OPTIMAL CONTEMPORARY GROUP-STRUCTURE TO MAXIMIZE GENETIC PROGRESS THROUGH GENETIC EVALUATION SWINE

Accuracies of sire EPD were calculated for a typical growth trait and a typical maternal trait for alternative contemporary group structures . For a given family size (number of progeny tested for a sire in a co ntemporary group), accuracy increased as the number of sires increased and as the number of contemporary groups increased. Ad exponential eq uation was found to best predict accuracy from the number of sires and groups. Partial derivatives can be used to determine the optimal numb er of sires and groups for a given economic situation (fixed number of animals tested per group). It is recommended that progeny of at least two sires be represented in each contemporary group, but having more than five sires does not effectively increase accuracy further. Accura cy increases with a larger herd size, as more sires and more groups of pigs are tested. When the number of Litters that can be tested is at its limit, accuracy is maximized with a small number of sires, and pro geny divided among several contemporary groups. However, accuracy is o nly part of the herd's genetic improvement. Selection decisions must b e made to avoid inbreeding, which can be a problem, particularly in sm all herds.