Comparison Of Cidr Based Protocols To Synchronize Estrus In Beef Heifers
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Comparison of CIDR-based Protocols to Synchronize Estrus in Beef Heifers
Estrus synchronization and artificial insemination (AI) are reproductive management techniques that allow beef producers to enhance the reproductive efficiency and genetic composition of their cow herd. However, U.S. beef producers have been reluctant to adopt these reproductive management tools, largely due to time and labor. Recent research to synchronize estrus, therefore, has focused on the development of estrus synchronization protocols that facilitate fixed-time AI (FTAI). Although protocols have been developed that allow the successful use of FTAI in beef cows, the same degree of success in beef heifers has not been realized. Additionally, no published research has focused on characterizing the physiological responses to long- and short-term CIDR-based protocols in beef heifers. Experiment 1 evaluated ovulatory response to GnRH and synchrony of estrus and ovulation after PGF2[alpha] (PG) in beef heifers. The CIDR Select and Select Synch + CIDR protocols were evaluated among estrous cycling and prepubertal beef heifers and the CIDR-PG and Select Synch protocols were evaluated among estrous cycling beef heifers. A reduced variance for the intervals to estrus and ovulation was detected for estrous cycling heifers treated with the CIDR Select protocol in comparison to the other 3 treatments. The combined results of the estrous cycling and prepubertal heifers revealed an increased ovulatory response to GnRH for heifers treated with the CIDR Select protocol compared to the Select Synch + CIDR protocol, which ultimately resulted in a reduced variance for interval to estrus and ovulation after PG. Furthermore, no differences within treatment were detected in the variance for interval to estrus or ovulation among estrous cycling and prepubertal heifers treated with the CIDR Select protocol. These results suggest that the CIDR Select protocol may facilitate FTAI more effectively in mixed groups of estrous cycling and prepubertal beef heifers. Experiments 2 and 3 evaluated modifications to the CIDR Select protocol. Estrous cycling beef heifers were used in Exp. 2. The hypothesis tested was that reducing the interval from CIDR removal to GnRH administration by 2 d would facilitate an improvement in the synchrony of estrus after PG. Although a larger number of heifers that were assigned to the 28 d protocol were on d 5 and 6 at the time GnRH was administered, response to GnRH was not improved and synchrony of estrus was not enhanced following PG. In Exp. 3, a second modification to the CIDR Select protocol was evaluated using estrous cycling and prepubertal beef heifers. The hypotheses tested were: 1) reducing the interval from CIDR removal to GnRH may facilitate an improvement in the synchrony of estrus after PG, and 2) the addition of GnRH following CIDR removal is required to improve the synchrony of estrus after PG. Although no difference in estrous response was detected, mean intervals to estrus and variance for interval to estrus differed based on the interaction of treatment length, GnRH, and estrous cyclicity status. The results from Exp. 3 clearly suggest that further evaluation of long-term CIDR-based protocols is required.
Beef Heifer Development, An Issue of Veterinary Clinics: Food Animal Practice
Author: David J Patterson
language: en
Publisher: Elsevier Health Sciences
Release Date: 2013-12-28
The latest information on heifer development in beef cattle for the food animal practitioner! Topics include rebuilding the US cowherd, physiology and endocrinology of puberty, nutritional development and the target weight debate, long-term reproductive health, effect of prenatal programming on development, economics of development, synchronization of estrus and ovulation, post breeding heifer management, management strategies for adding value to heifers, and more!
Comparison of Long-term Progestin-based Protocols to Synchronize Estrus in Beef Heifers
Experiment 1 evaluated two long-term progestin-based and controlled internal drug release estrus synchronization protocols to determine their potential to facilitate fixed-time artificial insemination in estrous cycling and prepubertal beef heifers. Conception to AI, AI pregnancy, and final pregnancy rates did not differ between treatments. Experiment 2 compared two long-term progestin-based estrus synchronization protocols to evaluate their potential to facilitate fixed-time artificial insemination in estrous cycling and prepubertal beef heifers. Estrous response after PG was greater among CIDR treated heifers compared to MGA treated heifers. Conception to AI, AI pregnancy, and final pregnancy rates did not differ between treatments. In summary, the long-term CIDR protocol compared favorably with the MGA protocol. Experiment 3 was conducted to compare pregnancy rates resulting from fixed-time AI after administration of either one of two long-term CIDR-based protocols. CIDR-GnRH-PG and CIDR-PG treated heifers were fixed-time inseminated at 72 or 66 hr after PG, respectively. Fixed-time AI pregnancy rates tended to be higher among CIDR-PG compared to CIDR-GnRH-PG treated heifers. Final pregnancy rates did not differ between treatments. In summary, both long-term progestin-based protocols were effective in synchronizing estrus prior to fixed-time AI in beef heifers.