Effects of selection for rapid postweaning gain on maturing patterns of fat depots in mice.

Correlated responses to selection for rapid 3 to 6-wk postweaning gain in male mice were estimated for five fat depots weighed at specific degrees of maturity in body weight (37.5, 50.0, 62.5, 75, 87.5 and 100%). Fat pads measured were from regions of the subcutaneous hindlimb, subcutaneous forelimb, epididymides, mesentery and kidneys. At the same degree of maturity, selected mice (M16) were older (P less than .01) than controls (ICR). M16 had heavier (P less than .01) fat depots than ICR for all sites at each degree of maturity. From 62.5 to 100% maturity, M16 was larger than ICR in fat depot weight as a percentage of body weight at all sites. Mesenteric fat made up the largest percentage of total fat in both lines and perirenal fat the smallest percentage. Development of degree of maturity in each fat depot relative to degree of maturity in body weight was studied using the constrained quadratic and standardized allometric models. Both models showed similar trends, but the latter identified more significant line differences. The standardized allometric analysis indicated that total fat and all individual fat depots except mesenteric fat matured at a slower rate (P less than .01) in M16 than in ICR. Bivariate allometric analyses of ln fat depot weight on ln body weight showed that M16 exceeded (P less than .01) ICR in relative growth of all fat depots except mesenteric fat; at lower body weights, ICR had larger fat depots than M16, but the reverse was true at higher body weights.(ABSTRACT TRUNCATED AT 250 WORDS)