Theses and Dissertations


Adam I. Orr

Issuing Body

Mississippi State University


Rude, J. Brian

Committee Member

Lawrence, L. Mark

Committee Member

Kidd, T. Michael

Committee Member

Willard, T. Scott

Date of Degree


Document Type

Dissertation - Open Access


Animal Nutrition

Degree Name

Doctor of Philosophy (Ph.D)


College of Agriculture and Life Sciences


Department of Animal and Dairy Sciences


To better understand the facets of nutrient utilization, a series of in vivo and in vitro studies were undertaken to elucidate the effect of supplementation on utilization of moderate-quality bermudagrass hay and to identify mechanisms to evaluate the role of rumen bacterial populations on feedstuff utilization. A digestion trial was conducted using 6 ruminally cannulated steers receiving bermudagrass hay supplemented with soybean hulls (HULLS), cracked corn (CORN), or soybean hulls and cracked corn (MIX; 75% and 25%, respectively) in a 3x3 Latin Rectangle arrangement. Additionally, ruminal fluid was continuously cultured using the BioFlo® 110 fermentation system to evaluate the in vitro fermentive parameters of ground moderate-quality bermudagrass hay either alone (HAY; 20 g DM L-1 d-1) or supplemented (7 g DM L-1 d-1) with corn (CORN), soybean hulls (SBH), or both (25:75; MIX) in a randomized complete block. Genomic DNA from continuous culture as well as from pure bacterial culture samples were sought to differentially enumerate select bacterial strains via real-time PCR using specie-specific DNA primers. The information is to be used for elucidating responses in ruminal digestibility of varying feed-types. Finally, as an alternative to PCR, bioluminescence of transformed Escherichia coli was evaluated by measuring extent of photonic emission with and without antibiotic selection over time. Evaluations were also made of photonic emission by E. coli grown in ruminal fluid with and without additional feed particles. Data seem to indicate that replacing a portion of corn with soybean hulls may successfully improved fiber digestion and improved ruminal N-utilization. Real-time PCR shows potential for evaluating ruminal bacteria where as biophotonics may need further modification before meaningful in situ evaluations of live ruminants can be employed.