The swamp eel ( Monopterus albus ) is a commercially significant freshwater species that is widely cultivated in Asia. Garlic ( Allium sativum ) is known to contain bioactive compounds that possess antimicrobial, antioxidant, and immunostimulatory properties, and it has increasingly been used as a natural feed additive in aquaculture. This study examined the effects of dietary garlic powder levels (0, 5, 10, 15, and 20 g kg⁻¹) on the growth performance and hematological indices of M. albus fry over two consecutive 45-day rearing phases. The experiments were conducted using a completely randomized design with three replicates in 16.4-liter plastic trays containing 4 cm in Experiment 1 and 7 cm in Experiment 2. In Experiment 1, fry were used at the onset of exogenous feeding (0.026 ± 0.003 g). The 10 g kg⁻¹ dosage significantly improved weight gain, daily weight gain, specific growth rate in weight, and feed conversion ratio (FCR) compared to higher dosages (15–20 g kg⁻¹) (P ≤ 0.05). Survival was significantly higher at 10–15 g kg⁻¹ than for those at other levels (P ≤ 0.05). Erythrocyte, leukocyte, lymphocyte, and monocyte counts peaked at 5 g kg⁻¹ and significantly declined at 15–20 g kg⁻¹ (P ≤ 0.05). Experiment 2 used larger fry that had been pre-reared for 45 days (0.84 ± 0.24 g). No significant differences in growth or length parameters (P ≥ 0.05) and survival reached 100% across all groups, while fry fed a 10 g kg⁻¹ dosage exhibited a significantly lower FCR (P ≤ 0.05). Erythrocyte counts remained stable at 0–10 g kg⁻¹ and gradually decreased at higher dosages. Leukocyte, lymphocyte, and monocyte counts increased significantly at 5 g kg⁻¹ compared with the control (P ≤ 0.05) and remained stable across the 5–20 g kg⁻¹ range, while neutrophil counts were significantly elevated at 5–10 g kg⁻¹ (P ≤ 0.05). Overall, dietary garlic powder at 5–10 g kg⁻¹ appears optimal for balancing growth, feed efficiency, survival, and hematological stability, whereas higher levels may inhibit growth performance and physiological status in M. albus fry.
Huynh et al. (Sat,) studied this question.