Variability in the response to super-ovulatory treatments in Bos indicus, Bos taurus,
and their crosses was reported to be a fundamental biological difference in reproductive function between them and has been a major barrier to the adoption of similar superovulation protocols. Therefore, this study was designed to optimize the super-ovulatory protocol for the Boran x Holstein crossbred cows. A total of 36 Boran x Holstein crossbred and pure Holstein cows 3-8 years of age were utilized for this study. A 7-day CIDR treatment was initiated on Day 0, and cows were treated on Days 4-7 with 500, 650, or 800 IU of Pluset® (combined FSH and LH product) administered at 12-hour intervals in a decreasing dose regimen. Estrumet (Prostaglandin F2α analogue) was given on day 7 before CIDR withdrawal. Each super-ovulated cow was monitored for 72 hours to assess behavioral estrus in response to super-ovulatory treatment. Ovarian response was also assessed by counting the number of corpora lutea and number of un-ovulated follicles via transrectal ultrasound scanning, the number of total collections, and the number of viable embryos. From the super-ovulated donor cows, Boran X Holstein crosses had a higher (P<0.009) number of corpora lutea (15.45 ± 0.5) than pure Holstein (8.67± 3.06). The number of collected embryos/oocytes and the number of viable embryos collected was significantly higher for crossbred cows (p<0.01, p=0.06) than the pure Holstein cows. Although it was not statistically significant, from the three Pluset® (combined FSH and LH product) dose levels the 650 IU dose have produced a higher response in terms of corpora lutea number and number of collected viable embryos. From the five-scale body condition scoring (Recorded 2.5 to 5) cows with 3.5 and 3.8 scales have produced a higher number of corpora lutea (15.74 ± 0.59; 14.33 ± 2.90, respectively), while those with 3.8 scores had the highest total number of collections (6.33 ± 2.60). From the findings, it can be concluded that Boran X Holstein crossbred cows have a better ovarian response to lower doses of exogenous gonadotropins than pure Holstein cows. The 650IU Pluset® dose level is the optimal level for superovulation of crossbreeds.
