The concept of "productive adaptability" of domestic animals in tropical and subtropical regions.

The complex trait "productive adaptability" is shown to be a useful parameter for selection work in tropical climates. Characters such as rectal temperature in poultry and hair colour and structure in cattle used as indicators of heat tolerance prove to be of little value. "Productive adaptability" is also genetically more suited for selection procedures. Our results confirm that body size is a significant indicator of an animal's productive adaptability and that it is a suitable criterion for use in improving the genetic potential of livestock in warm climates. The special use of major genes in breeding programmes to improve productive adaptability is demonstrated.