PSXIV-12 Effect of the addition of canola oil on digestibility, rumen fermentation and methane emissions in beef cattle in the Mexican tropic

Abstract

Abstract An experiment was performed to evaluate the effect of canola oil (CO) supplementation at 4 inclusion rates [CO0=0%, CO2=2%, CO4=4%, and CO6=6% of dry matter intake (DMI)] on digestibility, volatile fat acids (VFA), a mmonia nitrogen (NH3-N), protozoa and methane (CH4) emissions, in cows grazing a tropical grass (Brachiaria sp.). Four cows (Bos taurus × Bos indicus) with rumen cannula (658 ± 92 kg) were randomly assigned to a Latin Square design with 4 treatments and 4 periods (19-d each). Treatments were offered daily at 0600 h and 1500 h together with a commercial concentrate (1% of EBW). Fecal output was measured using an external marker (Cr2O3) dosed once per day for 9 days. Fecal output along with digestibility data were used to estimate DMI. Methane production was monitored twice a day, for 5 consecutive-days, using infrared gas analyzers (Guardian Plus) at the time of CO supplementation. Rumen contents were collected at 0300 h and every 4-h during the last 2-d of each period. Data of digestibility were analyzed as a Latin Square using a mixed model procedure (SAS Inst. Inc., Cary, NC). For ruminal fermentation parameters, collection time was considered a repeated measure. Orthogonal polynomials were performed to evaluate linear and quadratic effects. No effect was observed on fiber digestibility, or any nutrient evaluated with up to 6% CO inclusion. Total protozoa (x104cells/mL), methane emission and acetate molar proportion decreased (P < 0.01) while propionate increased (P < 0.01) with consequent reduction on the acetate:propionate ratio (CO0=3.2, CO2=2.8, CO4=2.6, CO6=2.4; P < 0.01) as the level of CO increased. In conclusion, supplementing CO to animals consuming a tropical forage-based diet, may represent a viable option to reduce CH4 emissions without having a negative effect on the digestibility of the NDF.