Oregano essential oil and monensin in supplementing cattle on deferred pasture

The aim of this study was to evaluate the effects of adding oregano essential oil (OEO) and monensin as supplements for Nellore cattle raised on deferred pasture of Urochloa brizantha 'Marandu'. A protein-energy supplement was provided at a rate of 5 g/kg of body weight with the following treatments: Control - no additives, Monensin-60 mg/kg of supplement, OEO3-3 g/animal/day of OEO, and OEO6-6 g/animal/day of OEO. Twenty-four Nellore cattle were used, with an average age of 16 ± 3 months and average weight of 209 kg ± 5.4 kg distributed over 12 paddocks. A completely randomised design was employed with three replications (paddocks). The supplements were added for 84 days split into three 28-day grazing cycles. Animal performance and forage availability were evaluated. There was no interaction between the use of additives and the grazing cycle or the effect of these factors on the variables related to forage (p > 0.05). Additionally, there was no effect from the interaction or the use of additives on body weight, average daily gain, total weight gain and stocking rate (p > 0.05). A reduction in animal performance was seen during the third grazing cycle along with an increase in the stocking rate (p < 0.05). There were no additional gains in terms of performance or productivity per area from the use of OEO or monensin in the protein-energy supplementation of cattle raised on deferred grazing.