Abstract. Pedigree and molecular data were used to evaluate genetic diversity in the Polish populations of the Polish primitive horse (also known as Polish Konik) and Hucul breeds over the time period of 30 years . Based on genotypes in 12 microsatellite loci (for 3865 Polish primitive horses and 1627 Huculs), as well as on pedigree data derived from over 7000 individuals (both breeds), several indices describing structure of the analysed populations were estimated. For both analysed breeds, we observed an increasing trend of inbreeding since 1980 which seems to be much more stable (oscillating around 10 % in the Polish primitive horse and 5 % in Hucul) since the beginning of 2000s when they were included in conservation programs in Poland. We observed that generally, indices related to genetic diversity are higher in the Hucul breed. Our study indicated that genetic diversity in the Polish primitive horse and Hucul breeds in Poland is still relatively high and conservation programs should be continued to keep it on the "safe" level in the future.

Three non-synonymous single nucleotide polymorphisms (T221C, T232A and C233T) were detected in exon 4 of the porcine leptin receptor (LEPR) gene. The T232A substitution could be identified as a (Tsp509I) restriction fragment length polymorphism. The frequency of genotype TT varied in six genetic groups from 0.62 (Duroc) to 0.99 (Polish Large White). Sequencing of exon 4, performed for 30 animals, revealed that only two intragenic haplotypes (TC and AT at nucleotide position 232-233) were present. The phenotypic effect of the Tsp509I polymorphism was tested for the Polish Landrace (n = 241) and a synthetic line 990 (n = 243). There was no statistical evidence for the direct effect of the LEPR polymorphisms on fatness traits. However, in Polish Landrace allele A at position 232 was associated with thicker backfat over shoulder.

Porcine leptin gene (LEP) and its association with production traits was analysed in the Polish Large White (PLW, n ¼ 135), Polish Landrace (PL, n ¼ 120) and synthetic line 990 (L990, n ¼ 184). Two fragments of exon 3 of LEP were studied with the use of RFLP and SSCP techniques. The frequencies of C allele for the T3469C polymorphic site were 0.11, 0.10 and 0.11 in PLW, PL and L990, respectively. Phenotypic data were collected for the average daily weight gain, the feed conversion ratio, the weight of abdominal fat, backfat thickness (five measurements), intramuscular fat, meat content, loin weight, loin muscle area, ham weight and ham cut weight. The contrasts between TT and TC genotypes at the T3469C polymorphic site were estimated in the unitrait Animal Model with genotype at the RYR1 locus included. The lowest p values occurred for association test between T3469C polymorphism and intramuscular fat content in PLW (0.26 ± 0.14%, p ¼ 0.05) and loin weight in L990 ()0.32 ± 0.13 kg, p ¼ 0.01). We conclude that the detected associations are populationspecific and the analysed polymorphism of the LEP gene does not contribute directly to genetic variability of growth and carcass traits in pigs.Das porcine Leptin-Gen (LEP) und Assoziationen mit Produktionsmerkmalen wurden in der Polnischen Large White (PLW, n ¼ 135), Polnischen Landrasse (PL, n ¼ 120) und der Synthetischen Linie 990 (L990, n ¼ 184) analysiert. Dazu wurden zwei Fragmente von Exon 3 des LEP mittels RFLP-und SSCPTechniken untersucht. Die Frequenzen des C-Alleles fü r die polymorphe Stelle T3469C betrugen 0,11, 0,10 beziehungsweise 0,11 in PWL, PL und L990. Phänotypische Daten wurden gesammelt fü r die durchschnittliche Tageszunahme, die Futterverwertung, das Gewicht des abdominalen Fetts, die Rü ckenspeckdicke (5 Messpunkte), das intramuskuläre Fett, den Fleischanteil, das Lendengewicht, die Lendenmuskelfläche, das Schinkengewicht (abgespeckt) und das Gesamtschinkengewicht. Die Gegensätze zwischen dem TT-und dem TC-Genotyp an der polymorphen Stelle T3469C wurden in einem Ein-Merkmal-Tier-Modell unter Einbeziehung des Genotyps am RYR1-Locus geschätzt. Die niedrigsten P-Werte traten beim Assoziationstest zwischen dem T3469C-Polymorphismus und dem intramuskulärem Fettgehalt bei PWL (0,26 ± 0,14 %, p ¼ 0,05) sowie dem Lendengewicht bei L990 ()0,32 ± 0,13 kg, p ¼ 0,01) auf. Wir schließen daraus, dass die nachgewiesenen Assoziationen populationsspezifisch sind und der analysierte Polymorphismus des LEP-Gens nicht direkt zur genetischen Variabilität der Wachstums-und Schlachtkö rpermerkmale in Schweinen beisteuert.

Apart from the well-known role of somatic cell count as a parameter reflecting the inflammatory status of the mammary gland, the composition of cells isolated from milk is considered as a valuable material for gene expression studies in mammals. Due to its unique composition, in recent years an increasing interest in mare's milk consumption has been observed. Thus, investigating the genetic background of horse’s milk variability presents and interesting study model. Relying on 39 milk samples collected from mares representing three breeds (Polish Primitive Horse, Polish Cold-blooded Horse, Polish Warmblood Horse) we aimed to investigate the utility of equine milk somatic cells as a source of mRNA and to screen the best reference genes for RT-qPCR using geNorm and NormFinder algorithms. The results showed that despite relatively low somatic cell counts in mare's milk, the amount and the quality of the extracted RNA are sufficient for gene expression studies. The analysis of the utility of 7 potential reference genes for RT-qPCR experiments for the normalization of equine milk somatic cells revealed some differences between the outcomes of the applied algorithms, although in both cases the KRT8 and TOP2B genes were pointed as the most stable. Analysis by geNorm showed that the combination of 4 reference genes (ACTB, GAPDH, TOP2B and KRT8) is required for apropriate RT-qPCR experiments normalization, whereas NormFinder algorithm pointed the combination of KRT8 and RPS9 genes as the most suitable. The trial study of the relative transcript abundance of the beta-casein gene with the use of various types and numbers of internal control genes confirmed once again that the selection of proper reference gene combinations is crucial for the final results of each real-time PCR experiment.

We describe for the first time a 245 bp fragment of the porcine leptin gene promoter in the proximity of the transcription start site. Altogether, 720 pigs were screened with the PCR-SSCP technique for polymorphism in this region. Four SNPs, segregating as two haplotypes, have been identified, one of them (C113G) in the putative consensus site for the AP-2 transcription factor. This polymorphism was evenly distributed in the Duroc breed (n=21) and was absent in the Polish Landrace (n=248) and Pietrain breed (n=12). In the Polish Large White (n=191) and synthetic line 990 (n=243), allele G occurred with a very low frequency. The investigation was performed to test if the C113G SNP affects leptin mRNA level in subcutaneous fat and leptin protein concentration in serum. Additionally, the effect of this polymorphism on fatness traits was statistically analyzed. Although there was a trend toward decreased expression in GG animals, the differences were not significant between genotypes. We also found no evidence for an association of the LEP promoter genotype with the analyzed fatness traits.