RESUMO
Obtaining the maximal number of calves from each cow according to its natural genetic reproduction ability is the main condition of intensification of reproduction and increase of milk production. Twins rate in the black-and-white cattle population in Lithuania is 2.4%. Cows whose mothers have calved twins at least 1 time during reproductive life have twins in 5.6% of all calvings, the others--in 1.9%. Twins rate in separate bulls daughters range from 1% to 6.1%. Twins rate in cows range from 0.4% to 5% by separate bulls-getters. Productivity of 305 days lactation after having twins is better (551.2+/-68.1 kg of milk, 18.4 +/-2.9 kg of fat and 21.5+/-2.4 kg of protein, P < 0.001). The rate of twin births increases when lactation is increased. The influence of lactation on rate of twin births is 0.6% in total dispersion (P < 0.001). The influence of calving season on twins rate is statistically insignificant but the parts of twins by calving seasons are distributed differently.
