Background: Selenium (Se) is important for the postnatal development of the calf. In the first weeks of life, milk is the only source of Se for the calf and insufficient level of Se in the milk may lead to Se deficiency. Maternal Se supplementation is used to prevent this.

Selenium concentration and activity of glutathione peroxidase (GSH-Px) as direct and indirect indicators of selenium status were determined in whole blood samples collected from 326 cattle in 30 herds kept in various regions of the Czech Republic. The GSH-Px activity in the samples was measured by the UV method, using the set supplied by Randox. Selenium in the sample was measured using the hydride technique AAS. The two variables showed a close and significant correlation (r = 0.90; p < 0.01). The regression line, defined by the equation y = 6.44x + 21.4, allowed us to determine the GSH-Px activity of 665.4 µkat . l -1 as equivalent to selenium concentration in whole blood 100 µg . l -1 . Mean selenium concentration and mean GSH-Px activity found in whole blood samples were 78.25 ± 46.67 µg . l -1 and 525.51 ± 335.56 µkat . l -1 , respectively. Insufficient or marginal supply of selenium was diagnosed in 64% of the animals in terms of selenium concentration, in 63% of the animals in terms of GSH-Px activity and in 55% of the animals with selenium concentrations <100 µg . l -1 and GSH-Px activity < 665.4 µkat . l -1 . In this study, close dependence of GSH-Px activity and selenium concentration in the blood of cattle was found. Activity values of GSH-Px were determined for the use in diagnosis of insufficient selenium in cattle in the Czech Republic.

The objective of the present investigations was to help the early diagnosis of hepatic steatosis. The experiment was carried out in 10 dry dairy cows in very good nutritional condition. The feed ration was restricted in the 2nd week after parturition. On the 4th day of this restriction hepatic biopsy was performed and according to the results the dairy cows were divided into group S (7 cows), i.e. those suffering from various stages of hepatic steatosis, and group N (3 cows), i.e. those with no increased deposition of fat in the liver. Blood and urea for laboratory examinations were sampled in the last week prior to parturition, in the 1st week after parturition, in the 2nd week after parturition (on the day of hepatic biopsy) and in the 4th week after parturition. The group of cows suffering from hepatic steatosis showed higher concentrations of FFA as compared with controls (0.598 ± 0.319 vs. 0.229 ± 0.017 mmol.1· I), total bilirubin (6.230 ± 2.97 vs.4.030 ± 1.24 Ilmol.l· I), AST (1.82 ± 0.528 vs. 1.21 ± 0.195 Ilkat.!·I), LD (28.76 ± 7.14 vs. 20.81 ± 1.84 Ilkat.!·I), oxidized ketone bodies (0.346 ± 0.280 vs. 0.176 ± 0.015 mmol.l· I ), gamma-globulins (34.57 ± 12.36 vs. 29.52 ± 12.27 g.I·I) as well as a higher OIT ratio (33.98 ± 25.8 vs. 13.84 ± 5.85%). On the other hand, the concentration oftriacylglycerids (0.027 ± 0.014 vs. 0.113 ± 0.09 mmol.l· l ) and the NG ratio (0.597 ± 0.192 vs. 0.691 ± 0.166) were lower. Based on our investigations, the following indices appeared to be suitable for the diagnosis of hepatic steatosis: increased AST above 1.4llkat.!·I, increased LD activity above 29 j,lkat.l· I • increased level of total bilirubin above 5.2Ilmol.l·I, increased level of oxidized ketone bodies in the blood plasma above 0.2 mmol.l· l . We recommend to check the respective indicators of lipid metabolism (FFA, total cholesterol. triacylglycerois) using diagnostic criteria given in the present paper. Dairy cows. hepatic steatosis, blood plasma. metabolic profileAccording to findings from slaughterhouses, incidence of hepatopathies in cattle is continuously increasing. The most frequent form of hepatopathy in cows is hepatic steatosis which appears most frequently during puerperium. In this period it has a negative effect not only on reproduction of the dairy cows but also on milk composition (III e k et al. 1995).Clinical methods suitable to study hepatic steatosis are limited because they cannot be successfully applied until in an advanced stage of the disease. For diagnosis of the onset and subclinical hepatic diseases it is necessary to employ laboratory methods. The most reliable method for the detection of hepatic steatosis is considered to be the examination of hepatic tissue by biopsy (Johansen et al. 1990). Many indicators of the metabolic profile are recommended for diagnosis of the fat mobilization syndrome, but main attention is devoted to examination of the functional activity of the liver and to energy metabolism. Changes in energy metabolism are reflected. in particular. in increased FFA concentr...

