Effects of exogenous somatotropin during early gestation on maternal performance, fetal growth, and compositional traits in pigs.

Abstract

The objective of this study was to determine the effects of maternal treatment with porcine somatotropin (pST) during early gestation on embryonic survival, fetal development, and internal environment for fetal growth. Sixty-two crossbred gilts received daily injections of either 3 mL of a placebo (control, n = 31) or 6 mg of pST (n = 31) from d 10 to 27 of gestation. Representative gilts were slaughtered on d 28, 37, and 62 of gestation. The remaining gilts were allowed to farrow. It was found that embryonic survival was not influenced by pST treatment (P > 0.10). However, pST affected the growth and composition of the maternal (endometrium) and fetal (chorion) parts of the placenta. Thus, endometrial RNA concentration tended to be increased by pST at d 37 (P = 0.15), and it was increased at d 62 (P < 0.05) of gestation, which is indicative of increased capacity for protein synthesis. At birth, placental chorion weight (P < 0.10) and contents of DM and protein (P < 0.05) were increased due to pST treatment, but no effects were detectable up to d 62 of gestation. Maternal pST treatment was effective at increasing nutrient supply to the embryo as suggested from elevated glucose concentrations in amniotic and allantoic fluids (P < 0.05) at d 28 of gestation. With regard to prenatal growth, embryonic DNA concentration was slightly elevated at d 28 (P < 0.10), but pST did not induce any changes in average embryonic, fetal, or neonatal weights. However, within litters, the birth weights of piglets in the 25% lowest weight group (LW) were increased by pST treatment vs control LW pigs (1,241+/-55 vs 1,099+/-59 g, P < 0.10). Thirty-eight neonates from 15 litters divided among the three weight groups were examined for body composition. The weight of the intestinal tract was increased above average after maternal pST treatment (P < 0.01). Additionally, the amounts of tissues such as bone (P = 0.12) and s.c. fat (P = 0.06), and of protein, fat (P = 0.10), and ash (P < 0.05) were increased, whereas the relative body composition remained unchanged by pST (P > 0.10). On average, muscle protein concentration was elevated due to pST (P < 0.01), and, in LW piglets, plasma IGF-I concentration was increased (P < 0.10). The results suggest that maternal somatotropin is a critical factor in early pregnancy capable of influencing placental nutrient transfer and placental growth. It thereby selectively improves the growth conditions for the smaller littermates.

Obstetric and neonatal outcomes to recombinant porcine somatotropin administered in the last third of pregnancy to primiparous sows

“…However, weight gain was associated with back fat loss in the latter group. These changes were previously reported in other studies and may be explained by the repartitioning effect of rpST (energy from fat to muscle) observed in growingfinishing pigs and in ST-treated sows (Cromwell et al 1992, Rehfeldt et al 2001.…”

“…Ltd, Victoria, Australia) in 1 ml saline (n=10 sows) from days 80 to 114 of gestation. The dose of rpST had previously been proved to increase fetal growth (Rehfeldt et al 2001).…”

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).…”

“…work showed that injections of 6 mg of pST from days 10 to 27 of gestation increased placental development and improved growth of the smaller littermates (Rehfeldt et al 2001a). Sterle et al (1995) also reported more pronounced effects of rpST on growth of foetuses with shorter placentation length.…”

Growth-hormone-releasing factor given to early-pregnant Genex-Meishan and Large White gilts: Effects on growth, carcass, meat quality and histochemical traits of the progeny

“…The administration of porcine somatotropin (ST) or growth hormone (GH) to pregnant gilts increased foetal growth and muscle development in newborn piglets (Sterle et al 1995;Rehfeldt et al 2001a;Gatford et al 2003). This likely resulted from the higher availability of glucose and free fatty acids and the higher number of proliferating myoblasts promoted by the elevated maternal GH concentrations (Rehfeldt et al 1999).…”