Relationship of birth weight with the size, number and proportion of fibres in the pig semitendinosus muscle

Abstract

P>The objective of this study was to determine the relationship between body weight and the size, number and proportion of muscle fibre types in the pig semitendinosus muscle at birth. Based on weight at birth, 68 specimens selected from 21 different litters from the same farm were allotted in two equal groups (G1 and G2). G1 included 34 piglets < 1.1 kg and G2 34 pigs >= 2 kg. Fifteen piglets per group were killed at birth and the remaining 19 piglets in each group were reared until weaning (21 days) and post-weaning (67 days). The weight and total cross-sectional area of the semitendinosus muscle were recorded at birth. Then, type I and type II fibres from the superficial portion of the muscle were identified according to histochemistry and immunohistochemistry techniques and percentages, average size of each fibre type, and the total number of muscle fibres were estimated by morphometry. Birth weight in G1 was 54.74% lower than that in G2. Correspondingly, the total cross-sectional area of the semitendinosus, as well as the size and number of muscle fibres, was significantly lower in G1 (P < 0.001). Weight at birth still influenced weights at weaning and post-weaning, hence it was 43.17% and 28.38% lower respectively in G1. It is concluded that pig weight at birth is associated with muscle cellularity of the semitendinosus muscle of pig, which may influence the postnatal muscle growth and final size of muscle fibres and meat quality.