Breed differences
often breeds differ in mature size
different breeds have the same percentage composition at maturity
there is no difference between breeds in the rate at which muscle, bone and fat mature relative to total body weight
therefore breed effects on composition largely reflect differences in the stage of maturity at which the comparisons are made, rather than breed differences per se
Sex differences
Entire male vs females
entire males have a greater mature weight than females (ca. 40%)
sexes differ in mature composition; entire males have less fat, more muscle and more bone than females
there is a difference between the sexes in the rate at which tissues mature relative to total body weight
therefore sex effects on body composition tend to vary depending upon the stage of maturity or body weight at which the comparisons are made
Entire male vs castrates
entire males and castrates tend to have similar mature weights
entire males and castrates differ in mature composition; entire males have less fat and more muscle and bone than castrates
there is no difference between entire males and castrates in the rate at which tissues mature relative to total body weight
therefore differences between entire males and castrates depends upon the body weight (or stage of maturity) at which the comparisons are made