Treatment of underfed pigs with GH throughout the second quarter of pregnancy increases fetal growth

Circulating growth hormone (GH) concentrations increase in pregnancy and ad ministration of GH during early-mid pregnancy increases fetal growth in wel l-fed pig. To determine whether increased maternal GH could promote fetal g rowth when feed availability is restricted, fifteen cross-bred primiparous sows (gilts) were fed at approximately 30% of ad libitum intake, from matin g onwards and were injected daily i.m. with recombinant porcine GH (pGH) at doses of 0, 13.4+/-0.3 and 25.6+/-0 5 mu g/kg live weight from day 25 to d ay 51 of pregnancy (term similar to 115 days). Treatment with pGH increased maternal backfat loss between day 25 and day 51 of pregnancy, and increase d maternal plasma IGF-I concentrations measured at day 51 of pregnancy. Fet al body weight, length and skull width at day 51 of pregnancy were increase d by maternal treatment with pGH. Fetal plasma glucose concentrations were increased and maternal/fetal plasma glucose concentration gradients were de creased by maternal PGH treatment at 13.4, but not 25.6 mu g/kg.day. Fetal plasma concentrations of urea were decreased by both levels of pGH treatmen t. Overall, fetal weight was negatively correlated with fetal plasma concen trations of urea, positively correlated with maternal plasma alpha-amino ni trogen concentrations and unrelated to glucose concentrations in either mat ernal or fetal plasma. This suggests that the availability of amino acids, not glucose, limits fetal growth in the first half of pregnancy in underfed gilts, and that maternal GH treatment may improve amino acid delivery to t he fetus.