Systems Biology and Engineering Approach for Addressing Nitrogen Utilization Efficiency and Sustainability Issues Facing the World Swine Production

摘要

Major sustainable issues facing intensive pig production systems include i) rural social and economic sustainability; ii) resource and environment sustainability; and iii) human health management associated with an increasing consumption of pork products as a major red meat. Our integrative systems biology analysis suggests that the current intensive pig production systems have dramatically improved the scale and speed of converting feeds into pork with a much reduced fat content, i.e., producing lean pork, however, have a limited improvement in the efficiency of nitrogen (N) and energy utilization. Management strategies, including reduction in stress levels and good welfare in handling pigs, high health status and operation of small- to medium-scale of pig feeding units with straw bedding, solid manure handling systems and manure field application in the spring season, are recommended for capturing feed N and improving the overall N utilization efficiency and minimizing N losses into the environment between swine and crop production systems. Effective feed processing technologies need to be further developed to improve the digestive efficiency of amino acid (AA) N utilization in feed ingredients by pigs. The fecal gastrointestinal endogenous N loss is a significant component of the whole body metabolic N excretion contributed primarily by the high visceral organ protein synthetic activities. Several nutritional strategies, such as dietary supplementation of antibiotics, organic acids, herbs, bioactive peptides, prebiotics and probiotics, have been developed to improve gut health and minimize the fecal metabolic endogenous N excretion. The largest single N excretion in pigs is the urinary N excreted largely in the form of urea from in vivo AA catabolism. Formulating low-crude protein (CP) swine diets by using crystalline limiting essential AA on the basis of true ileal digestible AA supply according to the ideal protein concept can reduce manure N excretion for up to about 28%. Novel microbial genomic enzyme engineering biotechnologies via producing exogenous supplemental enzymes or other bioactive peptide compounds and developing transgenic pigs can help improve efficiency of digestive utilization of N in feed ingredients for swine. A relatively low skeletal muscle protein synthetic activity in coupling with an active protein degradation rate in the post-weaned pig is the major metabolic reason of poor efficiency of N and energy utilization associated with the swine production. Muscle metabolic modifiers such as recombinant porcine growth hormone and the β-agonist ractopamine Paylean have been approved to use in swine production in some countries for improving lean growth and efficiency of N utilization. Animal biotechnologies such as down-regulating the negative muscle growth regulators myostatin and tuberous sclerosis complex (TSC) as well as modulating essential AA carbolic pathways by transgenic approach will greatly improve efficiency of N utilization in swine production in the long run. Finally, increased consumption of red meats including pork is associated with increased risks of developing fatal chronic diseases such as obesity, cardiovascular disease, type-II diabetes, chronic inflammatory bowel diseases and colorectal cancer. Efforts made by using pigs as a relevant animal model for studying basic biology of these health issues will contribute to the understanding of biological mechanisms of these disease development and help maintain the health benefits of pork consumption and swine production on the global scale. Therefore, systems biology and engineering approach, integrating strategic planning, resource management, nutrition, the application of biotechnologies, and the study of basic biology of interactions among diets, nutrition and human health with the pig as a valid model, will help address the major sustainability issues facing the world swine production.