Effects Of Bacillus Subtilis And Lactobacillus On Production Performance,meat Quality,Immune Organs And Cecal Microflora Of Heat-stressed Broilers

Heat stress can damage the immune organs of poultry,affect the intestinal health and immunity,reduce the production performance of poultry,increase t he infection rate and mortality rate,and cause social and economic losses.With the development and transformation of Chinese aquaculture industry in recent years,green feed additives have become a research hotspot,among which prob iotics have been widely used.This test by Bacillus subtilis is added in the fodd er and Lactobacillus preparation,research on the thermal stress poultry producti on performance,slaughter performance and meat quality,serum biochemical ind exes,feed digestibility,cecal microflora,immune organ index and the effect of antioxidant index,in order to research and development and application of pr obiotic feed additives to provide theory basis.Two hundred Cobb broiler chickens with similar body weight at the age of one day were selected and randomly divided into 5 groups,with 10 chickens in each group for 4 replicates.The 5 groups were:Control group(CON group);Heat stress group(HS group);Heat stress+Bacillus subtilis group 300mg/Kg(BS group);Heat stress+Lactobacillus group 500mg/Kg(LAB group),composed of Lactobacillus and Enterococcus faecium,adding ratio was 3:2;Heat stress+Bacillus subtilis+Lactobacillus group(combined group),Bacillus subtilis 300mg/Kg+Lactobacillus 500mg/Kg.The CON group was reared in a temperate environment(temperature:23±1℃,humidity:about 60%).The HS group and each additive group were reared in a high temperature environment(temperature 33±1℃,humidity about 70%).The pre-trial period was 21 d,and the trial period was 21 d.The results are as follows:1.Adding Bacillus subtilis and combined bacteria into the diet significantly increased the ADFI of 22～28 day old broiler chickens under heat stress(P<0.05),and there was no significant difference in the effect of the two(P>0.05).Compared with the heat stress group,the production performance of broilers a ged 29～35 days and 36～42 days in the three probiotic additive groups was not significantly affected(P>0.05).2.Bacillus subtilis significantly reduced the abdominal fat rate of heat-stres sed broiler chickens at 35 days of age(P<0.05),and significantly increased the semi-clean broiler rate of heat-stressed broiler chickens at 42 days of age(P<0.05).Lactobacillus significantly increased the slaughter rate of heat-stress ed broiler at 35 days of age(P<0.05)and that of heat-stressed broiler at 42 days of age(P<0.05).The combined bacteria had no significant effect on the slaughter performance of heat-stressed broiler at three days of age(P>0.05).3.Bacillus subtilis significantly increased the tenderness of chest muscle,t he PH of leg muscle and the redness A*in 42-day-old heat-stressed broiler(P<0.05),and significantly reduced the loss of dripping water(P<0.05).The effects of Lactobacillus and combined bacteria were similar,both of which sig nificantly increased the PH,tenderness and redness A*of broiler leg muscles i n the HS group(P<0.05).4.The addition of Bacillus subtilis,Lactobacillus and combined bacteria to diet had no significant effect on serum biochemical indexes of heat-stressed broiler chickens(P>0.05),but showed a trend of improvement to some extent.5.Bacillus subtilis significantly increased the bursa index of 35 days old h eat-stressed broiler(P<0.05).Compared with HS group,the addition of Lactob acillus in diet significantly increased the thymus index(P<0.05)and T-SOD a ctivity(P<0.05)in the thymus of broiler chickens at the age of 28 days(P<0.05).Among the three probiotic additives,Lactobacillus had the most signif icant effect,but the two bacteria were not synergistic when added together..6.Bacillus subtilis,Lactobacillus and combined bacteria had no significant effect on the apparent digestibility of nutrients in heat-stressed broilers(P>0.05),but they all promoted the digestion and absorption of fat and protein in b roiler chickens under heat stress to a certain extent.7.Bacillus subtilis and Lactobacillus significantly increased the number of Lactobacillus cecum in 42-day-old heat-stressed broiler(P<0.05),while Lact obacillus significantly reduced the number of Escherichia coli in 35-day-old he at-stressed broiler(P<0.05).Compared with the HS group,there was no signi ficant change in the amount of microbe in the caecum of broiler chickens in t he combined group(P>0.05).The single addition of Bacillus subtilis and Lact obacillus was significantly better than the combined addition of the two.Conclusion:In conclusion,adding Bacillus subtilis or Lactobacillus into diet can improve the slaughter performance and meat quality of broilers under heat stress,effectively reduce the oxidative damage of immune organs of broilers under heat stress,increase the number of beneficial bacteria in cecum and reduce the number of Escherichia coli.The combined addition of Bacillus subtilis and Lactobacillus showed no significant synergistic effect,it is better to add them separately.