MATERNAL TREATMENT WITH SOMATOTROPIN ALTERS EMBRYONIC-DEVELOPMENT ANDEARLY POSTNATAL-GROWTH OF PIGS

A possible management strategy to alter fetal development and enhance sow productivity and progeny performance was examined by maternal admi nistration of porcine somatotropin during early gestation. Eighteen cr ossbred gilts were bred naturally to boars of similar genetics, and pr egnancy was confirmed between Days 21 and 24 of gestation by ultrasoun d. All animals were allowed ad libitum consumption of a 16% CP gestati on diet through Day 21 of gestation and 3.0 kg/d for the remainder of gestation. Gilts were injected twice daily with 0 (n = 10) or 15 mu g/ kg body weight (BW) (n = 10; total, 30 mu g/kg BW per d) pituitary-der ived porcine somatotropin (pST) during Days 28 to 40 of gestation. Dat a were collected postmortem during embryonic, neonatal, and market-wei ght phases. At 41 d of gestation, pST treatment increased embryonic su rvival (87.9 versus 77.0%; P < 0.05) and embryo crown rump lengths (77 .96 versus 65.14 mm; P < 0.01), but embryo weight was not altered (10. 15 and 9.03 g; P > 0.10). Pigs from pST-treated gilts had increased (P < 0.01) crown rump lengths at birth (31.5 versus 30.4 cm) and 21 d (5 0.9 versus 48.4 cm). However, no differences were observed in birth or 21-d weights as a result of pST treatment (P > 0.10). Neonatal carcas ses of progeny (20 kg BW) from the pST-treated gilts had heavier semit endinosus muscles (76.1 versus 66.0 g; P < 0.10), larger longissimus m uscle cross-sectional area (10.1 versus 8.2 cm(2); P < 0.05), longer s ides (51.2 versus 47.9 cm; P < 0.001), and decreased 10th rib backfat (6.67 versus 8.64 mm; P < 0.001) compared with those of controls. Carc asses of market-weight progeny (100 kg BW) from pST-treated gilts had larger longissimus muscle cross-sectional area (P < 0.10), heavier tri mmed loins (P < 0.10), and longer carcass sides (P < 0.05). Data are s upportive of a hypothesis that mechanisms during early embryonic devel opment are sensitive to manipulation through selected management strat egies of the sow and that modifications of this strategy may serve as a model for the examination of molecular and cellular events controlli ng early embryonic growth.