Paul J. Kononoff
Date of this Version
A dissertation presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Doctor of Philosophy
Major: Animal Science (Ruminant Nutrition)
Under the supervision of Professor Paul J. Kononoff
Lincoln, Nebraska, December 2023
Forage quality is the potential of a forage to produce a production response in animals. Because of how essential they are in dairy cattle rations, forages can have major influence on the behavior and production of dairy cattle. In experiment 1, the effect of forage fragility on the rumen environment and digestibility was evaluated. Increasing the inclusion of a less fragile forage led to greater rumen retention time, which resulted in lower rumen pH and greater NDF digestibility. Experiment 2 evaluated the effects of diets high in either corn silage or alfalfa haylage supplemented with either corn- or soybased protein on the production, energy, and N utilization. Supplementing corn-based protein did not affect milk production or components in both corn silage and alfalfa haylage diets. Corn silage diets had the greatest N intake and urinary N but the lowest fecal N. The effects of lower-lignin (LoL) and conventional (CON) alfalfa on energy and N utilization was evaluated in experiment 3. No difference was observed in DMI, but methane production was lowest in the diet with a 50:50 blend of LoL and CON alfalfa. Intake of N linearly decreased while urinary N increased with increasing LoL alfalfa inclusion. In experiment 4, the effect of forage quality on feed preference of lactating dairy cattle was examined. Cows most preferred hay with a higher forage quality. Surprisingly, low quality hay was the next most preferred followed by moderate quality hay. Experiment 5 continued the comparison of LoL and CON alfalfa with evaluating NDF content and digestibility across a growing season. Overall NDF content was affected by variety and cutting, but no difference was observed in NDF digestibility. No difference was observed in NDF for the first, third, and fourth cuttings between LoL and CON alfalfa, but NDF was greatest in the second cutting. Results suggest that differences in forage quality can have diverse effects on production and energy metabolism in dairy cattle.
Advisor: Paul J. Kononoff