THE EFFECT OF LONG-TERM SELECTION FOR THE PARAMETERS OF THE ALLOMETRIC MODEL ON FITNESS IN THE RAT

The long-term effect of selection for the parameters of the allometric model on fitness is investigated to evaluate the allometric model for long-term selection purposes. Fitness is defined as the number of mat ure animals/female mated/100-day period, where mature animals are defi ned as animals at the age of joining (standardized at 90 days). The re sults of 23 generations of selection for the intercept (ln (a)) and 32 generations of selection for the slope (b) of the allometric function w = ln (a) + bv [where w = ln (body mass) and v = ln (cumulative feed intake], are discussed. Fitness decreased as a correlated response to selection for ln (a) and b. The response in fitness with selection fo r ln (a) and b is best described by a quadratic regression. It was con cluded that the parameters of the allometric growth function can be us ed as selection criteria in long-term selection experiments, but speci al attention should be given to fertility in the breeding plan. This c an be realized by concurrent selection for fertility or, for example, in the poultry industry, by selecting male lines for the parameters of the growth model and female lines for growth and reproductive perform ance.