Masters Theses

Date of Award

8-1974

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

C. C. Chamberlain

Committee Members

J. B. McLaren, D. O. Richardson

Abstract

A six-year study with growing-finishing beef heifers was conducted to: 1. Compare cottonseed meal (CSM) and urea as protein supplements for corn silage; 2. To evaluate cattle performance when sulfur was added to urea-treated corn silage; 3. Test the value of different levels of urea additions to corn silage if the N:S ratio is held constant; and 4. Compare organic and inorganic sources of sulfur added to urea-treated corn silage. Each year 40 or 48 medium or good grade heifer calves (450-500 pounds) were allotted into eight lots of five or six each. Two lots were randomly assigned to each treatment. The finishing period was divided into a silage phase and a concentrate phase. The heifers were weighed every 28 days and subjectively evaluated at the beginning and end of each feeding phase. When the heifers reached an average con-dition grade of good, they were slaughtered. During the silage phase the CSM-supplemented heifers gained sig-nificantly faster (P < .05) than the urea-supplemented heifers. At the end of the total feeding period the CSM-supplemented heifers had a higher Average Daily Gain (ADG) than the urea-supplemented heifers, but the difference was non-significant (P > .05). There was no significant difference (P > .05) between groups in feed conversion due to source of protein. During 1968 and 1969 sulfur-supplemented heifers required signif-icantly more (P < .05) silage dry matter per pound of gain than heifers fed urea-treated corn silage without added sulfur. However, there was no significant difference (P > .05) in ADG between treatments in any feeding phase. Also, there was no significant difference (P > .05) in ADG or feed efficiency between groups of heifers fed urea-treated corn silage with and without added sulfur in 1970-1973. In 1970 and 1971 when ten pounds and 20 pounds of urea were added per ton of corn silage with the N:S ratio held constant, there was no significant difference (P > .05) in ADG or feed efficiency in any of the groups of heifers due to silage treatment. Sodium sulfate and methionine-hydroxy-analogue (MHA) were com-pared as sulfur sources in 1972 and 1973. There was no significant difference (P > .05) in ADG or feed conversion in any feeding phase due to sulfur source. Grain was not fed during the silage phase in 1968 and 1969 but was fed during the silage phase of the 1970-73 trials. All heifers in all years were fed to the same slaughter weight and grade, but the heifers in 1970-73 averaged 44 fewer days on feed and required less feed per pound of gain than those in 1968 and 1969.

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