Effect of stocking rate on pig performance in a wean-to-finish production system

Crossbred pigs (n = 1,296) were used in a randomized complete block design to evaluate three stocking rate treatments (22, 27, or 32 pigs pen^-1) on growth performance from weaning [5.0 ± 0.01 kg body weight (BW); 15 ± 1 d of age] to 24 wk post-weaning. Floor and feeder spaces per pig were 0.78 m² and 4.2 cm, 0.64 m² and 3.4 cm, and 0.54 m ² and 2.9 cm for group sizes of 22, 27, and 32, respectively. During the first 8 wk post-weaning there was a tendency for average daily gain (ADG) (511, 505, and 497 g d^-1, respectively; P = 0.07) and BW (35.1, 34.7, and 34.3 kg, respectively; P = 0.08) to decrease linearly as stocking rate increased. Moreover, from week 8 to 18, week 18 to 24, and for the overall period (weaning to week 24) both ADG (688, 660, and 635 g d^-1 for the overall period, respectively) and BW (121.8, 117.1 and 113.1 kg at week 24, respectively) decreased linearly (P < 0.001) with increasing stocking rate. There were no treatment differences in the coefficient of variation in pig BW within a pen at any stage of the study. Morbidity and mortality rates increased linearly (8.5, 10.2, and 12.7%; P < 0.05) with increasing stocking rate. In conclusion, decreasing group size, thereby increasing floor and feeder space pig^-1, reduced morbidity and mortality and increased growth rate after 8 wk post-weaning resulting in heavier pigs at 24 wk post-weaning for the smaller groups.