| Experiments were conducted to evaluate the relationship between early and late growth performance and carcass composition of pigs under modern management conditions. Results of the first study indicated pigs with heavier BW (1.8 vs 1.3 kg; P < 0.001) at birth were heavier ( P < 0.001) at weaning and had greater (P < 0.001) ADG and ADFI, similar (P > 0.05) gain:feed, and required fewer days (7) to reach 110 kg BW. In contrast, feeding supplemental milk replacer to piglets during lactation accelerated early growth rate, but had little impact (P > 0.05) on growth performance after weaning. In general, these results suggest a greater impact of BW at birth than increased nutrient intake during lactation on pig growth performance. In the second study, it was determined that penning pigs in large groups (50 and 100 compared to 25 pigs/pen) resulted in poorer early growth performance; however, for the period from weaning to slaughter, pigs had similar (P > 0.05) levels of performance in all three group sizes. In a following study, doubling the number of pigs per pen (104 vs 52 pigs/pen) immediately post-weaning restricted growth rate (P < 0.01) to wk 10, but when double-stocked pigs were split into single-stocked pens an improved feed efficiency to slaughter (P < 0.05) was observed. These results were confirmed in two later studies which demonstrated that pigs exhibiting a decreased post-weaning growth rate due to restricted access to floor, feeder-trough space, or both, had increased feed efficiency (P < 0.01) in the subsequent period to slaughter. In addition, feeding piglets a simple compared to a complex diet in the period immediately post-weaning significantly (P < 0.01) lowered pig performance during the early period after weaning, but did not impact (P > 0.05) subsequent growth to slaughter. In general, pig growth performance for the entire period from weaning to slaughter was largely unaffected (P > 0.05) by variations in growth rate during early periods post-weaning. Moreover, factors that produced variations in the early growth rate of pigs had little impact (P > 0.05) on carcass backfat and loin-eye depth at slaughter. Therefore, in conclusion, management strategies that maximize pig growth rate during the early period post-weaning may not be necessary to achieve an optimum overall growth performance from weaning to market. |
