110 PREGNANCY RATES OF BOVINE EMBRYOS AND HEMI-EMBRYOS TRANSFERENCE

Abstract

Embryo transfer (ET) in cattle speeds up genetic gains, but its use is limited by cost-benefit analysis. In addition other techniques can be developed, such as sexing and bipartition of embryos. An alternative to improve the economic viability of ET in cattle would be to bipartition embryos in order to increase the yield of the technique. The aim of this study was to investigate the operational viability of embryo bipartition technique in an ET program in cattle and to study aspects related to the viability and development of bovine hemi-embryos (HE) compared with intact ones. The embryos were collected by nonsurgical technique 7 days after the onset of oestrus. Viable structures (130) from 49 embryo collections from 25 Aberdeen and Simmental donor cows and heifers were used. Only embryos in compact morula, early blastocyst and blastocyst stage, with a morphological range from excellent to good grade (IETS Grade 1), were split. The embryos, split (78) or not (52), were transferred into the uterine horn ipsilateral to the corpus luteum of the recipients 7 days after oestrus. The treatment groups evaluated were T1 (intact embryo, n = 52), T2 (1 HE, n = 27) and T3 (2 HE, n = 51). Crossbred heifers were used as recipients and pregnancy diagnosis was done at 60 to 80 days of gestation. The embryos of T1, T2 and T3 were classified morphologically as excellent or good and by developmental stage as morula, early blastocyst, or blastocyst, distributed as follows: T1: 30, 22 and 16, 17 and 19; T2: 15, 12 and 7, 9 and 11; and T3: 29, 22 and 15, 15 and 21, respectively. The birth rate per original embryos was greater for T2 than for T1 and T3 (Table 1). The pregnancy rates for excellent and good embryos and morulae, early blastocysts and blastocysts were not different (P > 0.05). The T1, T2 and T3 twin births were 0, 1 and 5, respectively. It is concluded that embryo bipartition technique applied in a commercial ET program is a viable operational technique. Table 1.Pregnancy at 60 to 80 days and birth rate per original embryos used Supported by CAPES, CNPq, FAPEMIG and BIOTRAN.