Effects of Active Immunization with Inhibin α Subunit on Reproductive Characteristics of Turkey Hens1

Abstract

The hypothesis for the present study is that the active immunization of female turkeys with inhibin (INH) would neutralize endogenous INH, and increase levels of circulating follicle stimulating hormone (FSH) and the number of preovulatory follicles, and subsequently enhance egg production. Two experiments were conducted with female turkeys in their first (30 wk of age) and second (62 wk of age) laying cycles. Treatment groups included control turkeys immunized with keyhole limpet hemocyanine (KLH) and experimental turkeys immunized with recombinant turkey inhibin alpha conjugated to KLH (rtINH), vasoactive intestinal peptide (VIP) conjugated to KLH or rtINH+VIP. Egg production increased (P < 0.05) in VIP and rtINH+VIP immunized birds, but not in rtINH immunized hens in comparison with a control group. A similar number of ovarian follicles, arranged in the follicular hierarchy of laying hens, was observed in all experimental groups. However, there was a larger number of nongraded yellow follicles in rtINH-immunized (62.5%) and rtINH+VIP-immunized (73.5%) groups compared with that of controls, suggesting overstimulation by FSH. Anterior pituitary FSH beta subunit, LH beta subunit, and prolactin (PRL) mRNA contents were determined by Northern blot analysis and reverse transcriptase-polymerase chain reaction (RT-PCR) in laying hens at the end of the experimental period. Hens immunized with rtINH showed increased FSH beta subunit mRNA content, but no change in the content of LH beta subunit or PRL mRNA. Hens immunized with VIP or rtINH+VIP had significant increases in both pituitary LH beta subunit and FSH beta subunit mRNA contents, accompanied by a decline in PRL mRNA abundance. The magnitude of the increase in FSH beta subunit to INH immunoneutralization was greater in first-cycle hens than in second-cycle hens. These data suggest that active immunization of female turkeys with INH neutralizes endogenous INH and increases both circulating FSH and the number of preovulatory follicles. However, no significant increase in egg production was observed in INH-immunized hens. The data confirm previous reports that VIP immunoneutralization increases egg production in turkey hens and shows for the first time that it also increases FSH beta subunit and LH beta subunit gene expression.

Identification of Dopamine, Gonadotrophin‐Releasing Hormone‐I, and Vasoactive Intestinal Peptide Neurones Activated by Electrical Stimulation to the Medial Preoptic Area of the Turkey Hypothalamus: A Potential Reproductive Neuroendocrine Circuit

“…To verify the specificity of the c‐fos probe used for in situ hybridisation experiments, Northern blot analysis was performed as described (33, 34) except using mRNA instead of total RNA. Briefly, bilateral ES/MPOA was performed on the laying hen brains.…”

The effect of parachlorophenylalanine treatment on the activity of gonadal and lactotrophic axes in native Polish crested chickens stimulated to broodiness

“…Active immunization against the VIP decreased PRL concentration in turkey hens during the first and second cycle of reproduction ( El Halawani et al., 2000 ) as well as in birds with heat-induced hyperprolactinemia ( Rozenboim et al., 2004 ). In the study by Ahn et al., (2001) , VIP immunoneutralization of turkey hens resulted in decreased PRL mRNA expression followed by increased pituitary LHβ and FSHβ mRNA expression. These findings are further supported by studies in broiler breeder hens showing changes in PRL mRNA expression ( Mobarkey et al., 2013 ) and in aging roosters as decreased VIP/PRL gene expression is associated with VIP immunoneutralization ( Avital-Cohen et al., 2015 ).…”

Expression of Vasoactive Intestinal Peptide Receptor Messenger RNA in the Hypothalamus and Pituitary Throughout the Turkey Reproductive Cycle1

“…Central infusion of VIP into laying turkeys lowers their circulating luteinizing hormone and terminates egg-laying activity [63]. VIP immunoneutralization upregulates pituitary LH-␤ and FSH-␤ subunit mRNA content and increases egg-laying activity [64,65]. Active immunization against VIP delays the onset of photorefractoriness and extends reproductive activity in starlings [66].…”