Zinc Supplementation and Somatic Cell Count in Milk of Dairy Cows

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 ± 68.7 103 ml-1 vs. 208.60 ± 148.1 103 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

Contents of Zn, Cu, Mn and Se in Milk in Relation to their Concentrations in Blood, Milk Yield and Stage of Lactation in Dairy Cattle

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