Influence of intrauterine infections and follicular development on the response to GnRH administration in postpartum dairy cows |
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| Authors: | Peter A I Bosu W I |
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| Affiliation: | 1. Department of Chemical Biology and Therapeutics, St. Jude Children''s Research Hospital, Memphis, TN 38105, USA;2. Department of Structural Biology, St. Jude Children''s Research Hospital, Memphis, TN 38105, USA;3. Department of Molecular Interaction Analysis Shared Resource, St. Jude Children''s Research Hospital, Memphis, TN 38105, USA;1. University of Londrina (UEL), Laboratory of Animal Reproduction, Londrina, PR, Brazil;2. São Paulo State University (UNESP), Institute of Biosciences, Department of Pharmacology, Botucatu, SP, Brazil;3. Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brazil;4. Center for Natural and Human Sciences, Federal University of ABC, Santo André, SP, Brazil;5. Department of Chemistry and Center for Analytical Instrumentation Development, Purdue University, United States |
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| Abstract: | The effects of intrauterine infections and prior follicular development on the response to gonadotropin releasing hormone (GnRH) administration in postpartum dairy cows were studied. Fifty lactating Holstein cows were assigned at random to one of two groups after calving. Group I (control) consisted of 25 cows given a single intramuscular injection of saline on Day 15 postpartum. Group II (treated) consisted of 25 herdmates given a single i.m. injection of 100 mug of GnRH on Day 15 postpartum. Palpation per rectum and real-time ultrasonography were used to monitor ovarian activity, and endometrial swabs were cultured to determine the presence of uterine infection. Blood samples were collected for progesterone (P(4)) and luteinizing hormone (LH) analysis. Fourteen cows (control, n = 5; treated, n = 9) did not ovulate during the first 60 d postpartum. Ovaries in these cows contained 4 to 8-mm size follicles and both P(4) and LH remained at basal concentrations. Fourteen other cows (control, n = 6; treated, n = 8) ovulated by Day 15 postpartum. Follicles >/= 10 mm were demonstrable in the ovaries of these cows before or by Day 12 postpartum. GnRH treatment had no effect on the lifespan of the existing corpus luteum in these cows. In the remaining cows, 7 of 14 Control and all 8 Treated cows ovulated within 3 d of treatment. All cows ovulating within this period were free of uterine infection and the ovaries contained follicles
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