Animal performance and meat quality characteristics from feedlot-finished steers fed increasing levels of wet distillers grain.

One hundred forty-four steers were group-housed in 24 pens that were randomly assigned to one of four dietary treatments defined by the proportion of wet distiller grain plus solubles (WDGS; 0, 15, 30, or 45%) and fed for 84 d pre-slaughter. Animal performance was evaluated using the pen as the experimental unit. Whereas for carcass and meat quality characteristics, meat oxidative stability, and the consumer sensory quality of longissimus thoracis muscle one animal from each pen was randomly selected and used as the experimental unit. No differences (P > 0.05) were observed for subcutaneous fat thickness, rib eye area, marbling score or pH, color parameters, proximate composition, sarcomere length, Warner Bratzler shear force, and cooking loss. Feeding WDGS linearly increased total PUFA (P = 0.05), C18:2 n-6 (P = 0.004) proportions, and n-6/n-3 ratio (P < 0.01) but reduced C16:1 to C18:0 ratio (P < 0.01). Lipid oxidation was greater in beef from steers fed 30% and 45% WDGS (P = 0.05). Dietary WDGS linearly improved (P < 0.05) flavor and overall linking score in the consumer sensory panel.

Effect of slow-release urea inclusion in diets containing modified corn distillers grains on total tract digestibility and ruminal fermentation in feedlot cattle.

Ruminal degradable intake protein (DIP) deficit may result when cattle are fed diets containing a greater inclusion of processed corn grain and small to moderate inclusion of corn distillers grains (DG). This deficit may arise from greater proportions of rapidly fermentable carbohydrates and RUP in corn grain. Urea-derived N is 100% DIP; however, rates of degradation of carbohydrates and conventional urea (CU) may not match. Therefore, beneficial effects may result from the use of slow-release urea (SRU) sources over CU when added to DIP-deficient diets. An experiment was conducted to evaluate the effect of increasing DIP concentration through inclusion of 1 of 2 SRU sources or CU in DG-containing feedlot diets on ruminal fermentation and total tract digestibility. In addition, an in situ experiment was conducted to characterize N disappearance of urea sources from polyester bags. Four ruminally cannulated steers (initial BW = 588 ± 8 kg) were arranged in a 4 × 4 Latin square design and assigned randomly to 1 of 4 dietary treatments containing 0% (CON) or 0.6% urea in the form of CU (UREA) or SRU as Optigen II (polymer-encapsulated urea; OPTI) or NitroShure (lipid-encapsulated urea; NITRO), and 30% corn earlage, 20% modified corn DG with solubles, 7.8% corn silage, 4.3% dry supplement, and dry-rolled corn (DM basis). Dietary DIP was estimated at 6.6% and 8.3% for CON and urea-containing dietary treatments, respectively. Steers were fed ad libitum once daily. Differences in purine derivatives-to-creatinine (PDC) index between treatments were used as indicators of differences in microbial CP synthesis. Intake of OM, digestibility of OM, NDF, CP, and starch, ruminal pH, total VFA ruminal concentration, and PDC index were not affected by treatment ( ≥ 0.21). Concentration of ammonia-N noticeably peaked at 4 h after feed delivery for cattle fed UREA (treatment × time, = 0.06) and measured at least 5.5 mg/dL for any treatment and at any hour after feed delivery. During the first 12 h after incubation, N disappearance was greater for CU and NitroShure than Optigen II (urea source × time, < 0.01). Supplementing DIP through inclusion of CU or SRU did not affect feed intake, digestibility, or most of the ruminal fermentation parameters evaluated, which may relate to the lack of need of urea supplementation in the present experiment. More research is warranted to evaluate the use of SRU in DIP-deficient diets.

Effect of urea inclusion in diets containing corn dried distillers grains on feedlot cattle performance, carcass characteristics, ruminal fermentation, total tract digestibility, and purine derivatives-to-creatinine index.

Increased availability of rapidly fermentable carbohydrates and a great proportion of corn-derived CP in the diet may result in a degradable intake protein (DIP) deficit. Therefore, ruminal DIP deficit may result from high dietary inclusion of processed corn grain and small to moderate inclusion of corn distillers grains (DG). Two experiments were conducted to evaluate the effect of increasing dietary DIP concentration through the inclusion of urea on feedlot cattle performance, carcass characteristics, ruminal fermentation, total tract digestibility, and purine derivatives-to-creatinine (PDC) index. In Exp. 1, 42 steers (428 ± 5 kg initial BW) were assigned randomly to 1 of 3 diets containing (DM basis) 0 (control [CON]), 0.4 (low urea [LU]), or 0.6% urea (high urea [HU]) to provide 6.4, 7.5, or 8.0% dietary DIP, respectively, and 12% high-moisture corn (HMC), 20% corn dried DG with solubles (DDGS), 10% ryegrass haylage, 2.9% dry supplement, and dry-rolled corn (DRC). Steers were fed ad libitum once daily using a Calan gate system. Carcass-adjusted final BW and DMI were similar among treatments (P ≥ 0.58). Carcass-adjusted ADG was greater (P ≤ 0.04) for the HU diet compared with the LU and CON diets and was similar (P = 0.73) between the LU and CON diets. Carcass-adjusted G:F was greater (P = 0.03) for the HU diet compared with the LU diet, tended (P = 0.09) to be greater compared with the CON diet, and was similar (P = 0.61) between the LU and CON diets. Carcass characteristics were similar (P ≥ 0.34) among treatments. In Exp. 2, 4 ruminally cannulated steers (347 ± 18 kg initial BW) were randomly assigned to a replicated 2 × 2 Latin square design. Steers were fed the same CON or HU diet used in Exp. 1 ad libitum once daily. Differences in the PDC index were used as indicators of differences in microbial CP synthesis. Ruminal pH, OM intake, and starch and CP digestibility were not affected by treatment (P ≥ 0.13). Digestibility of OM and NDF and ruminal concentration of ammonia-N and total VFA were greater (P ≤ 0.04) for the HU diet compared with the CON diet. The PDC index was similar (P = 0.81) between treatments at 2 h before feed delivery: 4% lower and 14% greater for the HU diet compared with the CON diet at 4 and 10 h after feed delivery, respectively (P < 0.01). These results suggest that, due to limited DIP supplied by a DRC- and HMC-based feedlot diet containing 20% DDGS, urea supplementation resulted in improved ruminal fermentation and feed digestibility, which may explain the concurrently improved cattle performance.