Evaluation of response to super-ovulation, estrous synchronization and embryo transfer in local Zebu or crossbred dairy cattle

Abstract

An experiment was conducted at Holetta and Debre Zeit Agricultural Research Centers dairy herd in 2011 to evaluate the number of embryos collected per super-ovulated donor cow, estrus rate (ER) and pregnancy rate (PR) of recipient cows/heifers after embryo transfer. For super-ovulation treatment a total of 19 Holstein Friesian (HF) x Boran crossbred cows were selected as embryo donors and treated with super-ovulation hormones. For embryo recipient about 113 females of pure Boran and Holstein Friesian x Boran crossbred cows and heifers synchronized with estrous synchronization hormones. Out of 52 cows and heifers in estrous after estrous synchronization 34 of them used as embryo recipient out of which 23 females received fresh embryos and 11 frozen embryos. All data were analyzed using frequency distribution and Chi-square test. Results from super ovulation response indicated that out of 19 cows super-ovulated 15 (79%) cows responded to super-ovulation treatment. A total of 31 embryos collected out of which 23 embryos (77%) were transferable and the rest were not suitable for transfer. Mean number of embryo collected per donor was 2.07. Results from recipient estrous synchronization indicated that the overall recipient ER to estrous synchronization was 46% and significantly (P < 0.05) influenced by body condition score (BCS) while the effect of synchronization protocols, parity and breed were not significant. The overall recipient PR to embryo transfer was 20% and significantly influenced by BCS (P < 0.05). It can be concluded that the number of embryo obtained per super-ovulated donor in present study is low. Moreover recipient PR to embryo transfer was also very low. The poor PR of recipient females to embryo transfer could be attributed to high early embryonic mortality. Further research is required to investigate the possible cause of low number of embryo per donor cows and the poor PR of recipient females to embryo transfer.