Egg Transfer in the Cow: Factors Affecting Pregnancy and Twinning Rates Following Bilateral Transfers

Abstract

A total of 112 heifers was used in an egg transfer study to examine some of the factors affecting egg survival and twinning rates following bilateral transfers. Seventy-two recipient heifers were involved and pregnancy rates of 82\m=.\0%,66\m=.\7% and 61\m=.\5% were recorded for recipients in oestrus on the same day as (Day 0), 1 day before (Day +1) and 1 day after (Day \m=-\1) the donor respectively. Short-term (10-day) intravaginal progesterone, or intramuscular prostaglandin treatments for synchronization of oestrus in recipient animals did not depress pregnancy rate following egg transfer. One egg was transferred to each uterine horn and twinning rates of 55\m=.\6%,44\m=.\4% and 20\m=.\0% were recorded for transfers on Days 0, + 1 and \m=-\1,respectively. Of the recipients becoming pregnant following transfers on Day 0, 74\m=.\1% had twins. Embryo survival was higher (69\m=.\2%) in the uterine horn adjacent to the ovary containing the CL than in the opposite horn (30\m=.\8%). The storage period in vitro in TC 199 (37\m=+-\1\s=deg\C) affected subsequent egg survival rates following transfer, with fewer eggs surviving the longer storage periods. The pH of the medium used for egg collection and storage did not affect the pregnancy rate between pH values of 7\m=.\0to 8\m=.\6. Day of transfer (Days 3 to 7) did not seem to affect the pregnancy rate. The high pregnancy and twinning rates already reported following closely synchronized transfers were confirmed.

Pregnancy rates and births after unilateral or bilateral transfer of bovine embryos produced in vitro

“…Rowson et al (1971) suggested that competition between embryos within a single uterine horn seemed to occur after unilateral transfer of two embryos. Rowson et al (1972) (Rowson et ai, 1971;Sreenan et al, 1975Sreenan et al, , 1978Anderson et al, 1978) and with that reported after unilateral transfer of two embryos (Boland et ai, 1975;Testart et ai, 1975 (Rowson et al, 1969;Hasler et al, 1987 (Shea, 1981;Lindner & Wright, 1983;King et al, 1985;Hasler et al, 1987). The transfer of embryos produced in vitro evaluated as morphologically excellent, good or fair, resulted in a higher pregnancy rate than the transfer of poor embryos ( Table 2).…”

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

“…It has been confirmed that a higher incidence of twin pregnancy can be induced in beef heifers by bilateral embryo transfer than by unilateral transfer [8,11], although Sreenan and Diskin [26] showed no difference in the twin pregnancy, twin calving or overall embryonic mortality rates between unilateral and bilateral embryo distribution. Unlike pigs or ewes, transuterine migration of ova or embryos rarely occurs in cattle [27].…”

“…The definitive method of twin production by embryo transfer still remains unestablished, although several factors influencing the success of twin pregnancy have been previously elucidated [8].…”

Fetal survival rate after the surgical transfer of two bovine embryos

“…This appeared to be the result of competition between embryos within a single uterine horn. Other workers have confirmed the high pregnancy and twinning rate which may be achieved after bilateral embryo transfer (Sreenan, Beehan & Mulvehill, 1975) which appears therefore to be the method of choice for inducing twin pregnancy. In practice, because economic considerations preclude the use of surgery, twinning would only be induced by non-surgical methods: (1) one embryo may be placed non-surgically into the contralateral horn of a previously inseminated recipient (Boland, Crosby & Gordon, 1975;Boland & Gordon, 1978;Sreenan, 1978) or (2) one embryo may be transferred into each uterine horn (Heyman, Renard, Ozil & du Mesnil du Buisson, 1978).…”