Nutritional strategies for mitigating the negative effects of heat stress in broilers

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Heat stress is an increasing concern for the poultry industry worldwide due to climate change. Canada deals with some of the greatest temperature extremes on the planet and recent reports estimate it is warming at double the global rate. Recent reviews report climate change effects on food security as a major human health issue for Canadians. Broiler chickens make up a major part of Canadian food security and the economy. The temperatures at which poultry are reared are tightly regulated, with any heat or cold stress resulting in reduced welfare and production. With heat stress feed intake is reduced, metabolic rate and pathways altered, and digestibility of protein sources impaired. Therefore, the actual dietary requirements for essential amino acids of heat stressed birds are likely altered by the physiological response to the stress and are largely unknown. This project will investigate the best ways to nutritionally alleviate heat stress in broilers through three studies. The first will investigate how the type and level of energy interact with the protein levels in the diet to affect growth. The second will determine the precise sulfur amino acid form and requirement. The final study will determine which dietary essential amino acid changes have the largest effect on growth and survivability. From these studies, we expect to elucidate specific dietary recommendations for broiler chickens reared under heat stress. This will not only improve bird welfare, as their resistance to heat stress will be improved, but will also improve the return on investment for producers during the summer months. Additional costs of veterinary interventions, unnecessary mortalities, and wasted nutrients will be avoided. A thorough understanding of the effects of crude protein levels and essential amino acid requirements in the diets of heat stressed broilers will allow for precision in formulating diets to exactly meet the needs of the bird, without wasting resources. This reduces the cost of the feed by limiting the use of expensive high protein ingredients that are often imported from other countries. Additionally, formulating diets to meet the needs of essential amino acids is known to reduce nitrogen excretion as an environmental pollutant.