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

加拿大的乳制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，确保他们照顾的奶牛有高质量的环境和饮食，以支持它们的健康和福祉。在夏季，高温会增加患热应激的风险。热应激改变了牛的呼吸速率，减少了采食量，增加了瘤胃酸中毒的风险，增加了胃肠道的通透性。如果管理不善，这些后果可能对牛的健康产生负面影响。可以通过增加饲粮中正负离子平衡（也称为DCAD）来改变奶牛的日粮，以减轻热应激。增加DCAD可以提供更多的钠和钾来取代在唾液分泌过程中丢失的矿物质，但这些来源通常以碳酸盐的形式提供。碳酸盐具有帮助稳定瘤胃酸度的潜力，因此碳酸盐缓冲液也可能在缓解热应激条件下发挥作用。与Papillon农业有限公司合作，我们将在轻度热应激条件下测试DCAD和缓冲器的重要性，同时培养一名高素质的研究生完成研究。与研究生合作，奶牛将被喂食具有高或低DCAD和高或低缓冲物（碳酸盐）浓度的日粮。我们将评估采食量、瘤胃发酵、胃肠道吸收和渗透功能、营养物质消化、产奶量和乳成分。学生将在完成研究和与行业合作伙伴的互动中，在奶牛营养和管理方面获得宝贵的经验。该学生将在科学会议、乳制品生产商和奶牛营养学家参加的行业会议以及通过社交媒体吸引更广泛的受众方面发挥关键作用，解释和分享研究成果。我们预计这项研究将回答DCAD和缓冲源如何促进奶牛健康的重要缺失环节。

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.