Impact of hard vs. soft wheat and monensin level on rumen acidosis in feedlot heifers1

Abstract

Many feedlot finishing diets include wheat when the relative wheat prices are low. This study was conducted to examine the responses in ruminal pH and fermentation as well as site and extent of digestion from substituting soft or hard wheat for barley grain and to determine whether an elevated monensin concentration might decrease indicators of ruminal acidosis in feedlot heifers. Five ruminally cannulated beef heifers were used in a 5 × 5 Latin square with 2 × 2 + 1 factorial arrangement. Treatments included barley (10% barley silage, 86% barley, 4% supplement, with 28 mg monensin/kg DM) and diets where barley was substituted by either soft or hard wheat with either 28 or 44 mg monensin/kg diet DM. Intake of DM was not affected by grain source, whereas increasing monensin with wheat diets reduced (P < 0.02) DMI. Mean ruminal pH was lower (P < 0.04) and durations of pH < 5.8 and pH < 5.5 greater (P < 0.03) for wheat than for barley diets. However, ruminal pH was not affected by wheat type or monensin level. Total VFA concentrations were greater (P < 0.03) for wheat than barley diets with no effect of wheat type. The molar proportion of propionate was greater (P < 0.04), whereas butyrate (P < 0.01) and ratio of acetate to propionate tended to be lower (P < 0.09), with the high as compared to low level of monensin. Replacing barley with wheat in finishing diets did not affect the duodenal flow or the digestibility of OM, likely as a result of greater (P < 0.01) NDF digestion from barley offsetting the increased (P < 0.03) supply of digested starch from wheat. Feeding soft vs. hard wheat delivered a greater (P < 0.03) duodenal supply of OM and nonammonia N with no differences in total tract nutrient digestion. The increased monensin concentration decreased the flow of OM (P < 0.01), total N (P < 0.05), and microbial protein (P < 0.05) to the small intestine due to decreased DMI. These results indicated that hard and soft wheat exhibited digestive characteristics similar to barley, but ruminal pH measurements indicate that compared with barley, wheat increased the risk of ruminal acidosis. Although an increased level of monensin had limited impact on ruminal indicators of acidosis, an increase in propionate would be expected to improve efficiency of feed use by heifers fed wheat-based finishing diets.

Performance, carcass and ruminal fermentation characteristics of heifers fed concentrates differing in energy level and cereal type (corn vs. wheat)

“…microbes to starch granules (McAllister et al, 2006). Although the endosperm in different wheat types differs in hardness, all wheat types are digested more rapidly than corn in the rumen (Yang et al, 2014), and greater in situ disappearance rates and theoretical degradability values for wheat compared to corn have been reported (0.302 vs. 0.058%/h and 90.1 vs. 58. 4%, respectively;Bacha, 1991).…”

“…However, most of scientific research to evaluate the dietary effects of corn and wheat has been carried out in dairy cows (reviewed by Ferraretto et al, 2013). Some comparative studies have also been conducted with beef cattle but, in most of them, the concentrates also included monensin, which is currently banned in Europe and can mask the effects of different cereals on ruminal fermentation (Yang et al, 2014). In addition, the response of beef cattle to corn and wheat-based concentrates, as measured by feedlot performance, may be influenced by the rest of the ingredients in the diet, which, in turn, determine its energy level.…”

Use of Wheat Distiller Grains in Ruminant Diets

“…On average, wheat grain contains 65% starch, 15% protein, 14% ibre, 2.2% oil and 10% moisture [1]. With expansion of fuel ethanol production in North America and other places in the world during the last decade wheat grain has been used as second feedstock after corn for ethanol production due to its high starch content.…”

Nutritional strategies to control ruminal acidosis in feedlot cattle

“…In contrast, the protein matrix of wheat is more diffuse and does not hamper the access of ruminal microbes to starch granules (McAllister et al, 2006). Although the endosperm in different wheat types may differ in hardness, in general all wheat types are digested more rapidly than corn in the rumen (Yang et al, 2014).…”

“…In contrast, the protein matrix of wheat is more diffuse and does not hamper the access of ruminal microbes to starch granules (McAllister et al, 2006). Although the endosperm in different wheat types differs in hardness, all wheat types are digested more rapidly than corn in the rumen (Yang et al, 2014), and greater in situ disappearance rates and theoretical degradability values for wheat compared to corn have been reported (0.302 vs. 0.058%/h and 90.1 vs. 58.4%, respectively; Bacha, 1991).…”