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

由于气候变化，热应激是全球家禽业日益关注的问题。加拿大是地球上温度极端程度最高的国家之一，最近的报告估计，加拿大的变暖速度是全球的两倍。最近的审查报告说，气候变化对粮食安全的影响是加拿大人的一个主要人类健康问题。肉鸡是加拿大食品安全和经济的重要组成部分。饲养家禽的温度受到严格管制，任何热应激或冷应激都会导致福利和产量下降。随着热应激，采食量减少，代谢率和途径改变，蛋白质来源的消化率受损。因此，热应激鸟类对必需氨基酸的实际膳食需求可能会因对应激的生理反应而改变，并且在很大程度上是未知的。本项目将通过三项研究，探索以营养方式缓解肉仔鸡热应激的最佳途径。第一项研究将研究能量的类型和水平如何与饮食中的蛋白质水平相互作用，从而影响生长。第二步将确定精确的硫氨基酸形式和需求。最后的研究将确定哪种饮食必需氨基酸的变化对生长和存活率的影响最大。通过这些研究，我们希望阐明在热应激条件下饲养的肉鸡的具体饲粮建议。这不仅会提高鸟类的福利，因为它们对热应激的抵抗力将会提高，而且还会提高夏季生产者的投资回报。将避免兽医干预的额外费用、不必要的死亡和营养浪费。深入了解热应激肉鸡饲粮中粗蛋白质水平和必需氨基酸需求的影响，将有助于在不浪费资源的情况下，精确地配制出满足肉鸡需求的饲粮。这就限制了从其他国家进口的昂贵的高蛋白成分的使用，从而降低了饲料的成本。此外，制定饲料以满足必需氨基酸的需求，已知可以减少氮作为环境污染物的排泄。

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.