Group size and floor-space allowance can affect weanling-pig performance

Crossbred weanling piglets (n = 1,920; mean initial BW, 5.3 ±.7 7 kg) were used in two 9-wk trials employing a randomized block design in a 2 x 2 factorial arrangement of treatments to determine effects of group size (20 [Small = S] or 100 [Large = L] pigs/ pen) and floor-space allowance (calculated requirement [CR] or calculated requirement less 50% of estimated free space [CR-50]) on growth performance. Free space was estimated for each group size. From wk 1 through 4 after weaning, S and L groups at CR were allowed a floor space of.17 m 2 /pig, and at CR-50, S and L groups were allowed.15 m 2 /pig and.13 m 2 /pig, respectively. From wk 5 through 9 after weaning, all CR treatment pigs were provided a floor space of.38 m 2 /pig, and for the CR-50 treatment, S and L pigs were allowed.32 m 2 /pig and.28 m 2 /pig, respectively. Piglets had free access to feed and water. Feeder-trough space per pig was the same for both group sizes. Feed-intake data were collected for only wk 1 through 4. Group size by floor-space allowance interactions (P .05). Piglets in CR groups had greater ADG (5%; P <.01) throughout the trial, with a greater G/F (P <.05) for wk 1 through 4, and were heavier (P <.01) than those in CR-50 groups at the end of wk 4 (3%) and 9 (4%). Pigs in L groups had a greater within-pen coefficient of variation in BW at the end of wk 9 than pigs in S groups. Large groups and reduced floor-space allowance reduced piglet growth performance in the nursery.