Effects of maternal plasmid GHRH treatment on offspring growth

To differentiate prenatal effects of plasmid growth hormone-releasing hormone (GHRH) treatment from maternal effects mediated by lactation on long-term growth of offspring, a cross-fostering study was designed. Pregnant sows (n = 12) were untreated (n = 6) or received either a Wt-GHRH (n = 2) or HV-GHRH (n = 4) plasmid. At birth, half of each litter was cross-fostered (treated to controls and controls to treated only). Piglets from plasmid-injected sows were heavier at birth (HV-GHRH, 1.65 ± 0.07 kg; Wt-GHRH, 1.46 ± 0.05 kg vs. Controls, 1.27 ± 0.03 kg; P ≥ 0.001) and at weaning (Wt-GHRH, 6.01 ± 0.21 kg and HV-GHRH, 6.34 ± 0.15 kg vs. Controls, 5.37 ± 0.14 kg; P ≥ 0.02, respectively). Control piglets cross-fostered to plasmid-injected sows grew faster to weaning (Wt-GHRH, 5.61 ± 0.15 kg and HV-GHRH, 5.70 ± 0.29 kg vs. Controls, 5.08 ± 0.22 kg; P > 0.05, respectively). Piglets from plasmid-injected sows that suckled on control sows were larger than control piglets on control sows (Wt-GHRH, 5.93 ± 0.20 kg and HV-GHRH, 6.2 ± 0.19 kg vs. Controls, 5.08 ± 0.22 kg; P > 0.05, respectively), but smaller than their littermates left on their treated mothers. The observed improvements were maintained until the end of the study when the offspring were 170-day-old. The results suggest that the improved growth of offspring of GHRH plasmid-treated sows pre-weaning is attributable to improved maternal performance, while after weaning the effects on the pituitary component are relevant.