Doctoral Dissertations

Date of Award

8-1988

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

Karl M. Barth

Committee Members

R. A. McLean, J. B. McLaren, J. C. Waller

Abstract

Corn silage was either left untreated (control) or treated with a-amylase (.05% wet basis, a fermentation stimulant), sorbic acid (.10% wet basis, a fermentation inhibitor), or both in a 2 x 2 factorial arrangement. Experiments were conducted to ascertain treatment effects on: 1) fermentation and aerobic deterioration dynamics, 2) rumen micirobial activity as estimated by in vitro gas production, and 3) the nutritive value of these silages by measuring performance and carcass characteristics of cattle. During a 9-day fermentation study, silages treated with sorbic acid appeared to be better preserved since no yeast or mold growth was observed and because more (P<.02) water-soluble carbohydrates were retained as compared to the other silages (12.2 vs 9.0 % DMB). However, the concentrations of butyric (P<.01) and isobutyric acids (P<.01) were also elevated in sorbic acid-treated silages, indicating clostridial degradation. Silages treated with sorbic acid were more aerobically stable as exhibited by lower temperatures (P<.01), fewer total aerobes (P<.06) and more retention of water-soluble carbohydrates (P<.01) as compared to the other silages. Dry matter loss during ensiling was not significantly affected by treatment. The average dry matter loss during ensiling was 9.7% and ranged from a low of 9.1% for the sorbic acidtreated silage to a high of 10.3% in the a-amylase-treated silage. Spoilage losses were significantly decreased (P<.07) by sorbic acid treatment (7.5 vs 5.7%). Rumen microbes from cattle fed a-amylase-treated silages produced more (14.5 vs 13.0 μl/g/min, P<.09) gas in vitro as did those from cattle fed sorbic acid-treated silages (14.4 vs 13.1, P>.16). During an 85-day silage feeding trial with beef heifers, treatment with a-amylase resulted in no difference in DM intake (mean 5.7 kg/d), greater (P<.01) average daily gain (.84 vs .79 kg/d), and increased weight gain per feed intake (.146 vs .137, P<.01). This improved performance due to α-amylase treatment may have been caused partly by the increased microbial activity and partly by an increased (P<.09) nitrogen-free extract content (45.0 vs 43.2% DMB) of the silage. Results from these studies indicate that sorbic acid treatment of silages resulted in improved preservation and protection from aerobic deterioration. Treatment with α-amylase resulted in improved animal performance. Therefore, better preservation may not result in improved animal performance.

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