AbstrACt:The object of an experiment was inorganic and organic forms of zinc, copper and manganese applied in mineral mixtures to dairy cows. The experiment was carried out on 90 cows with average milk yield for previous lactation of about 9 500 kg milk. The cows received mineral mixtures containing inorganic or organic forms of zinc, copper and manganese for 6 weeks before calving and during the first three months of lactation. The application of microelements as bioplexes in amounts covering 30% of daily requirements of cows had a positive effect on an increase in colostrum dry matter content from 20.9 to 23.35% as well as on the concentration of protein and fat, and the level of minerals -calcium, phosphorus, magnesium, zinc and copper. In cows' milk in the 2 nd and 3 rd month of lactation there were no differences in contents of minerals. However in the blood serum of cows in the 1 st and 2 nd month of lactation an increase in calcium concentration from 1.96 to 2.14 g/kg was observed while the content of phosphorus also increased average from 1.76 to 2.22 g/kg in the first trimester of lactation.

In vitro ruminal fluid fermentation as influenced by corn-derived dried distillers' grains with solubles. Folia Biologica (Kraków) 62: 345-351. This study was conducted to evaluate changes to in vitro ruminal fluid fermentation due to the use of corn-derived dried distillers' grains with solubles (corn DDGS) as a partial or complete replacement for crushed cereal and oilseed meals in the fermentation substrate. The control substrate consisted of mixed cereal and oilseed meals (barley, wheat, soybean and rapeseed), while the experimental substrates were the same meals with increasing portions replaced with corn DDGS. Including corn DDGS decreased the total VFA concentration (P<0.05), ammonia level (P<0.001), methane emission (P<0.05) and total gas production (P<0.001) during microbial fermentation. Using DDGS-containing substrates did not change the proportions of acetate, propionate and butyrate, but did decrease the proportions of isobutyrate and isovalerate (P<0.001). The fermentation efficiency, VFA utilization index, cell yield coefficient and pH of the ruminal fluid also remained unchanged. The partial replacement of cereal and oilseed meals with corn DDGS had no deleterious effects on ruminal fluid fermentation.

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In cattle, the prevention of diseases might be possible using dietary methods, with nutritional optimization of feed rations. For years significant influence has been associated with the addition of biotin, methionine and zinc (each given individually, or as chelate -Zn-methionine). The aim of this study was to evaluate the influence of biotin or biotin + Zn-methionine additives on the health and performance of cows, in the first and second trimester of lactation.This study was carried out in 3 groups of cows, 30 animals in each group. In the first group cows were fed the usual fodder used on the farm. In the second group biotin at 10 mg/day/cow was added. In the third group both biotin at 10 mg/day/cow and Zn-methionine at 5 g/day/cow were added. The administration of biotin increased the milk yield and reduced the occurrence of retained placenta, as well as endometritis puerperalis. However, the high doses of biotin suppressed ovulation and oestrus symptoms in the investigated cows (low progesterone levels on days 15, 21 and 45 after calving). Zn-methionine in comparison to biotin had a lower effect on the milk yield in the cows. Moreover, its supplementation improved the milk content, as well as some of the blood parameters; it also decreased the number of somatic cells in milk. The concurrent administration of biotin and zinc-methionine seemed to be a good method for the prophylaxis of subacute mastitis and for the improvement of the high yielding dairy cows' productivity.