Effect of Encapsulated Nitrate and Microencapsulated Blend of Essential Oils on Growth Performance and Methane Emissions from Beef Steers Fed Backgrounding Diets.

A long-term study (112 days) was conducted to examine the effect of feeding encapsulated nitrate (NO₃-), microencapsulated blend of essential oils (EO), and their combination on growth performance, feeding behavior, and enteric methane (CH₄) emissions of beef cattle. A total of 88 crossbred steers were purchased and assigned to one of four treatments: (i) control, backgrounding high-forage diet supplemented with urea (1.17% in dietary DM); (ii) encapsulated NO₃- (EN), control diet supplemented with 2.5% encapsulated NO₃- as a replacement for urea (1.785% NO₃- in the dietary DM); (iii) microencapsulated blend of EO (MBEO), control diet supplemented with 150 mg/kg DM of microencapsulated blend of EO and pepper extract; and (iv) EN + MBEO, control diet supplemented with EN and MBEO. There was no interaction (p ≥ 0.080) between EN and MBEO on average dry matter intake (DMI), average daily gain (ADG), gain to feed ratio (G:F), feeding behavior, and CH₄ emission (using GreenFeed system), implying independent effects of feeding EN and MBEO. Feeding MBEO increased CH₄ production (165.0 versus 183.2 g/day; p = 0.005) and yield (18.9 versus 21.4 g/kg DMI; p = 0.0002) but had no effect (p ≥ 0.479) on average DMI, ADG, G:F, and feeding behavior. However, feeding EN had no effect on ADG and G:F (p ≥ 0.119) but reduced DMI (8.9 versus 8.4 kg/day; p = 0.003) and CH₄ yield (21.5 versus 18.7 g/kg DMI; p < 0.001). Feeding EN slowed (p = 0.001) the feeding rate (g of DM/min) and increased (p = 0.002) meal frequency (events/day). Our results demonstrate that supplementing diets with a blend of EO did not lower CH₄ emissions and there were no advantages of feeding MBEO with EN. Inclusion of EN as a replacement for urea reduced CH₄ emissions but had no positive impact on animal performance.