Fixed-time insemination in peripuberal, lightweight replacement beef heifers after estrus synchronization with PGF2alpha and GnRH
| Autor: | C. M. Zehnder, Graham Cliff Lamb, L. R. Miller, Carl R Dahlen, Alfredo DiCostanzo |
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| Rok vydání: | 2003 |
| Předmět: |
Male
Ovulation endocrine system Time Factors animal structures animal diseases media_common.quotation_subject medicine.medical_treatment Ice calving Biology Dinoprost Insemination Gonadotropin-Releasing Hormone Animal science Food Animals Pregnancy medicine Animals Sexual Maturation Small Animals Insemination Artificial media_common Estrous cycle Equine Artificial insemination Body Weight medicine.disease Breed Estrus Detection Female Animal Science and Zoology Estrus Synchronization |
| Zdroj: | Theriogenology. 59:1827-1837 |
| ISSN: | 0093-691X |
| Popis: | Estrus synchronization contributes to optimizing the use of time, labor, and financial resources by shortening the calving season, in addition to increasing the uniformity of the calf crop. We determined whether acceptable pregnancy rates could be achieved after synchronization of ovulation and fixed-time artificial insemination (AI) in peripuberal replacement beef heifers using gonadotropin-releasing hormone (GnRH) and PGF2alpha. Crossbred heifers from two herds (MH, n=239; SS, n=330) were wintered at a single location. After a prebreeding examination revealed that 55 heifers had a reproductive tract score (RTS) of 1 (infantile reproductive tracts), they were culled and the remaining heifers were assigned randomly to one of three treatment groups: administration of 25mg PGF2alpha i.m. on Days -12 and 0 followed by estrus detection and insemination between 10 and 14 h after an observed estrus (Control; n=173); administration of 100 microg GnRH i.m. on Day -6, followed by 25 mg PGF2alpha i.m. on Day 0, then fixed-time AI and administration of 100 microg GnRH i.m. on Day +2 (GPG; n=172); and, treatment as for group GPG in addition to administration of 100 microg GnRH i.m. on Day -12 (GGPG; n=169). Bulls were introduced 10 days after AI for 60 days to breed heifers which did not conceive after AI (clean-up bulls). On Days -12, -6, and 0 transrectal ultrasonography was used to monitor ovarian structures in a subset of heifers (30 per treatment). At 30-35 days after AI, ultrasound was used to determine the presence of a viable fetus. Presence of a fetus and stage of pregnancy were determined via palpation per rectum 61-63 days after the conclusion of the breeding season. Heifers in the MH herd (309+/-1.9 kg) were heavier (P |
| Databáze: | OpenAIRE |
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