Effects of dietary nutrient levels on the emission of pollutants from pig manure

The continuous expansion of pig industry has triggered widespread concern regarding the emission of pollutants from pig excrement on farms. Air pollution, heavy metal (HM), and pathogens caused by pig production have become crucial issues that restrict the sustainable development of pig industry. This review summarizes the classifications and causes of pollutants in pig manure and discusses the effects of dietary nutritional levels, dietary types, and feed additives on the pollutants from pig manure. In summary, low-protein diets containing balanced amino acids can reduce fecal nitrogen content, while the precise supply of minerals can decrease HM emissions. Non-corn and non-soybean diets simultaneously reduce nitrogen and phosphorus emissions, and greenhouse gas production. In addition, functional additives such as probiotics, enzymes, plant extracts, and acidifiers can reduce antibiotic residues and malodor in manure through microbial metabolism, HM complexation, and improvement of gastrointestinal pH. In the future, it will be necessary to analyze the interaction network among nutrition, hosts and microorganisms. It will also be necessary to develop regional adaptation schemes for feed resources and establish a comprehensive evaluation system that links environmental benefits and breeding costs. This will encourage the industrial application of technologies that reduce emissions of fecal pollutants.