Effect of Wheat and High-Moisture Sorghum Grain Fed Singly and in Combination on Ruminal Fermentation, Solid and Liquid Flow, Site and Extent of Digestion and Feeding Performance of Cattle

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Abstract
Two experiments were conducted to determine how varying the proportion of wheat (W) and high-moisture sorghum grain (SG) in 80% grain diets would affect ruminal fermentation, liquid and solid flow, site and extent of digestion (Exp. 1) and feeding performance of cattle (Exp. 2). In Exp. 1, three ruminal, duodenal and ileal cannulated steers (average weight 295 kg), fed at 1.54% of body weight, were used in a six-period crossover design. Treatments were: W, 50W: 50SG (W:SG) and SG. Increasing wheat level decreased ruminal pH, molar proportion of acetate, and acetate:propionate ratio (P<.05) and increased (P<.05) L-lactate concentration, molar proportions of propionate and valerate and total volatile fatty acid concentration. Ruminal liquid dilution and outflow rates were faster (P<.05) and retention time was shorter (P<.05) for the W diet. Duodenal and ileal liquid flow increased (P<.05), and solid flow decreased (P<.05), as dietary level of wheat increased. Apparent ruminal digestion (% of intake) of dry matter (DM) and organic matter (OM) was greater (P<.01) with the wheat-containing diets. Intestinal DM and OM digestion (percent of intake) was higher (P<.05) with the SG and W:SG diets. Ruminal, small intestine, large intestine and total tract starch digestion (percent of intake) was 93.5, 5.6, .7, 99.8, 71.5, 20.4, 5.7, 97.6; and 48.0, 32.5, 10.5, 91.0 with the W, W:SG and SG diets, respectively. In Exp. 2, group-fed (24 pens) steers (avg initial weight 341 kg) were fed ad libitum once daily for 121 d. Treatments were: W, 67W:33SG, 33W:67SG and SG. Rates of gain (kg/d) with the W (1.32), 67W:37SG (1.33) and 33W:67SG (1.30) diets were similar (P>.05), but faster (P<.05) than those with the SG diet (1.16). Feed intake was lower (P<.01) with the W and 67W:33SG diets, but the wheat-containing diets were utilized more efficiently (P<.01). Increasing the proportion of wheat in sorghum grain feedlot diets improved cattle performance by optimizing ruminal and post-ruminal digestion. Copyright © 1987. American Society of Animal Science . Copyright 1987 by American Society of Animal Science.