Growth performance of Lowline Angus x Thai native crossbred beef under tropical condition.

Thai native cattle (Bos indicus) have high fertility rates and strong mothering abilities; however, their slight size, slow growth rate and low meat quality have not proved suitable for a commercial fattening system. Their progeny from crossbreeding with exotic sire particularly the Bos Taurus could present greater production performance. Lowline Angus sires and frozen semen were used to produce Lowline Angus x Thai native crossbreds. All cattle were raised in the same condition which was mainly through a grazing system. Throughout 5 years of data collection, calves' gender, birth weight, and weight gains were recorded until 1 year of age. There was no interaction effect between calves' gender, breed, and birth season on weight at birth and yearling, as well as growth rate. The birth weight of male calves (14.0 kg) were greater than female calves (13.3 kg). The calves' birth weights did not differ between levels of Lowline Angus blood, but all crossbred males were found to be significantly bigger than indigenous females. It must be noted that yearling weight did not differ between breeds. However, females 75% Lowline Angus, 25% Thai native crossbred (139.3 kg) weighed significantly higher than Thai native purebred females (115.9 kg). The calves' birth weights had positive correlation with Lowline Angus blood levels: birth weights increased when Lowline Angus blood levels were increased. The sharpness in the growth curve of Lowline Angus crossbreds was higher than purebred Thai indigenous cattle. Moreover, the 25% Lowline Angus crossbred had the highest graph slope as opposed to the 50% or 75% Lowline Angus crossbred. The growth performance of Lowline Angus x Thai native crossbred was shown unsuccessful under low-quality grazing situation. Additive effect of the crossbred presented quite low but well adapted to tropical environment. Greater productivity performance of the crossbred possibly will be excess with a higher quality feedlot condition.