Parasitological examinations and the investigation of polymorphism in locus DRB1, belonging to MHC class II, were conducted in a flock of Polish Heath Sheep in the years 1995-1998. The intensity of parasite infection of dams ranged from 0 to 24 000 eggs, whereas for lambs it reached up to 27 000 nematode eggs in 1 gram of faeces. In the years 1995-1997 nematode species dominant in the infection were//, contortus and T. colubriformis, while in 1998 the predominant was T. circumcincta. DNA analysis of the examined sheep showed the presence of 20 alleles in locus DRB1, established on the basis of the length of a fragment of this gene amplified using PCR (exon 2 and microsatellite in intron 2). The analysis of variance conducted for the FEC trait in genotypic groups showed a statistically significant (P<0.01) association between the genotype in locus DRB1 and number of nematode eggs in sheep faeces. The presence of a given DRB1 allele in the genotype of animals examined had significant effect on parasite resistance. Moreover, the significant association between the FEC value in allelic groups of paternal half-sibs and the segregation of paternal alleles was also significant (P<0.05).

In recent years, the knowledge regarding molecular mechanisms of skin, hair and eye colouration in vertebrates has significantly broadened. It was found that some of the identified coat colour genes show negative pleiotropic effect. They are associated with hereditary diseases, often of a lethal character. Most of these diseases have their counterparts in humans. There is no effective treatment for these diseases, therefore animal models can help to identify the genetic background of diseases and to develop appropriate treatment. Much less is known on the association of coat colour with animal performance. However, there are reports on the effect of coat colour on body measurements and milk production in subtropical environments. The knowledge on pleiotropic effects of coat colour genes is important for breeders who should be aware of the consequences of their decision on mating animals with given genotype.

Over a 4-year period, from May (1995) or June (1996June ( -1998 to November, in a flock of Polish Heath sheep, faecal samples from 246 ewes, 9 rams and 429 lambs were examined for gastrointestinal nematode eggs by the McMaster method. Faecal cultures were run to identify the nematode species present. The prevalence of positive egg counts was, on average, 43 to 69% in ewes and 68 to 80% in lambs. Two nematode genera predominated: Haemonchus contortus and Trichostrongylus colubriformis. In the last three samplings in 1998 increased frequency of Ostertagia (Teladorsagia) circumcincta infections was noticed.Animal model restricted maximum likelihood was used to estimate the heritability and repeatability for faecal nematode egg count (FEC) and correlations with productive traits.The obtained values of these parameters were 0.128 (±.0.011) and 0.068 (±0.005) for repeatability and heritability, respectively. A negative influence of faecal worm egg count on fleece weight of ewes and weight gain from birth to 3 rd month, from 3 rd month to 12 th month and during 12 months of lambs' life was observed. The estimated genetic correlations were: -0.014 (±0.053), -0.197 (±0.046), -0.204 (±0.073), and -0.174 (±0.074), respectively.

Key words: sheep, mastitis, bacteria, SCC, WBCMammary gland health status is one of the main factors that determines the efficiency of sheep production. Inflammation of the mammary gland (mastitis) may adversely affect milk production and quality, cause rearing losses (lower weight gains of lambs, mortality) and result in the need to remove sick ewes from the flock. Microorganisms, in particular pathogenic bacteria, are the main cause of mastitis (Ber-* Project financed from statutory activity. Unauthenticated Download Date | 5/12/18 7:44 PM

The variability of morphological traits of sheep udders was studied in the Polish Lowland, Polish Merino and Polish Highland sheep, which are bred for different purposes. Beside differences among breeds, intrabreed differences were found as regards the analyzed traits. The ewes of the breeds studied differed as regards udders shape and frequency of such anomalies as asymmetry of udder lobes or extra teats. The genetic parameters (heritability, repeatability and correlation) evaluated had moderate to high values, depending on the trait. This indicates a possibility of selection for improvement of udder health and shape and for increased productivity.