Superovulatory response, embryo quality and fertility after treatment withdifferent gonadotrophins in native cattle

We studied native Mertolengo cattle to evaluate superovulatory (SOV) treatm ents, subsequent fertility of donors and pregnancy rate of recovered embryo s. In Experiment 1 we compared superovulatory response (SR), embryo quality and plasma progesterone (P4) levels between donors treated with eCG (10 co ws and 5 heifers) vs. FSH (pure, FSH-I, n=10 cows and crude, FSH-2, n=10 co ws), during progestagenic impregnation. We also compared fertilization rate s and embryo quality of bred and inseminated eCG and FSH-1 donors. Signific antly more viable embryos were yielded by FSH than by eCG treated donors. L ess FSH-I than FSH-2-treated donors showed SR, but the response was identic al in responder donors of both groups. Fertilization rates were significant ly higher in bred than in inseminated donors. Plasma P4 levels were only si gnificantly different (higher) between responder and non-responder donors o n the day of embryo recovery. Experiment 2 compared FSH treatments (FSH-2, crude, n=11 cows and FSH-3, pure, n=10 cows) started at the midluteal phase . The mean number of viable embryos was significantly higher in FSH-3 than in FSH-2 treated donors. Both FSH treatments exerted a similar luteotrophic effect upon injection. The FSH-2 donors treated during the midluteal phase yielded more ova and showed significantly higher plasma P4 levels at all s ampling days than those treated during progestagenic impregnation. The preg nancy rates of recipient cows were 67% and 46% for fresh and frozen-thawed embryos respectively. In Experiment 3, the fertility of donors (n=20) after SOV treatments was compared with that of untreated cows (n=40). Time to co nception of donors, after mating with a bull 14 days after embryo recovery, was identical to that of control cows. There was some delay to conception in eCG-treated cows, but the difference was not significant. These prelimin ary results suggest that response to SOV treatments in Mertolengo cattle mi ght be affected by the type of gonadotrophin and by the treatment protocol. The fertility of a traditional breeding season after SOV treatments was no t impaired. Cryopreserved embryo banking can be used to preserve the breed. (C) 2001 by Elsevier Science Inc.