L-Arginine Supplementation for Nulliparous Sows during the Last Third of Gestation

SIMPLE SUMMARY: Nutrition of gestating sows plays an important role in the uteroplacental efficiency, muscle development, birth weight and viability of the piglets. This is especially important for nulliparous sows, since the reproductive performance of nulliparous sows is lower compared to multiparous ones. Previous studies have shown that arginine enhances angiogenesis and placental growth, being beneficial to fetus growth. Because during its formation process skeletal muscle tissue compete for nutrients with other organs also in formation during the intrauterine development, the increase of nutrient flow by enhancing angiogenesis may benefit the skeletal muscle formation during the fetal stage. In this sense, arginine supplementation for sows seems to be a promising nutritional strategy to maximize myogenesis and muscle development of piglets. In the present study, piglets born from sows fed diet with 1.0% L-arginine (ARG) had greater mRNA expression of the gene encoding myoblast determination protein (MYOD) and myogenin (MYOG) compared to the piglets born from sows at the control group. The mRNA expression of IGF-2 gene tended to be greater in piglets born from ARG sows compared to those born from control sows. Despite differences in gene expression, no differences in the histomorphometric variables of skeletal muscle were observed between piglets from arginine-supplemented and control sows. In conclusion, supplementation of 1.0% L-arginine for nulliparous sows from 85 to 114 days of gestation increased mRNA expression of the myogenic regulatory factors MYOD and MYOG and IGF-2 in skeletal muscle of piglets. ABSTRACT: We evaluated the effects of L-arginine supplementation during the last third of gestation on molecular mechanisms related to skeletal muscle development of piglets and litter traits at birth. Twenty-three nulliparous sows averaging 205.37 ± 11.50 kg of body weight were randomly assigned to the following experimental treatments: control (CON), where pregnant sows were fed diets to meet their nutritional requirements; arginine (ARG), where sows where fed CON + 1.0% L-arginine. Skeletal muscle from piglets born from sows from ARG group had greater mRNA expression of MYOD (p = 0.043) and MYOG (p ≤ 0.01), and tended to present greater mRNA expression (p = 0.06) of IGF-2 gene compared to those born from CON sows. However, there were no differences (p > 0.05) in the histomorphometric variables of fetuses’ skeletal muscle. The total weight of born piglets, total weight of born alive piglets, piglet weight at birth, coefficient of variation of birth weight, and the incidence of intrauterine growth restriction (IUGR) piglets did not differ between groups. No stillborn piglets (p < 0.01) were verified in the ARG sows compared to CON group. The blood levels of estradiol (p = 0.035) and urea (p = 0.03) were higher in ARG sows compared to those from the CON group. In summary, our data show that arginine supplementation of nulliparous sows at late gestation enhance mRNA expression of key myogenic regulatory factors, which likely contribute to improve animal growth rates in later stages of development.