Birds use contact incubation to warm their eggs above ambient temperature required for embryonic development. In contrast, birds in the industry as well as many birds in breeding programs and scientific studies are incubated in conventional incubators that warm eggs via circulating warm air. This means that contact incubated eggs have different thermal properties than eggs incubated in a conventional incubator. In light of previous studies showing that small differences in incubation temperature can affect chicks post-hatching phenotype, we investigated the consequences of incubating Red jungle fowl eggs at the same temperature (37 °C) either via contact incubation or warm air incubation. We found that contact incubated chicks had a more robust body composition, were more explorative and had a higher temperature preference early in life, as well as a sex dependent difference in plasma Corticosterone levels pre-hatch (measured in down-feathers) and post-hatch (measured in plasma) compared to chicks incubated in a conventional warm air incubator. While previous studies have demonstrated that embryonic development and post-hatch phenotype is sensitive to small variations in temperature, our study demonstrates for the first time that the way heat is distributed to the egg has a similar magnitude of effect on post-hatch phenotype and highlights the sensitivity of the incubation period in shaping birds post-hatch phenotype.

鸟类使用接触孵化将它们的蛋加热到胚胎发育所需的环境温度以上。相比之下，行业中的鸟类以及育种计划和科学研究中的许多鸟类都在传统孵化器中孵化，该孵化器通过循环热空气加热鸡蛋。这意味着接触孵化的鸡蛋与在传统孵化器中孵化的鸡蛋具有不同的热特性。鉴于之前的研究表明孵化温度的微小差异会影响雏鸡孵化后的表型，我们研究了通过接触孵化或暖空气孵化在相同温度 (37 °C) 下孵化红原鸡的后果。我们发现接触孵化的雏鸡在生命早期具有更健壮的身体成分，更具探索性和更高的温度偏好，以及与在传统暖空气孵化器中孵化的小鸡相比，孵化前（在羽绒中测量）和孵化后（在血浆中测量）血浆皮质酮水平的性别依赖性差异。虽然之前的研究表明胚胎发育和孵化后表型对温度的微小变化很敏感，但我们的研究首次表明，热量分配给鸡蛋的方式对孵化后表型有相似的影响，并强调孵化期在塑造家禽孵化后表型中的敏感性。