Buserelin overcomes the effect of the corpus luteum on ovarian follicular development in postpartum cycling cows |
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| Institution: | 1. Centre de Recherche en Biologie de la Reproduction, Département des Sciences Animales, Université Laval, Laval, Québec G1K 7P4, Canada;2. Agriculture and Agri-Food Canada Research Station Lennoxville, Québec J1M 1Z3, Canada;3. Agriculture and Agri-Food Canada Experimental Farm, Kapuskasing, Ont. P5N 2X9, Canada;4. Kapuskasing Veterinary Clinic, Kapuskasing, Ont. P5N 2T2, Canada;1. Department of Agrarian Production, Technical University of Madrid (UPM), 28040, Madrid, Spain;2. Department of Biological Science, Technical University of Loja (UTPL), 1101608, Loja, Ecuador;3. Department of Biochemistry and Molecular Biology, Veterinary Faculty, Complutense University of Madrid (UCM), 28040, Madrid, Spain;4. Department of Animal Reproduction, National Institute for Agriculture and Food Research and Technology (INIA-CSIC), Avda. Puerta de Hierro, 28040, Madrid, Spain;5. Department of Anatomy and Embryology, Veterinary Faculty, Complutense University of Madrid (UCM), 28040, Madrid, Spain;6. Department of Biomedical & Clinical Sciences (BKV), BKH/Obstetrics & Gynaecology, Faculty of Medicine and Health Sciences, Linköping University, SE-58185, Linköping, Sweden;7. Department of Biotechnology, National Institute for Agriculture and Food Research and Technology (INIA-CSIC), Cta de La Coruña Km 7,5, 28040, Madrid, Spain |
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| Abstract: | Follicular development after treatment with a gonadotropin-releasing hormone agonist (buserelin) was compared in ovaries of postpartum cows bearing (CLO) or not bearing (NCLO) a corpus luteum (CL). In the first experiment, 16 cows on day 7 of the estrous cycle (day 0 of treatment) were treated either with saline or 8 μg of buserelin. Both ovaries were collected on day 3 or day 6 (n = 4 per group per day) and follicles over 1.57 mm in diameter were observed histologically. Compared with day 3 in the saline group, there was a greater decrease in the percentage of Class I total (1.57–3.67 mm; P < 0.08) and Class 1 atretic follicles (P < 0.04) but a greater increase in that of Class 2 total (3.68–8.57 mm; P < 0.06), Class 2 atretic (P < 0.04) and early atretic (P < 0.05) follicles on day 6 in the CLO than in the NCLO. In the buserelin group however, all follicular responses (except for Classes 1 and 2 nonatretic follicles, P < 0.08) were similar (P > 0.1) between CLO and NCLO within 3 days after treatment. In the second experiment, follicular responses in CLO and NCLO were compared by daily ultrasonography in cows that had (n = 6) or did not have (n = 4) a buserelin-induced ovulation. After buserelin treatment, the numbers of medium (5–10 mm) and large (over 10 mm) follicles were not different (P > 0.1) between the CLO and the NCLO whether ovulation occurred or not. Results indicate that treatment with buserelin overcame most of the local effects of the CL on the growth and atresia of ovarian follicles in postpartum cycling cows within a 6 day period and this occurred whether ovulation was induced or not. |
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