Doses of lemongrass (Cymbopogon citratus) essential oil for Nellore steers fed with a-based diet

The aim was to evaluate whether doses of lemongrass essential oil supplementation affect DMI, apparent nutrient digestibility and methane production in Nellore steers fed forage-based diets. According to their initial fasting BW, 32 Nellore steers (BW = 332 +/- 19 kg; age = 19 +/- 1 months) rumen cannulated and castrated, were allocated in individual pens in a randomized complete block design. The treatments were randomly assigned to the animals: CON= forage-based diet without addition of lemon-grass EO; 200EO= CON diet plus 200 mg/kg lemon grass EO; 400EO= CON diet plus 400 mg/kg lemongrass EO; or 600EO= CON diet plus 600 mg/kg lemongrass EO. The experimental diets contained 95% Tifton-85 haylage and 5% ground corn. The experimental period lasted 21 days, 15 days for diet adaptation and 6 days for sample collection. Samples of haylage, concentrate and total feces production were collected from day 15 to 20, to determine the total apparent digestibility of nutrients. On the 21st day at 0, 6 and 12 h after feeding, rumen fluid was collected to determine the parameters of rumen fermentation and methane production. Significant effects were adopted when P <= 0.05. The main active compounds of the EO of lemongrass used were geranial (42.5%) and neral (30.49%). No treatment effects were detected for DM and nutrient intake. The increasing EO levels of lemongrass did not affect the apparent Livestock Science 276 (2023) 105318 digestibility of nutrients. There was an increasing linear effect (P < 0.05) of treatment in the in vivo analysis, where the highest dose had the highest valerate concentration. There was no effect for any other variables in vivo. Effects on fermentation parameters were identified in the ex situ technique. For acetate, there was a quadratic treatment effect with higher values for the 400EO for the variable production (g/kg day; P = 0.02) and gross energy (Mcal/kg day; P = 0.02). There was linear increase for butyrate production (g/kg day; P = 0.04) and gross energy (Mcal/kg day; P = 0.04). There was a quadratic effect with higher values for the 400EO for production (g/kg day; P = 0.02) and gross energy (Mcal/kg day; P = 0.02) of SCFA. There was a quadratic effect for REL (P = 0.01), with lower loss in the 400EO. There was no treatment effect for propionate (P >= 0.97) and methane production (P >= 0.19). In conclusion, 400 mg/kg lemongrass EO optimized ruminal fermentation, minimizing energy loss due to methane emissions.