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Calf removal improves conception rates to the Ovsynch and CO-Synch protocols
T W Geary1, J C Whittier, D M Hallford
1USDA-ARS, Fort Keogh, Miles City, MT 59301, USA. tgeary@larrl.ars.usda.gov
Journal of Animal Science
|February 24, 2001
Summary
Synchronization protocols for beef cows were evaluated, finding that the CO-Synch + calf removal method improved conception rates in both cyclic and anestrous cattle. This protocol offers efficient handling and high success for timed insemination.
Area of Science:
- Reproductive endocrinology and artificial insemination in cattle.
- Livestock management and breeding technologies.
Background:
- Effective ovulation synchronization is crucial for improving reproductive efficiency in beef cattle operations.
- Existing protocols like Ovsynch and CO-Synch aim to synchronize ovulation for timed artificial insemination (AI).
- The impact of calf removal on the efficacy of these protocols requires further investigation.
Purpose of the Study:
- To compare the efficacy of Ovsynch and CO-Synch ovulation synchronization protocols, with and without 48-hour calf removal, in beef cows.
- To evaluate the influence of estrous status (cyclic vs. anestrous) on conception rates within these protocols.
- To determine the optimal protocol for maximizing conception rates in beef cows undergoing timed AI.
Main Methods:
- Four hundred seventy-three beef cows were stratified and randomly assigned to Ovsynch or CO-Synch protocols, with or without 48-hour calf removal during days 7-9.
- Protocols involved GnRH and PGF2alpha administration at specific intervals, followed by timed AI.
- Serum progesterone was analyzed to determine estrous status (cyclic or anestrous) prior to treatment initiation.
Main Results:
- Overall conception rates were 63% for CO-Synch + calf removal, 61% for Ovsynch + calf removal, 54% for CO-Synch, and 52% for Ovsynch (P = 0.50).
- Conception rates were significantly higher in cyclic cows (66%) compared to anestrous cows (53%) (P = 0.01).
- Conception rates tended to be higher in cows with 48-hour calf removal (62%) versus those without (53%) (P = 0.09).
Conclusions:
- The CO-Synch protocol combined with 48-hour calf removal effectively synchronizes ovulation and induces fertile ovulations in both cyclic and anestrous beef cows.
- This protocol requires minimal handling (three times) and achieves high conception rates from timed insemination.
- The CO-Synch + calf removal strategy is a valuable tool for beef herd reproductive management and synchronization of ovulation.