Toxicological insight of metiram: immuno-oxidative, neuro-behavioral, and hemato-biochemical changes during acute exposure of Nile tilapia (Oreochromis niloticus).

BACKGROUND: The inappropriate use of pesticides including fungicides creates severe biological hazards that can endanger fish health and impede sustainable aquaculture. OBJECTIVE: This study investigated the negative impacts of metiram (MET), a fungicide on the health status of Nile tilapia (Oreochromis niloticus) for a 96-hour duration as an acute exposure in a static renewal system. METHODS: Three hundred fish (average body weight: 37.50 ± 0.22 g) were assigned into six groups (50 fish/group) with five replicates (10 fish/replicate). Fish were exposed to various six concentrations (0, 1.5, 3, 4.5, 6, and 7.5 mg/L) of MET as a water exposure to for 96-hour without water exchange. The fish's behavior, clinical signs, and mortalities were documented every day of the exposure period. Additionally, MET's impact on blood profile, stress biomarkers, hepato-renal functions, immune-antioxidant status, and brain biomarker were closely monitored. RESULTS: The lethal concentration (LC50) of MET estimated using Finney's probit technique was 3.77 mg/L. The fish's behavior was severely impacted by acute MET exposure, as clear by an increase in surfacing, loss of equilibrium, unusual swimming, laterality, abnormal movement, and a decline in aggressive behaviors. The survivability and hematological indices (white and red blood cell count, differential white blood cell count, hematocrit value, and hemoglobin) were significantly reduced in a concentration-dependent manner following MET exposure. Acute exposure to MET (1.5-7.5 mg/L) incrementally increased stress biomarkers (nor-epinephrine, cortisol, and glucose), lipid peroxides (malondialdehyde), and brain oxidative DNA damage biomarker (8-hydroxy-2-deoxyguanosine). A hepato-renal dysfunction by MET exposure (4.5-7.5 mg/L) was evidenced by the significant increase in the alanine and aspartate aminotransferases and creatinine values. Moreover, a substantial decline in the immune parameters (lysozyme, complement 3, serum bactericidal activity, and antiprotease activity) and antioxidant variables (total antioxidant capacity, superoxide dismutase, and glutathione peroxidase) resulted from acute MET exposure. CONCLUSION: According to these findings, the 96-hour LC50 of MET in Nile tilapia was 3.77 mg/L. MET exposure triggered toxicity in Nile tilapia, as seen by alterations in fish neuro-behaviors, immune-antioxidant status, hepato-renal functioning, and signifying physiological disturbances. This study emphasizes the potential ecological dangers provoked by MET as an environmental contaminant to aquatic systems. However, the long-term MET exposure is still needed to be investigated.

Influence of housing systems on duck behavior and welfare.

OBJECTIVE: This experiment was conducted to assess the effects of the housing system on the welfare and growth performance of the Muscovy duck. MATERIALS AND METHODS: A total number of 48 Muscovy duck aged 3-week old were divided randomly into two groups (24 duck on each): deep litter system and cage system. Each group was subdivided into three replicates (8 birds on each) were identified with wing rings. RESULTS: The study showed that feeding and drinking behaviors significantly increased (p < 0.05) in duck reared at the cage system. While there was no noticeable effect on lying and feather pecking, duck raised in the deep litter had better growth performance with a substantial difference, which achieve a higher feed conversion rate with lower feed efficiency. Physical conditions were significantly better at cage management. The level of stress indicating hormones indicating free Thyroxin was increased with the cage. Therefore, the litter system improves duck welfare and their performance. CONCLUSION: It is concluded that the duck managed under the litter system has more opportunities that facilitate the expression of more natural behavior, and thus improve their health and performance, as a result of improved feed conversion rate and feed efficiency.