The effect of subclinical ketosis on indices of insulin sensitivity and selected metabolic variables in transition dairy cattle

Up to now, there have been several endeavors describing the extent of insulin resistance (IR) in dairy cows with particular emphasis on transition period, but it is not fully explicit what IR plays in the etiology of subclinical ketosis (SCK) in transition cows. The present study was therefore conducted on a commercial dairy herd with a stock population of 730 Holstein-Friesian cows to evaluate the extent of IR in transition cows with SCK. Blood samples were collected initially from each of the transition cows (n = 24) to estimate serum levels of β-hydroxybutyrate (BHBA). Cows with no clinical signs but having serum BHBA >1.20 to 2.9 mmol/l were considered to have SCK (n = 20), while those having serum BHBA concentrations <1.00 mmol/l were considered as controls (n = 4). Blood samples were then used for estimating values of serum non-esterified fatty acid (NEFA), glucose, insulin, and cortisol. Different surrogate indices for insulin sensitivity were also calculated. Our findings demonstrated that values of BHBA, NEFA, and insulin were significantly higher in cows with SCK than those of controls (P < 0.05), while values of cortisol and glucose, despite being higher in diseased cows than controls, did not reach statistical significance (P = 0.605 and ​0.269). Indices of insulin sensitivity showed a significant decrease in revised quantitative insulin sensitivity check index (RQUICKI) (P = 0.047) and a significant increase in homeostasis model assessment (HOMA) in diseased cows compared with controls (P = 0.007). The elevated values of serum glucose, insulin, cortisol, NEFA, and BHBA are therefore suggestive of impaired whole-body insulin sensitivity and were consistent with decreased RQUICKI in the diseased cows. Further studies are needed to use prophylactic feed additives to enhance insulin sensitivity and to help mitigate the deleterious consequences of bovine ketosis during the transition phase.