Abstract
Individual differences in size at any age tend to be genetically highly correlated with size at other ages (Brinks et al., 1964; Taylor and Craig, 1965), where size may be measured as weight, height, etc. Size differences between immature individuals of the same age and environmental history may thus largely reflect differences in mature size. Size at any age can be partitioned into two components, one measuring this effect of proportionality to mature size, and the other measuring the extent of deviations from proportionality to mature size resulting from individual differences in rate of maturing or earliness of maturing. Differences in mature size are unlikely to be associated with differences in biological efficiency of production (Brody, 1945; Kleiber, 1947). On the other hand, individual differences in rate of maturing are likely to be associated with differences in productive efficiency (Blaxter, 1968; Taylor and Young, 1966). It is, therefore, of interest to investigate this component of size which relates to maturing rate and to estimate genetic variation, heritabilities and genetic correlations for maturing rate and degree of maturity at different stages of growth. Copyright © 1971. American Society of Animal Science . Copyright 1971 by American Society of Animal Science.