The aim of the study was to evaluate whether oral administration of Lactobacillus plantarum 299v (LP299v) would have positive effects on the performance, blood metabolites, rumen fermentation and bacterial communities of preweaning calves. Twenty-four Holstein calves (3 days old; 41.87 ± 1.98 kg body weight (BW)) were grouped by BW and thereafter randomly allocated to 1 of 2 treatment groups: (1) an untreated control group (the CON group) or (2) a group treated with daily dose of 1 × 10¹⁰ cfu per calf (the LP299v group). LP299v was fed to the calves daily through mixing with the milk in the morning feeding. The experiment was finished before the calves were weaned and the relevant indicators from samples collected were detected. The results showed that feeding LP299v not only tended to decrease the fecal score (P = 0.09) and fecal pH (P = 0.07) but also decreased (P = 0.02) the diarrhea incidence of calves. Conversely, significant increases in starter intake (P = 0.03) and average daily gain (P = 0.04) were observed in LP299v-fed calves. The age at which starter intake reached 900 g per day for 3 consecutive days of calves was significantly (P = 0.04) advanced after feeding LP299v. Feeding LP299v to calves not only tended to increase the plasma concentration of immunoglobulin G (P = 0.07) but also increased the concentrations of glucose (P = 0.003), total superoxide dismutase (P = 0.02), immunoglobulin A (P = 0.01), interferon-γ (P = 0.02) and soluble CD₄ (P = 0.02). However, the plasma concentrations of cholesterol (P = 0.06) and interleukin-6 (P = 0.03) were lower in LP299v-fed calves compared to those in CON calves. Moreover, trends toward increased ruminal concentration of butyrate (P = 0.08) and increased concentration of microbial protein (P = 0.04) were observed in LP299v-fed calves. The relative abundance of Bacteroidetes in the feces was higher (P = 0.03) in the LP299v group (50.7%) than in the CON group (33.0%). However, the relative abundances of Firmicutes (P = 0.04) and Proteobacteria (P = 0.07) in the feces were lower in LP299v-fed calves (CON vs. LP299v, 46.3% vs. 35.3%, 15.3% vs. 10.3%, respectively). The Simpson (P = 0.02), Chao1 (P = 0.01) and Ace (P = 0.03) indices in the feces were higher in LP299v-fed calves. These results indicated that preweaning calves fed LP299v exhibited increased growth performance and antioxidant and immune capacity, decreased diarrheal incidence, and diversified fecal bacterial community composition.

该研究的目的是评估口服植物乳杆菌299v（LP299v）是否会对断奶前犊牛的生产性能，血液代谢产物，瘤胃发酵和细菌群落产生积极影响。将24只荷斯坦犊牛（3天大； 41.87±1.98公斤体重（BW））按体重分组，然后随机分配至2个治疗组中的1个：（1）未经治疗的对照组（CON组）或（2 ）每日剂量为1×10 ^10的组每头犊牛cfu（LP299v组）。LP299v通过在早晨喂奶中与牛奶混合，每天喂给小牛。在犊牛断奶之前完成实验，并从采集的样品中检测相关指标。结果表明，饲喂LP299v不仅会降低粪便得分（P  = 0.09）和粪便pH（P  = 0.07），而且会降低（P  = 0.02）小牛腹泻的发生率。相反， 在LP299v饲喂的犊牛中，观察到的起动机摄入量显着增加（P  = 0.03）和平均日增重（P = 0.04）。连续3天小牛的起始摄入量达到900 g /天的年龄显着（P = 0.04）在送入LP299v之后提前。向犊牛饲喂LP299v不仅会增加免疫球蛋白G的血浆浓度（P  = 0.07），而且还会增加葡萄糖的浓度（P  = 0.003），总超氧化物歧化酶（P  = 0.02），免疫球蛋白A（P  = 0.01），干扰素-γ（P  = 0.02）和可溶性CD ₄（P  = 0.02）。然而，与 CON犊牛相比，以LP299v喂养的犊牛的胆固醇（P  = 0.06）和白介素6（P = 0.03）的血浆浓度较低。此外，反刍动物体内丁酸浓度的增加趋势（P = 饲喂LP299v的牛犊中，微生物蛋白的浓度升高（P = 0.08）（P = 0.04）。 LP299v组（50.7％）的粪便中拟杆菌的相对丰度（P = 0.03）高于CON组（33.0％）。然而，相对丰度厚壁菌门（P  = 0.04）和变形杆菌纲（P 在粪便= 0.07）在LP299v喂养的小牛较低（CON与LP299v，46.3％和35.3％，15.3％和10.3％，分别）。辛普森（P  = 0.02），Chao1（P  = 0.01）和Ace（P = 0.03）在以LP299v喂养的犊牛中，粪便中的指数较高。这些结果表明，饲喂LP299v的断奶前犊牛表现出增加的生长性能和抗氧化和免疫能力，减少了腹泻的发生率，并且粪便细菌群落组成多样化。