Crossbreeding in tropical areas with emphasis on milk, health, and fitness.

Although use of European breeds for grading up of local cattle in tropical areas has been underway for nearly one century, few countries have definitive policies on utilization of crossbreeding systems. Crosses with European breeds have excelled local types in age at first calving, milk yield, days in milk, and calving interval. In general, crosses by Holstein sires have proven superior to crosses from other breeds. Contrary to findings in temperature areas, addition of a second improved breed (three-breed cross) has tended to deter rather than to improve performance. The cross 5/8 one breed has performed as well or better than two-breed crosses, but few evaluations have been on farms. The cross 3/4 European usually exceeds the two-breed cross slightly in milk yield, but reproduction is poorer. Mortality losses in 3/4 crosses up to 3 mo often have been high, 14 to 29%. Similarly, experiences with inter se matings of two-breed crosses has proven disappointing. Milk yield of 1/2 crosses of two-breed progeny has been 30 to 60% lower than for first generation two-breed crosses. Numerous attempts have been made to form synthetic groups from crossbred foundation. Most of these gene pools of breed combinations are approximately 5/8 improved breed and 3/8 local. Performance of five synthetic groups and their roles is discussed. Evidence has showed that with high dependence on tropical grasses and crop residues best sustained milk yield is 1800 to 2200 kg of milk per lactation. This means that more attention should be given to breeding plans to raise animal productivity from low to intermediate rather than providing genetic potential for productivity that cannot be supported economically in tropical areas.