| Four hundred Wan Nan Huang broilers of 1-day-old were allotted to five groups randomly, 80 broilers for each group. The probiotics composed of Bacillus Licheniformis and Bacillus Subtilis were added to the diet at the level of 0, 0.2%, 0.4%, 0.6%, 0.8% respectively. Each group was fed with an assigned diet for 6 weeks. Growth performances, slaughter performances, chemical components of the breast muscle, meat quality parameters were measured to evaluate the effects of different levels of probiotics on Wan Nan Huang broilers.The results showed that during 0-3 weeks Wan Nan Huang broilers fed with probiotics had a slightly higher average body weight (P>0.05), higher daily gain and less daily feed intake than the control. Feed conversion rates of probiotic groups were higher by 1.30%. 4.65%, 3.85%, 2.55% than the control respectively. The groups at 0.4% and at 0.6% had more efficient feed conversion rates. By the end of week 4, the average body weights of probiotic groups increased by 3.35%, 5.71%, 5.79%, 2.50% and the feed conversion rates improved by 3.38%, 9.89%, 11.03%, 3.30% than the control respectively. The average body weights of the groups at 0.4%, 0.6% were significantly higher than that of the control (p<0.05), and those of the groups at 0.2% and 0.8% did not significantly defer from that of the control. The average body weights were not significant among probioticgroups. By the end of week 5, the average body weight of each probiotic group increased by 4.47%, 6.29%, 11.00%, 2.57% respectively. The average body weights of the groups at 0.4% and at 0.6% were significantly higher than that of the control (p<0.05). The average body weight of the group at 0.6% was significantly higher than those of the groups at 0.2% and 0.8% (p<0.05). All probiotic groups except the group at 0.8% had high feed conversion rates. By the end of week 6, probiotic groups had worse feed conversion rates than the control; the average body weights of all groups were not significantly different (p>0.05). During the whole feeding period, the groups at 0.4% and at 0.6% increased average body weight, reduced average daily intake, improved feed conversion rate; on the contrary, the average daily gams and feed conversion rates of the groups at 0.2% and 0.8% were worse even than those of the control.Net carcass percentage of the group at 0.2% was significantly lower than that of the control (p<0.05) and the breast muscle rate of the group at 0.6% was higher than that of the group at 0.8%(p<0.05), but the other slaughter performance parameters of the probiotic groups were not significantly different from those of the control. Probiotics had no effects on the chemical components of the breast muscle, neither on amino acids contents, however, the group at 0.8% had a tendency to increase the contents of some ammo acids.Muscle fiber diameter was not influenced by the probotic treatments. Probiotics did not improve drip loss and Napole yield of the breast muscle. The Napole yields of the probiotic groups were lower than that of the control. The cooking losses of the probiotic groups were higher than that of the control by 31.07%, 38.28%, 16.22%, 41.17% respectively, so the cooking losses of all probiotic groups except for the group at 0.6% were significantly different from that of the control (p<0.05). This showed that the probiotics did not improve water- holding capacity of breast muscle, but could reduce it, with water- holding capacity of the group at 0.8% at the lowest level.L* values of the probiotic groups were slightly higher than that of the control (p>0.05). There were no significant differences of a* values between the probotic groups and the control, however, a* values were significantly different amongprobotic groups. The a* value of the group at 0.8% was higher than that of the group at 0.4% (p<0.05). Both the group at 0.6% and at 0.8% had higher b* values than the control (p<0.05); the groups at 0.2% and at 0.4% had higher b* values than the control, but not significantly. The group at 0.8% had highe...
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