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.

The objective of the study was to assess the effect of actual daily milk production and lactation stage on concentrations of Zn, Mn, Cu and Se in milk, and monitor correlations between milk and blood concentrations of these microelements.The study was performed in a herd of Holstein cattle with the average milk yield of 8,562 kg. Thirty-five dairy cows housed in one group were included in the study. Blood and milk samples were taken during two separate milk yield checks done 4 weeks apart. Actual milk production of monitored cows ranged from 19.6 to 62.6 l daily. For lactation stages we evaluated results of examinations performed from 7 to 188 days of lactation.Blood examinations showed that the cows included in our study had good supplementation with the microelements in question. Milk concentrations of individual microelements were as follows: 3855.2  814.7 μg/l of Zn; 36.3  14.4 μg/l of Cu; 20.1  8.3 μg/l of Mn, and 28.6  7.1 μg/l of Se. The effect of daily milk production on milk concentrations of the microelements was identified only for copper (r = -0.302, p  0.05). The variable of days of lactation (not considering days of the colostrum period) showed a positive correlation in manganese (r = 0.419, p  0.01); copper and selenium showed negative correlations (Cu: r = -0.258, p  0.05; Se: r = -0.277, p  0.05). The daily milk production influenced negatively only Cu concentration in milk, but Se, Zn and Mn was not influenced.With advancing lactation after colostrum period the concentration of Mn in milk raised, the concentration of Cu and Se declined and the concentration of Zn was unchanged. Cows, microelements, blood plasma

Pechová A., L. Pavlata, E. Lokajová: Zinc Supplementation and Somatic Cell Count in Milk of Dairy Cows. Acta Vet Brno 2006, 75: 355-361.The goal of the study was to test the possibility of raising milk zinc (Zn) concentration by increasing the supplementation of Zn, and to assess the effect on the somatic cell count. The experiment was performed at a farm with Czech Pied cattle, with 500 dairy cows and average milk yield 6,390 l. The experiment included 40 dairy cows, assigned to either an experimental (E, n = 20) or a control group (C, n = 20) based on the principle of balanced pairs (efficiency, lactation stage). The experimental group was supplemented Zn in the chelate form (Bioplex Zn, Alltech Inc., Nicholasville, KY), at the dose of 440 mg Zn per animal per day. Blood and milk samples were taken at the start of the experiment and at the end of months 1, 2 and 3.The average milk Zn concentration during the experiment was 57.36 ± 10.54 µmol·l -1 , ranging from 38.02 to 86.13 µmol·l -1 . A trend towards a positive effect of Zn supplementation on the health of the mammary gland was identified in association with the somatic cell count, which was significantly lower in the experimental group (114.90 ± 68.7·10 3 ·ml -1 vs. 208.60 ± 148.1·10 3 ·ml -1 ; p < 0.05) by the end of month 3. A negative correlation was found between the somatic cell count and Zn concentration in milk (y = -0.0327 x + 61.557; r = -0.441; p < 0.01). Our results indicate that milk Zn concentration is not directly affected by the level of zinc supplementation in the feed ration, but zinc supplementation has a positive effect on the somatic cell count. Cattle, blood, milk, microelements, somatic cell count, organic ZnZinc (Zn) is the most abundant intracellular microelement, characterized by a number of catalytic, structural and regulatory functions. Zinc is a biomembrane component playing an essential role in RNA, DNA and ribosome stabilization; it is also present in a number of transcription factors, stabilizes some complexes of hormones and their receptors, plays a role in insulin production and has antioxidant effects. Zn is also crucial for maintenance of integrity and the barrier function of skin and is involved in the immune system in complex ways. All these functions underlie the positive effect of Zn on the health status of the mammary gland (Boland et al. 1996), too. Although the specific mechanism of this action has not been known, the assumption is that the increased resistance of the mammary gland is based on the positive effect of Zn on keratin in the teat duct, its effect on cellular immunity, and the presence of Zn in a number of acute inflammation proteins (Harmon 1998).The research of zinc has been devoted much of attention in both human and veterinary medicine. To provide a sufficient status of this microelement in both animals and humans, a range of supplements are used, containing mostly inorganic zinc (oxide, sulphate). Organic zinc, which is more readily utilizable, has recently been used, too. As far as human nu...

The aim of this experiment was to verify the option of providing microelement supplementation to dairy cows in the dry period through supplemented mineral lick, and then to compare the content of microelements in the blood, colostrum and milk. The experiment was carried out on a farm with Czech Fleckvieh dairy cows. We formed an experimental group (E), supplied with mineral lick ad libitum enhanced with organic forms of microelements (Se, Zn, Cu, Mn) for four to five weeks before parturition and 1 week after parturition. The control group (C) did not receive any mineral lick. The use of mineral lick by cows was very uneven, its total consumption oscillated between 0 to 250 g of lick per animal per day. Lick feeding did not result in evidential increase of concentrations of monitored microelements in the cows' blood, colostrum and milk. Only a tendency to increased concentrations of Se and Cu in the blood of group E of cows was observed; the average Se concentration increased by 60 µg·l -1 (Cu by 9 µmol·l -1 ), whereas in group C, Se increased only by 30 µg·l -1 (Cu by 6 µmol·l -1). The concentration of microelements in colostrum after parturition dropped quickly. Significant drops were determined for Se, Cu and Zn on the first (for Mn on the second) day after parturition. Selenium concentration in the first colostrum was 5 times higher than in milk, Cu concentration 3 times higher, Zn concentration 4 times higher and Mn concentration 1.3 times higher.