Induction of ovulation with gonadotropin-releasing hormone during proestrus in cattle: influence on subsequent follicular growth and luteal function |
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| Institution: | 1. Department of Clinical Veterinary Sciences, Saari Unit, University of Helsinki, Pohjoinen pikatie 800, FI-04920 Saarentaus, Finland;2. Department of Obstetrics and Gynaecology, Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden;1. Department of Surgical Oncology, Osaka City University Graduate School of Medicine, Osaka, Japan;2. Molecular Oncology and Therapeutics, Osaka City University Graduate School of Medicine, Osaka, Japan;3. Department of Diagnostic Pathology, Osaka City University Graduate School of Medicine, Osaka, Japan;1. Laboratory of Experimental Nutrition, Department of Nutrition and Dietetics, Nutrition College, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil;2. Medical College, Rio de Janeiro Feredal University – Campus UFRJ, Macaé, Rio de Janeiro, Brazil;1. UMR BDR, INRA, ENVA, Université Paris Saclay, 78350, Jouy en Josas, France;2. Unité de Biochimie Hormonale - Nutritionnelle, Centre Hospitalier Universitaire de Grenoble, Département de Biologie - Toxicologie - Pharmacologie, 38043 Grenoble cedex 9, France;1. Theriogenology Department, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt;2. Animal Reproduction and AI Department, Veterinary Division, National Research Centre, Giza, Egypt;1. Veterinary Reproduction Group, Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, University of Cordoba, 14071 Cordoba, Spain;2. Equine Reproduction Center, Centro de Selección y Reproducción Animal (CENSYRA-Extremadura Government), 06007 Badajoz, Spain;3. Department of Biology, Genetics Unit, Autonomous University of Madrid, 20849 Madrid, Spain;1. Division of Research and Development for Minimally Invasive Treatment, Cancer Center, Keio University, School of Medicine, Tokyo, Japan;2. Department of Pathology, Keio University, School of Medicine, Tokyo, Japan;3. Department of Surgery, Keio University, School of Medicine, Tokyo, Japan;4. Division of Diagnostic Pathology, Keio University, School of Medicine, Tokyo, Japan |
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| Abstract: | Induction of ovulation by administration of gonadotropin-releasing hormone (GnRH) is commonly practiced in cattle to treat repeat breeders or cows exhibiting long estrous periods. This treatment may, however, disturb normal reproductive functions if timing is incorrect. The objective of the present study was to investigate the effect of exogenous GnRH on estradiol secretion of the ovulatory follicle, occurrence of ovulation, development and function of the corpus luteum (CL) and growth of a dominant follicle after ovulation in the bovine, when GnRH treatment was given before the expected physiological LH-surge. Luteolysis was induced by cloprostenol (PG) in three cows and six heifers. Every animal was assigned once to each of the following treatment or control manipulations, receiving either a single dose (0.1 mg) of GnRH (gonadorelin) at (1) 24 h (T1), (2) 48 h (T2), or (3) 72 h (T3) after PG, or (4) no gonadorelin (control manipulation, C). Ovaries were scanned by ultrasound and blood samples were collected for progesterone (P4) and estradiol-17β (E-17β) determination. Growth curves of dominant follicles between treatment 1 and the control differed significantly (P<0.01). One day after ovulation, the diameter of the dominant follicle was almost 1 mm larger in T1. This difference remained almost unchanged during the entire follow-up period. The recruitment of a new follicular wave after ovulation seemed to occur earlier. Development of CL and levels and profiles of P4-production remained unaffected. When GnRH was given 1 day after PG injection, two animals showed significantly different development of CL (P<0.05) and of P4-production (both in concentrations P<0.05] and profile P<0.01]). After normal ovulation and CL development, luteolysis took place on days 5 or 6 after ovulation, and animals ovulated on days 9 and 10. It is suggested that early induction of ovulation with GnRH can cause shortened luteal function in cattle and, ultimately, reduced fertility. |
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