Stability Of Feed Additive Lactobacillus Salivarius SNK-6 And Its Application In Quality Chicken Breeder

Lactobacillus salivarius is a probiotic lactic acid bacterium with important applications as a feed additive in production.It has antibacterial activity,immunomodulatory effects,and the ability to regulate gut microbiota.Lactobacillus salivarius SNK-6 is a strain isolated by Shanghai Academy of Agricultural Sciences in2018.It has functions of reducing dark spots in eggs,improving chicken survival rate and egg quality,regulating gut microbiota balance,and enhancing the immune system.As a live microorganism,Lactobacillus salivarius SNK-6 requires a certain number of live bacteria to exert its probiotic effects.One of the challenges of its application as a feed additive is its susceptibility to stability damage during storage and feeding,which can result in the strain becoming inactive.This study explored the factors affecting the stability of Lactobacillus salivarius SNK-6 in feed additives and investigated the colonization of the bacteria and its effects on broiler chickens during the chick-rearing and egg-laying periods.The results provide theoretical and practical foundations for the storage and scientific application of Lactobacillus salivarius.This study is divided into three parts.1.Factors affecting the stability of Lactobacillus salivarius SNK-6 were investigated.（1）The experimental bacteria powder of Lactobacillus salivarius SNK-6was selected as the research object.The effects of different temperatures,humidities,and light on the stability of the bacteria powder were designed,and feeding and drinking water tests were carried out to detect changes in the number of viable bacteria in the bacteria powder.The results showed that compared with the control group with a viable cell count of 11.30 log CFU/g,the viable cell count of the Lactobacillus salivarius SNK-6 bacteria powder stored at-17℃,4℃,and 25℃for 5 days significantly decreased（P<0.05）,but the viable cell count was still 11.26 log CFU/g,11.26 log CFU/g,and 11.25 log CFU/g,respectively.The viable cell count of the bacteria powder stored at 40℃and 60℃for 1 day decreased to 10.93 log CFU/g and 0,respectively.The viable cell count of the bacteria powder stored at-80℃for a long time（360 days）did not change significantly.Humidity had a greater impact on the bacteria powder,and the bacteria powder became completely inactive when stored at 60%RH and 70%RH for 5 days.Compared with 0 LX,the viable cell count of the bacteria powder stored at 60 LX for 1 day did not change significantly,but the viable cell count significantly decreased（P<0.05）with the extension of storage time.The water content of feed affected the viable cell count of the bacteria powder in the feeding test,but the viable cell count was still high after 1 day.In the drinking water test,the survival rate of the bacteria powder suspended in water for 2 hours was 38.18%.This indicates that the Lactobacillus salivarius SNK-6 bacteria powder should be stored in low-temperature,sealed,and light-shielded conditions,and mixed with feed during feeding.（2）The fermented bacteria powder of Lactobacillus salivarius SNK-6 was selected as the research object,and different embedding materials and embedding methods were designed.After the embedding was completed,the freeze-dried bacteria powder was subjected to a 70%RH.The results showed that the freeze-dried bacteria powder in the control group was completely inactive after being stored at 70%RH for 5 days,but the group with Ca CO₃ added still had strains of bacteria surviving,indicating that Ca CO₃can be used as an embedding material for the bacteria powder.Adding Ca CO₃ as an embedding material during the fermentation process can increase the initial fermentation activity,and compared with commercial bacteria powder,the group with Ca CO₃ added can improve the stability of the bacteria powder in high humidity environments.2.Effects of feeding Lactobacillus salivarius on the growth and development of high-quality broiler chickens.Seven-day-old Shiqiza Chicken were selected as the research subjects,and 5 different concentrations of live Lactobacillus salivarius SNK-6were added to the feed,including treatment 1:control group（basic feed）,treatment 2:1.0E+08 CFU/kg feed,treatment 3:5.0E+08 CFU/kg feed,treatment 4:2.5E+09CFU/kg feed,and treatment 5:1.25E+10 CFU/kg feed.During the feeding process,feces from each treatment group were collected for lactobacillus and Escherichia