Growth performance of juvenile Piaractus brachypomus fed diets containing Hesperozygis ringens essential oil under different thermal conditions

Water temperature is one of the main environmental factors affecting fish growth and feed utilization in aquaculture systems. Phytogenic feed additives have been increasingly explored as natural alternatives to improve productive performance and physiological adaptation. This study investigated the effects of dietary supplementation with Hesperozygis ringens essential oil (HREO) on the growth performance of juvenile Piaractus brachypomus reared under different thermal conditions. Juveniles of P. brachypomus (n = 448; initial weight 9.38 ± 0.07 g) were distributed in recirculating aquaculture systems and maintained for 30 days under a completely randomized 2 × 4 factorial design. Fish were exposed to two water temperatures (27 and 31 °C) and fed diets supplemented with four HREO inclusion levels (0.00, 0.75, 1.00, and 2.00 g kg⁻¹ feed). The experimental diets contained 35% crude protein, and pulegone was identified as the main compound of the essential oil (93.72%). Growth performance was assessed through weight gain, daily weight gain, specific growth rate, feed conversion ratio, feed intake, Fulton’s condition factor, biomass gain, and survival. Statistical analyses were performed using two-way ANOVA followed by Tukey’s test (p < 0.05). Water temperature influenced growth performance, with fish reared at 31 °C exhibiting superior growth, greater biomass gain, and improved feed utilization efficiency compared with those maintained at 27 °C (p < 0.05). The elevated temperature likely promoted more favorable metabolic conditions for nutrient assimilation and growth. Fish fed intermediate HREO concentrations (0.75 and 1.00 g kg⁻¹) showed more consistent productive responses, while the highest supplementation level (2.00 g kg⁻¹) did not provide additional benefits. Rearing juvenile P. brachypomus at 31 °C enhanced growth performance and feed efficiency. Dietary supplementation with intermediate HREO levels was well tolerated and may contribute to productive stability under different thermal conditions, demonstrating its potential as a natural additive in aquaculture nutrition. Financial support was received from CAPES and CNPq.