AGB 211: Livestock and Poultry Breeding (2+1)

CAUSES OF HETEROSIS

• Difference in gene frequency between two population for several generations.
• Dominance, overdominance and epistasis.

Complementarity is the second reason for cross breeding. This refers to the additional profitability obtained from crossing two populations resulting not from heterosis but from the manner in which two or more characters complement each other. E.g. Crossing Angus carcass quality with Zebu Brahman (adaptability).

Complementarity is not heterosis. Complementarity is due to additive gene action. If there is complementarity, the crossbred progeny are in midway between these two breeds. Traits which show heterosis would rank above the average of parental breeds in the crossbred progeny and often would be superior to either.