Dietary propylene glycol mitigates cold stress and improves physio-metabolic responses in Pangasianodon hypophthalmus (Sauvage, 1878) fingerlings reared at low temperature.

A 60-day feeding trial was carried out to determine the effect of propylene glycol (PG) on feed intake and growth in Pangasianodon hypophthalmus (striped catfish) reared at low temperature (18.0 ± 1.0 °C) re-circulatory aquaculture system (RAS) with a flow rate of 1.6 L min^-1. Six isonitrogenous (370.0 g kg^-1) and isocaloric (17.22 MJ kg^-1 dietary energy) practical diets were designed and prepared with varying levels of PG, viz., control (0 ml kg^-1 PG), T_2.5 (2.5 ml kg^-1 PG), T_5.0 (5.0 ml kg^-1 PG), T_7.5 (7.5 ml kg^-1 PG), T_10.0 (10.0 ml kg^-1 PG), and T_12.5 (12.5 ml kg^-1 PG) diet. Fish were fed twice daily till satiation. The result showed that dietary supplementation of propylene glycol showed significantly higher feed intake in the treatment groups than in control (p < 0.05). The highest feed intake, growth rate, and feed conversion were observed in T_10.0 group (p < 0.05). However, these did not vary within T_2.5, T_5.0, and T_7.5 fed groups (p < 0.05). The highest protease and amylase activities were found in fish fed with 10.0 and 10.0-12.5 ml kg^-1 PG fed group (p < 0.05). However, lipase activity showed an increasing trend with the PG supplementation (p < 0.05). Metabolic enzymes and oxidative stress enzymes activities were highest in T_10.0 group fed with 10.0 ml kg^-1 PG. Serum total protein and albumin were also increased with PG supplementation and exhibited maximum values at 10.0 ml kg^-1 PG supplementation. These findings suggest that dietary supplementation with propylene glycol at a dose of 7.5-10.0 ml kg^-1 can improve feed intake, growth, feed conversion, and metabolic activities in P. hypophthalmus fingerlings raised at low temperature.