Cm. Dwyer et al., THE INFLUENCE OF MATERNAL NUTRITION ON MUSCLE-FIBER NUMBER DEVELOPMENT IN THE PORCINE FETUS AND ON SUBSEQUENT POSTNATAL-GROWTH, Journal of animal science, 72(4), 1994, pp. 911-917
In the pig, undernutrition in utero causes low birth weight, a decreas
e in muscle fiber number, and a reduction in postnatal growth rate. Th
e effect on fiber number is mediated via a reduced secondary fiber pop
ulation. Within a litter of pigs, lighter-weight pigs have probably su
ffered some deficit in muscle fiber number. In an attempt to improve t
he number of fibers in the lighter-weight pig fetuses, four maternal f
eeding regimens were used, one serving as the control. Maternal feed i
ntake was doubled for one of three time periods during pregnancy: 1) d
25 to 50 (HE) immediately before fiber hyperplasia; 2) d 50 to 80 (HL
) during fiber hyperplasia; or 3) d 25 to 80 (HT) covering both develo
pmental events. Controls were fed at levels routinely used for pregnan
t sows on the farm. Sows farrowed normally and pig birth weights were
recorded. Estimates were made of total myofiber number, total primary
fiber number, and mean secondary:primary fiber number ratio (S:P) for
the semitendinosus of each pig at 5 wk postnatal or 80 kg (HT and two
control litters only). The progeny of all supplemented sows had a sign
ificantly greater mean S:P ratio (P < .05), and the HE pigs tended to
have a greater number of muscle fibers than control pigs (403,840 +/-
8,197 vs 370,970 +/- 12,720). Postnatal growth rate to 80 kg was also
investigated for the HT group of pigs. The HT pigs had a faster growth
rate from d 70 to slaughter at 80 kg (924.4 +/- 18.75 g/d vs 840.1 +/
- 17.48 g/d, P = .017) and an increased gain:feed ratio (.433 +/- .011
vs .401 +/- .007, P = .025) compared with controls. These results sug
gest that the mean number of secondary fibers formed in a litter of pi
gs can be improved by increasing maternal feed intake during d 25 to 5
0 of gestation. This may have additional benefits in terms of improved
growth rate and growth efficiency in the latter stages of pig growth
to 80 kg.