Abstract
An 8-week breeding experiment was conducted to study the impacts of adding different levels (0%, 3.1%, 6.2%, 9.3%, 12.4%, and 15.5%) of hydrolyzed feather meal (HFM) in place of fish meal (FM) in the feed on the growth performance, immune function, and antioxidative ability of juvenile largemouth bass (Micropterus salmoides), with fishmeal substitution levels (FSLs) of 0% (control group; FSL0), 10% (FSL10), 20% (FSL20), 30% (FSL30), 40% (FSL40), and 50% (FSL50), respectively. The findings show that there were no notable differences observed among the different treatment groups when contrasted with FSL0. However, as the substitution level increased, final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) declined, while the feedback coefficient rate (FCR), condition factor (CF), hepatosomatic index (HSI), and viscerosomatic index (VSI) increased. With an increase in the FSL, catalase (CAT) activity increased in all the groups and was significantly higher in the FSL20 and FSL50 groups than the control group; SOD activities in FSL40 and FSL50 significantly increased, and the plasma MDA contents in FSL40 and FSL50 significantly decreased. The gene expression levels of IL-10 and IL-8 in the groups FSL20 to FSL50 significantly decreased. When compared with FSL0, the gene expression levels of CHOP and ATF6 were also significantly lower in the FSL10 to FSL50 groups. The overall expression level of ASK1 was significantly reduced in the FSL20 group. Similarly, the expression level of JNK1 was also significantly reduced in the FSL20 group. To sum up, replacing FM with HFM at 50% did not impact the growth of juvenile largemouth bass. An FSL range of 20%-50% can enhance the antioxidant capacity of largemouth bass, reduce inflammation and stress states, and have beneficial effects on the body. It is beneficial for maintaining the healthy growth of largemouth bass.