Masters Theses

Date of Award

6-1979

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Ronald R. Johnson

Committee Members

W. R. Backus, K. M. Barth, J. W. Holloway

Abstract

This study was conducted initially to monitor changes occuring in ruminal pH, volatile fatty acid and ciliate protozoa concentrations as steers were adapted from all-forage rations to all-grain rations of whole shelled corn or mixtures of whole shelled corn and whole wheat. In addition, the effects of monensin additions and protein supplement type on these same rumen parameters in steers consuming basal rations of whole shelled corn were determined. Finally, the effects of varying levels of whole wheat, fed in combination with whole shelled corn, upon these same rumen parameters were determined.

In trial 1, four steers were adapted from all-forage rations to all-grain rations composed of whole shelled corn over a 15 day period (adaptation phase). The same steers were then fed whole shelled corn basal rations with and without monensin, supplemented with a commercial protein supplement or soybean meal for 112 days (switchover phase).

In trial 2, 4? steers were adapted from all-forage rations to all-grain rations composed of varying proportions of whole shelled corn and whole wheat over a 21 day period (adaptation phase). After adaptation to the all-grain rations, the same steers continued to receive the same corn - wheat rations for 50 days (finishing phase).

The effects of treatment on rumen variables observed within each trial are presented at a 5 percent level of significance. During the adaptation phase of trial 1, rumen fluid pH remained relatively high (6.70-6.85), but did decrease on day 15 (6.28). Total volatile fatty acid concentration did not change during the adaptation phase (69.8- 107.9 μ/ml), molar percent acetate decreased (73.6-49.7) and molar percent propionate tended to remain stable (12.6-15.0), but did increase (23.9) on day 12. Molar percents butyrate and valerate increased (9.4-29.7, respectively) during the adaptation phase. Molar percent isoacids did not change (.6-3.8) and protozoa concentrations, composed primarily of Entodinium, increased initially (1.71-7.24 X 105/ml), and then decreased until all animals were defaunated after consuming all-grain, forage-free rations for 14 days.

During the adaptation phase of trial 2, rumen fluid pH (6.77-5.67), molar percent acetate (73.8-43.9) and molar percent butyrate (8.3-6.9) decreased, while total volatile fatty acid concentration (70.6-167.I μm/ml) and molar percent propionate (15.4-45.4) increased. Molar percent valerate (.4-3.2) and isoacids (.8-1.3) did not change significantly. Total ruminal protozoa concentrations did not change between days 6 and 7 of the adaptation phase (1.43-1.50 x 105/ml), however, by day 21, 85 percent of all steers were defaunated.

During the switchover phase of trial 1, monensin or protein supplement type did not effect ruminal pH (5.96-6.03), total volatile fatty acid concentration (121.0-130.0 μm/ml), molar percents acetate (43.7-46.7), propionate (39.0-44.0), butyrate (7.5-9.0), valerate (3.6-5.3) or isoacids (.4-.6).

During the finishing phase of trial 2, ruminal pH (5.94-6.22), total volatile fatty acid concentration (186.5-225.1 μm/ml), molar percents acetate (41.0-43.1), propionate (42.5-47.4), butyrate (7.3-10.4), valerate (2.1-2.2) or isoacids (.9-1.4) were not effected by varying levels of wheat in the ration.

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