Effects of Rosemary, Citronella, and Tea Tree Essential Oils on Fermentation Characteristics and Aerobic Stability of Sorghum Silage.

Abstract

This study evaluated the effects of increasing doses of rosemary, citronella, and tea tree essential oils on fermentation characteristics, nutritional value, microbial count, losses, and aerobic stability of sorghum silage. A completely randomized design was used in a 3 × 4 factorial scheme, consisting of three essential oils (citronella, rosemary, and tea tree) and four inclusion levels: 0 (control silage without additive), 500, 1000, and 2000 mg kg^-1 of fresh forage, with four replicates per treatment. The inclusion of rosemary essential oil increased crude protein content (p = 0.006), while reducing ammonia nitrogen (p = 0.029) and butyric acid concentration (p < 0.001). Increasing essential oil levels resulted in a quadratic response for silage pH (p = 0.003) and a linear decrease in lactic acid concentration (p = 0.018). Additionally, higher inclusion levels led to reduced dry matter recovery (p = 0.001) and increased lactic acid bacteria counts (p = 0.016). Regarding aerobic stability, the addition of 1000 mg kg^-1 of citronella essential oil increased stability by 96 h. Essential oil treatments also influenced silage pH dynamics during aerobic exposure (p < 0.05). Overall, essential oils modified the fermentation and aerobic stability of sorghum silage. Rosemary essential oil was associated with lower NH₃-N and butyric acid concentrations, whereas higher inclusion levels increased LAB counts.