MANAGEMENT ASPECTS OF INDUCED TWINNING IN BEEF SUCKLER COWS USING IN-VITRO FERTILIZED EMBRYOS

Twin and single pregnancies were induced in two groups of oestrus-sync hronised beef cows by using a combination of artificial insemination a nd the transfer of in vitro fertilised (IVF) embryos, Single IVF embry os transferred non-surgically to the uterine horn contralateral to the corpus luteum of 43 previously inseminated cows resulted in a calving rate of 72 per cent with a twinning rate of 38.7 per cent, In 45 cows , two IVF embryos were transferred non-surgically to one uterine horn resulting in a calving rate of 51.1 per cent with a twinning rate of 3 9.1 per cent, The median gestation length for cows bearing twins was 1 0 days shorter than that of cows bearing single calves (P<0.001). The proportions of cows that received assistance at calving were similar f or twin and single births (57 per cent vs 45 per cent, P>0.05), but th e incidence of retained fetal membranes was much higher after the birt h of twins (62 per cent vs 3 per cent, P<0.001), Nineteen per cent of twin calves were stillborn compared with 6 per cent of single calves ( P>0.05). The median birthweight of the twin calves was 32 kg (68 per c ent of the median weight of single calves), The nutrition of twin-bear ing cows in late pregnancy was adequate when assessed in terms of thei r plasma glucose, nonesterified fatty acid and beta-hydroxybutyrate co ncentrations, Serum immunoglobulin concentrations were similar in sing le and twin calves suggesting that the passive transfer of antibody wa s not compromised in the twin calves.