Bio-fuel byproducts in ruminant nutrition

Three experiments were conducted to determine the effects of distiller's grains with solubles (DGS), or crude glycerin, or both on (1) fermentation characteristics when co-ensiled with low quality forages, (2) performance, carcass characteristics, and circulating metabolites in finishing steers, and (3) performance, carcass characteristics and circulating metabolites in early weaned beef calves. In Experiment 1, wet DGS and dried DGS (DDGS) were co-ensiled with lower quality forages at varying levels to determine their effects on pH and aerobic stability. All mixtures had a pH at 14 weeks of 5.0 or less indicating proper fermentation. Additionally, aerobic stability of mixtures increased (P ≤ 0.05) with increasing levels of DGS when co-ensiled with either corn silage, soybean hulls, wheat straw or direct cut grass. In Experiment 2, DDGS were fed at either 25 or 50% of diet DM. Additional diets included added fat, protein, or both to determine if differences in measurement between 25 and 50% DDGS diets were due to increased fat, CP, or both that is associated with elevated levels of DDGS in the diet. Diets with 25% DDGS had greater ADG than 50% DDGS diets (P = 0.04). Marbling score and quality grade were decreased (P ≤ 0.03) as both a result of increased protein and fat in the diet. Glucose and insulin were not affected by DDGS inclusion rate (P ≥ 0.39). In Experiment 3, diets containing either 15 or 30% crude glycerin in combination with DDGS were compared with one negative and two positive control diets. Optimal ADG, HCW, marbling scores and quality grades were noted in 15% glycerin fed calves (P ≤ 0.05). Glucose and beta-Hydroxybutyrate levels in 15% glycerin fed cattle were not different from (P ≥ 0.05) positive control diets. In conclusion, co-ensiling low quality forages with DGS results in a good quality fermentation and increased aerobic stability of the co-ensiled product. Increasing DDGS in the diets of finishing cattle to 50% reduces both performance and carcass quality. However, when combined with 15% crude glycerin in the diet, diets containing 30% DDGS increased performance and carcass quality.