coli detection,and changes in body weight and survival rate were recorded.The results showed no significant difference in body weight between the control group and the experimental groups.Compared with the control group,the survival rate of Shiqiza Chicken during the rearing period significantly increased in treatment groups 2,3,4,and 5（P<0.05）.After feeding with Lactobacillus salivarius SNK-6,the fecal lactobacillus count in the experimental group was significantly higher than that in the control group every week,and the fecal Escherichia coli count was significantly lower than that in the control group（P<0.05）.After stopping the feeding for 14 days,the lactobacillus count in the experimental group was still significantly higher than that in the control group,and the Escherichia coli count was significantly lower than that in the control group（P<0.05）.This indicates that Lactobacillus salivarius SNK-6 can increase the number of intestinal lactobacilli and reduce the number of Escherichia coli,and based on a comprehensive analysis of body weight,survival rate,lactobacillus count,and Escherichia coli count,treatment 3 concentration of Lactobacillus salivarius SNK-6 has met the probiotic effect.3.Effects of feeding Lactobacillus salivarius on the egg-laying performance of high-quality laying hens.40-week-old New Pudong Chicken were used as the research subjects.The control group was fed with basic feed,while the experimental group was fed with 5.0E+08 CFU/kg feed concentration of Lactobacillus salivarius powder.The hatching rate and the changes in surface microorganisms of the eggshell during storage were detected for both control and experimental group eggs.The survival rate was recorded during the feeding process.Fecal samples from both groups were collected for lactobacillus and coliform bacteria testing and subjected to full-length 16S DNA sequencing.The proportion of Lactobacillus salivarius and Lactobacillus salivarius SNK-6 in lactobacillus was recorded to determine the colonization level of Lactobacillus salivarius SNK-6 with different feeding intervals.The results showed that feeding Lactobacillus salivarius SNK-6 significantly increased the hatchability,hatching rate of fertilized eggs,chick health rate,and hatching rate of fertilized eggs compared to the control group（P<0.05）.The number of lactobacillus on the eggshell surface of the experimental group after fumigation was significantly higher than that of the control group,while the number of coliform bacteria was significantly lower than that of the control group（P<0.05）.Moreover,the number of coliform bacteria on the eggshell surface gradually increased with storage time.Compared with the control group,the survival rate of the experimental group significantly increased with a feeding interval of 1,2,or 4 weeks（P<0.05）.Feeding Lactobacillus salivarius SNK-6 every two weeks resulted in the highest number of lactobacillus,Lactobacillus salivarius,and Lactobacillus salivarius SNK-6 in fecal samples from New Pudong Chicken,and the lowest number of coliform bacteria,indicating that feeding Lactobacillus salivarius SNK-6 every two weeks had the best colonization level and probiotic effect.These results indicate that Lactobacillus salivarius SNK-6 can improve the hatchability,hatching rate of fertilized eggs,chick health rate,and hatching rate of fertilized eggs of high-quality laying hens.Lactobacillus salivarius SNK-6 can colonize the intestines of New Pudong Chicken for two weeks,inhibiting the growth of coliform bacteria in the intestine and on the eggshell surface.Conclusion:（1）Lactobacillus salivarius SNK-6 should be stored in a sealed,light-shielded and frozen environment,and should be prepared and fed on the same day.Calcium carbonate can be used as an effective encapsulation material for Lactobacillus salivarius SNK-6.（2）Feeding Lactobacillus salivarius SNK-6 can increase the survival rate of Shiqiza Chicken during the rearing period,increase the content of lactobacillus in feces,and reduce the content of Escherichia coli.（3）Adding Lactobacillus salivarius SNK-6 to the feed can increase the hatchability,chick health,fertilized egg hatchability,and fertilized egg chick health of New Pudong Chicken,as well as increase the content of surface lactobacillus and reduce the content of Escherichia coli on eggshells.It can also improve the survival rate during the egg-laying period and increase the content of fecal lactobacillus while reducing the content of Escherichia coli.