Orange (Citrus sinensis) essential oil as feed additive for sheep: nutrient intake and apparent digestibility, nitrogen balance, and rumen fermentation characteristics

The study evaluated the effects of orange essential oil (OEO) as a feed additive on nutrient intake, digestibility, nitrogen balance, and rumen fermentation in meat sheep. Using ten rumen-cannulated Dorper × Santa Inês wethers in a 5 × 5 Latin square design, the treatments included four levels of OEO (0, 100, 500, and 1000 mg/kg DM) and a positive control (25 mg/kg DM of sodium monensin, M25). The diet consisted of a 90:10 concentrate-to-forage ratio. Increasing OEO did not influence overall nutrient intake but resulted in higher intake of DM, OM, CP, NDF, NFC, and TDN compared to M25. The apparent digestibility of NFC decreased with OEO inclusion, particularly at 1000 mg/kg DM, though it remained higher than M25. Other digestibility metrics, nitrogen absorption and nitrogen retention were unaffected. Treatments with OEO showed higher nitrogen intake than M25. Rumen fermentation characteristics, including SCFA profiles and pH, were not significantly impacted by OEO. The results indicate that OEO inclusion did not enhance nutrient digestibility, nitrogen balance, or rumen fermentation, with a minor negative effect on NFC digestibility at higher levels.