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Licensed under a Creative Commons Attribution 4.0 International License In this study we investigated the microbiological and chemical parameters during the composting of different substrates. Composting of two types of substrates amended with natural materials, manure mixed with zeolite (S1) and manure mixed with zeolite and lime (S2), was investigated and compared with that in the amendment-free substrate (C). During the composting the counts of coliform and faecal coliform bacteria in S2 and C differred significantly (P <0.001). There were also significant differences in coliform and faecal coliform bacterial counts between substrates S1 and S2 (P >0.01 and P >0.05, resp.). The total bacterial counts in C, S1 and S2 showed no significant differences throughout the composting (P >0.05). Degradation of organic matter was significantly increased in S2 compared to C (P <0.001) due to relatively rapid decomposition of organic matter by microorganisms in this substrate. Determination of chemical parameters also showed significant differences between individual substrates. The pH level in S2 was higher and varied from 9.16 to 7.99. Release of N-NH 4 + from S2 substrate was significantly reduced. The total nitrogen (N t) content in S2 substrate was increased by 45.01% compared to the other two substrates and resulted in a decreased C/N ratio towards the end of composting. Our results indicated that composting of manure amended with natural material provided promising results and has a potential for implementation in practice.

The peripartum period, which comprises the three weeks before and after parturition in dairy cattle, is characterized by marked physiological, metabolic and endocrine changes as the cow transitions from the metabolically demanding states of pregnancy to lactation. The dairy cows are at risk, and they are prone to various diseases (mastitis, metritis, ketosis) that could affect their productivity associated with immune suppression. The study aimed at evaluating the effect of peroral supplementing selenite at various concentrations on the selenium concentration (Se), glutathione peroxidase (GPx) activity and malondialdehyde (MDA) level of blood on the occurrence of mastitis in dairy cows during peripartum period. Forty five multiparous Holstein cows averaging 550 ± 50 kg of body weight in 2 to 4 parity were divided into three equal groups (n=15) at the end of gestation. The first experimental group (D1) was fed with addition of selenite at a dose of 0.3 mg.kg -1 of dry matter (DM). The second group (D2) was added the same form of selenium as in group D1 at a dose of 0.5 mg.kg -1 of DM. The control group (C) of cows) was fed with only selenium from native sources in content 0.2 mg per kg of DM. The blood samples for Se detection and activity of GPx were collected from the jugular vein of all tested cows month before the expected time of calving, on parturition day and at 14 th day after calving. In group (D2) with addition of selenium at a dose of 0.5 mg/kg of DM in diet, were increased the plasmatic concentration of selenium in blood plasma and colostrum as well as reduced levels of MDA. As a result, antioxidative protection was observed decreased occurrence of mastitis by 13.3% in D2 group during the first two weeks of lactation. The application of selenium in feed have economically significant impacts such as the reduction of mastitis and is one of the ways how to increase selenium in animal food and products.