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

RECURRENT SELECTION

• The principle of recurrent selection is developed out of convergent improvement. In this a highly inbred line presumably homozygous at most loci is selected as a tester. A large number of individuals are crossed with this line and their progeny are evaluated. Those giving best progeny are subsequently inter mated and a large number of their progeny are tested in the crosses on the inbred tester. The cycle is repeated over and over. This is done to take greater advantage of the interaction of genes and the resultant overdominance by selecting inbred lines during their developmental process for the purpose of better complementing each other.
• The success depends on the ability of the breeder to accumulate a greater number of genes having additive effects in two different parental lines that interact to greater advantage. If heterosis is largely dependent upon overdominance, this procedure should result in the line selected on cross performance becoming homozygous for different alleles than the inbred used as the tester. In other words when tester is aa, the selected line would become AA; the tester is BB, the selected line becomes bb etc.
• The application of recurrent selection to animal breeding appears to be more difficult than its application to plant breeding because
• The overall effects of inbreeding are deleterious
• The degree of fertility is lacking. It depends on survivability
• More number of animals are required and it involves longer generation interval and make this selection