LONG-TERM RESPONSES TO SELECTION FOR PARAMETERS OF THE ALLOMETRIC MODEL IN THE RAT

Rats (Rattus domesticus) were used in an experiment where selection wa s practised for the slope (b) and intercept (ln (a)) of the allometric function w = ln (a) + bv [where w = ln (body mass) and v = ln (cumula tive feed intake)]. Both upward and downward selection was practised f or ln (a) and b, for 23 generations and 32 generations, respectively. Selection for ln (a) primarily resulted in positive responses in corre lated characteristics during the first post-weaning growth phase, whil e selection for b primarily resulted in positive responses in correlat ed characteristics during the second post-weaning growth phase. Select ion for ln (a) and b both resulted in a change in efficiency (negative for ln (a) and positive for b), while the 60-day body mass and feed i ntake were not changed significantly. This result is of practical impo rtance in the pig and poultry industry.