Effects of Calcium, Available Phosphorus and Microbial Phytase on Ovarian FSHR and LHR Expression in Laying Hens

Folliculogenesis, steroidogenesis, ovulation, and vitellogenesis are regulated by the effect of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in the hypothalamus-pituitary-ovary axis and these hormones act via follicle stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) in the ovary. Poultry ration and food additives are essential in the regulation of reproductive activity. Phytase is a supplement frequently added to laying hen diets to increase phosphorus (P) utilization. The aim of this study was to reveal the effects of a newly isolated microbial phytase together with different concentrations of calcium (Ca2+) and available phosphorus (AP) on ovarian FSHR and LHR expressions. For this purpose, 90 Lohmann LSL-White layers were first divided into three main diet groups (standard Ca2+ and AP, standard Ca2+ and low AP, low Ca2+ and AP) and then into three subgroups (no-phytase, commercial phytase, and microbial phytase). At the end of the experiment, all chickens were slaughtered and ovarian tissues were fixed in formalin. Routine avidin-biotin complex immunohistochemistry was performed using anti-FSHR and anti-LHR primary antibodies. Immunohistochemically, FSHR and LHR were expressed in granulosa/theca cells, oocytes, interstitial cells, and vitellus. While the expression intensity of the receptors increased in the microbial phytase-treated groups, the strongest expression was obtained in the granulosa/theca cells and oocytes in the standard Ca and low AP group. In conclusion, we suggest that the addition of newly isolated microbial phytase to diets of laying hens and feeding standard Ca and low AP may have positive effects on reproductive performance by increasing the FSHR and LHR expression in ovaries.