The U.S. catfish industry is predominantly based in the southern states, with Alabama alone accounting for ~30% of total food catfish production in 2023. The industry has been actively searching for alternative feed solutions due to the high costs of ingredients in particular protein sources. In addition to cost challenges, during the summer months, high water temperatures lead to increased health issues. Interestingly, when these catfish are examined, they consistently show no signs of bacterial or parasitic infections but display bloated intestines filled with undigested feed. This may indicate an interaction of feed or protein sources within the feed and temperature.
Two trials were conducted with channel catfish and hybrid catfish to evaluate this temperature effect. For each trial, one recirculation system was maintained at 30±1°C (High temp; HT) and a second at 26±1°C (Regular temp; RT) each stocked with 15 subadults per tank. Four dietary treatments were tested with soybean meal as the primary protein source: 1) a control diet with 6% fishmeal, 2) 6% porcine meal, 3) 6% poultry meal, or 4) 6% beef bone and meat meal. At the end of the trial, fish were weighed to assess survival and growth, while blood and liver samples were collected for further analysis, including plasma lysozyme assays and physiological gene expression.
Upon analysis of growth parameters in the channel catfish trial, no differences were found between treatments or different temperatures, but survival (P=0.031) and FCR (P=0.032) were increased in RT groups. Plasma lysozyme activity was also higher in the same group (P=0.009; Fig. 1), indicating a temperature-related innate immune change. From the gene expression analysis of four genes (ghr, hsp70, igf1, and igf2), no differences were found among dietary treatments or between temperatures. However, hsp70 expression in the liver was greater in RT group (P=0.009). With respect to the hybrid catfish trial, mean weight (P=0.008), weight gain (P=0.007) and weight gain percent (P=0.010) were increased in RT group. No differences in plasma lysozyme activity were found in the hybrid catfish trial. Gene expression of the same 4 genes analyzed from liver tissue showed that igf2 were upregulated in RT groups (P=0.002).
The findings from the two trials highlight the impact of temperature on catfish feed efficiency, growth and immune responses providing insight into optimal feed management in commercial catfish farming.