酵母β-葡聚糖和抗生素对早期断奶犊牛生长性能和肠道菌群的影响

Effect of Yeast β-glucan and Antibiotics on Growth and Intestinal Microflora in Early-weaning Calves

分别在犊牛代乳粉中添加酵母β-葡聚糖和杆菌肽锌,研究其对早期断奶犊牛生长性能及肠道微生物菌群变化的影响。选取20头新生荷斯坦公犊牛,随机分为4个处理,每个处理5个重复,每个重复1头牛,分别饲喂以下日粮:试验A组为基础日粮组(对照组)、试验B、C组均为基础日粮+酵母β-葡聚糖75mg·kg-1、试验D组为基础日粮+杆菌肽锌60mg·kg-1。试验全期共28d,每日记录犊牛采食量、每2周逐一称重并计算日增体质量,在试验第21天晨饲时,给A、B、D3组犊牛口服大肠杆菌(O141∶K99)肉汤培养基进行攻毒,C组继续正常饲喂。于试验第28天晨饲前,采集犊牛直肠内约10cm处靠近上壶腹黏膜部的粪便样品用于测定肠道微生物区系变化。结果显示,大肠杆菌攻毒前,B组犊牛0～14d和14～21d两阶段ADG比A组分别提高了26.18%和24.93%(P<0.05);攻毒后,B、D组21～28dADG比A组分别提高了30.38%、30.82%(P<0.05)。试验各期F/G,B、D组均显著低于A组(P<0.05)。与A组相比,B、D组犊牛攻毒后12和24h时,直肠中大肠杆菌数量显著降低(P<0.05),同时D组犊牛直肠中乳酸杆菌数量也显著降低(P<0.05);C组犊牛直肠中乳酸杆菌数量显著高于A组(P<0.05)。利用变性梯度凝胶电泳(DGGE)技术分析显示,B、C两组条带数多于A、D组,且C组与A、D组相比差异显著(P<0.05);不同试验组犊牛的总菌区系相似性处于50%～75%。结果表明,在代乳粉中添加75mg·kg-1酵母β-葡聚糖可改善犊牛肠道微生物区系,优化肠道微生物结构,从而保证犊牛健康生长,并能在一定程度上替代或减少抗生素的使用。

This experiment was conducted to investigate the effect of yeast β-glucan and bacitracin zinc on growth performance and intestinal microflora in early-weaning calves. Twenty healthy Holstein male neonatal calves were randomly allotted to four treatments with five replicates each. The calves were fed with the diets supplemented with 0 （Treatment A）, 75 mg·kg-1 yeast β-glucan （Treatment B ane C）, 60 mg·kg-1 bacitracin zinc （Treatment D）. The experiment lasted for 28 days. On d 21, the calves of Treatments A, B and D were challenged orally with Escherichia coli （O141：K99）, and calves of Treatment C were fed normally. Feed intake （FI） was recorded daily, body weight was measured and average daily gain （ADG） was calculated every two weeks, and fecal samples were collected from superior ampullar mucosa of the rectum to determine the intestinal microflora. The results showed as follows： Compared with Treatment A, the ADG of calves in Treatment B increased by 26.18% and 24.93% in the two phases before the Escherichia coli challenged （P0.05）, the ADG of calves in Treatment B and D increased by 30.38% and 30.82% after the Escherichia coli challenged （P0.05）. As for the F/G, which in Treatment B and D were significantly lower than that in Treatment A （P0.05）. The amount of Escherichia coli in rectum was rapidly increased after the challenged, compared with Treatment A, the amount of Escherichia coli in rectum at 12 and 24 h in Treatment B and D were significantly decreased （P0.05）, and the amount of Lactobacillus was significantly decreased in the Treatment D （P0.05）. PCR-DGGE of 16S rDNA was used to investigate the similarity index, the band number in Treatment C was significant higher than that in Treatment A and D （P0.05）.The degree of similarities of treatments were range from 50% to 75%. According to the results, β-glucan could improve the growth of claves and adjust the structure of intestinal microflora, thus using β-glucan in calves feed may decrease the usage of antibiotics.