The percent weight gain (PWG) and feeding efficiency (FE) of Epinephelus coioides were calculated. The survival of Saccharomyces cerevisiae P13 in the posterior intestines using a specific primer pair of YMR245w-F/YMR245w-R, non-specific immune parameters of grouper, and its susceptibility to Streptococcus sp. and an iridovirus were determined when the fish were fed diets containing S. cerevisiae at 0 (control), 10(3), 10(5), or 10(7) colony-forming units (cfu) kg(-1) for 4 weeks. Results showed that grouper fed a diet containing S. cerevisiae at the levels of 10(3), 10(5), and 10(7) cfu kg(-1) had significantly increased PGW and FE especially in the 10(7) cfu kg(-1) group which were 211.6% and 1.2, respectively. S. cerevisiae was able to survive in the fish posterior intestines during the S. cerevisiae feeding period. Fish fed a diet containing S. cerevisiae at 10(7) cfu kg(-1) had significantly higher survival rates than those fed the 10(3) cfu kg(-1)S. cerevisiae diet and the control diet after challenge with Streptococcus sp. and an iridovirus, with increased survival rates of 26.6% and 36.6%, respectively, compared to the challenge control group. The phagocytic activity, respiratory burst and superoxide dismutase (SOD) level of head kidney leucocytes as well as serum lysozyme activity and serum alternative complement activity (ACH(50)) of fish fed diets containing S. cerevisiae at 10(5) and 10(7) cfu kg(-1) were significantly higher than those of fish fed the 10(3) cfu kg(-1)S. cerevisiae-contained diet and the control diets after 4 weeks of feeding, and had increased by 20% and 20%, 27.6% and 19.7%, 30.5% and 36.2%, 205.8% and 169.6%, and 90.8% and 80.3%, respectively, compared to the control group. We therefore recommend dietary S. cerevisiae administration of 10(5) and 10(7) cfu kg(-1) to E. coioides to promote growth and enhance immunity and resistance against Streptococcus sp. and an iridovirus especially in the 10(7) cfu kg(-1) group.
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