Approaches to Reduce Free-Choice Liquid Supplement Intake and Intake Variation in Beef Cattle

摘要

Three experiments were conducted to evaluate effects of acid source, pH and lick wheel modifications on sugarcane molasses based liquid supplement consumption by heifers or cows grazing bahiagrass pastures in summer or fall. In experiment 1, a 16 percent crude protein liquid supplement was offered as a control and pH was adjusted to 3.4, 2.9, and 2.3 using feed grade phosphoric acid added at 3, 6 and 9 percent, respectively. These supplements were offered to heifers grazing bahiagrass during the summer at two locations. Across both locations, daily consumption was decreased 13 percent for pH 3.4, 30 percent for pH 2.9 and 64 percent for pH 2.3 compared to control (pH 4.2). Variation in individual animal intake for the control supplement showed a 13 percent and 28 percent coefficient of variation for the two locations, and the pH 2.4 supplement showed a 17 percent and 64 percent coefficient of variation at the two locations. In experiment 2, the pH of liquid supplements were reduced from pH 4.2 topH 3.2 or pH 2.3 using phosphoric acid, sulfuric acid, or hydrochloric acid. These supplements were offered to gestating beef cows grazing bahiagrass during fall. When liquid supplements were adjusted to a similar pH, phosphoric acid was the most effective and hydrochloric acid was least effective in reducing liquid supplement consumption. Phosphoric acid (P) added to pH 3.2 lowered consumption 33 percent and P added to pH 2.3 lowered consumption 53 percent. Sulfuric acid (S) added to pH 3.2 lowered consumption 18 percent and S added to pH 2.3 lowered consumption 38 percent. Hydrochloric acid (H) added to pH 3.3 lowered (trend, P=0.13) consumption by 9 percent and H added to pH 2.3 lowered consumption 30 percent. Variation in individual animal intakefor the control supplement showed a 33 percent coefficient of variation (CV) and the six supplements with lower pH had similar variations (17 percent to 39 percent CV). In experiment 3, lick wheel width (2.5 vs 0.75 inches) and turning restrictions (nonevs restricted) were evaluated using a 16 percent crude protein liquid supplement offered to heifers grazing bahiagrass during the summer at two locations. Limiting the rotation of the standard width lick wheel reduced consumption 23 percent at one location but had no effect at the other location. Reducing wheel width to .75 inches reduced consumption 17 percent at one location but tended to increase (11 percent higher) consumption at the other location. Limiting lick wheel rotation of a narrow wheel (.75 inches) reduced intake by 23 percent and 40 percent at the two locations. Variation in individual animal intake for the standard lick wheel showed a 23 percent and 26 percent coefficient of variation for the two locations, and the narrow-restricted rotation wheels showed a 15 percent and 35 percent coefficient of variation at the two locations.