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

Abstract

Circulating growth hormone (GH) concentrations increase in pregnancy and administration of GH during early-mid pregnancy increases fetal growth in well-fed pigs. To determine whether increased maternal GH could promote fetal growth when feed availability is restricted, fifteen cross-bred primiparous sows (gilts) were fed at approximately 30% of ad libitum intake, from mating 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 µg/kg live weight from day 25 to day 51 of pregnancy (term 115 days). Treatment with pGH increased maternal backfat loss between day 25 and day 51 of pregnancy, and increased maternal plasma IGF-I concentrations measured at day 51 of pregnancy. Fetal body weight, length and skull width at day 51 of pregnancy were increased by maternal treatment with pGH. Fetal plasma glucose concentrations were increased and maternal/fetal plasma glucose concentration gradients were decreased by maternal pGH treatment at 13·4, but not 25·6 µg/kg.day. Fetal plasma concentrations of urea were decreased by both levels of pGH treatment. Overall, fetal weight was negatively correlated with fetal plasma concentrations of urea, positively correlated with maternal plasma -amino nitrogen concentrations and unrelated to glucose concentrations in either maternal 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 the fetus.

Effects of GRF in early gestation on foetal development in Large White and Genex-Meishan gilts

“…Similar conclusions were obtained when pregnant gilts received pST or rpST in the first half of gestation (Kelley et al 1995;Sterle et al 1995;Gatford et al 2000;Rehfeldt et al 2001a). Yet, under crowded uterine conditions obtained by unilateral hysterectomy-ovariectomy, rpST increased uterine weight of gilts (Sterle et al 1996).…”

“…On the other hand, foetal uptake in the present experiment might have been further increased should other placental components have been affected by GRF. Gatford et al (2000) hypothesized that a ST treatment increases foetal growth by increasing the availability of one or more amino acids that usually limit full growth potential of the foetuses.…”

Responses to maternal GH or ractopamine during early–mid pregnancy are similar in primiparous and multiparous pregnant pigs

“…This corresponds to the period of most rapid placental growth and differentiation in the pig (Knight et al 1977). We and others have shown that daily maternal injections of gilts with porcine GH (pGH) during early-mid pregnancy increases fetal growth (Kelley et al 1995, Gatford et al 2000, numbers of muscle fibers in fetuses or progeny at birth (Rehfeldt et al 1993(Rehfeldt et al , 2001b) and increases growth rates and muscle size of their postnatal progeny (Kelley et al 1995, Gatford et al 2003. Some studies have reported that the greatest responses to pGH are greatest in the smallest piglets within each litter (Sterle et al 1995, Rehfeldt et al 2001a, Rehfeldt & Kuhn 2006, suggesting that the effects of pGH are greatest in the most restricted fetuses.…”

Maternal GHRH plasmid administration changes pituitary cell lineage and improves progeny growth of pigs

“…The pregnant gilt is highly sensitive to the metabolic effects of porcine GH and, when treated for various periods between 25 and 94 days of age, fetal growth is enhanced (13,29,31). GH modulates maternal metabolism and uteroplacental transport capacity, thereby promoting greater nutrient availability to the fetus and, consequently, more rapid growth.…”