Comparative Changes in the Serum Concentrations of Inhibin-B, Prolactin, Gonadotropins and Steroid Hormones at Different Reproductive States in Domestic Turkey Hens

Abstract

Abstract. The present study was undertaken to compare the changes in circulating levels of inhibin-B, prolactin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol-17β, progesterone and testosterone during the different reproductive states of turkey hens. Blood samples were collected during different reproductive states, at laying, incubating and out of lay. Inhibin-B was measured by ELISA, while other hormones were determined by Chemiluminescent Microparticle Immunoassay (CMIA). The results revealed highly significant differences among the hen's states for all serum hormone concentrations. The highest levels of inhibin-B and prolactin were observed in incubating hens, while the lowest values were observed in laying hens. In contrast, the highest levels of FSH, LH, estradiol-17β, progesterone and testosterone were found in the laying group, while the lowest values were found in the incubating group. The progesterone level was higher in the laying group compared with the other groups. These results clearly demonstrate that negative correlation was found between both the inhibin-B and prolactin levels and the gonadotropin and steroid hormone concentrations during the different reproductive states of the turkey hens. In addition, the results suggest that inhibin-B may be involved in control of FSH and LH secretion. . The existence of bioactive inhibin in testis preparations [3,4] and ovarian granulosa cells [5,6] has been reported. The effect of induction of ovarian regression and removal of ovarian follicles on plasma inhibin indicate that the ovary is the major source of inhibin in the hen [7,8]. Prolactin secretion from the avian anterior pituitary gland is principally maintained by tonic stimulation from hypothalamic prolactinreleasing factors [9]. Prolactin secretion markedly changes during the reproductive cycle of the turkey hen. The hyperprolactinemia associated with incubation behavior (broodiness) induces ovarian regression, resulting in a substantial loss of egg production in commercial breeder flocks [10]. Administration of exogenous prolactin suppresses plasma gonadotropins necessary for egg production in domestic fowl [11]. However, there is additional evidence that suppression of gonadotropin secretion in incubating birds also involves a mechanism independent of increased prolactin secretion [12,13]. In turkey hens, the changes in the concentrations of inhibin-B, prolactin, gonadotropins and progesterone have been poorly documented. Therefore, in the present study, we investigated the changes in inhibin-B, prolactin, FSH, luteinizing hormone (LH), estradiol-17β, progesterone and testosterone hormones during the different reproductive states. Materials and Methods Animals and experimental designDomestic turkey hens (local Egyptian strain) were used in the present study. The turkeys were in the first year of production. The hens received a stimulatory photoperiod of 14 h of light:10 h of dark throughout the experimental period and were maintained in floor pens with trap nests. They...

Age-related changes of yolk precursor formation in the liver of laying hens

“…In the oviparous vertebrates, VTGII and ApoB are synthesized by the liver in response to estrogens (Verderame and Limatola, 2010;Hess et al, 2011;Yilmaz et al, 2015). Our results showed that the serum E 2 level of D280 hens was significantly higher than that in hens at other stages, and these findings are in line with a previous report that in the domestic Turkey hens the serum E 2 level during the laying period was higher than that in incubating or out-of-lay hens (Khalil et al, 2009). These data also concur with a previous report that the plasma E 2 level in 17-weekold hens was higher than that in 13-week-old hens (Reddy et al, 2002).…”