摘要
The present study examined the influence of leucine metabolite β-hydroxy-β-methylbutyrate （HMB） on the nonspecific cellular and humoral defence mechanisms and protection against Yersinia ruckeri and Aeromonas salmonicida in juvenile pikeperch （Sander lucioperca）. The fish was fed with a commercial trout pellets, containing either 0 （control group） or 50 mg HMB kg^-1 body weight day^-1 （HMB fed group）. After four weeks feeding, 20 pikeperch from each group were anaesthetised and blood and pronephros samples were taken. The levels of the following immunological parameters were measured： respiratory burst activity of phagocytes, potential killing activity of phagocytes, lymphocytes proliferation stimulated by concanavaline A or lipopolisaccharide, lysozyme activity in serum, ceruloplasmin activity in serum, total protein in serum and total immunoglobulin （Ig） level in serum. A disease challenge test using Yersinia ruckeri or Aeromonas salmonicida was conducted after 4 weeks of feeding. The levels of all immunological parameters excluding ceruloplasmin activity and total protein in serum were statistically significantly higher （P 〈 0.05） in the HMB treated group compared to the control group. Feeding with HMB has led to a significant decrease in the mortality after the challenge trial with Y. ruckeri （30% lower mortality than in the control group） and with theA. salmonicida （40% lower mortality than in the control group）. The current study strongly suggests that feeding pikeperch with HMB in dose 50 mg kg^-1 body weight day^-1 may improve the innate immunity and decrease the mortality rates after experimental infection with pathogenic bacteria Y. ruckeri and A. salmonicida.
