Masters Theses

Date of Award

12-1982

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

H. Eiler

Committee Members

R.L. Murphee, M.H. Sims

Abstract

It has been demonstrated that a single LHRH injection will produce elevated LH levels in the hen and cockerel, and will induce premature ovulation in the laying hen (Furr et al., 1973a and Tanaka et al.., 1974). However, reports on the effects of continuous infusion of LHRH over a relatively long period in both the laying hen and the cockerel have not been found in the literature. The purpose of this research was to determine, by tritiated estradiol metabolism studies and histological evaluation of various reproductive tissues, and by observing the laying performance, the effect on the laying hen of a continuous infusion of LHRH over a six day period. A companion study was conducted in cockerels, consisting of tritiated testosterone uptake studies and histological evaluation of various endocrine organs, to determine whether LHRH acts directly on the pituitary or on the gonads themselves in the bird. Twenty-four 64 week old laying hens were intra-jugularly infused with either 857 or 429 yg synthetic LHRH using a subcutaneously implanted Alza (model 2ML1, 10 μl/hr infusion rate) osmotic pump. Egg production was recorded six days prior to and six days during the infusion period. Eighteen 12 week old cockerels were similarly infused with 214 μg synthetic LHRH. At the end of the six day period, one hour before death, hens and cockerels were intravenously injected with 10 μCi tritiated estradiol or 10 μCi tritiated testosterone, respectively. Immediately after death the hen oviduct, ovary, and pituitary were removed and weighed and either tritiated estradiol was extracted and counted or histological sections were prepared and evaluated. The testes, adrenals, ductus deferens, and pituitary were removed and weighed in cockerels, tritiated testosterone uptake was determined and histological sections were made of these organs. LHRH treated hens and sham hens exhibited decreased egg production and significantly decreased (P<0.05) whole ovarian weight without a reduction in stroma ovarian weight. Magnum function was severely reduced as shown by significantly (P<0.05) reduced tissue cross sectional area, increased ciliated and secretory cell number, and absence of luminal secretions. Circular tunica muscularis thickness and villi diameter were significantly reduced in the shell gland. The numbers of normal microscopic and atretic microscopic follicles per 100 μm2 and the size of these microscopic follicles were not significantly affected (P<0.05) by LHRH treatment. Pituitary alcian blue periodic acid-Schiff positive basophil cell number (gonadotrophs) per 1000x field was not significantly different between control and LHRH hens. LHRH treated cockerels exhibited significantly (P<0.05) reduced number of basophil cells per 1000x field, and significantly increased chromaffin cell number percentage as compared to control cockerels. There were no significant differences (P>0.05) observed in body, comb, pituitary, testis, or adrenal weights in LHRH treated cockerels as compared to controls. These results indicate that in the laying hen LHRH infusion could not overcome the effect of stress induced follicular and oviductal atrophy, and that probably the results observed were not due to an LHRH deficiency. Results of the study in cockerels indicate that LHRH may act directly at the level of the pituitary in the bird.

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