Effect of interval between induction of ovulation and artificial insemination (AI) and supplemental progesterone for resynchronization on fertility of dairy cows subjected to a 5-d timed AI program
| Autor: | José E. P. Santos, M. G. Favoreto, William W. Thatcher, R.S. Marsola, L.F. Greco, Rafael Bisinotto, Eduardo S. Ribeiro, Carlos A. Risco, L.T. Martins |
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| Rok vydání: | 2010 |
| Předmět: |
medicine.medical_specialty
Time Factors Pregnancy Tests media_common.quotation_subject medicine.medical_treatment Insemination Andrology Gonadotropin-Releasing Hormone Ovulation Induction Pregnancy Internal medicine Blood plasma Genetics medicine Animals Ovulation Dairy cattle Insemination Artificial Progesterone media_common Estrous cycle business.industry Artificial insemination Fertility Agents Female medicine.disease Endocrinology Fertility Animal Science and Zoology Cattle Female Reproduction business Estrus Synchronization Food Science Program Evaluation |
| Zdroj: | Journal of dairy science. 93(12) |
| ISSN: | 1525-3198 |
| Popis: | Objectives were to investigate 2 intervals from induction of ovulation to artificial insemination (AI) and the effect of supplemental progesterone for resynchronization on fertility of lactating dairy cows subjected to a 5-d timed AI program. In experiment 1, 1,227 Holstein cows had their estrous cycles presynchronized with 2 injections of PGF(2α) at 46 and 60 d in milk (DIM). The timed AI protocols were initiated with GnRH at 72 DIM, followed by 2 injections of PGF(2α) at 77 and 78 DIM and a second injection of GnRH at either 56 (OVS56) or 72h (COS72) after the first PGF(2α) of the timed AI protocols. All cows were time-inseminated at 72h after the first PGF(2α) injection. Pregnancy was diagnosed on d 32 and 60 after AI. In experiment 2, 675 nonpregnant Holstein cows had their estrous cycles resynchronized starting at 34 d after the first AI. Cows received the OVS56 with (RCIDR) or without (RCON) supplemental progesterone, as an intravaginal insert, from the first GnRH to the first PGF(2α). Pregnancy diagnoses were performed on d 32 and 60 after AI. During experiment 2, subsets of cows had their ovaries scanned by ultrasonography at the first GnRH, the first PGF(2α), and second GnRH injections of the protocol. Blood was sampled on the day of AI and 7 d later, and concentrations of progesterone were determined in plasma. Cows were considered to have a synchronized ovulation if they had progesterone1 and2.26 ng/mL on the day of AI and 7 d later, respectively, and if no ovulation was detected between the first PGF(2α) and second GnRH injections during resynchronization. In experiment 1, the proportion of cows detected in estrus at AI was greater for COS72 than OVS56 (40.6 vs. 32.4%). Pregnancy per AI (P/AI) did not differ between OVS56 (46.4%) and COS72 (45.5%). In experiment 2, cows supplemented with progesterone had greater P/AI compared with unsupplemented cows (51.3 vs. 43.1%). Premature ovulation tended to be greater for RCON than RCIDR cows (7.5 vs. 3.6%), although synchronization of the estrous cycle after timed AI was similar between treatments. Timing of induction of ovulation with GnRH relative to insemination did not affect P/AI of dairy cows enrolled in a 5-d timed AI program. Furthermore, during resynchronization starting on d 34 after the first AI, supplementation with progesterone improved P/AI in cows subjected to the 5-d timed AI protocol. |
| Databáze: | OpenAIRE |
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