Abstract
The influences of line, sex, bundle size and additive genetic variation on porcine muscle fiber type, diameter and number were investigated on 136 barrows and 131 gilts. Relationships among several porcine histological, carcass and growth measurements were also studied. Differences among the lines of swine were less prevalent for measures of fiber diameter than for staining properties which determined fiber type in bundles from class 1 (small bundles). However, the differences among lines were highly significant for most measures of fiber diameter and fiber type in bundles from class 2 (large bundles), Yorkshires possessed bundles with the greatest proportion of dark Staining fibers. Crossbred pigs had smaller fibers than either of their parent lines, however, in general, crossbreds possessed about the same proportion of each fiber type as their lowest parent line. In both classes of bundles, gilts possessed fibers that were significantly larger than those observed in barrows, however, differences between sexes did not influence any of the measures of fiber type. Percentage area of the bundle represented by intercellular space was not affected by differences between sexes and only slightly affected by differences among lines. Analyses showed that variation among the lines, but not between the sexes, was significant for the estimate of the total number of fibers in the muscle. It was concluded that all of the histological traits in this study are lowly heritable. Copyright © 1975. American Society of Animal Science . Copyright 1975 by American Society of Animal Science.