| Abstract: | Multiple investigations were undertaken to determine the effect of various strategies for improving forage intake, digestion, and ruminal fermentation parameters in Bos indicus and Bos taurus steers. Protein supplementation strategies and monensin inclusion have the potential to improve animal production efficiency while mitigating enteric CH₄ production; reducing the economic and environmental impact of cattle production systems. Effects of different levels and sources of supplemental protein on ruminal methane-producing activity, rate of NH₃ production, and concentrations of methanogens, protozoa, amino acid-utilizing, and trypticase-metabolizing bacteria were investigated. Subspecies differences were not observed for any of the measured parameters (P >= 0.28). Additionally, the effects of monensin inclusion and withdrawal on intake, digestion, and ruminal fermentation parameters were investigated. During the monensin inclusion phase, a subspecies difference was observed (P = 0.04) for total digestible OM intake, and a tendency (P = 0.07) for a subspecies difference was observed for CH₄-producing activity. During the monensin withdrawal phase, subspecies differences were observed (P <= 0.01) for total digestible OM intake and OM digestibility, and a tendency (P <= 0.09) for subspecies differences were observed for pH and forage OM intake. Overall, results suggest that the difference in ability of Bi and Bt cattle to utilize forage is diet dependent and may be altered by protein supplementation and monensin inclusion to improve production efficiency and mitigate enteric CH₄ production. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155117 |
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