Effect of Feed Restriction and Photoperiod on Reproduction and LEPR, MELR mRNA Expression of Layers
ABSTRACT Photoperiod and nutrition are major factors that affect the reproductive efficiency particularly in female animals. In this study we examined the interaction of photoperiod and food restriction on growth, sexual maturation and receptor mRNA expressions of leptin, melatonin, and estrogen in abdominal fat and the ovary of pullets. There were no interaction effects between photoperiod and feeding level on body weight, abdominal fat weight, ovary weight at both 14 wk and 18 wk. Abdominal fat weight of feed restriction group was significantly lower compared with the control group at the age of 14 wk, 18 wk, and age of the first egg (AFE) (p<0.05). Ovary LEPR (Leptin receptor) gene expression showed an interaction effect of the first egg. Restricted feeding significantly inhibited ovary ER (Estrogen receptor), LEPR and MELR1B (Melatonin 1B receptor) gene expression at 14 wk, 18 wk and the first egg. At 14-week-old, abdominal fat LEPR gene expression was significantly lower in long photoperiod group compared with the short photoperiod group. At the first egg, short photoperiod and feed restriction group reduced abdominal fat LEPR gene expression. The results indicated that the reproductive activity of pullets is sensitive to feed intake and photoperiod. Feed restriction down regulated the ER, LEPR, MELR1A (Melatonin 1A receptor) and MELR1B mRNA expression of the ovary at 14 wk, 18wk and AFE. Long photoperiod enhanced the LEPR, MELR1A and MELR1B mRNA expression of abdominal fat at AFE.