Effect of Photoperiod on the Egg Production, Plasma Luteinizing Hormone, Follicle-Stimulating Hormone, Gonadal Hormones, and Mrna Levels of Lh and Fsh in the Hypothalamic-Pituitary-Gonadal Axis of Pigeons

Abstract

We investigated the egg production, changes in luteinizing hormone (LH), follicle-stimulating hormone (FSH), gonadal hormones, and their mRNA levels in the hypothalamic-pituitary-gonadal axis of White King pigeons submitted to different photoperiods. The treatments consisted of three photoperiods (8 h light (L):16 h dark (D), 12L:12D, and 16L:8D), with three replicates of twelve pairs of adult pigeons. The birds were exposed the photoperiods for 45 days. Egg production performance was recorded daily. Six pigeon pairs per replicate were selected for plasma collection, and six pigeon pairs per replicate for the resection of the hypothalamic-pituitary-gonadal (HPG) axis. Egg production was significantly improved by long-day lighting (16L:8D), while no differences in egg shape index were detected. Higher average egg weight was obtained in 16L:8D group, whereas broken egg percentage was higher in the 8L:16D group. Female LH level was significantly higher in long-day lighting, and the FSH level significantly lower in short-day lighting. The females in the 16L:8D group had higher estrogen level. The photoperiods had a minor effect on plasma LH and testosterone in males, whereas the FSH level was significantly higher in the 16L:8D group. The level of LH mRNA expression was higher in both females and males of the 16L:8D group. Similar trends in FSH mRNA expression observed in both females and males. The 16L:8D photoperiod not only improved egg production, but also stimulated plasma LH, FSH, gonadal hormones, and promoted LH and FSH mRNA expression in pigeons.