Glucose tolerance test in the assessment of endocrine pancreatic function in cows before and after surgical correction of left diplaced abomasum

Abstract

The aim of this study was to examine the secretory capacity of endocrine pancreas beta cells in healthy cows and cows suffering from left displaced abomasum (LDA) by determination of glucose and insulin concentrations in the peripheral circulation during glucose tolerance test (GTT). A total of twenty healthy cows (Control group) and twenty cows suffering from left abomasal displacement (Experimental group) were chosen for this study. Cows in the control group were exposed to GTT once, while cows in the experimental group were exposed on the day, day 3 and day 6 after the diagnosis of LDA, as well as 3 days after surgical treatment and reposition of the abomasum. Initial blood glucose concentrations in healthy cows were significantly lower than in the cows suffering from LDA only on day 3 (P<0.05) and day 6 (P<0.01) after the disease was diagnosed. All the glucose values determined both in healthy and diseased cows at 30. minutes after the start of glucose infusion were much higher than physiological values. Regardless to the decline of glucose levels from 60 to 180 minutes after start of glucose infusion, hyperglicemia maintained in both healthy cows and cows suffering from LDA. Compared to healthy cows the rate of decline was slower in cows suffering from LDA at the day of diagnosis, as well as 3 and 6 days after the diagnosis. At the end of the experiment, 240 minutes after the start of the infusion, glucose concentrations were significantly higher in diseased cows on the day of diagnosis and day 3 and 6 after diagnosis than in the control group (P<0.001, respectively) and in diseased cows 3 days after surgery (P<0.001, respectively). Mean initial concentrations of serum insulin were significantly higher in healthy cows than in cows suffering from LDA only on day 6 after diagnosis. From 30 to 240 minutes after the start of glucose infusion, insulinemic responses to intravenous glucose administation were statistically higher in healthy cows than in experimental cows on the day of diagnosis, day 3 and day 6 after diagnosis, as well as 3 days after surgery. On the day of diagnosis and three days after, insulinemia decreased to initial levels 180 minutes after the start of the infusion. Six days after diagnosis, insulinemia decreased to initial values at 120 minutes after the start of the glucose infusion. Three days after surgery, insulinemia decrased to values similar to initial at 240 minutes after the start of the infusion. Glucose tolerance test results showed that the best validation of pancreas endocrine function was between 60 and 120 minutes, as well as 180 and 240 minutes after the glucose infusion started. Our results also confirmed that cows suffering from LDA are in the stage of pancreatic endocrine disfunction and that the rate of this disfunction was higher when the disease lasted longer. The highest rate of pancreatic endocrine disfunction was observed 6 days after diagnosis. On day 3 after surgical treatment and reposition of the abomasum, glucose tolerance test results showed that the pancreatic endocrine function recovered.