Date of Award:

5-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Committee Chair(s)

Kara Thornton-Kurth

Committee

Kara Thornton-Kurth

Committee

Chad Page

Committee

Allen J. Young

Abstract

In this study we determined the impact of increasing dietary whole cottonseed (WCS) on rumen fermentation, nutrient digestibility, and microbial community composition. This study contributes novel information to the dairy community deepening the understanding of how including different levels of WCS can affect the rumen environment. This research was conducted in continuous culture fermenters. Treatments included a control diet without WCS, or the control diet plus 5, 10, or 15% (dry matter) WCS. The control diet was a 50:50 orchardgrass hay:concentrate mixture fed twice daily. In the second experiment, soybean meal and cottonseed meal (CSM) were included, and rations were balanced for fiber and protein. For the first experiment, no treatment effect was observed for neutral detergent fiber (NDF) or starch digestibility, or for acetate concentration. Butyrate and ammoniacal nitrogen concentrations increased, while propionate concentration tended to decrease as WCS was added. Increasing WCS in the diet decreased protozoa count and relative abundance of archaea. Firmicutes abundance increased whereas Bacteriodetes decreased with the addition of WCS. Lachnospiraceae and Prevotellaceae were the most abundant bacteria families in all the samples. The two most abundant genera across samples were Prevotella and Pseudobutyribrio, and the addition of WCS decreased the abundance of both. For the second experiment, with diets adjusted for fiber and protein, inclusion of WCS did not affect NDF digestibility or ammonia production. Acetate and propionate decreased with the addition of WCS while no treatment effect was observed for butyrate production. Bacteria population increased with inclusion of WCS while the opposite was observed for archaea. Our results indicate that increasing levels of WCS up to 15% (dry matter) diet do not negatively impact fiber and starch digestion in the rumen. Furthermore, inclusion of WCS at affected the microbial community composition at different levels. In conclusion, supplementation of WCS had an overall positive impact on the rumen as it did not affect rumen fermentation or nutrient digestibility, and it increased bacteria population and decreased archaea concentrations.

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