Amino Acid Supplementation to Reduce Environmental Impacts of Broiler and Pig Production: A Review

Abstract

Poultry and swine farming are large contributors to environmental impacts, such as climate change, eutrophication, acidification, and air and water pollution. Feed production and manure management are identified as the main sources of these impacts. Reducing dietary crude protein levels is a nutritional strategy recognized to both decrease the use of high-impact feed ingredients and alter manure composition, reducing emissions of harmful components. For a successful implementation of this technique, feed-grade amino acid supplementation is crucial to maintaining animal performance. Reducing crude protein lowers nitrogen excretion, especially excess nitrogen excreted in urea or uric acid form, improving nitrogen efficiency. At the feed-gate, low–crude protein diets can reduce the carbon footprint of feed production through changes in raw material inclusion. The magnitude of this reduction mainly depends on the climate change impact of soybean meal and its land-use change on the feed-grade amino acids used. Reducing dietary crude protein also lowers the environmental impact of manure management in housing, storage, and at spreading: nitrogen emissions from manure (ammonia, nitrates, nitrous oxide) are reduced through reduction of nitrogen excretion. Moreover, synergetic effects exist with nitrogen form, water excretion, and manure pH, further reducing emissions. Volatilization of nitrogen is more reduced in poultry than in pigs, but emissions are more studied and better understood for pig slurry than poultry litter. Ammonia emissions are also more documented than other N-compounds. Low–crude protein diets supplemented with amino acids is a strategy reducing environmental impact at different stages of animal production, making life cycle assessment the best-suited tool to quantify reduction of environmental impacts. Recent studies report an efficient reduction of environmental impacts with low–crude protein diets. However, more standardization of limits and methods used is necessary to compare results. This review summarizes the current knowledge on mitigation of environmental impacts with low–crude protein diets supplemented with amino acids in poultry and swine, its quantification, and the biological mechanisms involved. A comparison between pigs and poultry is also included. It provides concrete information based on quantified research for decision making for the livestock industry and policy makers.

Influence of increasing glycine concentrations in reduced crude protein diets fed to broilers from 0 to 48 days

“…The many benefits of implementing reduced CP diets in broiler production have been reviewed extensively ( Powers and Angel, 2008 ; Greenhalgh et al, 2020 ; Cappelaere et al, 2021 ). The ongoing challenge in successfully reducing dietary CP has been to determine the nutrients that limit performance once CP reductions meet certain thresholds (as reviewed by Aftab et al, 2006 ).…”

Different amino acid supplementation patterns in low-protein diets on growth performance and nitrogen metabolism of goslings from 1 to 28 days of age

“…Nitrogen excretion is one of the primary sources of pollution in poultry production. Excessive fecal nitrogen excretion affects poultry's growth performance and health and contributes to air and water pollution ( Cappelaere et al, 2021 ). Many studies on low-protein diets of chickens ( Bezerra et al, 2016 ; Donato et al, 2016 ) and turkeys ( Applegate et al, 2008 ) have proved that low-protein diets supplemented with AA can effectively reduce nitrogen excretion.…”

β-Mannanase Supplementation as an Eco-Friendly Feed Strategy to Reduce the Environmental Impacts of Pig and Poultry Feeding Programs

“…However, the pig and poultry sectors share some similarities not only from an organizational point of view but also from an environmental one. Pig and poultry production systems have been pointed out as large contributors to environmental impacts, such as climate change, eutrophication, and acidification (3,27). Feeding both pigs and poultry requires tremendous amounts of feed resources, especially rich in protein and/or energy, with several studies indicating it as the most important source of environmental impact (2,4).…”