Copaiba and Thyme Essential Oils as Natural Alternatives to Ionophores: Impacts on Digestion, Nitrogen Utilization, Ruminal Fermentation, and Methane Emissions in Sheep
Abstract
Feed additives are important dietary tools to improve efficiency. The present study aimed to evaluate the impact of Copaiba and/or Thyme essential oils as dietary additives for sheep on nutrient intake, apparent digestibility, nitrogen metabolism, ingestive behavior, infrared thermography, ruminal parameters, and methane production. Four castrated and rumen cannulated Santa Inês (52.2±3.1 kg) male sheep were randomly assigned to a 4×4 Latin square design. The treatments were: basal diet without essential oil (EO; CON); basal diet with 50 mg/kg DM of monensin (MON); basal diet with 500 mg/kg DM of EO of Copaiba (CO); and basal diet with 500 mg/kg DM of EO of Thyme (TM). The inclusion of additives (MON, CO, and TM) in the diet of sheep increased dry matter intake (p<0.001). EO increased CP intake, whereas MON decreased it (p=0.03). CO increased crude protein digestibility (dCP) by approximately 14.46% compared with CON. The additives improved microbial efficiency (p<0.05) compared to CON. However, CO showed better nitrogen balance (p=0.01) than the other treatments. MON resulted in the shortest rumination period (p=0.01) and reduced (p=0.04) rumen temperature. MON reduced acetic acid concentrations (p<0.001) and, consequently, methane emissions (p<0.001). CO also reduced estimated methane production compared to TM and CON (p<0.001). In conclusion, additives increased dry matter intake, and CO and TM enhanced crude protein digestibility. EOs improved nitrogen balance, while MON reduced rumen temperature and decreased methane. EOs showed effects similar to those of MON in mitigating estimated methane production and improving feed efficiency in sheep.
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