The effects of group size and subtherapeutic antibiotic alternatives on growth performance and morbidity of nursery pigs: a model for feed additive evaluation

Olsen, Kristin M; Gabler, Nicholas K; Rademacher, Chris J; Schwartz, Kent J; Schweer, Wesley P; Gourley, Gene G; Patience, John F

For the overall period (days 0-41), there were impacts of both dietary treatment and group size, and their interaction, on piglet growth performance. There was an interaction between diet and group size for ADG (P = 0.012) and ADFI (P =0.015). Pigs fed the PC had higher ADG and ADFI than the NC for both group sizes (P < 0.05), and pigs fed the ZA diet only had a higher ADG and ADFI than the NC in the large groups (P < 0.05). Small groups fed the NC and DR diets had higher ADG compared to large groups fed these diets (P < 0.05). However, small and large groups had similar ADG for the PC and ZA diets (P > 0.05). The mean ADG for large groups was 0.280 kg and was 0.293 kg for small groups (main effect P = 0.006). Small groups had similar ADFI to large groups except for the NC control diet where small groups had higher ADFI (P < 0.05). There was no interaction between diet and group size for G:F; pigs fed the PC diet were more efficient than pigs fed the NC, ZA, and DR diets (diet P < 0.001), and small groups were more feed efficient than large groups (group size P = 0.004). There was no impact of the DR diet on growth performance (P > 0.05).