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Title: Effects of gonadotrophin-releasing hormone and bovine somatotrophin on hormone profiles and ovarian function in postpartum beef cows
Author: Pinto de Andrade, Luis Pedro Mota
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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Reproductive efficiency in beef cows is limited by the length of the postpartum anoestrous period which in turn is controlled by pituitary gonadotrophins and gonadal steroids and/or proteins. The first aim of this study was to elucidate the role of LH pulses in the development of ovarian activity in postpartum beef cows, specifically to determine whether or not the normal, relatively slow process of follicular development could be accelerated in cows in low body condition (BC) with pulses of gonadotrophin-releasing hormone (GnRH). The second aim was to determine the role of the metabolic hormones and in particular growth hormone (GH) in ovarian follicle development and function. Treatment of cows in low BC with pulsed intravenous infusions of 2μg every 2 hours from 5 to 7 weeks postpartum induced ovulation in 10 out of 12 cows. Saline infusions resulted in ovulation in only 1 of 12 cows in high BC and 1 of 11 cows in low BC groups. Plasma concentrations of GH, IGF-I and insulin were not affected by GnRH treatment, but cows in high BC had higher IGF-I and lower GH levels than cows in low BC. Gonadotrophin profiles, luteinizing hormone (LH) pulse frequency and LH pulse amplitude were not affected by either GnRH treatment or BC. Numbers of small (3-7.9 mm diameter) and large (≥ 8 mm diameter) follicles present at week 7 postpartum and numbers of LH receptors in theca and granulosa tissue were not affected by GnRH treatment or BC. The number of granulosa cells present in large follicles at week 7 postpartum was also unaffected. Intrafollicular concentrations of oestradiol, testosterone and IGF-I in large follicles at 7 weeks postpartum were not significantly affected by GnRH treatment or BC but there was a marked trend towards higher concentrations of oestradiol in cows in high BC compared with cows in low BC.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available