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

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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.