ABNORMAL OFFSPRING FOLLOWING IN-VITRO PRODUCTION OF BOVINE PREIMPLANTATION EMBRYOS - A FIELD-STUDY

Data on 944 calves from 2228 in vitro-produced (IVP) bovine preimplant ation embryos were compared with data on 2787 AI calves born in the sa me herds in 1995. Bovine preimplantation embryos were produced in vitr o following ovum pick up (OPU) from donor cows and pregnant heifers in an open nucleus breeding program. After 7 d of in vitro culture on a BRL cell monolayer in the presence of 10% FCS, frozen-thawed expanded blastocysts and fresh morulae to expanded blastocysts were transferred into recipient heifers and cows at 119 contracted farms throughout th e Netherlands. The pregnancy rate, as confirmed by palpation per rectu m between 90 and 150 d after transfer was 43.5% for both fresh and fro zen embryos. Data on IVP and AI calves were registered by the farmers. The percentage of calves with a congenital malformation and the perce ntage of male calves were related to the total number of calves born. Gestation length, birth weight (measured by a balance), perinatal mort ality and ease of calving were analyzed in a subdataset (699 IVP and 2 543 AI calves, respectively) by a comparative analysis of variance (AN OVA). The ANOVA model included herd, month of calving, sire nested wit hin AI or IVP, parity and breed of the inseminated cow/embryo recipien t, sex of calf, type of calf(AI or IVP) and two-way interactions betwe en type of calf and sex, parity and breed. The percentage of calves wi th congenital malformations was 3.2% and 0.7% for IVP and AI calves, r espectively. An increased incidence of hydro-allantois and abnormal sp inal cords and limbs was observed in IVP calves. The percentage of mal e calves was significantly different between IVP and AI, 55.5% and, 48 .9%, respectively (Chi-square, 1 degree of freedom, P<0.05). On the av erage, IVP calves showed a significant increase of birth weight by 10% (4-5 kg), a 3-d longer gestation period, 2.4% more perinatal mortalit y and a more difficult calving process compared to AI calves (P<0.05). From these results it is concluded that calves produced by IVP deviat e significantly from calves produced by AI. (C) 1998 by Elsevier Scien ce Inc.