THE EPIGENETIC IMPACT OF WEANING ON CRANIOFACIAL MORPHOLOGY DURING GROWTH

Miniature pigs (Sus scrofa) were used as a model to investigate whethe r the time of weaning (a nongenetic factor) affects skeletal growth ra tes for both pre- and postweaning time periods. Control litters were w eaned at the normal time of 32 days. Two Litters were weaned early (at 20 days) and two late (at 46 days). We digitized cranial landmarks fr om radiographs taken three times a week for a total of 70 days. We use d analysis of covariance to test for differences in growth rates betwe en pre- and post-weaning periods, as well as differences in growth rat es among treatments. In both the late weaned pigs and the controls, fa cial length, facial width, basicranial length, and basicranial width g rowth rates slowed significantly at the time of weaning. However, in t he early weaned pigs, there were no significant changes in growth rate s for any of the facial or basicranial measurements at weaning. Furthe rmore, the postweaning rates of growth were different among treatments . One possible implication is that early growth rates could be under t ight genetic control while later growth rates can be epigenetically re gulated through nutritional changes. (C) 1996 Wiley-Liss, Inc.