Effect Of Bacillus Subtilis On The Growth Performance Of Broilers And Its Approach To The Mechanism

Bacillus as one of beneficial strains have been developed into various forms of feed-grade probiotics used in animal production. So far, The effects of growth promotion by baccilus had been reported, but the results are not consistent. At the same time, research of the antioxidation capability was rare. On the basis of the biological characteristics study of Baccilus subtilis (S01), effect of S01 on growth performance and antioxidation capability of broilers were reserached.Feeding trail:600 one-day-old medium-growth-speed broiler cocks were divided into 4 groups. Each group had 3 equal replicates with 50 cocks for one replicate. Group 1 was fed with basal diet, and Groups 2-4 was fed with different concentrations (250mg/kg,500mg/kg and 750mg/kg) of 108CFU/g S01 preparation. The trail last 11 weeks and was carried out in two period (1-5 weeks,6-11 weeks). At the end of the trail, 9 cocks from group 2 and group 4 was randomly selected to slaughter, contents and mucosas of duodenu, jejunum and caecum was collected for further analysis. The main findings were as follows:Biological characteristics research of Baccilus subtilis (S01):Survival rate and antioxidation capability in defferent stress conditions were analyzed in this trail. When heating S01 with water bath at 90℃for 30 min or treating it in 0.25%-2.0% bile salt for 3 h or at defferent pH (1.5,2.5,3.5 and 6.8) for 3 h, they survivaled and the survival rate were 50.49%,33% and 72% respectively. Moreover, When the concentration of protease and amylase was 41.16U/mL,2.14 U/mL in the supernatant, scavenging activity of DPPH, scavenging activity hydroxyl radical and inhibition rate of lipid peroxide were 43.69%,18.16% and 53.72% in the cell free extract separately, higher than those in the supernatant. In contrary, total reducing activity and glutathion peroxidase (GSH-Px) activity were 53.53 and 157.5 IU in the supernatant, higher than those the in cell free extract. Superoxide dismutase (SOD) activity wasn't dectected either in the supernant or in the cell free extract.Results showed that the in the early period (1-5 weeks) compared with control average daily gain (ADG), feed intake (FI) and feed conversion (FC) were not significantly. In the late period (6-11 weeks), the optimal additive mout was 750mg/kg. Compared with control, average weight and weight gain of groups 4 was increased by 6.72%(P<0.05),10.75%(P<0.05). In the whole trail, ADG increase of groups 2-4 were 2.53%,5.87% and 6.93%(P<0.05) respectively, but the FC was not obviously changed between groups.Intestinal microflora was also made better by SO1 preparation. Compared with control, adding 750g/kg SOI made the total aerobics and Escherichia coli decreased by 10.94%(P<0.05) and 13.20%(P<0.05), Bacillus and Lactobacillus raised by 10.64%(P<0.05) and 14.57%(P<0.05) in the jejunum. Similar effect was found in the jejunum, the total aerobics and Escherichia coli were decreased by 15.88%(P<0.05) and 15.35%(P<0.05), Bacillus and Lactobacillus were raised by 19.78%(P<0.05) and 19.51%(P<0.05).Digestive enzyme activity and digestibility were subsequently determined. In comparison with control, Those adding 750mg/kg S01 have more improved enzyme activity and digestibility. Trypsase, amylase lipase and total proteolytic enzyme activity in the duodenum was raised by 45.07%(P<0.01),9.62%(P<0.05),65.12%(P<0.01) and 26.49%(P<0.01) individually. Bsides, dry material, crude protein, crude fat, and ash was eleveted by 12.62%(P<0.01),14.67%(P<0.01),8.50%(P<0.05) and 12.29% (P<0.05).Otherwise, Jejunum mucosal strcture was improved by750mg/kg SO1,750mg/kg villus height was increased by 11.48%(P<0.05) and crypt depth was reduced by 4.19% and Villus height:crypt depth ratio was raised by 16.14%(P<0.05). All data between treatment group and control was not significant.Analysis of mucosal inmmune index indicated that after supplement 750mg/kg S01,IL-2,IL-4,IL-6,IL-10,IL-12 and TNF-αof cecum mucosa was significantly enhanced by 19.38%,20.57%,25.42%,45.16%,8.70% and 17.99%. Similarly, IL-2,IL-4, IL-6, IL-10, IL-12, TNF-a and sIgA of ileum mucosa was significantly increased by 20.23%,34.44%,19.68%,23.08%,46.81%,24.69% and 50.06%. In addition, antioxidation capability was improved by adding S01 too. In the serum, total antioxidation capability, GSH-Px, SOD, catalase, superoxide anion was enhanced by 25.75%(P<0.05),20.10%(P<0.05),18.12%(P<0.05),7.14%(P<0.05 and 14.48% (P<0.05), malonaldehyde and NO correspondingly decreased by 5.73%(P<0.05) and 10.47%(P<0.05). In the jujunum mucosa, total antioxidation capability, GSH-Px, SOD, vitamin C and xanthine was heighterned by 28.57%(P<0.05),32.53%(P<0.05),2.8%, 36.36%(P<0.05) and 26.53%(P<0.05).Above all, by refining the composition of intestinal flora and intestinal structure, Baccilus SO1 could improve the digestive enzyme activities, enhance the intestinal mucosal immune, as well as the level of antioxidation level, ultimately promote the growth of the broilers.