Early weaning has minimal effects on lifetime growth performance and body composition of pigs

Abstract

Two hundred and forty pigs (120 entire boars and 120 gilts) were selected in three replicates of 40 boars and 40 gilts and housed in pens of 20 pigs of the same sex. Pigs were allocated to a 2 by 2 factorial experiment, with the respective factors being sex (entire male or female) and age at weaning (13 or 21 days). Pigs within each replicate were weaned on the same day, with the pigs’ farrowing date differing by ~8 days for the two weaning ages. Pigs were offered ad libitum access to feed for the entire experimental period. Eight randomly selected pigs from each pen were tagged as focus animals. These animals underwent dual energy X-ray absorptiometry (DXA) scanning six times from weaning through to slaughter to measure changes in body composition. The animals weaned at 13 days of age were lighter at weaning (4.68 ± 1.16 and 6.84 ± 1.34 kg, respectively, for the animals weaned at 13 and 21 days, P < 0.001). During the first 4 days after weaning pigs weaned at 21 days of age consumed more feed (72.1 v. 30.9 g/day, P < 0.001) and gained faster (35.0 v. –63.0 g/day, P = 0.042) than those weaned at 13 days. The pigs weaned at 13 days did, however, ‘catch up’ to be the same weight as those weaned at 21 days by 53 days of age (17.4 and 17.8 kg, respectively, P = 0.33). Daily gain from birth to 146 days of age did not differ across treatments (610, 597, 640, 657 g/day, respectively, for the gilts weaned at 13 days, gilts weaned at 21 days, boars weaned at 13 days and boars weaned at 21 days, P = 0.31). DXA analyses indicated that the animals weaned at 13 days had a greater percentage of lean tissue at 119 days of age (78.4 and 76.8%, respectively, P = 0.039) although this was not maintained through to slaughter. There were no treatment effects on the percentage of adipose tissue from 90 to 146 days of age, although the DXA estimated adipose tissue mass was greater at 146 days of age in the animals weaned at 21 days (13.8 and 15.2 kg, respectively, for the animals weaned at 13 and 21 days of age, P = 0.023, s.e.d. 0.60). These data suggest that weaning age predominately influences growth immediately after weaning, and does not have a major influence on lifetime growth performance or body composition at commercial slaughter weights.