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Animal Industry Report

Extension Number

ASL R1931

Topic

Equine

Summary and Implications

Soybean hulls (SH) have been successfully fed to ruminant animals as an economical substitute for hay. This feedstuff is a source of highly digestible fiber and does not contain starch. The purpose of this trial was to evaluate SH as a replacement fiber in horse diets. Four cecally cannulated Quarter Horse geldings, aged 6 to 10 years and averaging 502 kg, were used in a 4x4 Latin Square design with 21-day periods. Diets consisted of alfalfa-bromegrass hay (14.4% CP, 58.1% NDF, 39.1% ADF) with the addition of either 0, 25, 50, or 75% unpelleted SH (13.1% CP, 60.6% NDF, 43.7% ADF). Diets were offered at 2% of bodyweight (as fed) daily and body weights were measured weekly. Cecal samples (90-min post-feeding) and total fecal collections (3 d) were taken at the end of each treatment period. Fecal collection bags were emptied every 6 hours and 10% of the total amount was frozen for later analysis. Total cecal VFA production increased linearly from 70 mM to 109 mM as proportions of SH in diets increased (P = 0.02). Proportions of propionate increased linearly (P < 0.01) and cubically (P = 0.03) with means of 15.7, 18.0, 16.6, and 21.9 moles per 100 moles total VFA for the 0, 25, 50, and 75% SH diets respectively. Proportions of butyrate decreased linearly (P < 0.01) from 5.3 to 3.9 moles per 100 moles total VFA. The acetate to propionate ratio decreased linearly (P = 0.02) and cubically (P = 0.03) with means of 4.9, 4.2, 4.9, and 3.3. Apparent digestibility of DM, OM, NDF, ADF, cellulose, and hemicellulose did not differ (P > 0.24) with treatment. Apparent digestibility of N decreased linearly (P < 0.01) as concentrations of SH increased in the diet, most likely due to increased cecal fermentation and microbial biomass production. Cecal pH decreased linearly (P = 0.01) from 7.00 to 6.45 as the level of SH increased, but there was no change (P linear = 0.68) for cecal ammonia (mean concentration of 3.85 mM). Soybean hulls appear to stimulate cecal fermentation and to be a suitable replacement for hay in equine diets. This may be an especially important finding for owners of geriatric horses that often have difficulty consuming roughages.

Copyright Holder

Iowa State University

Language

en

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