Regulation of ruminal pH: an investigation into the role of the dietary cation-anion difference and buffer source for Holstein cattle during heat stress

加拿大的乳品业提供加拿大人喜欢的营养食品，如牛奶、奶油、奶酪、黄油、冰淇淋和酸奶。为了为这些产品提供牛奶，加拿大奶农勤奋工作，确保他们照料的奶牛拥有高质量的环境和饮食，以支持它们的健康和福祉。在夏天，炎热的温度会增加热应激的风险。热应激改变牛的呼吸频率，减少饲料摄入量，增加瘤胃酸中毒的风险，并增加胃肠道的通透性。如果不加以有效管理，这些结果可能会对牛的福祉产生负面影响。给奶牛喂食的饮食可以通过增加饮食中的阳离子-阴离子平衡(也称为DCAD)来缓解热应激。增加DCAD提供更多的钠和钾，以补充唾液中流失的矿物质，但这些来源通常是以碳酸盐的形式提供的。碳酸盐有可能帮助稳定瘤胃中的酸度，因此碳酸盐缓冲液也可能在缓解热应激条件方面发挥作用。与Papillon农业有限公司合作，我们将测试DCAD和缓冲器在温和热应激条件下的重要性，同时培训一名完成研究的高素质研究生。与研究生合作，奶牛将被饲喂具有高或低DCAD和高或低缓冲(碳酸盐)浓度的日粮。我们将评估饲料摄入量、瘤胃发酵、胃肠道的吸收和渗透功能、营养物质消化、产奶量和牛奶成分。在完成研究的同时，通过与行业合作伙伴的互动，学生将在学习奶牛营养和管理方面获得宝贵的经验。这名学生将在科学会议、乳制品生产商和奶牛营养学家参加的行业会议上解释和分享研究成果方面发挥关键作用，并通过社交媒体吸引更广泛的受众。我们预计，这项研究将回答关于DCAD和缓冲源如何有助于促进奶牛健康的一个重要缺失环节。

The dairy industry in Canada provides nutritious food products that Canadians enjoy such as milk, cream, cheese, butter, ice-cream, and yogurt. To provide the milk for such products, Canadian dairy farmers work diligently to ensure that the cows within their care have a high quality environment and diet to support their health and wellbeing. During summer, hot temperatures can increase risk for heat stress. Heat stress alters the respiration rate of cattle, reduces feed intake, increases risk for rumen acidosis, and increases permeability of the gastrointestinal tract. If not managed effectively, these outcomes can have negative effects on the wellbeing of cattle. The diet fed to cows can be altered to mitigate heat stress by increasing the dietary cation-anion balance (also known as DCAD). Increasing the DCAD provides more sodium and potassium to replace minerals lost during salivation, but these sources are often provided in the form of carbonates. Carbonates have the potential to help stabilize the acidity in the rumen, hence it is possible that carbonate buffers also play a role in mitigating heat stress conditions. In partnership with the Papillon Agricultural Company Ltd., we will test the importance of DCAD and buffers under mild heat stress conditions while training a highly qualified graduate student as they complete the research. Working with the graduate student, dairy cows will be fed diets that have either a high or low DCAD with high or low buffer (carbonates) concentrations. We will assess feed intake, rumen fermentation, absorptive and permeability functions of the gastrointestinal tract, nutrient digestion, milk yield, and milk composition. The student will gain a valuable experience while learning about dairy cow nutrition and management while completing the research and through interactions with the industry partners. The student will play a key role in interpreting and sharing the research findings at a scientific conference, industry conferences attended by dairy producers and dairy cattle nutritionists, and through social media to capture a broader audience. We anticipate that this research will answer an important missing link for how the DCAD and buffer sources contribute to promote the wellbeing of dairy cattle.