Prof. Alemayehu Lemma, Dr. Tamrat DegefaHamid, Jemal2022-05-032023-11-302022-05-032023-11-302021-08http://etd.aau.edu.et/handle/123456789/31552The difference in dairy breed type can determine the success of bovine embryo transfer by influencing the quantity and quality of embryos during in vivo embryo production. This is particularly true since response to the superovulatory hormone treatments varies because of breed and doses of the hormone. In this study, the quantity and quality of embryos were evaluated for Boran and HF*Boran (50% and 75% cross breed) dairy cows alternatively using semen from HF and Boran sires. Total of 42 HF*Boran and HF cows were used to study superovulatory response, 33 HF*Boran cows for evaluation of estrus behavior and 36 HF*Boran and Boran dairy cows for evaluation of embryo quality as three separate experiments. In experiment one, three different dosages of Pluset® (FSH hormone) (500 IU, 650 IU and 800 IU) were evaluated for their best response. In experiment two, types and strength of estrus behaviors were characterized as predictor of superovulatory responses. In experiment three, the donor dams and sires were alternatively used from different breeds to evaluate breed effect on qualities of embryos flushed on Day-7 post AI. In experiment one, the superovulatory response rate was significantly higher (P<0.05) in the HF*Boran than HF cows. The mean ± (SE) highest response based on CL count was 14.6 ± 1.1 and the lowest 11.0 ± 1.3, in HF*Boran, at Pluset® dose of 650 IU and 500 IU, respectively. In experiment two, the overall average time required for commencing estrus signs after CIDR removal was 37.4 ± 1.5 hrs and the duration of estrus was 28.5 ± 1.2 hrs. Behavioral estrus was weak in 48.5% (16/33), moderate in 39.4% (13/33) and strong in 12.1% (4/33) of cows regardless of the breeds. Cows with strong estrus behavior had significantly higher superovulatory response (p<0.05) and also vi produced a significantly higher (P=0.000, χ2=31.6) number of UFO than cows who had moderate or weak estrus. In experiment three, 88.9% of the Boran and 83.3% HF*Boran donors responded to the superovulation with no significant breed differences. Total recovery rate was relatively lower (56.5%) in Boran compared to crosses (67.4%). The mean (±SE) total flush output was 6.5±0.8 for Boran and 6.9±0.7 for HF*Boran with no significant breed difference. Mean (±SE) recovery of transferrable embryo was significantly higher (5.3 ± 0.8; p<0.05) in HF*Boran dams inseminated with HF sire semen. Boran cows yielded a significantly higher (p<0.05) proportion of UFO (3.6 ± 0.6) irrespective of the sire breeds. Boran cows inseminated with HF sire semen yield significantly higher proportion of G1 embryos (64.7%, n=22) while HF*Boran produced more G2 embryos (43.1%, n=25). This study demonstrated that doses of FSH determines the ovarian response and the presence of breed related differences in both the quality and quantity of in vivo produced Bovine embryos. Boran breed consistently produced higher proportion of UFO irrespective of the breed of sires while HF*Boran cows produced a significantly higher number of transferable embryos when inseminated with semen from HF sires. It concludes the significance of breed during selection of donors for a successful embryo transfer.enDonor damCL countembryo qualityembryo transfersuperovulationThesis