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Activity Number: 30 - SPEED: Statistics and Econometrics
Type: Contributed
Date/Time: Sunday, July 29, 2018 : 2:00 PM to 3:50 PM
Sponsor: Quality and Productivity Section
Abstract #329743 Presentation
Title: Repeated-Measures ANCOVA for an Antibiotic-Free Experiment in Swine
Author(s): Danielle Wilson-Wells* and Tom A. Rathje and Caitlyn E Bruns
Companies: DNA Genetics and DNA Genetics and DNA Genetics
Keywords: Repeated Measures; ANCOVA; experimental design

A current issue facing swine producers today has been to understand how to ensure that pigs can reach market weight with an adequate rate of gain, given that they have been raised without the use of medicated feed or water. Litters were assigned an antibiotic-free or conventional feed and water treatment at birth. At weaning, pigs were assigned to pens by sex and treatment. Pens were weighed at 7-time points throughout the nursery-finish period. Performance traits were analyzed. Each time period was analyzed separately resulting in exaggerated treatment differences. Antibiotic-free pigs were treated if they became ill and removed from the pen as they were no longer antibiotic free. Removal increased the available space for remaining pigs, masking true values for each treatment as pigs with more space have better growth due to less competition for food and space. A repeated-measure ANCOVA model was used which included fixed effects for sex, barn, and treatment. A penalization covariate for square footage per pig was used get a true comparison of the treatments over time. Pigs receiving the antibiotic free treatment that did not require treatment grow similarly to conventional pigs.

Authors who are presenting talks have a * after their name.

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