name: FEEDS AND FODDERS FOR LIVESTOCK AND POULTRY
Plants and many agro-industrial by-products incorporated into livestock diets may harbor a range of anti-nutritional compounds. These substances can adversely affect optimal nutrition by deactivating specific nutrients, obstructing the digestive process, or diminishing the metabolic efficiency of feed, ultimately leading to negative consequences for animal health and productivity. The naturally occurring plant compounds found in feed that disrupt feed utilization (FCR), lower production levels, and compromise animal health are referred to as anti-nutritional factors. Additionally, natural toxicants present in feed can hinder the absorption and utilization of nutrients in livestock. Therefore, it is essential to implement effective detoxification methods for these feed materials to mitigate toxic effects and ensure their safe incorporation into animal diets. A foundational understanding of these toxicants is crucial prior to undertaking detoxification and subsequent use in livestock feeding.
Natural toxicants can be categorized based on their chemical properties into several groups: Proteins, Glycosides, Phenols, and Miscellaneous toxicants. The chemical characteristics, pathogenic effects, and detoxification strategies for these compounds are briefly outlined below.
Proteins
1. Protease inhibitors: Protease inhibitors are prevalent throughout the plant kingdom, particularly in the seeds of many cultivated legumes. These inhibitors possess the capability to obstruct the function of proteolytic enzymes in the gastrointestinal systems of animals. Specifically, trypsin inhibitors form irreversible complexes with trypsin, rendering the enzyme unable to fulfill its role in protein digestion. This interaction prompts the intestine to secrete cholecystokinin, which in turn stimulates pancreatic enlargement. The presence of trypsin inhibitors in raw soybean can hinder the availability of methionine, leading to adverse effects in young chickens fed raw soybean meal,
including pancreatic hypertrophy, reduced growth rates, gallbladder contraction and increased bile acid excretion, similar to observations in other monogastric animals. In contrast, ruminants can effectively utilize untreated leguminous seeds. Consequently, the amino acids that would typically be released by trypsin are not reabsorbed, leading to their loss when trypsin interacts with these inhibitors. These substances, which are proteinaceous in nature, hinder the activity of certain digestive enzymes, ultimately impairing the growth and performance of non-ruminant animals. High concentrations of protease inhibitors are found in various leguminous seeds, such as soybean, kidney bean and mung bean. There are two primary types of protease inhibitors: a) Kunitz inhibitors, which possess a single active site that binds exclusively to trypsin and b) Bowman-Birk inhibitors, which contain two active sites that can bind both trypsin and chymotrypsin, thereby inhibiting both enzymes. Detoxification: These protease inhibitors are primarily heat-sensitive and appropriate heat treatment of leguminous seeds-such as roasting, toasting, popping, autoclaving (at 120°C and 15 lbs psi for 20 minutes), and cooking-can effectively inactivate them. It is important to avoid overheating during these processes.