Masters Theses

Date of Award

12-1984

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Monty J. Montgomery

Committee Members

R.N. Heitmann, B.R. Bell

Abstract

Two continuous feeding trials were conducted during 1982-83 and 1983-84 to compare the effect of complete mixed rations utilizing either corn silage or cottonseed hulls (CSH) as roughage on the performance of dairy heifers. Thirty Hoi stein heifers in 1982-83, and 25 Hoi stein heifers in 1983-84 were fed one of two different rations. For the 1982-83 trial, ration 1 consisted of two stages. Stage lA contained 30 percent CSH, 50 percent corn, and 20 percent soybean meal (SBM) plus vitamines and minerals fed ad libitum until calves reached 18 weeks of age; stage IB contained 50 percent CSH, 40 percent corn, and 10 percent SBM plus vitamines and minerals fed ad libitum until calves reached 31 weeks of age. Ration 2 consisted of a 3:1 ratio of corn silage plus 16 percent crude protein dairy feed fed ad libitum from two weeks until 31 weeks of age. For the 1983-84 trial, ration 1 consisted of two stages. Stage 1A contained 40 percent CSH, 45 percent corn, and 15 percent SBM plus vitamines and minerals fed ad libitum until 18 weeks of age; stage 1B contained 60 percent CSH, 30 percent corn, and 10 percent SBM plus vitamines and minerals fed ad libitum from 18 until 30 weeks of age. Ration 2 consisted of a 3:1 ratio of corn silage and 16 percent crude protein dairy feed, fed ad libitum from two until 30 weeks of age. Dry matter intake was significantly higher (P < .05) for calves fed ration 1 on both trials. Crude protein intake and acid detergent fiber intake were significantly higher (P < .05) for calves fed ration 1 on the 1982-83 trial. Calves fed ration 1 on the 1982-83 and the 1983-84 trials had significantly higher body weights during week nine and week eight respectively, and remained significantly higher (P<.05) for the remainder of each trial. Paradoxically there were no significant differences in body measurements between rations except for body length for calves fed ration 1 on the 1983-84 trial which was significantly longer (P<.05) on week 30. The lack of difference in body measurements suggest that the difference in body weights might be due to fill. For calves on the 1983-84 trial, butyrate (moles/100 moles) was higher (P<.05) when heifers were fed corn silage versus CSH. When heifers were fed 60 percent CSH for the final 12 weeks, acetate (moles/100 moles) increased (P<.05) and propionate decreased (P<.05). Total volatile fatty acid concentration (millimoles/liter) was significantly higher (P<.05) for calves fed ration 2. The higher level (P<.05) of volatile fatty acid concentration (millimoles/liter) of ration 2 indicates that ration 2 had more fermentable carbohydrates than ration 1. Cottonseed hulls were shown to have 2.16 times the feeding value of corn silage on an as fed basis when fed at the levels reported for ration 1 and 2. These data suggest that Hoi stein heifers can be successfully raised utilizing complete rations using either CSH or corn silage as roughage sources. This study also suggests that CSH's should only be used when they can be purchased for less than 2.16 times the cost of the same unit of corn silage.

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