Effects of photoperiod on performance, ovarian morphology, reproductive hormone level, and hormone receptor mRNA expression in laying ducks

Abstract

We investigated the effect of photoperiod on performance, ovarian morphology, reproductive hormones levels, and their receptors mRNA expressions in laying ducks. After adaption, 300 252-day-old Jinding laying ducks were randomly allocated to 5 groups, receiving 12L:12D, 14L:10D, 16L:8D, 18L:6D, or 20L:4D, respectively. Each treatment had 6 replicates of 10 birds each. The feeding trial lasted 8 wk. Egg production, egg mass, and ADFI increased linearly and quadratically with increasing photoperiods ( P < 0.05), and the higher values of them occurred in photoperiods ≥ 16 h, compared with 12L:12D ( P > 0.05). Initial and bare stroma weight increased quadratically, while total large white follicle ( LWF ) number and weight increased linearly and quadratically, with increasing photoperiods ( P < 0.05). The higher values of them occurred in 16L:8D and 18L:6D treatments as well as the higher total LWF weight also occurred in 20L:4D, compared with 12L:12D ( P > 0.05). Besides, 16.93 and 16.93 h were the optimal photoperiods for bare stroma (follicles ≥ 2 mm in diameter removed) weight and total LWF weight, respectively, calculated from reliable regression equations ( R 2 ≥ 0.5071). Compared with 12L:12D, the higher levels of estradiol, progesterone, follicle-stimulating hormone ( FSH ) as well as the higher expressions of estrogen, luteinizing hormone ( LH ) and progesterone receptors were observed in ≥16 h photoperiods ( P < 0.05), while the higher LH level and FSH receptor expression only occurred in 16L:8D and 18L:6D ( P < 0.05). In the hypothalamus, higher mRNA expression of gonadotropin-releasing hormone occurred in 16L:8D and 18L:6D groups ( P < 0.05). Meanwhile, gonadotropin-inhibitory hormone and prolactin increased in 20-hour photoperiod ( P < 0.05), and the latter may be due to theup-regulation of vasoactive intestinal peptide expression ( P < 0.05). To sum up, an appropriate photoperiod could improve the performance and reproductive organ and ovarian follicles development through reproductive hormones and their receptors, and 16.56 to 10.93 h is an adequate photoperiod for laying ducks.

Effect of Changes in Photoperiods on Melatonin Expression and Gut Health Parameters in Laying Ducks

“…The level of melatonin increased with increasing photoperiods from 12 to 20 h at 0:00 and decreased at 6:00 and 12:00 in this research, and 16 h may be a moderate photoperiod for melatonin synthesis and secretion. Besides, melatonin was supposed to stimulate the release of the gonadotropin-inhibitory hormone by the avian hypothalamus (Chowdhury et al, 2010), which was coincident with our previous report (Cui et al, 2021a).…”

“…In that study, the gonadotropin-inhibitory hormone increased from 12 to 20 h photoperiods (sample collection between 11:00 and 12:00), while melatonin levels decreased from 12 to 20 h photoperiods at 12:00 in this study. The changes of the gonadotropin-inhibitory hormone as well as other reproductive hormones in response to different photoperiods (Cui et al, 2021a) also indicated that the changes of melatonin in response to different photoperiods in the current study could be reliable. As is known to all, melatonin was supposed to be the most important hormone in the circadian rhythm regulation of birds (Berra and Rizzo, 2009).…”

“…A total of 180 Jinding laying ducks (252 days old) were randomly allocated into three treatments with a corn–soybean meal diet for 58 days ( Cui et al, 2021a ). Each group had six replicates with 10 ducks per replicate.…”

Effect of photoperiod on eggshell quality and quality characteristics of tibia, femur, and ulna in laying ducks

“…Photoperiod serves as a vital environmental factor in poultry production, which has biological and physiological significance through regulating circadian rhythms, and changing the time for rest or regeneration ( Malleau et al., 2007 ). The potential benefits of photoperiod on laying ducks have been extensively reported, such as promoting bone and reproductive system development during the pullet phase ( Cui et al., 2019a , b ), and improving productive performance and reproductive function during the laying phase ( Cui et al., 2021 ). Besides, different photoperiods can affect the manner and percentage of raw materials supply for eggshell formation ( Miller, 1992 ).…”

“…Then, we started our formal experiment. A total of 300 Jinding laying ducks (252-day-old) were randomly divided into 5 treatments with a corn-soybean meal diet ( Cui et al., 2021 ) for 8 wks. Each group contained 6 replicates with 10 ducks per replicate.…”