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Induction of Twins in Cattle with Bilateral and Unilateral Embryo Transfer

University of California³, Davis 95616

Abstract

One embryo was transferred to each uterine horn (bilateral transfer) of 21 Hereford cows and 21 Hereford heifers 5 days after estrus. Seventeen Hereford cows and 18 Hereford heifers were bred at estrus and received an additional embryo 5 days later transferred to the uterine horn contralateral to the corpus luteum (unilateral transfer). Pregnancy rates at 45 days from bilateral and unilateral transfers (cows and heifers combined) were 76% and 60%, respectively; twinning rates in pregnant recipients were 72% and 70%, respectively. Pregnancy rates at 45 days for cows and heifers (unilateral and bilateral transfers combined) were 71% and 67%, respectively. Twinning rates in these two parity groups were 75% and 67%, respectively. A lower pregnancy and twinning rate in the unilateral heifer group than in the other groups, presumably due to low fertility at AI, affected the pregnancy and twinning rates for unilateral transfers and for heifers. Birth weights were lower for twins than singles regardless of whether they were born to cows (P<.001) or heifers (P<.01). Twins produced by heifers were smaller at birth than twins produced by cows (P<.05), but the difference in the birth weight for singles from cows and singles from heifers was not significant. A shorter gestation period for twins than singles was observed in heifers (P<.01), but not in cows. The incidences of dystocia requiring assistance for dams producing twins and singles were 20% and 21%, respectively. The incidence of retained placenta was 14% for dams that produced twins and none for dams producing singles. Palpation per rectum either early (45days) or late (180 to 200 days) in pregnancy was shown to be effective for diagnosing twin pregnancy.

¹ Department of Reproduction, School of Veterinary Medicine. Present address: College of Veterinary Medicine, Univ. of Florida, Gainesville 32610.

² The authors acknowledge the important contributions of the members of the Embryo Transfer Group at U.C.D. We thank the Upjohn Co. for supplying the prostaglandin F2 a used in this study.

³ Dept. of Animal Science.

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