Jong Kyu Ha

Document Type

Dissertation - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Animal Science

First Advisor

R.J. Emerick


Experiments using lambs were conducted to study the effects of buffers or roughages against acidosis occurring during rapid dietary changes. Experiments using rats were conducted to investigate vitamin A and thiamin stability and/or utilization as influenced by bentonite. Incubating rumen fluid in vitro at a pH lower than 6 reduced volatile fatty acid (VFA) production and increased lactate accumulation. Limestone or bentonite at levels of 2% in 92% concentrate diets had little effect on feed intake or rumen and blood parameters during a 7-day treatment period using rumen-canulated sheep. However, 2% NaHCO3 increased rumen pH and feed intake on the third day of high-concentrate feeding. These buffers included in all-concentrate diets in another experiment raised rumen pH and reduced lactate production with little effect on rumen VFA or blood parameters during the first 3 days of concentrate feeding. Alfalfa hay at a 10% level proved to be as effective as the buffers in all criteria. Lambs fed NaHCO3 excreted an alkaline urine compared with an acidic urine for all others. In a digestive trial conducted after 20 days adaptation, dietary buffers tended to increase ration digestibility and fecal pH and reduce fecal starch, but only 2% NaHCO3 improved starch digestibility significantly. Magnesium retention was increased by bentonite, calcium by limestone, and sodium and magnesium by NaHCO3. In another experiment, 2% bentonite or 2% limestone in 92% concentrate diets slightly improved lamb performance during the initial 21 days but were without effect during an extended feeding period. An equal mixture of both buffers at levels totaling 2% and 4% reduced lamb performance. In another instance when lambs were rapidly changed to high-concentrate diets, alfalfa and brome hay at 10% levels reduced acidosis-related death losses from 72% for the controls to 31% for the lambs fed the diets containing hay. Bentonite limited vitamin A utilization by rats with the major loss occurring through adsorption during die t mixing and/or storage. Particle size of bentonite was a main f actor associated with this effect. Complexing bentonite with proteins or nonionic organic materials was highly effective in preventing adsorption of vitamin A by bentonite. Bentonite tended to depress rat growth with a marginal level of thiamin in the diet but not with excess thiamin.

Library of Congress Subject Headings

Lambs -- Feeding and feeds




South Dakota State University