Fellow: Rafael C. Neves

Mentor: Jessica McArt

DESCRIPTION (provided by applicant): 

Advances in dairy cattle nutrition and management have significantly minimized macromineral imbalances capable of causing clinical disease. Despite this progress, hormonal and metabolic challenges associated with macromineral homeostasis during the transition period still result in subclinical disorders that influence dairy cow health and performance. The lack of comprehensive research on subclinical macromineral disorders, specifically calcium, magnesium, and potassium, stresses the importance of epidemiological studies in this area to improve management practices aimed at optimizing a cow’s transition into early lactation. Cows with subclinical hypocalcemia also had lower blood magnesium concentrations during the pre- and postpartum period. Hypomagnesemia can reduce parathyroid hormone secretion in response to hypocalcemia as well as tissue sensitivity to parathyroid hormone, reducing the amount of calcium available for proper physiological functioning. However, an association between magnesium and calcium in the periparturient period of dairy cows and their combined effects on health and production outcomes has not yet been quantified. A different dietary strategy used in dry cow rations to maintain a negative DCAD is to incorporate forages with low potassium contents in an attempt to decrease the quantity of anionic salt additives. Although eating a low-potassium diet, cows maintain adequate NRC requirements of potassium assuming sufficient dry matter intake5; however, stress related to parturition and the associated reduction in feed intake can affect blood potassium concentration as stores of this mineral are minimal. In addition, potassium homeostasis can be influenced by magnesium; human patients with hypomagnesaemia are significantly more likely to be diagnosed with hypokalemia. The pathophysiology behind this relationship is known: magnesium is necessary for proper functioning of cellular Na-K-ATPase. Magnesium deficiency impairs the function of this pump, leading to decreased cellular uptake of potassium and increased renal excretion. Research exploring the relationship between magnesium and potassium in dairy cattle and the effects of hypokalemia on health and production outcomes in periparturient cows is scarce and merits further investigation.