Degree Type

Creative Component

Semester of Graduation

Fall 2019


Animal Science

First Major Professor

Nick Serao


Master of Science (MS)


Animal Breeding and Genetics


Porcine reproductive and respiratory syndrome (PRRS) and porcine epidemic diarrhea (PED) are diseases that have been plaguing the swine industry for years and strategies to prevent and control them have shown limited success. Studies have suggested that selection for improved performance during PRRS infection is possible. In this thesis, we analyzed the effects of PRRS and PED on reproductive performance in commercial sows. The first chapter of this thesis is a review of the current literature related to the impact, causes, clinical signs, and methods of control for both PRRS and PED. This chapter also encompasses the genetic response to disease and methods to select for improved performance. The second chapter presents results of a genetic analysis for reproductive traits in commercial sows infected or not with PRRS or PED viruses. Results show that disease (PRRS or PED) was significant (P< 0.05) for all reproductive traits, except for total piglets born. Performance during PED and Clean was similar for all traits, with the exception of number of piglets weaned and abortion, which were lower for PED than for Clean. Heritability estimates were generally low, but these increased during for PED and PRRS compared to Clean. Genetic correlations within trait, between disease statuses, estimates ranged from -0.17 (number weaned between PRRS and PED) to 0.99 (abortion between Clean and PRRS). Overall, genetic correlations were positive between disease statuses, indicating that relationships between clean and disease are favorable for selection. Overall, these results indicate that selection for improved performance during PRRS and PED in commercial sows is possible and would not negatively impact performance in clean environments.

Copyright Owner

Scanlan, Cassandra

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