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

北美的生长和育肥肉牛通常饲喂高谷物日粮（约90%谷物，日粮基础），以经济有效的方式实现最大生产力。以谷物为基础的饲料喂养的一个限制是，消化系统疾病，特别是亚急性瘤胃酸中毒的患病率明显增加。亚急性酸中毒的特征是由酸的积累引起的瘤胃pH值低。酸中毒对饲料（纤维）的消化和瘤胃营养物质的吸收产生负面影响，是一个动物福利问题。使用瘤胃接种法对奶牛的瘤胃酸中毒发生率进行了测量，该方法收集了来自多个奶牛群的大量奶牛（bbb500）的数据。然而，瘤胃形成存在挑战，包括：高劳动要求；患腹膜炎的风险；而且，它只能在一个时间点上为每只动物提供一个数据点来确定预测的风险。最近，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长时间瘤胃pH值模式的全面数据。然后，这些数据可用于描述瘤胃酸中毒的患病率、发病率和严重程度，例如，根据饲喂天数和群饲牛的饲喂时间。虽然预计饲养场牛可能会出现瘤胃酸中毒，但目前还没有已知的研究记录饲养场牛在整个育肥期的发病率、流行程度或严重程度。本研究将确定整个肥育期瘤胃酸中毒的关键危险期，并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会改变瘤胃吸收和屏障功能。因此，拟议的研究将提供量化瘤胃酸中毒对饲养场牛的影响所需的基础知识，并确定关键风险期，以便制定策略，以尽量减少饲养场瘤胃酸中毒的风险、患病率和严重程度。

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.