The aim of the work was to assess the effects of supplemental chromium (Cr) on metabolism of dairy cows in the peripartal period. Rations fed to dairy cows in a herd of Holstein cattle with mean milk yield of 7 500 l were supplemented with chromium-enriched yeast (Co-Factor III Chromium Yeast, Alltech, 0.1% Cr 3+ ) at 10 mg of Cr per animal per day. The treatment was started 21 days before the expected delivery date and discontinued 30 days after the delivery. Blood and urine samples were collected from ten experimental and ten control cows at weekly intervals, the state of health was monitored by regular clinical examinations, and milk yield for the first 100 days of lactation was recorded. The results indicate favourable effects of the supplementation on energy metabolism. The Cr-supplemented cows showed significantly higher blood glucose concentrations at post-partum (p.p.) weeks 4 (4.25 ± 0.21 vs. 3.74 ± 0.36 mmol·l -1 ; p < 0.01) and 5 (4.06 ± 0.41 vs. 3.64 0.28 mmol·l -1 ; p < 0.05) and lower ketone bodies concentration at p.p. week 4 (0.88 ± 0.11 vs. 1.38 ± 0.66 mmol·l -1 ; p < 0.05). The Cr-supplemented cows showed also significantly lower bilirubin concentration at p.p. week 2 (3.93 ± 0.84 vs. 6.47 ± 3.25 µmol·l -1 ; p < 0.05) and lower catalytic activities of aspartate aminotransferase at p.p. weeks 3 (1.37 ± 0.14 vs. 1.66 ± 0.20 µkat·l -1 ; p < 0.01) and 5 (1.16 ± 0.08 vs. 1.47 ± 0.18 µkat·l -1 ; p < 0.01) and lactate dehydrogenase at p.p. week 5 (27.35 ± 3.76 vs. 33.61 ± 5.61 µkat·l -1 ; p < 0.05). No effects on the metabolism of nitrogen substances or minerals, insulin concentration in blood serum, and blood Cr concentration were observed. Chromium excretion in urine increased after parturition; higher concentrations were found in Cr-supplemented cows at p.p. weeks 3 (7.14 ± 1.72 vs. 5.00 ± 1.26 µg·l -1 ; p < 0.01) and 4 (8.40 ± 3.13 vs. 4.04 ± 1.32 µg·l -1 ; p < 0.01). Although chromium supplementation in the peripartal period significantly improved variables characterising the energy metabolism, no effects on milk yield for the first 100 days of lactation or on the incidence of clinical diseases were demonstrable.

Selenium status was assessed directly by determination of selenium concentration, or indirectly by measurement of glutathione peroxidase activity in whole blood samples collected from 879 cattle (733 cows, 63 calves, 42 heifers, 41 finishing bulls) reared on 93 farms in 12 of the 14 regions of the Czech Republic. Selenium deficiency or marginal values were found in 50 % of the tested animals and on 54 % of the farms. In terms of animal categories, deficient or marginal selenium status was found in 42 % of cows, 80 % of calves, 100 % of heifers, and 90 % of bulls. Seleniumdeficient herds were detected in almost all regions of the Czech Republic. The lowest selenium concentrations (< 20 µg . l -1 whole blood) were found in western, northern, and north-eastern Bohemia and in northern Moravia. It is evident that selenium deficiency in cattle is a topical problem in the Czech Republic and that selenium status must be monitored within preventive diagnostics in all age groups of cattle to decide correctly on the most effective way of supplementation.