ABSTRACTForty-two piglets were used to study the effects of heavy and light birth weight, and of four levels of feeding, ranging from 37 to 91 g dry matter per kg M0 75 per day, on growth between 5 days of age and 6·5kg live weight, and on body composition, and the cellularity of muscle and subcutaneous adipose tissue, at the latter weight. The effects of birth weight and level of feeding to 6·5 kg on performance between 6·5 and 11 -5 kg, and on body composition at 11·5 kg, were also investigated.Light birth weight piglets grew more slowly to 6·5 kg than those of heavy birth weight (P < 0·05). However, birth weight had no effect on food conversion efficiency or on body composition.Each increment in feeding level resulted in increases in growth rate (P < 0·01), body fat content (P < 0·01) and average fat-cell diameter (P < 0·01) at 6·5 kg, but in decreases in body protein and water (P < 0·01).The weight of the m. semitendinosus at 6·5 kg was unaffected by either birth weight or level of feeding. However, the deoxyribonucleic acid content of the muscle at both 6·5 and 11·5 kg was less in light birth weight piglets fed at the lowest level prior to 6·5 kg (P < 0·05). These piglets also exhibited poorer growth performance subsequent to 6·5 kg than their heavier birth weight counterparts.Nevertheless, piglets of both light and heavy birth weight, fed at the lowest level to 6·5 kg, grew faster and more effficiently between 6·5 and 11·5kg (P < 0·05), and were leaner at 11·5kg than those previously fed at the highest level (P < 0·01). Average fat-cell diameter at 11·5kg was also less in pigs fed at the lowest level prior to 6·5kg (P < 0·01). Total deoxyribonucleic acid in subcutaneous adipose tissue at 11·5kg was unaffected by either birth weight or level of feeding prior to 6·5 kg.
Influence of birth weight on gene regulators of lipid metabolism and utilization in subcutaneous adipose tissue and skeletal muscle of neonatal pigs