RESUMO
Nonsurgical recoveries and transfers of embryos were performed at the McKellar Embryo Transplant Center from 122 superovulated Brahman cows. FSH-P (Armour) was used to superovulate all cows at dose levels ranging from 36 to 48 mg total FSH-P. Luteal regression was induced by use of 40 mg PGF(2(alpha)) in all 122 cows. Embryos were transferred into recipients 6, 7 or 8 days after observed estrus. Embryos were successfully collected from 82% of the FSH-P treated cows. The dose level of FSH-P affected numbers of embryos collected (P<.05). Numbers of embryos collected from cows superovulated with 36-38, 40, 42, 43, 44, 45, 46 and 47-48 mg FSH-P were 2.8 +/- 1.0, 6.8 +/- 1.1, 9.4 +/- 1.4, 10.0 +/- 2.7, 7.1 +/- 1.6, 6.8 +/- 2.0, 5.0 +/- 1.7 and 4.6 +/- 2.0 embryos, respectively. The dose level of FSH-P also affected numbers of embryos transferred (P<.10). Number of embryos transferred from cows superovulated with 36-38, 40, 42, 43, 44, 45, 46 and 47-48 mg FSH-P were 2.8 +/- 1.9, 5.2 +/- 0.9, 6.9 +/- 1.2, 6.7 +/- 2.1, 4.8 +/- 1.3, 5.1 +/- 1.4, 3.4 +/- 1.2 and 3.2 +/- 2.1 embryos, respectively. The developmental stage (D) of the embryo was also a factor in pregnancy rate of recipients (morula = 13.8%, blastocyst = 22.1% and expanded blastocyst = 29.9%; P<.005). The skill of the technician (T) transferring the embryo had a dramatic effect upon subsequent pregnancy rate of the recipients (T 1 = 46.0% vs T 2 = 22.6% pregnancy rate; P<.005). Pregnancy rate of recipients was also affected by the stage postestrus (S) at which the embryo was transferred (day 6 = 23.5%, day 7 = 25.5% and day 8 = 42.3% pregnancy rate; P<.05). Interactions were found between T x S, T x D, S x D and T x S x D (P<.05). These data indicate that use of 40, 42, or 43 mg total doses of FSH-P were quite effective in superovulating the Brahman cow. Recipients transferred on day 8 postestrus achieved higher pregnancy rates than recipients transferred on days 6 or 7 postestrus. Embryos transferred in the expanded blastocyst stage of development proved to yield the highest pregnancy rates in recipients.
