Effect of feeding 25-hydroxycholecalciferol on prenatal porcine skeletal muscle development

To determine the effects of feeding the circulating metabolite of vitamin D, 25-hydroxycholecalciferol (25OHD₃), on prenatal skeletal muscle development, 38 gilts (BW on d −5 = 138 kg) in 4 replicates were randomly assigned to one of 2 corn-soybean meal-based diets. The control diet (CTL) was formulated to contain 2,500 IU D₃/kg diet, while the experimental diet (25OHD₃) contained 500 IU D₃/kg diet + 50 μg 25OHD₃/kg diet. Gilts were fed 2.7 kg of their assigned diet once daily beginning 42 d before breeding. Gilts were artificially inseminated 12 and 24 h after showing signs of estrus. At gestational d 90 (±2), when fetal muscle fiber number is established, gilts were harvested, fetuses (n = 291) were extracted and a portion of the longissimus muscle (LM) was collected for analysis. Fetal LM were cryosectioned and immunofluorescence stained. Fetal LM area, fiber number, fiber cross-sectional area and number of Pax7+ cells were analyzed.

Regardless of treatment, female fetuses had significantly larger LM areas than males (P = 0.01). No treatment difference was observed in fetal LM area (P = 0.25). Fetuses from 25OHD3-supplemented gilts had significantly more LM fibers (P = 0.04) that tended to be smaller in cross-sectional area compared with CTL fetuses (P = 0.11). A numerical increase in the total number of Pax7+ myogenic precursor cells was also observed in fetuses from 25OHD3-supplemented gilts (P = 0.12). The combination of additional muscle fibers and Pax7+ myogenic precursor cells could result in enhanced postnatal muscle hypertrophy in the progeny of 25OHD₃-supplemented gilts.

Overall, these data suggest that feeding 25OHD₃ to gilts during gestation may positively impact the red meat yield of their offspring.