Evaluation of Brassica Carinata Meal on Ruminal Metabolism and Nutrient Digestibility of Beef Cattle

Brassica carinata is a new oilseed crop in Florida with the potential of producing high-quality biodiesel for use as jet biofuel. A high-protein meal (~40% CP) is obtained as a byproduct of oil extraction; however, this meal has not been tested as a potential protein supplement for cattle. A duplicated 4 × 4 Latin square design was used to determine the effects of supplementation with B. carinata meal on ruminal fermentation, digestibility, and blood profile in beef cattle consuming bahiagrass hay (Paspalum notatum), compared with frequently used protein supplements. Eight Angus crossbred steers (473 ± 119 kg initial BW) were randomly allocated to 8 pens, over 4 periods of 28 d each. Within period, steers were assigned to one of four treatments: 1.62 kg/d cottonseed meal (CSM), 2.15 kg/d dry distillers grains with solubles (DDGS), 1.39 kg/d B. carinata meal pellets (BCM), or 1.17 kg/d soybean meal (SBM), supplemented daily, on an isonitrogenous basis. Steers had ad libitum access to bahiagrass hay and water. Intake was measured using the GrowSafe system. Following a 14 d adaptation, feed and fecal samples were collected twice daily for 4 d to determine apparent total tract nutrient digestibility using iNDF as an internal marker. Blood and ruminal fluid samples were collected every 3 h, during a 24 h period, to analyze blood urea nitrogen (BUN) and glucose in plasma, as well as pH, NH₃-N, and VFA concentrations in ruminal fluid. Data were analyzed using PROC MIXED of SAS with repeated measures. Model included the fixed effects of treatment, time, treatment × time, square, and period, and the random effects of steer(square) and steer(treatment). No effect of treatment (P > 0.05) was observed for pH, NH₃-N, or glucose concentration. An effect of treatment (P < 0.01) was observed for BUN, with steers receiving SBM having greater concentrations. There was no effect of treatment (P > 0.05) on total VFA concentrations. Steers consuming CSM had greatest acetate molar proportion, and greater acetate to propionate ratio when compared with DDGS and BCM. Steers consuming DDGS had greatest molar proportions of butyrate and greater molar proportions of propionate compared with SBM and CSM. There was no effect of treatment (P > 0.05) on DMI or apparent total tract digestibility of DM, OM, CP, NDF, or ADF. Brassica carinata performed similarly to commonly used protein supplements, excluding VFA profile, indicating its viability as a protein supplement for beef cattle.