Effect of Administration with Low-dose FSH to Recipient Cows on Embryonic Survival after Bilateral Nonsurgical Embryo Transfer

抄録

The aim of the present study was to examine the survival rate of embryos after bilateral nonsurgical transfer in recipient cows given a superovulatory treatment of low-dose FSH. In total, 54 parous Holstein or Japanese Black breed cows were used as recipients. These recipients were assigned to the three groups based on hormonal treatments during the preceding estrous cycle. The treatments included A) FSH (10 or 15 mg) and PGF_2α (n=18), B) PGF_2α (n=14), and C) no treatment (n=22). Morula to blastocyst-staged embryos that were transferred were derived either from in vitro maturation & in vitro fertilization or they were collected from superovulated Japanese Black heifers. Some embryos collected from donors were routinely frozen and thawed. Most of the cows (83%, 15/18) that were given the combination of FSH and PGF₂α formed corpora lutea (CLs) on the ovaries (mean number CLs ± s.e. per cow=3.1 ± 0.48). Pregnancy rates on day 30 in groups A, B and C were 67% (12/18), 64% (9/14) and 55% (12/22), respectively (P>0.05). The rates of twin pregnancies to all pregnancies were 50% (6/12), 22% (2/9) and 42% (5/12), respectively (P>0.05). Consequently, 19 cows carried their pregnancies to term, producing 25 calves, including six pairs of twins. Calving rates in the three groups were 67% (8/12), 33% (3/9), and 67% (8/12), respectively (P>0.05). Calf crop rates were 125% (10/8), 133% (4/3), and 138% (11/8), respectively (P>0.05). The embryonic survival rate at Day 30 in group A was likely to be higher than those of cows in the other two groups (50% [18/36] vs 39% [28/72]). No difference between the origins of embryos was observed in the embryonic survival rates. These results suggested that superovulatory treatment with low-dose FSH to recipients bilaterally receiving embryos would be beneficial for increasing embryonic survival, although the results were not statistically significant.