Abstract. This study was conducted on a sample of 2237 Polish Holstein-Friesian cows. The aim was to estimate the effect of selected environmental factors on the level of urea in cow's milk and on its genetic parameters, i.e. the heritability coefficients, and genetic correlation with other selected traits of milk production. The present study has revealed the existence of a highly significant influence of herd, year of calving, parity, lactation phase, and milk performance level on the urea content in cow's milk. A high urea level in milk was detected in samples collected from older animals, both during the winter season and the middle phase of lactation (101-200 days).The heritability estimates were generally at a low level, particularly in terms of milk yield (0.183) and urea content (0.152-0.159), which may indicate the dominant role of the environment in shaping them. Relatively low values of genetic correlation (−0.097-0.140) between the urea content and other traits suggest that improvement of milk yield and its composition modify the urea level in milk only to a small degree.

The Polish Energy Sector is one of the most difficult lines of business because among other things, of the existing legal provisions, and standards relating to pollutant emissions. In the coming years, in the Polish Energy Sector breakthrough changes related to develop the energy facilities and with respect to the environmental protection will have to be introduced. During the generation of electricity harmful residues are produced, which are counteracted by equipment designed for flue gas cleaning. The Energy Sector should be concentrating on searching for the implementation of innovations to achieve emission standards.

This article shows the methods and techniques that are used for cleaning exhaust fumes from dust–gas particles. The pollutants come from a complicated electricity production process in a thermal power station, whose main fuel is a hard coal or a brown coal. In the recent years, using purification installations has been the result of changing regulations in the field of environmental protection and increasing public awareness. The methods are aimed to reduce nitrogen oxides, sulphur oxides and dust emissions to the environment, not exceeding the emission limit values for individual chemical compounds.

The defensive function of the intestinal mucosa depends both on the ability to secrete immunoglobulin A and communication with the mucus microbiome. In horses, the functioning of this system is also influenced by the presence of nematode eggs. Feces collected from healthy horses were examined to determine the fecal egg count, immunoglobulin A level (ELISA), microbiome composition (Next-Generation Sequencing, NGS, V3–V4 and V7–V9 hypervariable regions of the 16S rRNA gene analysis and short-chain fatty acid (SCFA) production ((high-performance liquid chromatography, HPLC). In the taxonomic analysis within the phylum, the following order of dominance was found: Firmicutes, Bacteroidota, Verrucomicrobiota and Fibrobacterota. The coefficient of phylogenetic diversity of the microbiome positively correlated with both secretory immunoglobulin A (SIgA) [μg/g of feces] (p = 0.0354, r = 0.61) and SIgA [μg/mg of fecal protein] (p = 0.0382, r = 0.6) and with the number of Cyathostomum eggs (p = 0.0023, r = 0.79). Important components of the key microbiome in horses, such as phylum Proteobacteria and species Ruminococcus flavefaciens, were positively correlated with the fecal SIgA (p < 0.05). All the obtained results indicate the existence of significant relationships between the host response (SIgA production) and composition and SCFA production in the microbiome as well as the presence of small strongyles in the digestive tract of horses.