The aim of this study was to examine the characteristics of the metabolic profile and complete blood count in cows in the periparturient period on the basis of the intensity of lipolysis and ketogenesis (concentration of non esterified fatty acid - NEFA and betahydroxybutyrate - BHB). Based on median values of NEFA and BHB cows were divided into 3 groups: cows physiologically burdened with catabolism (NEFA and BHB levels above the median one week after parturition), cows significantly burdened with catabolism (NEFA and BHB levels above the median one week before and after parturition) and cows that are not burdened with catabolism (NEFA and BHB below the median, i.e. the control group). The median value of NEFA was 0.27 mmol/L one week before parturition and 0.61 mmol/L one week after it. The median value of BHB was 0.51 mmol/L one week before parturition and 0.99 mmol/L one week after it. A significant group effect was shown for each week separately, so that cows physiologically burdened with catabolism and/or cows significantly burdened with catabolism compared to the control group have the following features of the metabolic profile and complete blood count: higher concentrations of NEFA and BHB (weeks: -1, 1, 2, 4, 8), lower concentrations of glucose (weeks: 1, 4), lower concentration of cholesterol (week 8), lower concentrations of total protein (weeks: 1, 2), lower concentrations of urea (weeks: 1, 2, 4, 8) and a higher concentration of bilirubin (weeks: - 1, 1, 2, 4, 8), increased levels of AST (weeks: -1, 1) and ALT (weeks: -1, 2), lower value of Ca (week -1), lower hemoglobin concentration (week -1), lower white blood cell count (week 4), a larger number of neutrophils (weeks: -1, 1, 2) and a higher number of lymphocytes (week 4). Using the method of factor analysis and principal components showed that NEFA, BHB and glucose are the major components that affect the metabolic profile and blood count, making 71.8% of the variability of all parameters. Cows with hypoglycemia, hypocalcemia, hypoalbuminemia, hyperbilirubinemia, decreased hemoglobin concentration and/or red blood cell count and neutrophil to lymphocyte ratio >1 showed significantly higher concentrations of NEFA and BHB compared to cows with parameters within normal ranges. Complete ROC (receiver operating characteristics) analysis showed that NEFA and BHB are important diagnostic indicators that allow the separation of cows with parameters out of the reference values from cows with normal values of parameters in the metabolic profile and blood count (0.5<AUC<0.87). Reliability of identification of cows with parameters that are out of the reference value increases with increasing concentrations of NEFA and BHB, which confirms that intense lipolysis and ketogenesis start a series of compensatory processes in the metabolism in cows. The results confirm that NEFA and BHB significantly affect the value of numerous metabolic and hematological parameters in the periparturient period. [Projekat Ministars...

Insulin resistance is a phenomenon which accompanies the ongoing metabolic adaptation in cows during early lactation. The aim of our study was to determine the linear correlations of HOMA (Homeostatic Model Assessment), QUICKI (Quantitative Insulin Sensitivity Check Index) and RQUICKI (Revised Quantitative Insulin Sensitivity Check Index) indexes of insulin resistance with the metabolic status of cows (concentration of hormones, metabolites and body condition score). The experiment included 40 Holstein-Frisian cows in the fi rst week after calving. Indexes of insulin resistance valued: 18.68±5.43 (HOMA), 0.39±0.06 (QUICKI) and 0.45±0.06 (RQUICKI). Linear correlations were examined by testing the coeffi cient of correlation (r), determination (r 2 ,%) and regression parameter beta (b) in linear equation. A negative correlation was found between HOMA and IGF-I (insulin growth factor I) (r=-0.51, r²=25.0, b=-1.1257, p<0.01). HOMA showed a positive correlation with BHB (betahidroxybutyrate) (r=0.48, r²=23.2, b=0.0234, p<0.01). A positive correlation was found between QUICKI and IGF-I (r=0.30, r²=10.0 b=46.7900, p<0.05) and cholesterol (r=0.44, r²=18.3, b=1.9021, p<0.01). In contrast, QUICKI and BHB (r=0.51, r²=27.1, b=-1.7241, p<0.01), just like QUICKI and BCS (r=0.46, r²=20.9, b=-2.424, p<0.01), showed a negative correlation. RQUICKI showed positive correlations with IGF-I (r=0.48, r²=22.8, b=28.1230, p<0.01), T4 (r=0.47, r²=22.1, b=87.142, p<0.01) and triglycerides (r=0.36, r²=13, b=0.0407, p<0.05) but negative correlations with cortisol (r=-0.36, r²=13.0, b=-9.0332, p<0.05), STH (somatotropic hormone) (r=-0.42, r²=17.3, b=-5.4976, p<0.01), BHB (r=-0.62, r²=38.3, b=-1.1872, p<0.01), total bilirubin (r=-0.58, r²=33.7, b=-7.131, p<0.01) and BCS (body condition score) (r=-0.6, r²=36.4, b=-1.8347, p<0.01). In conclusion, indexes of insulin resistance may be used to evaluate the metabolic status of cows in early lactation. RQUICKI might be the most appropriate predictor of metabolic status due to its linear relationship with most of the parameters included in homeorhetic process.

