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

由于气候变化，全球家禽养殖业越来越担心热应激。加拿大正在应对地球上一些最极端的气温，最近的报告估计，加拿大变暖的速度是全球的两倍。最近的评论报告说，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控制，任何热或冷压力都会导致福利和产量下降。由于热应激，采食量减少，代谢率和代谢途径改变，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要量可能会因应激的生理反应而改变，而且在很大程度上是未知的。本项目将通过三项研究来研究从营养上缓解肉鸡热应激的最佳方法。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来影响生长。第二步将确定含硫氨基酸的精确形态和需要量。最终的研究将确定哪些饮食必需氨基酸的变化对生长和生存能力的影响最大。从这些研究中，我们希望阐明在热应激下饲养的肉鸡的具体饮食建议。这不仅将改善鸟类的福利，因为它们对热应激的抵抗力将得到提高，还将提高生产者在夏季几个月的投资回报。兽医干预的额外成本、不必要的死亡和浪费的营养将被避免。彻底了解热应激肉鸡日粮中粗蛋白质水平和必需氨基酸需求的影响，将有助于精确制定日粮，以完全满足禽类的需要，而不浪费资源。这通过限制使用通常从其他国家进口的昂贵的高蛋白成分来降低饲料成本。此外，众所周知，制定满足必需氨基酸需求的饮食可以减少作为环境污染物的氮的排泄。

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.