The polyunsaturated fatty acid (PUFA) content of M. longissimus thoracis was determined in Hereford, Limousine and Charolais fattening bulls fed concentrate and maize or grass silage as the basie feed for 7 months. The PUFA n-3 content was higher in Charolaise bulls than in other breeds, and was significantly higher in animals fed on grass than on maize silage. The ratio of PUFA n-6/n-3 was the most advantageous in Hereford bulls.

Abstract. The experiment was performed on 121 primiparous Polish Holstein-Friesian (PHF) cows and 36 primiparous Jersey (JER) cows. The highest decrease in casein yield was noted in JER cows at 7.36 % on day 90 of lactation, 15.95 % on day 150, 26.78 % on day 210, 37.01 % on day 270 and 39.67 % on day 330. In PHF cows this decrease was substantially lower, at 4.98 %, 7.65 %, 8.72 %, 10.50 % and 16.19 % respectively. The casein content of milk from primiparous PHF cows ranged from 2.38 % (LGB – day 60) to 3.09 % (LGB BB – day 330), and it was found to be considerably lower in JER cows, varying between 2.35 % (CSN3 BB – day 30) and 3.61 % (CSN3 BB – day 210). The highest casein yield was recorded in PHF cows with the following genotypes: LGB AA (day 60), CSN1S1 BB (day 60), CSN2 AB (day 270), CSN3 BB (day 150). In JER cows the highest casein yield was noted on day 90 of lactation with respect to the following genotypes: LGB BB, CSN1S1 BC, CSN2 AA and CSN3 BB. In PHF cows the greatest effect on whey protein yield was exerted by the following genotypes: LGB AA (day 90), CSN1S1 BC (day 60), CSN2 AA (day 90); the CSN3 BB genotype influenced whey protein yield in cattle of both breeds (day 90). In JER cows the highest daily yield of whey proteins was observed on day 90 of lactation, with regard to the following genotypes: LGB BB, CSN1S1 BC, CSN2 AB and CSN3 BB.

The experiment was performed on 33 young beef bulls of the following breeds: 16, Limousine (L), 9, Hereford (H), and 8, Charolaise, aged 7 to 14 months. The bulls were fed grass silage, maize silage and a concentrate, according to IZ-INRA standards (2001), assuming body weight gains of 1100-1200 g/d. At the end of the fattening period the bulls were slaughtered and samples of M. thoracis (MT) and M. semitendinosus (MS) were taken for fatty acid analysis. The intramuscular fat of MS, compared with MT, contained a significantly higher percentage of UFA, especially PUFA with 20 or 22 carbon atoms, and a lower concentration of SFA (P≤0.01). MS contained more n-6 and n-3 PUFA (P≤0.03), and was characterized by a slightly lower n-6/n-3 ratio (P= 0.07).

The experiment was conducted on two groups of Black-and-White cows (10 animals per group) during the perinatal period. Cows in the experimental group received a ration with 300 g/d/animal of whole-plant Echinacea purpurea meal for 3 weeks from the 10"' day before the expected calving. Whole Echinacea meal contained 1.26% of a biologically active substance -coffeic acid. Milk samples were collected three times a day to determine somatic celi count, and colostrum for determination of the lactoimmunoglobulin (o, p) level. Blood samples from calves and cows were collected to determine the immunoglobulin (a, p\ y) content. Statistically significant differences (P<0.01) were found only in the content of y-immunoglobulins in cows from the experimental group after three weeks of Echinacea administration. Differences in somatic celi count between the groups in successive samplings of milk were not significant (P>0.05).

The experiment was performed in the years 1998–2000 on two farms located near to Vistula Lowlands. The experimental materials were comprised of 52 daughters of bull Paran, among which 21 possessed the mLys-mic 7 allele and 31 – the mLys-mic 3 allele. The serum and whey bacteriolytic activity of the lysozyme, concentrations of selected mineral elements, technological properties of milk at successive the first lactation stages (30, 100, 150 and 200 days), somatic cell count and bacterial count were investigated in this study. The results obtained indicate that Lys-mic polymorphism has low suitability as a marker for milk production capacity in cows. The lysozyme gene, treated as a mastitis resistance factor, showed no effects on somatic cell count and bacterial count. Further investigations, conducted not only during the first lactation, but also during the next lactation in a herd threatened by a variety of pathogenic factors, would be carried to validate this Lys-mic gene polymorphism on mastitis resistance.