Aquaculture America 2024

February 18 - 21, 2024

San Antonio, Texas

OPTIMIZATION OF GROWTH AND IMMUNITY OF CHANNEL CATFISH Ictalurus punctatus THROUGH DIETARY SUPPLEMENTATION BY A HUMIC SUBSTANCE OR A PROTEASE COMPLEX

Abdulmalik A. Oladipupo* Anita M. Kelly, D. Allen Davis, and Timothy J. Bruce

 

School of Fisheries, Aquaculture, and Aquatic Sciences

203 Swingle Hall

Auburn University

Auburn, AL 36849

aao0022@auburn.edu

 



Commercial humic substances (HS) and  a protease complex (PC) have previously been shown to  improve resistance  to columnaris disease  and demonstrate growth potential  in  juvenile channel catfish .  Although  additives enhance fish health, some also have the potential to improve feed efficiency through enhanced digestibility of alternative protein sources.  However, it is believed that the duration and period of application may interact with  growth or immune enhancement. A feeding trial was designed to optimize the inclusion of  HS  or  PC in a low-protein commercial catfish diet, employing varying feeding regimens to assess the ir impacts on  growth performance and health.

 An 8-week feeding study  was conducted in thirty-six r ecirculating tanks. Channel catfish fingerlings (2.01±0.94g) were fed a control diet ( commercial catfish feed,  CTL; 28%) or supplemented diets (PC or HS; 28% ).  The control diet was fed in four replicates on a satiation schedule for 8 weeks .  The treatment diets were administered through four feeding regimens also in four replicates each: 1) every day for 8 weeks , 2)  for the first 4 weeks, 3)  for the final 4 weeks , and 4) every other week. Fish were fed the control diet when the supplemented diets were not fed.  Following  the feeding trial, catfish were sampled for growth performance, blood, and organs for baseline health indicators.  Individual  additives regimen groups were compared with the control.

The trial demonstrated a high survival rate (98.4±0.05 %) across all treatment groups. Growth results indicated an improved growth pattern in the  supplemented diets compared to the basal-fed group. C ontinuous supplementation of HS  or PC  significantly reduced FCR compared to the CTL group after 8 weeks (P=0.0 04; P<0.001) .  Similarly,  supplementing PC or HS during the last 4 weeks contributed to a lower FCR than the control (P =0.046; P<0.001) and  was  indifferent to continuous  feeding of any additives . Regarding the percent weight gain (WG%), tank biomass gain (TBG), and thermal growth coefficient (TGC), continuous supplementation of PC or HS  also  offered the best performance. Feeding PC for the final four weeks significantly improved TBG and higher percent weight gain (WG%) than the control group. In addition , continuous PC treatment enhanced sera lysozyme  compared to the control (P=0.041). While no significant trend was observed in sera lysozyme for different HS regimens, skin mucus lysozyme was significantly improved after offering HS in the last four weeks compared to the control (P=0.032) .  These findings demonstrated that  continuous  supplementation of  PC or HS in  commercial catfish  diets best improves growth and enhances the non-specific immune response, indicating immunostimulation properties linked with these additives.