Modern broilers have been selected for rapid growth but demonstrate reduced heat tolerance toward market age. As the poultry industry expands globally, strategies must be developed to support broiler performance in challenging climates. The objective of this study was to evaluate the effect of embryonic thermal manipulation (TM) and dietary fat source during the finisher period on broiler performance during acute heat stress (AHS) close to market age. The cyclic exposure to high temperatures during mid-incubation used in TM has been demonstrated to improve broiler tolerance to heat stress. However, high incubation temperatures can be detrimental to embryonic development and impair posthatch broiler performance. Embryos were exposed to 39.5°C for 12 h daily from incubation day 7 to 16 to assess the impact of TM on hatching and broiler performance. Dietary fat is commonly added to poultry diets during heat stress and it was theorized that differences in fat source may further impact bird performance. Finisher diets were supplemented with soya oil, poultry fat, or olive oil at 4.5% each. Broilers were exposed to a period of AHS at 43 d. Embryo mortality was increased, and hatchability was reduced by TM. Broiler performance was also decreased for the TM birds, but mortality during AHS was markedly reduced. Dietary fat source did not influence bird performance but was shown to interact with incubation treatment. Overall, the present data suggest optimal performance in modern broiler strains may be at odds with improved heat tolerance.

选择了现代肉鸡以使其快速生长，但显示出其对市场时代的耐热性降低。随着家禽业在全球范围内的发展，必须制定策略来支持在恶劣气候下的肉鸡生产。这项研究的目的是评估育肥期胚胎热处理（TM）和饮食脂肪源对急性热应激（AHS）肉鸡生产性能的影响。）接近市场年龄。在TM中使用的中温孵化过程中，周期性地暴露于高温可以提高肉鸡对热应激的耐受性。但是，较高的温育温度可能不利于胚胎发育并损害孵化后的肉鸡性能。从孵育第7天到第16天，每天将胚暴露于39.5°C，持续12 h，以评估TM对孵化和肉鸡生产性能的影响。日粮通常在热应激期间向家禽日粮中添加脂肪，据推测脂肪来源的差异可能会进一步影响禽类的生长。在精加工日粮中补充了豆油，家禽脂肪或橄榄油，每种含量为4.5％。肉鸡在第43天暴露于AHS时期。TM可以提高胚胎死亡率，并降低孵化率。TM鸡的肉鸡生产性能也下降了，但AHS期间的死亡率显着降低。饮食中的脂肪来源不影响禽类的生长，但与孵化过程相互作用。总的来说，目前的数据表明，现代肉鸡菌株的最佳性能可能与耐热性不符。