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

It is clear that the PRRSV challenge impacted the performance of this group of pigs. Based on the standard feed budget used at this farm, expected feed intake during phase 3 would be 1.0-1.2 kg/ pig/day. Pigs consumed, on average, only 0.52 kg/ pig/day during this period. Compared to estimates from NRC (2012) for 11-25 kg pigs, the pigs gained 46% less and ate 45% less per day. However, in phases 1 and 2, prior to the PRRSV outbreak, pigs performed as expected (0.212 kg/day compared to the 0.21 kg/day estimate for 5-7 kg pigs, and 0.31 kg/day compared to the 0.34 kg/day estimate for 7-11 kg pigs; NRC, 2012). Severely reduced feed intake and low growth rate demonstrates the impact of the PRRSV challenge on growth performance, which is typical for pigs challenged with this virus (Schweer et al., 2017b) . The present results were likely influenced by this health challenge, especially in phase 3 when pigs were consuming far less feed than expected and therefore were not receiving the desired amount of the AGP alternatives, potentially decreasing their effect.