PSXIV-3 - 3-Nitrooxypropanol dosages to reduce methane emission by feedlot beef cattle

Abstract: Our objective was to evaluate the effects of 3-nitrooxypropanol (3-NOP, Bovaer®, DSM Nutritional Products) at different levels in feedlot beef cattle diets on productive performance, biological efficiency, and methane (CH₄) emissions. Thirty Nellore bulls (iBW, 407±6 kg) were randomly assigned to three treatments with ten replicates (animal) per treatment. The animals were fed a high-concentrate feedlot diet for 87 days, according to the three treatments: 1) 0, Control (no addition of 3-NOP); 2) Bovaer75 (75 mg/kg DM of 3-NOP), 3) Bovaer100 (100 mg/kg DM of 3-NOP,). Gas emissions (CH₄ and H₂) were evaluated individually using the GreenFeed® unit (C-Lock, USA), while the variables of dry matter intake (DMI) were evaluated using digital feeders (Intergado^® system, Brazil). Yearling bulls' BW were recorded after 16-h fasting at the beginning and end of the experiment. Data were submitted to be analyzed using PROC MIXED from SAS 9.4, evaluated by orthogonal contrasts, with a significance level of 5%. Initial BW was used as a covariate when significant to adjust the statistic model. No differences on DMI (kg/d and %BW, P=0.323) were observed between control animals and those fed with Bovaer^®. Animals fed with Bovaer75 had greater ADG than control and Bovaer100, (1.73 vs. 1.63 and 1.60 kg/d; P=0.038 and P=0.025, respectively) and better biological efficiency than control (⁓127.0 vs 135.3 kg DMI/15 kg carcass produced, P< 0.023). A similar result was observed for carcass gain, in which animals supplemented with Bovaer 75 had greater gains than the control. Animals fed 75 and 100 mg/kg DM of Bovaer^® emitted respectively 33.7% and 42.7% less methane per se (g/d, P< 0.01) compared with control, and additionally produced more hydrogen (P< 0.01) vs control. There were significant reductions in the measured methane yield in relation to DMI (CH₄: DMI, P< 0.01) and methane intensity (CH₄/ADG, P< 0.01) for animals fed the two levels of Bovaer^®, in comparison with the control, as well as a significant difference in the reduction of CH₄ in relation to the biological efficiency for the animals fed with Bovaer^® (P< 0.01). We conclude that feeding Bovaer^® consistently reduces methane emission from feedlot cattle, in which the reduction intensity increased over the dosages evaluated in the current study.