Determining the incidence, prevalence, and severity of ruminal acidosis in feedlot cattle

北美生长和育肥肉牛通常饲喂高谷物日粮(90%谷物，DM基础)，以经济有效的方式实现最大生产力。饲喂以谷物为基础的日粮的一个限制是消化系统疾病患病率的增加，特别是亚急性瘤胃酸中毒。亚急性酸中毒的特征是酸的积累导致瘤胃低pH。酸中毒对饲料(纤维)消化、瘤胃养分吸收有负面影响，是动物福利问题。使用瘤胃穿刺法对奶牛的瘤胃酸中毒发生率进行了测量，作为一种从许多牛群收集数据的方法(&gt；500)。然而，反胃穿刺术也存在一些挑战，包括：高劳动要求；腹膜炎风险；以及它只能导致每只动物确定预测风险的单一数据点。最近，有研究使用留置pH计评估了瘤胃酸中毒的患病率和严重程度。这些系统提供了关于延长持续时间的瘤胃pH模式的全面数据。然后，这些数据可用于表征瘤胃酸中毒的患病率、发病率和严重程度，例如，基于集体饲喂牛的饲喂天数和饲喂时间。虽然预计饲养场牛可能会经历瘤胃酸中毒，但目前还没有已知的研究记录整个育肥期饲养场牛的发病率、患病率或严重程度。这项研究将确定整个育肥期内瘤胃酸中毒的关键风险期，并将确定瘤胃酸中毒的发生率、患病率和严重程度。这将包括使用小型围栏和商业规模的饲养作业。此外，我们将评估经历更严重的瘤胃酸中毒的牛是否改变了瘤胃吸收和屏障功能。因此，拟议的研究将提供所需的基本知识，以量化瘤胃酸中毒对饲养场牛的影响，并确定关键风险期，以便制定策略，将饲养场的瘤胃酸中毒的风险、流行率和严重性降至最低。

Growing and finishing beef cattle in North America are typicallyfed high grain diets (> 90 % grain, DM basis) to achieve maximum productivityin a cost-effective manner. A limitation to feeding grain-based diets is the perceived increase in the prevalence of digestive disorders, particularlysub-acute ruminal acidosis. Sub-acute acidosis is characterized bybouts of low pH in the rumen caused bythe accumulation of acids. Acidosis negativelyaffects feed (fiber) digestion, nutrient absorption from the rumen, and is an animal welfare concern. The incidence of ruminal acidosis has been measured in dairycattle using ruminocentesis as a method to collect data from numerous cows (>500) across manyherds. However, there are challenges with ruminocentesis including: high labour requirement; risk for peritonitis; and that it onlyresults in a single-data point in time for each animal to determine predicted risk. More recently, studies have evaluated the prevalenceand severityfor ruminal acidosis using indwelling pH meters. These systems provide comprehensive data regarding ruminal pH patterns over an extended duration. This data can then be used to characterize the prevalence, incidence, and severityfor ruminal acidosis based on, for example, days on feed and timing of feeding using group-fed cattle. While it is expected that feedlot cattle mayexperience ruminal acidosis, there are currentlyno known studies that document the incidence, prevalence, or severityin feedlot cattle throughout the finishing period. This research will determine critical risk periods for ruminal acidosis throughout the finishing period and will determine the incidence, prevalence, and severityfor ruminal acidosis. This will include the use of both small-pen and commercial-scale feeding operations. Furthermore, we will evaluate whether cattle experiencing more severe ruminal acidosis have altered ruminal absorptive and barrier functions.As such, the proposed research will provide the fundamental knowledge needed to quantifythe impact of ruminal acidosis on feedlot cattle as well as identifying critical risk periods so that strategies can be developed to minimize the risk, prevalence, and severityof ruminal acidosis in feedlots.