Changes in Blood Values of Glucose, Insulin and Inorganic Phosphorus in Healthy and Ketotic Dairy Cows after Intravenous Infusion of Propionate Solution

Djoković R., H. Šamanc, Z. Nikolić, S. Bošković Bogosavljević: Changes in Blood Values of Glucose, Insulin and Inorganic Phosphorus in Healthy and Ketotic Dairy Cows after Intravenous Infusion of Propionate Solution. Acta Vet. Brno 2007, 76: 533-539. The aim of the present study was to determine the degree of blood glucose utilization by peripheral tissue on the basis of changes in blood concentrations of glucose, insulin and inorganic phosphorus in healthy (n = 10) and ketotic cows (n = 10) after intravenous infusion of propionate solution. Blood samples were taken in both groups of examined cows at the following time intervals: just before (time 0) and 8, 30, 60, 120, 180, 240 and 480 min after the intravenous infusion of 1.84 mol·l-1solution of propionate in the amount of 1ml·kg-1 of body weight. Glucose and insulin blood serum values in both groups of cows increased significantly within 120 min of the experiment (p < 0.05). Significantly lower values (p < 0.05) of glucose in blood of ketotic cows, compared to the blood value of glucose in healthy cows were established within 30, 60, 120 and 240 min of the experiment, as a consequence of the decreased gluconeogenic ability of the liver in the ketotic cows. Significantly lower values (p < 0.05) of insulin in blood of ketotic cows in comparison with healthy ones were established within 240 and 480 min of the test. That indicates that the ability of beta cells of the endocrine pancreas to release insulin is reduced in cows suffering from ketosis. After intravenous administration of propionate, it was established that values of inorganic phosphorus were reduced in blood in both groups of cows after 8, 30, 60, 120, 240 and 480 min. Within 480 min of the test there was a significant decrease (p < 0.05) in blood value of inorganic phosphorus in ketotic cows in comparison with healthy ones. This is linked with the active entry of glucose into glucolytic pathway of peripheral tissues. It can thus be concluded that there is a higher degree of blood glucose utilization by peripheral tissues in ketotic cows. Gluconeogenesis, ketosis, glucose utilization, peripheral tissue The optimal supply of liver and extrahepatic tissues with glucose has an important role in preserving the health of dairy cows in the early stage of lactation. Glucose concentration in blood of dairy cows in early lactation completely depends on the process of gluconeogenesis in the liver. If the degree of gluconeogenesis does not satisfy increased needs of glucose in dairy cows, the state of hypoglycaemia, ketonemia and ketonuria occurs (Young 1977). The first metabolic change in primary ketosis in dairy cows in early lactation is hypoglycaemia. It causes serious metabolic changes in the cow’s body, which are manifested through lipid mobilisation from body reserves and ketogenesis and lipogenesis in the liver (Bruss et al. 1986; Veenhuizen et al. 1991). Propionate loading test in ruminants is used for estimating the intensity of gluconeogenesis in the liver, such as the ability of endocrine pancreas for synthesis and secretion of insulin (Gröhn 1985; Sano et al. 1993; Šamanc et al. 1996; Constable 2000). The ability of endocrine pancreas for insulin release after intravenous infusion of glucose is well known. The insulin concentration in blood is reduced in ketotic cows, compared to healthy animals ACTA VET. BRNO 2007, 76: 533-539; doi:10.2754/avb200776040533 Address for correspondence: Dr Radojica Djoković Department of Animal Science, Faculty of Agriculture Čačak, University of Kragujevac Cara Dušana 34, 32000 Čačak, Serbia and Montenegro Phone +381 32/303 400,313 410 Fax: +381 32/303 401 E-mail:[email protected] http://www.vfu.cz/acta-vet/actavet.htm before and after infusion of a glucose solution (Hove 1978; De Cupere et al. 1991; Šamanc et al. 1996). Similar results have been reported by other authors after intravenous infusion of propionate solution, because propionic acid directly stimulates pancreatic secretion of insulin in ruminants (Peters et al. 1983; Peters and Elliot 1984; Sano et al. 1993; Šamanc et al. 1996; Lee and Hossner 2002). During the propionate loading test, it is very difficult to estimate on the basis of glycaemia whether the metabolic disorder was induced by liver disease or hypofunction of the endocrine pancreas. At the same time, an estimation of the concentration of inorganic phosphorus in blood can be helpful. Namely, the decrease of its concentration in blood after intravenous infusion of glucose is linked with the active utilization of glucose into the glycolytic pathway of peripheral tissue, especially muscles, while a considerably smaller amount of glucose is used for glycogenesis in the liver (Stojić 1993; Bringhurst et al. 2003). The aim of the present study was to determine the degree of blood glucose utilization by peripheral tissues on the basis of changes in blood concentrations of glucose, insulin and inorganic phosphorus in healthy and ketotic cows after intravenous infusion of propionate solution. Materials and Methods Healthy cows (C; control group; n = 10) and ketotic cows (E; experimental group; n = 10) were chosen from a Holstein dairy herd. Ketosis was diagnosed on the basis of clinical symptoms (reduced appetite, rumen atonia, behavioural changes) and determined urinary ketone in high concentrations. The presence of ketone bodies in urine was examined by using Lestradet test (Rosenberger 1979; Kégl and Gaál 1992). Ketotic animals were included in the experiment 1 2 days after the occurrence of clinical symptoms and before commencing the medical treatment. Healthy cows did not show clinical symptoms of ketosis and urinary ketone bodies were not determined in those cows. The trial cows were kept in tie-up stalls in barn housing. Cows were of similar body mass (650 kg), 4 6 years old, an average of 2.8 lactations with a mean milk yield of 7,750 l (calculated over 305 days) in the previous lactation and were all in the earliest stage of lactation (7 14 days post partum). The meal was prepared to meet the energy needs of animals in early lactation. Both groups were fed the same diet consisting of 4 kg lucerne hay, 15 kg maize silage (30% DM), 8 kg lucerne haylage, 4 kg maize ear silage (68% DM), 2 kg dry sugar beet pulp, 2 kg extruded soybean grains, 4.5 kg concentrate (30% CP). The dietary nutrient content for dairy cows with milk production of 35 l is given in Table 1. The test was carried out in the morning at 09:00 h, ca 3 h after feeding. A solution of sodium propionate (1.84 mol·l-1; Zdravlje, Leskovac) was injected intravenously during 5 min into a jugular vein of each animal at the dose 1 ml·kg-1 body mass. Blood samples (10 ml) were taken from the opposite jugular vein before and 8, 30, 60, 120, 240 and 480 min after injection. Portions of the blood samples were allowed to coagulate spontaneously at room temperature. The serum was then decanted, centrifuged and preserved at -18 °C until analysis. Glucose concentrations were determined in fresh whole blood using Dextrostix tracks and the values were read on an Eyeton Refractans colorimeter. Blood serum concentrations of insulin were determined using heterologous radioimmunoassay (RIA method) which included standard solutions of bovine insulin (Nikolić et al. 1989). Blood serum concentrations of inorganic phosphorus were determined using the UV method (023200) reagent Serbolab (Serbia). Biochemical indicators in the blood serum were assayed at the laboratory of Institute for the Application of Nuclear Energy in Agriculture (INEP) Zemun. The mean values and standard deviations (SD) for each group of cows were calculated at each time interval. 534 Table 1. Nutrient contents in daily ration for dairy cows with milk yield 35 litres Dry matter (DM), kg 21.5 Net energy of lactation (NEL), MJ 153.2 Crude protein (CP), % DM 18.3 Rumen non-degradable protein (RUP), % CP 39.69