Influence of estrus synchronization regimen on fertility of beef cattle mated by artificial insemination or selected as embryo recipients

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references: p. 31-34.American breedtype cows were allotted to one of three hics. groups and one of five different estrus synchronization regimens in order to evaluate the effectiveness and subsequent fertility of each regimen. Cows, less than 56 days postpartum, were synchronized using one of two protocols. The GIAPG group received norgestomet implants (6mg) and an injection of GIIRH (100ug, i.m.; Cystorelin) on day 0 and an injection of prostaglandinF2[] (25 mg, i.m.) on day 7. The PG group received a single injection of prostaglandinF2[] (25 mg, i.m.) on day 7. The GIIRH treated group expressed estrus and developed luteal tissue in significantly higher percentages than the PG treated group. Pregnancy rates to embryo transfer were not different between groups (p< .05) at 90 days post transfer. Trial 2 involved the use of two hormonal regimens for the synchronization of estrus. Cows in the I+L group received a norgestomet implant (6mg) on day 0 and an injection of prostaglandin Fi (25mg) on day 9. Cows in the SMB (Synchro-mate B) group received a norgestomet implant (6mg) and an injection of SMB indictable solution (3mg norgestomet, 5mg estradiol valerate) on day 0 and implants were removed on day 9. The percentage of females expressing estrus and the percentage of females having developed luteal tissue by day 7 post-estrus was significantly higher for the SMB treated group. The conception rate to first service was not significantly different between groups. Trial 3 involved 3 synchronization protocols used in cows bred via artificial insemination. SMB treated cows received a norgestomet implant (6mg) and an injection of SMB injectable solution(3mg norgestomet, 5mg estradiol valerate) on day 0 and implants were removed on day 9. Cows in the l+L group a norgestomet implant (6mg) on day 0 and an injection of prostaglandin F2. (25mg) on day 9. Cows in the SMB+L group received a norgestomet implant (6mg) and an injection of SMB injectable solution(3mg norgestomet, 5mg estradiol valerate) on day 0 and an and an injection of prostaglandin F2. (25mg) on day 9. Females were inseminated 12 hours post-estrus. The percentage of females expressing estrus was not significantly different between groups. Pregnancy rates were significantly higher for SMB+L and I+L groups as compared to the SMB [FOIIP]. These data indicate that GnRH is effective at synchronizing estrus during the F2a in conjunction with a norgestomet implant was successful in increasing pregnancy rates to artificial insemination over the use of the norgestomet implant and estradiol valerate