Sarabia Fragoso J, Pizarro Díaz M, Abad Moreno J C, Casanovas Infesta P, Rodriguez-Bertos A, Barger K
Cobb Española S.A., Alcalá de Henares, Madrid, Spain.
Reprod Domest Anim. 2013 Apr;48(2):345-52. doi: 10.1111/j.1439-0531.2012.02161.x. Epub 2012 Sep 10.
In a farm of grandparent broiler breeder chickens, we followed the development of 350 roosters from 6 to 55 weeks of age. Data collected and evaluated from these males included body weight, testicular weight, histologic and immunohistochemistry studies of the testes, hormone levels (testosterone, estradiol and corticosterone) and sperm production. The objective was to understand the factors that affect or influence hatch loss that is commonly observed after 45 weeks of age in breeder flocksare often correlated to broiler breeder male chickens. The results of this study showed that in conjunction with the weight of the rooster, the testicle weight increases quickly after the rooster receives light stimulation. At an older age, the study showed that there is a process of testicular shrinkage, and the same effect is seen in sperm production and testosterone levels in broiler breeder roosters. From the histology evaluation, we defined 5 histologic phases that illustrate the evolution of the testicular tissue: perinatal, infantile, puberty, adult and senile. We observed that the adult males with a body weight <3800 g were infertile or had subfertile levels and also had low levels of testosterone and high levels of corticosterone. In contrast, the heaviest males showed correct testicular vitality, high levels of testosterone and low levels of corticosterone. However, the roosters that had acquired this high body weight were also at risk of having less complete copulations because of their physical mass. The loss of uniformity of the males and the appearance of hierarchies within the flock accompany a decline in the percentages of hatches as a consequence of the poor confirmation of the males for copulation or the restriction to the access to the females. Results of this study show that the decrease in fertility from 45 weeks of age has been associated with a decline in testicular weight, sperm production and the testosterone levels in animals with a sub-par weight. Likewise, decreasing hatch in older flocks may also result from a loss of conformation, and the lack of complete copulations is possible because of animals that are grossly overweight.
在一个祖代肉种鸡养殖场，我们跟踪了350只公鸡从6周龄到55周龄的发育情况。从这些雄性鸡收集并评估的数据包括体重、睾丸重量、睾丸的组织学和免疫组织化学研究、激素水平（睾酮、雌二醇和皮质酮）以及精子生成情况。目的是了解影响或导致种鸡群45周龄后常见孵化损失的因素，这些因素通常与肉种鸡雄性有关。本研究结果表明，随着公鸡体重增加，公鸡接受光照刺激后睾丸重量迅速增加。在老龄阶段，研究表明存在睾丸萎缩过程，肉种鸡公鸡的精子生成和睾酮水平也有同样的变化。通过组织学评估，我们定义了5个组织学阶段来说明睾丸组织的演变：围产期、婴儿期、青春期、成年期和老年期。我们观察到体重<3800克的成年雄性不育或生育力低下，睾酮水平低而皮质酮水平高。相反，体重最重的雄性睾丸活力正常，睾酮水平高而皮质酮水平低。然而，体重达到这种高水平的公鸡由于体型原因也存在交配不完全的风险。由于雄性用于交配的能力差或接近雌性的机会受限，雄性均匀度的丧失和鸡群中等级制度的出现伴随着孵化率的下降。本研究结果表明，45周龄后生育力下降与体重不达标的动物睾丸重量、精子生成和睾酮水平下降有关。同样，老龄鸡群孵化率下降也可能是由于体型变化以及因严重超重导致交配不完全造成的。
