Navara Kristen J, Pinson Sara E, Chary Parag, Taube Patrick C
Department of Poultry Science, University of Georgia, Athens, GA 30602 USA
Department of Poultry Science, University of Georgia, Athens, GA 30602 USA.
Poult Sci. 2015 Jun;94(6):1346-52. doi: 10.3382/ps/pev103. Epub 2015 Mar 31.
Maximal profit in both the commercial egg and meat industries requires that the quantity of oviposited eggs closely matches the quantity of large yellow follicles maturing in the ovary. While laying hens are genetically selected for maximal egg production and strategies for management of broiler breeders have been constructed to achieve a similar outcome, a percentage of ovarian follicles that are selected into the ovulatory hierarchy in these hens still never make it to oviposition possibly due to atresia of large yellow follicles or internal ovulation of the oocyte into the peritoneal cavity rather than the oviduct. The causes and mechanisms responsible for these processes remain unclear, however, evidence in wild birds suggests that stressful and/or territorial challenges may stimulate oocyte losses. Since testosterone and corticosterone are central to the responses to territorial intrusions and stress, respectively, and since both large yellow follicles and the oviduct that will engulf them are sensitive to hormonal cues, one or both hormones may play a role in the loss of large yellow follicles via atresia and/or internal ovulation in laying hens. To test this, broiler breeder hens were treated with corticosterone or testosterone 5 h prior to ovulation and observed to see whether these treatments influenced the likelihood that a hen would lay an egg 24 h after the predicted ovulation time. A subset of hens that did not lay an egg were killed and dissected to look for evidence of follicle atresia and internal ovulation. Testosterone treatment resulted in significantly more oocyte losses, and 60% of these occurred due to internal ovulations, as was indicated by the presence of yolk in the peritoneal cavity. Corticosterone did not influence the rate of oocyte losses, follicle atresia, or internal ovulation. These results suggest that testosterone can cause disruptions that ultimately prevent the oviduct from capturing the oocyte after ovulation.
在商业蛋鸡和肉鸡产业中，要实现利润最大化，就要求产出的鸡蛋数量与卵巢中成熟的大黄卵泡数量紧密匹配。虽然蛋鸡经过基因选育以实现最大产蛋量，并且已经制定了肉鸡育种管理策略以达到类似的结果，但这些母鸡中仍有一定比例被选入排卵层级的卵巢卵泡最终未能产出，这可能是由于大黄卵泡闭锁或卵母细胞在腹腔内而非输卵管内排卵。然而，这些过程的原因和机制仍不清楚，不过野生鸟类的证据表明，压力和/或领地挑战可能会刺激卵母细胞损失。由于睾酮和皮质酮分别是对领地入侵和压力反应的核心，而且大黄卵泡和将吞噬它们的输卵管都对激素信号敏感，所以一种或两种激素可能通过闭锁和/或内排卵在蛋鸡大黄卵泡损失中起作用。为了验证这一点，在排卵前5小时给肉鸡育种母鸡注射皮质酮或睾酮，并观察这些处理是否会影响母鸡在预测排卵时间后24小时产蛋的可能性。对一部分未产蛋的母鸡进行宰杀解剖，以寻找卵泡闭锁和内排卵的证据。睾酮处理导致显著更多的卵母细胞损失，其中60%是由于内排卵，腹腔内存在卵黄就表明了这一点。皮质酮对卵母细胞损失率、卵泡闭锁或内排卵没有影响。这些结果表明，睾酮会导致干扰，最终阻止输卵管在排卵后捕获卵母细胞。
