Evidences of Gonadal Impairment and Growth Acceleration in Barbonymus gonionotus Fed Papaw Seed: Sustainable Green Alternatives for Energy Portioning

Growth stagnation in early-maturing fish is a concern for higher fish productivity and may be regulated with reproductive arrest using phytochemicals. In this line, the study attempts to improve the growth of silver barb, Barbonymus gonionotus, through dietary pawpaw (Carica papaya) seed (PS) supplemented diets during a 60-day trial (30-days of feeding PS, followed by a 30-day recovery period). Four levels of PS at 0, 2, 4, and 6 g kg⁻¹ diet were added to a commercial feed (32% crude protein) and fed to advanced fingerlings (19.08 ± 0.02 g) at 3% body weight, which forms the experimental groups, designated as control, T1, T2, and T3. Subsequent alterations in growth (% weight gain and specific growth rate), reproduction (gonadosomatic index (GSI) and gonadal histology), and physiological function (haematology and stress biomarkers, viz., cortisol and glucose) were examined at the end of the experiment. Observations noted at the end of the trial showed significantly (P < 0.05) enhanced growth in groups fed 2 g kg⁻¹, but not significantly with control. GSI showed an extreme reduction in all groups as the level of supplementation increased with the lowest being noted in T3. Sex change was observed in T2 and T3, wherein only male populations were noticed. Gonadal histology demonstrates tissue-level generation in T1, compared with control. Tissue alteration (atrophy and necrosis) was noticed in the T2 and T3. The haematological profile indicates a gradual decrease in erythrocyte and leucocyte counts, packed cell volume, and haemoglobin in the T2 and T3 groups, compared with the T1 and control groups (P < 0.05). Serum biochemistry followed a similar trend. The levels of blood glucose and cortisol were higher in T2 and T3 (P < 0.05) than in the control and T1. The overall findings from this study reveal that dietary PS supplementation at 2 g kg⁻¹ can enhance the growth of silver barb; however, higher doses suppress both growth and reproductive function, resulting in subsequent disturbances in physiology. Further studies regarding the molecular mechanism of such an outcome warrant immediate investigation.