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LHRH modulation of pituitary function and LH modulation of ovarian follicular growth during sexual maturation in beef cattle
Abstract
Three experiments were conducted to evaluate LHRH and LH modulation of pituitary and ovarian follicular growth in pre- and peripubertal beef cattle. From these experiments we hoped to further our understanding of the maturational events that precede puberty and the role of LH in ovarian follicle development during sexual maturation. Prepubertal Bos indicus bulls were utilized to evaluate pituitary and testicular function during and after treatment with the LHRH agonist deslorelin. The pituitary in these prepubertal bulls remained desensitized to LHRH for at least 20 days after cessation of treatment with a LHRH agonist. In contrast, desensitization did not occur at the testes which retained the capacity for a typical testosterone response to the LH that was released after administration of LHRH. In the second experiment, prepubertal Bos indicus heifers were used to determine pituitary function, ovarian follicle growth and plasma steroid concentrations during and after treatment with the LHRH agonist deslorelin. LHRH agonist treatment in prepubertal heifers was associated with an acute LH increase followed by a return of LH to concentrations similar to those of control heifers. Size of the largest ovarian follicle was greater in heifers treated with LHRH agonist and was associated with increased plasma concentrations of 17$\beta$-estradiol. After cessation of agonist treatment, the pituitary remained desensitized to LHRH for approximately 12 days. The third experiment utilized pre- and peripubertal Bos taurus heifers to determine the importance of LH in the control of ovarian follicular development and concentrations of ovarian steroids in follicles subsequent to treatments with exogenous LH, and the effect of stage of sexual maturity on response of ovarian follicles to exogenous LH. It was concluded that (1) steroidogenic capacity of follicles differs in pre- and peripubertal heifers and may depend upon changes in pattern of pulsatile release of LH as heifers approach puberty, and (2) treatment with LHRH antagonist influences the number of follicles in pre- and peripubertal heifers and this difference was independent of stage of maturation.
Subject Area
Anatomy & physiology|Animals|Livestock
Recommended Citation
Bergfeld, Ellen Geneva Marie, "LHRH modulation of pituitary function and LH modulation of ovarian follicular growth during sexual maturation in beef cattle" (1996). ETD collection for University of Nebraska-Lincoln. AAI9628223.
https://digitalcommons.unl.edu/dissertations/AAI9628223