Final answer:
Decreasing DCAD in dairy cattle impacts blood calcium by decreasing levels of 1,25-dihydroxycholecalciferol, impairing calcium uptake and altering muscle function and blood pressure. It can also modify inflammatory and metabolic markers, with potentially profound effects on adipose tissue and overall health. Maintaining appropriate levels of DCAD is crucial for calcium homeostasis, affecting both bone and metabolic processes.
Step-by-step explanation:
The impact of decreasing Dietary Cation-Anion Difference (DCAD) during the close-up dry period for dairy cattle is significant for managing blood calcium levels. Certain diets can decrease blood levels of 1,25-dihydroxycholecalciferol (activated vitamin D), which impairs the uptake of calcium by vascular smooth muscle cells, impacting muscle function and blood pressure. Reducing 1,25-dihydroxycholecalciferol can also lower oxidative stress and pro-inflammatory markers while increasing anti-inflammatory markers through a mechanism potentially involving Sirt1, a regulator of metabolism and insulin secretion.
Calcium intake directly influences the regulation of PTH and activated vitamin D levels. When serum calcium decreases, PTH is secreted, stimulating the release of calcium from bones and increasing calcium reabsorption from kidneys. However, lowering dietary calcium can increase parathyroid hormone activity, which, in turn, should upregulate activation of vitamin D by the kidneys, thus enhancing intestinal calcium absorption.
Overall, proper management of DCAD and calcium supplementation has implications for not only bone health but also for adipose tissue metabolism, blood pressure control, and inflammation. It is noteworthy that any decrease in plasma proteins is accompanied by a decrease in total calcium levels, as half of the blood calcium is non-diffusible and bound to these proteins.