Insulin resistance is a state in which the biological effect of insulin is reduced when its concentration decreases or when a compensatory mechanism increases its concentration. Insulin resistance is characterized by reduced insulin response to glucose, i.e. decreased pancreatic beta cell function (insulin hyporesponsiveness) and/or reduced sensitivity of glucose to insulin (reduced intake of glucose by peripheral tissues under the influence of insulin-eng. insulin sensitivity). Methods for estimating insulin resistance include direct methods (hyperinsulinaemic-euglycaemic clamp, golden standard), indirect methods (intravenous glucose tolerance test) and surrogate methods (indices calculated from basal concentrations of insulin, glucose, NEFA and BHB-HOMA, QUICKI, RQUICKI and RQUICKI-BHB). Surrogate indices show correlations with direct and indirect test results but they are inconsistent. Inconsistency occurs because the dependence of glucose concentrations on the degree of hepatic gluconeogenesis should be kept in mind when evaluating insulin resistance in ruminants. Therefore, the hyperinsulinaemic-euglicaemic clamp method is particularly suitable as it excludes gluconeogenesis in hepatocytes from analysis. Our results have shown a correlation between HOMA, QUICKI and RQUICKI indices and metabolic profile parameters. The correlation between dynamic and basal responses of NEFA, BHB, insulin, glucose and inorganic phosphorus is significantly dependent on RQUICKI-BHB index values in

Ketosis is a very frequent metabolic disease in dairy cows, resulting in lower milk production, impaired fertility and increased frequency of other diseases. The course of the disease is often subclinical, so early detection is very important. The aim of the study was to investigate the relation between the concentration of beta-hydroxybutyrate in blood and milk and to determine the cut-off value in milk for detection of subclinical ketosis. The study included 94 cows, which were in the first third of lactation. Beta-hydroxybutyrate (BHB) concentrations were measured in blood and milk serum using a biochemical analyser. The average concentration of BHB in the blood serum samples was 1.14 mmol/L while in the milk it was about ten times lower at 0.117 mmol/L. A statistically significant positive correlation between the concentration of BHB in blood and milk (r=0.705, p<0.001) was found. In cows with BHB in blood below 2.0 mmol/L a stronger correlation between blood and milk BHB was established (r=0.658, p<0.001) than in cows with blood BHB above 2.0 mmol/L (r=-0.292, p=0.206). Therefore, BHB in milk is a very suitable indicator in the diagnosis of subclinical ketosis as there is a good correlation between BHB in the blood and milk of cows with subclinical ketosis. The cut-off concentration of BHB in milk set at ≥0.080 mmol/L (AUC=0.91±0.03; p<0.001) is a significant indicator for subclinical ketosis in dairy cows. The sensitivity of the test was 94% and specificity 74%. Beta-hydroxybutyrate in milk is a good indicator of subclinical ketosis in dairy cows and can be measured accurately with a biochemical analyser.

Insulin resistance in early lactation includes low glucose concentration, low insulin release and responsiveness and high lipolysis. Niacin is important antilipolytic agent and leads to increase glucose and insulin concentration. The objectives of this study were to determine the influence of niacin on the insulin resistance in cows during early lactation using the difference of value and regression analysis between blood non-esterified fatty acid (NEFA), glucose and insulin concentrations, revised quantitative insulin sensitivity check index and glucose-to-insulin ratio. Niacin supplementation led to a decrease of NEFA concentration and an increase of glucose and insulin concentrations during the first three weeks after calving. Cows in the niacin group which were more resistant to insulin showed higher concentrations of non-esterified fatty acid in comparison with more sensitive cows from the same group, but still lower than the control. The regression analyses suggest the following characteristics of cows supplemented with niacin in comparison with the control group: the insulin response to glucose was more intense; the antilipolytic effect of insulin was lower; insulin efficiency expressed as glucose-to-insulin ratio increase with a decrease in NEFA. The metabolic changes due to niacin supplementation showed a dual influence on the insulin resistance in dairy cows during early lactation: decreased NEFA concentrations led to a decrease in the insulin resistance (due to an increase in insulin efficiency and insulin sensitivity index), but increased concentrations of insulin and glucose possibly caused an increase in the insulin resistance in dairy cows (due to lower insulin sensitivity index and possibly lower antilipolytic effects of insulin).