Influence Of Bacillus Subitilis Natto On Animal Performance And Histology, Morphological Features Of Ruminal Papillae In Dairy Calves

The experiment was conducted to study the effects of Bacillus subtilis Natto on animal performance,histology, morphological features in preweaning calves. 24 Holstein bull calves of 7±1d of age were divided into three groups. Natto was provided in two ways: first, nattto cultures were mixed with milk and provided to all the calves. Calves were weaned until the intake of starter was up to 2% of their weight, and four calves were slaughtered randomly after weaning. In the second experiment, natto cultures were fed directly and the calves were slaughtered 8 weeks after weaning. Ruminal epitheliums at the area of ventral rumen sac were obtained.Experiment1: The experiment was conducted to study the effects of Bacillus subtilis Natto on animal performance in preweaning calves. The results were as follows: BSN2 was good for the preweaning calf. The treatment group had improved the daily body weight gain about 26.5% (P<0.01) on average, and degraded the starter intake by 11.9%. Compared with the control group (57 d), The treatment group(49.7 d) could make the weaning date in advance, and difference was remarkable ( P<0.05).For the calves after weaning, the results were as follows: The treatment 1 enhanced average daily gain about 16.2% ( P=0.09), and the treatment 2 enhanced average daily gain about 22.1% ( P=0.02); Compared with the control, the DMI in the treatment 1 and treatment 2 increased 6.1% (P﹥0.05)and 5.6% (P﹥0.05), respectively;Compared with the control, the treatments degraded feed conversion ratio, but the difference was not remarkable (P﹥0.05);Compared with the control group, the treatments enhanced carcase yield with remarkable difference (P=0.01).Experiment 2: The results as follows: compared with the control group, the pH values were lower in the two groups which feed the culture throughout these two experiments, and the significant difference had been shown between group 1 and other two groups;The concentration of VFA in control group was higher than group 1 and group 2 with remarkable difference, The molar percentage of acetic acid in CK group was higher than group1,2 in the first experiment with no significance difference, in the second experiment, the lower molar percentage of acetate in the BSN2 group than CK group with remarkable difference. The molar proportions of propionic acid were always higher in group 1,2 than in the CK group, but the differences among three groups were significant only at the weaning. The molar proportions of butyric acid in group 1 did change significantly though the experiment, but it was the lowest in the first experiment and highest in the second, and no significant difference were exist between group 2 and control group. The acetate to propionate ratio was generally lower in the BSN2/BSN1 than in the CK group, the significant different were observed;In these two experiments, the mean NH3-N concentrations in the CK group were notably higher than those of two groups throughout the experiment, and the differences were significant, a significant difference existed in the first experiment, but no difference was observed in the second;The activity ofα-amylase and protease was higher in the control group, and the remarkable difference was observed in the activity of protease between control group and other two group throughout these two experiment. In the first experiment, the activity of exoglucanase in group 2 was higher than group 1 and control group with remarkable difference, and no significant difference was observed on the activity of endoglucanase andβ-glucosidase among these three groups;In the aspect of the rate of rumen and reticulo-rumen, the change between these two stage of calves were remarkable in group 1 and group 2, no remarkable difference was observed in control group. The number and the surface area of papillae per cm2 rumen wall of BSN1 and BSN2 treated groups were higher (P<0.1) than the control at weaning and 8 weeks period after weaning. Electron microscope examinations showed that the papillae of the Cont group was leaf-like, with narrow stalks and some clumping and parakeratotic. In contrast, the papillae from the BSN1 and BSN2 groups were flattened and tongue-shaped. At weaning the color of the papillae in the Cont group was straw-colored and it was lighter than BSN1 and BSN2 groups which were a dark-brownish color, but 44 d after weaning the color of Cont group was darker than BSN2 and BSN1 groups.