光照节律调控鸡繁殖性能机制研究进展

光照是生物体重要的环境因子。现代家禽生产普遍采用人工光照。禽类视觉敏感,光照对禽类的生长发育和繁殖的影响直接关系到生产效率。光照是温度、湿度和通风因素之外的另一个重要的环境因子。此外,鸡作为一种重要的模式动物,光照对其繁殖生理的影响和相关作用机制研究也具有重要科学意义。文章就禽类对光照的感知,光照节律对鸡性成熟和繁殖的影响进行归纳总结,同时概述了非自然光照节律、光照不应性和种蛋孵化期光照技术的研究进展,为深入理解光照节律对鸡繁殖性能的影响及其调控机制提供理论参考。禽类的光感受器如眼球(视网膜)、丘脑深部和松果体,能够将光信号转变为生物信号,并依靠神经内分泌系统,尤其是下丘脑-垂体-性腺轴,影响鸡的生殖系统发育和繁殖行为。育成期鸡群性腺发育很快,并对光照时间长短反应敏感。光照时长过短或者过长,可能导致鸡只生长受阻或者性成熟提前;每天维持恒定8或9 h的光照时长,可保证体况和体重在性成熟时达标,充分发挥繁殖潜力。产蛋期光照节律主要包括光照刺激时间和光照时长。光照刺激能促进鸡性成熟,但必须在恰当的阶段实施才能有效发挥其促进适时和整齐开产的作用。对于黄羽种鸡光照刺激时间的研究鲜有报道,生产中多参照蛋鸡的光照方案,或适当推延。进入产蛋期的鸡群,光照节律则由恒定短光照转变为恒定长光照,光照时长的选择也是提高鸡繁殖力的关键控制点之一。母鸡产蛋期需要较长的光照时长以维持其高产,但肉种鸡与蛋鸡在体况、饲喂方式和生理特点等不同,如光照不应性等生理特征。因此,肉种鸡的光照时长短于蛋鸡或蛋种鸡,一般为14或15h,而蛋鸡或蛋种鸡为16或17h。种公鸡性早熟在实际生产中具有重要作用,随着精液稀释和存储,以及种公鸡隔代利用等技术的应用发展,种公鸡光照调控技术研究也逐步开展。种公鸡性成熟后采取与母鸡同样的光照时长可能会降低精液品质,提示在公母分饲的条件下有必要对公鸡和母鸡进行有区别的光照节律管理。与常规24h光照节律不同,非自然光照节律的光照制度可以提高蛋重,但可能降低产蛋数。非自然光照周期不符合欧盟规定动物福利标准,与饲养人员的正常作息时间不一致,在实际生产中并未广泛应用,但是研究非自然光照周期对了解家禽的生物节律具有一定的参考价值。

Research Progress on the Regulatory Mechanism of Lighting Schedule Affecting the Reproduction Performance of Chickens

Light is an important environmental factor for the organism. Artificial lighting has been widely utilized in modern poultry production. The poultry is light-sensitive. Light regulates their growth, production, and reproduction, and therefore affects the production efficiency. Light has now been another important environmental factor for poultry industry besides temperature, humidity, and ventilation. As a classical model animal, the studies of the effects of light on chicken reproductive physiology and the underlying mechanism would be of scientific significance. The photoreception of poultry and the effects of light schedule on chicken sexual maturity and reproduction were summarized in this review. The research progress on ahemeral lighting schedule, photorefractory, and light management during eggs incubation was also included. This review aimed at providing better understanding the effect of light schedule on poultry reproduction and the underlying mechanism. Perceiving the lighting by photoreceptors including eyes (retina), the deep brain tissue, and the pineal gland, the poultry transfers the lighting information to biological signals and affect the neuroendocrine system, especially the hypothalamic-pituitary-gonadal axis to affect the growth and reproduction. The gonad of birds develops rapidly and shows sensibility for the lighting length during rearing period. Lighting length of too short or long may impede the development or accelerate sexual maturity. The studies showed that a constant light of 8 or 9 h might assure the body condition and potential of reproduction performance. The lighting schedule parameters during the laying period of poultry includes photostimulation and lighting length. Photostimulation must be applied at a right age to assure the concurrent sexual maturity. Because of limited researches in yellow-feathered laying hens, most often they follow the photostimulation strategy of high-producing hens or with slight delay of photostimulation age. Lighting length is also critical for the reproduction performance. Laying hens (breeders) need long lighting period to keep productive during the laying period. There are, however, many differences between broiler breeders and layer hens (breeders), such as body condition, feeding and physiological characters, and photo factory. Broiler breeders are suggested to have shorter lighting length (14 or 15 h) than laying hens (breeders) (16 or 17 h). The advanced sexual maturity is meaningful for poultry industry. With the development of semen dilution and preservation, and alternate use of male breeders, more and more studies are focusing on the effects of light on the reproduction of male breeders. Housing the male breeder underling the same lighting length as females after sexual maturity may reduce semen quality. It is therefore necessary to provide different lighting schedule management for male and female if condition permits. Different from the normal 24-h lighting schedule, ahemeral lighting schedule can increase egg weight, but may lessen production. It is not widely used in practice due to European standards for animal welfare regulations and its inconsistency with the regular schedule of the employee. The study of ahemeral lighting schedule is, however, still important for understanding of the biorhythm of poultry.