Muscle cellularity and postnatal growth in the pig1

Abstract

Fast-growing strains of pigs and of other animals tend to have more muscle fibers than do slow-growing strains. The relationship between fiber number and growth rate was extended by examining pigs within the same strain. Seven litters of pigs (n = 66) were weighted at monthly intervals from birth to approximately 80 kg. The semitendinosus muscle was removed and an estimation of total fiber number, total primary fiber number, and mean secondary:primary fiber number (S:P) ratio was made for each animal. Pig growth was divided into three approximately linear phases: birth to 6 kg, 6 to 25 kg, and 25 kg to slaughter weight. Average daily gain in the first two phases was correlated with birth weight (r = .3614, P < .05 and r = .5873, P < .001, respectively) but was not correlated with total muscle fiber number. In the third growth phase ADG was correlated with muscle fiber number (r = .4149, P < .001) and was not correlated with birth weight. The gain:feed ratio was also calculated for each pig during the third growth phase and was found to be correlated with fiber number (r = .4191, P < .001). These results suggest that muscle fiber number is an important determinant of postnatal growth such that pig littermates with a high fiber number tend to grow faster and more efficiently than littermates with a lower fiber number.

Intergenerational effects of birth weight on glucose tolerance and reproductive performance

“…Previous studies have demonstrated that larger piglets usually grow faster than their lighter littermates (Powell and Aberle, 1980;Dwyer et al, 1993), but the findings of the present study do not support this. Despite litter size being similar between L and N groups, there was a tendency for L mothers to rear fewer offspring compared to their N counterparts, but this was in part due to the occurrence of cross-fostering (decision made by the Pig Unit Management).…”

Number of conceptuses in utero affects porcine fetal muscle development

“…Dwyer et al (1992) suggested that a reduction in placental size might be the mechanism mediating negative effects of maternal undernutrition on birth weight and the number of secondary muscle fibres in the offspring (Handel & Stickland 1987, Dwyer et al 1994. Consistent with the earlier data of Hegarty and Allen (1978) indicating that runts have reduced muscle growth potential and needed 23 days longer to reach a weight of approximately 105 kg, Dwyer et al (1993) established a positive correlation between the total number of muscle fibres and postnatal growth potential. Furthermore, the effect of maternal nutrition was identified as occurring between days 25 and 50 of gestation, the period immediately preceding secondary muscle fibre hyperplasia (Dwyer et al 1994).…”

“…Although the scope of the present experiment did not allow analysis of postnatal growth effects, earlier studies (Handel & Stickland 1987, Dwyer et al 1993, 1994 have clearly demonstrated reduced postnatal growth potential due to quantitative effects on fetal muscle development through maternal undernutrition. The results of the present study extend the findings of previous work in the pig in which both naturally occurring IUGR within a litter (Aberle 1984) and nutritional manipulation during gestation (Dwyer et al 1994) preferentially affected secondary muscle fibre development.…”

Histological characteristics of longissimus dorsi muscle and their correlation with restriction fragment polymorphisms of calpastatin gene in F2 Jinghua × Piétrain crossbred pigs

“…These findings are consistent with those reported earlier (Lefaucheur et al, 2002 and2004). These slow fibres are also defined as primary fibres, and the number and size of these fibres determine muscle mass and individual size in mature animals (Wigmore and Stickland, 1983;Stickland and Handel, 1986;Dwyer et al, 1993).…”