Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Animal Science (PhD)

Degree Level



Animal Science


Jiangchao Zhao

Committee Member

Charles V. Maxwell

Second Committee Member

Yan Huang

Third Committee Member

Young Min Kwon


Feed additives, Growth performance, Gut microbiome, Weaning pigs


To secure animal welfare and maximum production, feed additives are often added to nursery pig diets to increase nutrition digestibility, enhance intestinal health, and prevent or mitigate disease, with the ultimate goal of improving growth performance. This thesis performed a longitudinal analysis using next-generation sequencing to investigate the dynamic changes of gut microbiota in weaned pigs fed commercial feed additives. Chapter II was used to evaluate the effects of organic acid mixture on growth performance and gut microbiota of weaning pigs. This study demonstrated that the inclusion of 0.035% (SBA0.035) or 0.070% (SBA0.070) sodium butyrate in a diet containing 0.5% benzoic acid improved the growth performance of weaning pigs. The SBA0.035 diet revealed the greatest gut microbial diversity and the enrichment of several potentially beneficial bacterial taxa such as Oscillospira, Blautia, and Turicibacter. The results showed that the gut community benefitted more in pigs fed this diet compared to the other diets used in this study. Chapter III evaluated the impact of peptides along with probiotic and ZnO on the growth performance and fecal microbiome of weaning pigs. Results indicated that the combination diet of peptides and ZnO can offer equivalent growth performance but at a lower cost as compared to the diet containing SDPP and ZnO. Gut microbiota analysis clearly showed that diet containing peptides plus ZnO had similar impacts on specific bacteria as dietary SDPP in combination with ZnO, which may have contributed to increased growth performance. In Chapter IV, we evaluated the growth performance and gut microbiota of weaning pigs subjected to different levels of peptides with or without the pharmaceutical level of ZnO supplementation in a nutrient‐deficient diet. Results revealed that the pharmaceutical level of ZnO conditioned the gut community to a point where the peptides could effectively restore growth performance in nursery pigs fed nutrient-deficient diets.

Available for download on Friday, January 06, 2023