Effects of inbreeding on ovarian responses and embryo production from superovulated Mantiqueira breed cows

The objective of the present experiment was to evaluate the effects of different levels of inbreeding on ovarian response and embryo production from superovulated cows. One hundred and thirteen Mantiqueira cows (a medium-size, Bos taurus native dairy cattle breed), with inbreeding coefficients ranging from 0 to 30%, were allocated into five classes of inbreeding and subjected to superovulation treatment. At induced estrus, cows were mated with Mantiqueira bulls (with minimal inbreeding). Six to eight days after mating, the cows were slaughtered, ovarian structures counted and embryos recovered by flushing the uterine horns and oviducts. Sire, season, age, weight, parity and age at first calving of donors did not significantly affect ovarian response or embryo production and quality. There were no effects of inbreeding class on number of total corpora lutea (CL) or number of CL present in the right ovary. However, the number of CL in the left ovary was reduced (P < 0.05) in cows with Class 5 (>9%) of inbreeding. The number of transferable, but not the number of nontransferable embryos or the total number of embryos from cows with Class 5 of inbreeding, was lower (P < 0.05) than those of cows from Classes 0 to 4 (<9%) of inbreeding. There was a quadratic decrease in the number of transferable embryos as inbreeding coefficient increased (Yˆ=11.077+0.34X−0.0529X2; R2 = 0.91, P < 0.01), but no significant linear or quadratic effect of inbreeding on total number of embryos or number of nontransferable embryos. In conclusion, an inbreeding coefficient > 9% reduced the quality of bovine embryos at the initial stage of development.