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

With future study design in mind, sample size calculations were conducted (Table 8 ) using the SD generated in the overall data to predict the sample size that would be needed to detect differences of practical significance and to determine if required sample size would differ according to pig group size. Though group size may be an important consideration in AGP alternative studies as previously discussed, it does not appear that a larger sample size would necessarily be needed for one pig group size over the other. In conclusion, the methodology used in this study resulted in the ability to compare the impact of dietary treatments on growth performance, morbidity, and medical treatments to establish a description of population health status. This was facilitated by careful planning and execution of the experimental protocol as well as strict record keeping and observation. The results suggest that group size is an important factor to consider when designing and interpreting AGP alternative studies. As research on AGP alternatives continues, the credibility and impact of future studies will be improved with proper design, protocol implementation, and consistent reporting of pertinent study information and results. Careful consideration of group size, sample size, the study components mentioned above, and how these factors may influence study outcomes will be advantageous to the swine industry's rate of progress in identifying effective alternatives to growth-promoting antibiotics.