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Assessment of the Digestibility and Nutritional Value of Cheatgrass (Bromus tectorum) with Energy and Nitrogen Supplementation in Cattle through the use of a Dual Flow Continuous System
AdvisorFaciola, Antonio P.
Agriculture, Veterinary and Rangeland Sciences
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Cheatgrass (B. tectorum) is an invasive noxious weed that dominates the Great Basin. Cheatgrass changes the fire cycle of sagebrush ecosystems and leads to fire damages across the Western US. A strategy to reduce the amount of cheatgrass is conservation grazing using livestock. This study aims to determine how supplementation of nitrogen (urea), carbohydrate (molasses), or both, affect cheatgrass diets in terms of nutrient flow, microbial protein synthesized, and digestibility through the use of a dual-flow continuous culture system. Eight fermenters were utilized in a 4 x 4 Latin square design using four 10-day periods. Experimental treatments (also called diets), on a dry matter basis, were cheatgrass only (control), cheatgrass plus urea, cheatgrass plus molasses, and cheatgrass plus urea and molasses. The fermenters were given 72 grams of their diet daily. The true digestibility of neutral detergent fiber and acid detergent fiber was not affected by experimental diets. Diets including molasses had higher true digestibility of organic matter, and the true digestibility of crude protein was greater in the molasses only diet. Diets with molasses had more acidic pH and higher concentrations of volatile fatty acids (VFAs). The combined diet led to a higher concentration of VFAs, with propionate concentrating greater and acetate concentration lower. Molasses only diet led to increased branch-chain volatile fatty acids. The urea only diet resulted in a higher concentration of NH3-N and nitrogen flow, but the other diets without urea led to more non-ammonia and bacterial nitrogen. There was no effect on bacterial efficiency, regardless of diet. These results suggest that adding urea and molasses to a cheatgrass diet could improve the amount of nutrients leaving to rumen and being available to the animal, especially VFAs and microbial nitrogen. However, supplementation did not appear to enhance cheatgrass digestion in regards to neutral detergent fiber digestion, which is significant since cheatgrass as a plant is prim