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。加拿大处理地球上一些最严重的极端温度，最近的报告估计它正在以全球速度的两倍变暖。最近的审查报告指出，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。肉鸡是加拿大粮食安全和经济的重要组成部分。家禽饲养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。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。本计画将透过三项研究，探讨从营养上减轻肉鸡热应激的最佳方法。第一部分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以影响生长。第二步是确定含硫氨基酸的精确形式和需求量。最后的研究将确定哪些饮食必需氨基酸的变化对生长和存活率的影响最大。从这些研究中，我们希望阐明具体的饮食建议下饲养的肉鸡热应激。这不仅会改善鸟类的福利，因为它们对热应激的抵抗力将得到改善，而且还将提高生产者在夏季的投资回报。将避免兽医干预的额外费用、不必要的死亡和营养素浪费。全面了解热应激肉鸡日粮中粗蛋白水平和必需氨基酸需求的影响，将允许精确配制日粮，以准确满足禽类的需求，而不会浪费资源。这通过限制使用通常从其他国家进口的昂贵高蛋白成分来降低饲料成本。此外，已知配制饮食以满足必需氨基酸的需要可减少作为环境污染物的氮排泄。

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.