Effect of Dietary Restriction on Carcass Composition and Adipocyte Cellularity of Swine with Different Propensities for Obesity

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Abstract
Experiments were conducted to determine whether dietary restriction altered body composition and adipocyte cellularity similarly in growing lean (Yorkshire) and obese (Ossabaw) swine. Yorkshire (YR) and Ossabaw (OR) swine were fed 65% of the weekly intake of ad libitum-fed Yorkshire (YA) and Ossabaw (OA) swine for 20 weeks. At 200 days of age, adipose tissue mass was 7-fold lower and muscle mass was 50% lower in YR than YA. However, adipose tissue mass of OR was only 2.6-fold less than OA. Furthermore, muscle mass did not differ between OR and OA. Adipocyte number per carcass was 6-fold higher in YA than YR. No differences in carcass adipocyte number were observed between OA and OR. Dietary restriction resulted in a reduced adipocyte size in both breeds of swine. However, adipocyte size for both dietary treatments was greater for obese than lean swine. When carcass adipocyte number was expressed per kilogram of muscle, there were no differences among YA, OA, and OR; however, this ratio was lower in YR. These results demonstrate: 1) that alterations in nutrient partitioning as measured by accretion of these tissues are different in lean and obese swine when intake is restricted, 2) that differences in adipose tissue mass of YA and OA are due to differences in cell size, and 3) that muscle growth and adipocyte hyperplasia in swine may have a physiological relationship.