Effects Of Bacillus Licheniformis And Its Combinations On Growth Performance And Ruminal Environment In Replacement Cattle

This study examined the effects of Bacillus licheniformis and its combinations on growthperformance and ruminal environment in Chinese Holstein replacement cattle.Twenty-four newbornHolstein calves were randomly divided into4groups with3males and3females each. Calves wereoffered a basal diet consisting of a milk replacer, starter diet and Chinese wildrye （control, group A）, orthe basal diet supplemented with Bacillus licheniformis （group B）, Bacillus licheniformis and Bacillussubtilis （group C）, or Bacillus licheniformis, Bacillus subtilis and Lactobacillus plantarum （group D）.The ratios of corresponding strains for groups C and D were1:1and1:1:1, respectively. Each calve wasoffered2×10¹⁰CFU of the probiotics daily.Experiment1aimed to study the effects of Bacillus licheniformis and its combinations on growthperformance and ruminal environment in Holstein calves aged0-8weeks. The8-week trial was dividedinto2-weeks intervals, meanwhile, body weight and body dimensions were recorded at the start and endof each interval. Rumen fluids and blood samples were collected fortnightly, feed intake and fecalscores were recorded daily. The results showed that, during the whole trial of8weeks, the average dailygain（ADG） of the calves from the group B was higher than that of group A （P<0.05）, but the ratio offeed to gains（F/G） did not differ among groups （P>0.05）. At the end of the trial, the index of bodystructures of groups B or D was higher than group A （P<0.05）. Dietary Bacillus licheniformis and itscombinations did not affect dry matter intake, fecal scores and serum biochemical parameters of calves（P>0.05）. The pH of ruminal fluids in calves from groups B or D was higher than that of group A whenthe calves were four weeks of age. Dietary Bacillus licheniformis reduced ruminal propionate andbutyrate proportions and increased acetate proportions when the calves were four weeks of age. DietaryBacillus licheniformis and its combinations increaced the Shannon index and Evenness index andruduced the Sinpson index. The results of Polymerase Chain Reaction-Denaturing Gradient GelElectrophoresis（PCR-DGGE）indicated that Prevotella ruminicola, Firmicutes, Ruminococcus,Bacteroidetes, Clostridiales lachnospiraceae and uncultured rumen bacteria were predominant in theruminal fluids of calves aged8weeks. Dietary Bacillus licheniformis and its combinations increased thenumber of cellulytic bacteria in rumen fluids. It was concluded that adding Bacillus licheniformis intothe diet increased ADG of the calves in the trial of0-8weeks and the index of body structures at the endof the trial, and adding Bacillus licheniformis, Bacillus subtilis and Lactobacillus plantarum into thediet increased the index of body structures at the end of the trial. However, adding Bacilluslicheniformis and its combinations into the diet had no effects on serum biochemical parameters ofanimals. Dietary Bacillus licheniformis and its combinations increased the proportion of acetate andpropionate and pH in ruminal fluids,and also changed the number of dominant bacteria in ruminalfluids. In addition, dietary Bacillus licheniformis and its combinations increased the number ofcellulytic bacteria in ruminal fluids.Experiment2aimed to study the effects of Bacillus licheniformis and its combinations on growth,development and ruminal environment in Holstein replacement cattle aged8-52weeks.Theresults showed that adding Bacillus licheniformis and its combinations improved the growth of bodylength and ADG,and increased the activity of AKP enzyme of serum. During the period of20-24weeks,ADG of replacement cattle from group D was111.88%higher than that of group A, and during theperiod of32-36weeks, ADG of replacement cattle from group B was41.76%higher than that of groupA.At the age of20,24,48and52weeks, the body length of replacement cattle from group B wasincreased by8.5,8.86,6.32and7.48%, respectively, when compared with that of group A. In addition,the activity of AKP enzyme of serum in group D was41.26and22.38%higher than that of group A atthe age of20and24weeks.In the first several weeks, dietary Bacillus licheniformis and itscombinations reduced the pH of ruminal fluids and the the proportion of ruminal acetate and propionate.Adding probiotics, especially Bacillus licheniformis, in the diet of replacement cattle increased thenumber of beneficial bacteria and the stability of ruminal environment.The number of beneficialbacteria in the first several weeks was higher than that in later several weeks,and the stability of ruminalenvironment was not comparable with that of later. In addition, probiotics improved the growth ofcellulytic bacteria in ruminal fluids.Experiment3aimed to examine the colonization of Bacillus licheniformis in the digestive tract ofreplacement cattle. The replacement cattle of groups A and B were both fed the basal diet. Fecal sampleswere collected at days1,3,5,7and14for spore coounts. The results showed that the number of fecalspores in group B was higher than that of group A at days1and3, but was the same as group A at days5and14. Therefore, dietary Bacillus licheniformis germinated and grew in the digestive tract ofreplacement cattle, but did colonize in the digestive tract of replacement cattle.In conclusion, dietary Bacillus licheniformis supplementation improved the growth peformenceand ruminal environment of replacement cattle, and increased the Shannon index, evenness index andRichness index of ruminal bacteria, but reduced the Sinpson index of ruminal bacteria. In addition,dietary probiotics improved the growth of cellulytic bacteria in rumen fluids. Bacillus licheniformis wasnot able to colonize the digestive tract of replacement cattle.