Selen ve výživě dojnic v ekologickém chovu

Šnajdr Vladimir: Selenium in the diet of dairy cows in organic farming, Final thesis, Mendelu Brno, 50 pages. Selenium is one of a number of trace elements that are indispensable for the life of all species. Exceeding limits of the daily dose of selenium in the diet can cause toxicity of tthe organism. However, selenium deficiency can lead to diseases, particularly for species with high susceptibility to various kinds of diseases. The aim of the thesis was to investigate the influence of dietary selenium on qualitative and quantitative parameters of dairy cows in organic farming. The experiment itself was made on an organic dairy farm. The experiment involved 20 pieces of Holstein breed cows. They were divided into two balanced groups being at same stage of lactation. All the cows were fed a basic ration in the form of TMR with the addition of mineral premix Detamin GA Spezial designed for organic farms. The experimental and control group of cows took of 20.5 kg dry matter of feed/head/day. The basal diet contained 0.17 mg selenium /kg. Animals had ad libitum access to water. Selenium was added to the diet at the dose of 0.3 mg/kg (as selenomethionine) in the first group of cows (n=10). The second group of cows (n=10) served as a control without addition of selenium (control group of animals received only selenium from native sources). At the end of the experiment was after administration of selenium in the diet after 15 days in the group of cows examined detectable amount of selenium, which was constant throughout the duration of the experiment. The experimental group with selenium level ranged from 15 to 45 days in the interval from 0.13 to 0.15 mg/ml. In the control group, the amount of selenium throughout the entire duration of the experiment under the detection limit. The quantity of somatic cells was significantly reduced in the test group cows 128 thous./ml (P <0.05). Reducing the number of somatic cells was also observed even in the control group (about 49 tis./ml). The urea concentration significantly decreased in the experimental and control groups of 14.3 mg/100 ml (P <0.05) respectively about 13.7 mg/100 ml (P