摘要
The study addressed the importance of yeast (Saccharomyces cerevisiae) viability for reducing the incidence of subacute ruminal acidosis (SARA) and improving total tract nutrient digestibility in beef heifers. Six ruminally cannulated beef heifers (680 ± 50 kg BW) were used in a replicated 3 × 3 Latin square design and were fed a diet consisting of 40% barley silage, 10% chopped grass hay, and 50% barley grain-based concentrate (DM basis). Treatments were 1) no yeast (Control), 2) active dried yeast (ADY; 4 g providing 1010 cfu/g; AB Vista, Marlborough, UK), and 3) killed dried yeast (KDY; 4 g autoclaved ADY). The treatments were directly dosed via the ruminal cannula daily at the time of feeding. The periods consisted of 2 wk of adaptation (d 1 to 14) and 7 d of measurements (d 15 to 21). Ruminal pH was continuously measured (d 15 to 21) using an indwelling system. Ruminal contents were sampled on d 15 and 17 at 0, 3, 6, 9, and 12 h after feeding. Total tract nutrient digestibility was measured using an external marker (YbCl3) from d 15 to 19. No treatment difference was observed for DMI (P = 0.86). Yeast supplementation (ADY and KDY) tended to increase total tract digestibility of starch (P = 0.07) whereas no effects were observed on digestibility of other nutrients. Both ADY and KDY elevated minimum (P < 0.01) and mean ruminal pH (P = 0.02) whereas no effects were observed on maximum pH (P = 0.12). Irrespective of its viability, yeast supplementation was effective in reducing time that ruminal pH was below 5.8 (P < 0.01) and 5.6 (P < 0.01). No treatment differences were observed for the ruminal VFA profile and lactate concentration. No treatment differences were observed on the relative population size of Streptococcus bovis, Fibrobacter succinogenes, and Megasphaera elsdenii (P > 0.10); however, the proportion of Ruminococcus flavefaciens in solid fraction of digesta was greater with KDY (P = 0.05). The study demonstrates the positive effects of yeast, irrespective of its viability, in reducing the severity of SARA. However, further studies are required to evaluate the importance of yeast viability for other dietary conditions, particularly when the risk of acidosis is high.
摘要译文
该研究阐述了酵母（酿酒酵母）生存能力对降低亚急性瘤胃酸中毒（SARA）发病率和改善牛犊母猪总肠道营养物质消化率的重要性。在重复的3×3拉丁方设计中使用六头瘤胃空心牛小母牛（680±50kg BW），并且饲喂由40％大麦青贮饲料，10％切碎的草干草，和50％大麦谷物基浓缩物（DM基准）。处理是1）无酵母（对照），2）活性干酵母（ADY; 4g提供10 10 cfu / g; AB Vista，Marlborough，UK），和3）杀死干酵母（KDY; 4g高压灭菌的ADY）。饲喂时，每天通过瘤胃套管直接给药。期间包括2周的适应（d 1至14）和7 d的测量（d 15至21）。使用留置系统连续测量瘤胃pH（d 15至21）。饲喂后0,3,6,9和12小时，在第15天和第17天采样瘤胃内容物。使用来自d 15至19的外部标记（YbCl 3）测量全部道营养物消化率。DMI没有治疗差异（P \x3d 0.86）。酵母补充（ADY和KDY）倾向于增加淀粉的总消化道消化率（P \x3d 0。07），而对其他营养物质的消化率没有观察到效果。 ADY和KDY均升高最低（P 0.01）和平均瘤胃pH（P \x3d 0。02）虽然没有观察到对最大pH的影响（P \x3d 0.12）。无论其生存能力如何，酵母补充可有效减少瘤胃pH值低于5.8（P 0.01）和5的时间。6（P 0.01）。对于瘤胃VFA曲线和乳酸盐浓度没有观察到治疗差异。对牛链球菌，琥珀色产碱杆菌和伊氏甲藻的相对种群大小没有处理差异（P 0.10）;然而，在KDY中，消化道固体部分中的瘤胃球菌比例较高（P \x3d 0.05）。该研究证明了酵母的积极作用，无论其生存能力如何，降低SARA的严重程度。然而，需要进一步的研究来评估其他饮食条件下酵母活力的重要性，特别是当酸中毒风险很高时。
D. Vyas;A. Uwizeye;R. Mohammed;W. Z. Yang;N. D. Walker;K. A. Beauchemin. The effects of active dried and killed dried yeast on subacute ruminal acidosis, ruminal fermentation, and nutrient digestibility in beef heifers[J]. Journal of Animal Science, 2014,92(2): 724–732