title: Effect of group size on pig performance in a wean-to-finish production system.
abstract: Crossbred pigs (n = 1,400) were used to evaluate the effect of group size (25 vs 50 vs 100 pigs/pen) in a wean-to-finish production system on growth performance and carcass measures. Pigs were weaned at 17 d (range = 15 to 19) of age with a mean initial BW of 5.9 +/- 0.02 kg and taken to a final mean pen weight of 116 +/- 0.9 kg. A 10-phase dietary regimen was used, and pigs had free access to feed and water. Feeder-trough space (4.3 cm/pig) and floor-area allowance (0.68 m2/pig) were the same for all group sizes. Compared to groups of 25, pigs in groups of 50 and 100 animals were lighter (P < 0.001) at the end of wk 8 after weaning and had lower (3%, P < 0.01) ADG and gain:feed (G/F) but similar (P > 0.05) ADFI during the first 8 wk of the study. At the end of the study, pig weight and the coefficient of variation in pig weight within a pen were similar (P > 0.05) across group sizes. During the period from 8 wk after weaning to the end of the study, pigs in groups of 100 compared to 50 animals had greater (3%, P < 0.01) ADG, and pigs in groups of 25 were intermediate for ADG. Average daily feed intake during this period was similar (P > 0.05) for all group sizes; however, G/F was greater (3%, P < 0.01) for groups of 100 compared to 25 or 50 animals. For the overall study period, ADG, ADFI, and G/F from weaning to slaughter weight were similar across group sizes (P > 0.05; 655, 648, and 658 g; 1,759, 1,755, and 1,759 g; and 0.37, 0.37, and 0.37; for ADG, ADFI, and G/F, respectively, for groups of 25, 50, and 100 pigs, respectively). Mortality was similar (P > 0.05) across group sizes; however, morbidity (pigs removed due to poor health or injury) was higher in groups of 25 pigs compared to the other two group sizes (7.0, 3.5, and 3.9% for groups of 25, 50, and 100, respectively; P < 0.05). Group-size treatment did not affect (P > 0.05) carcass dressing percentage, backfat thickness, or loin-eye depth. In summary, growth performance from weaning to market weight was not affected by group size.
authors.affiliation: Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
authors.forename: B F
authors.initials: BF
authors.lastname: Wolter
authors.forename: M
authors.initials: M
authors.lastname: Ellis
authors.forename: S E
authors.initials: SE
authors.lastname: Curtis
authors.forename: N R
authors.initials: NR
authors.lastname: Augspurger
authors.forename: D N
authors.initials: DN
authors.lastname: Hamilton
authors.forename: E N
authors.initials: EN
authors.lastname: Parr
authors.forename: D M
authors.initials: DM
authors.lastname: Webel
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D005260:Female; D006799:Housing, Animal; D008297:Male; D011897:Random Allocation; D013552:Swine / Q000254:growth & development*; D014886:Weaning