Photoperiod Management in Farm Animal Husbandry: A Review

Abstract

This review aims to examine the effects of the photoperiod on farm animals and to provide insights into how lighting management can optimize production performance, reproduction, and welfare. The production performance of farm animals is influenced by a variety of factors, such as diet, breed, and environment. Among these, lighting is a crucial component of the feeding environment. With the advancement of intensive farming, lighting measures are increasingly receiving attention. The photoperiod regulates the biological rhythms of animals and affects the secretion of hormones within the animal's body, particularly melatonin. Melatonin regulates the secretion and release of several other hormones through various pathways, such as growth hormone, prolactin, and gonadotropins. Therefore, the environmental light cycle participates in a variety of physiological activities within animals. An appropriate photoperiod can enhance the production performance, reproduction performance, and welfare conditions of farm animals. Choosing the appropriate lighting duration based on different animals, physiological stages, and production purposes can enhance the economic benefits of farms. In this review, we summarized the recent findings on the impact of photoperiods in different farm animal feeding environments on animal husbandry, although research on the suitable photoperiod for some animals might be outdated and is also discussed in this article. For lactating dairy cows, calves, poultry, pigs (excluding boars), and rabbits, continuous light exposure exceeding 12 h per day can be implemented to enhance growth and production performance. In contrast, for boars and goats, daily light exposure should be limited to less than 10 h to optimize reproductive and productive efficiency. Overall, this review aimed to provide theoretical support for research on the optimal photoperiod for farm animals.

Keywords: animal welfare; circadian rhythm; feeding environment; hormone secretion; photoperiod.

Figure 1

Structure of the retina. There are two types of photoreceptor cells in the retina, rod cells and cone cells. Light signals are converted into biological signals by the retina.

Figure 2

Inhibitory effect of melatonin on prolactin. When the environment is dark, nerve impulses generated in the suprachiasmatic nucleus (SCN) act on the pineal gland to promote its secretion of melatonin (MEL). MEL has an inhibitory effect on the pituitary gland and reduces prolactin (PRL) secretion. When the environment is bright, MEL secretion decreases, the inhibitory effect on the pituitary gland decreases, and PRL secretion increases. The arrows in the figure indicate a reduction in PRL secretion, with “⊖” representing inhibition of the process and “⊕” representing promotion of the process.

Figure 3

Lighting affects the hypothalamic–pituitary–gonadal (HPG) axis. The conversion of light signals into biological signals stimulates the hypothalamus to secrete gonadotropin-releasing hormone (GnRH). GnRH stimulates the pituitary gland to secrete gonadotropins (Gn). Gn acts on the gonads (testes in males, ovaries in females), which secrete sex hormones. Sex hormones, in turn, inhibit the activity of the hypothalamus and hypophysis.