MYOG and MYF6 belong to the MyoD gene family. They code for the bHLH transcription factors playing a key role in later stages of myogenesis: differentiation and maturation of myotubes. Three SNPs in porcine MYF6 and two in porcine MYOG were analysed in order to establish associations with chosen carcass quality and growth rate traits in Polish Landrace, Polish Large White and line 990 sows. No statistically significant effect of SNP in the promoter region of the MYF6 gene on its expression measured on mRNA level was found. Associations between the genotype at the MYF6 locus and carcass quality traits appeared to be breed-dependent. The C allele in the case of SNP in the promoter region and GC haplotype in exon 1 were advantageous for right carcass side weight in Polish Landrace sows and disadvantageous for this trait in Polish Large White sows. These gene variants were also the most advantageous for loin and ham weight in sows of line 990. The mutation in exon 1 of the MYOG gene had no statistically significant association with carcass quality traits and the mutation in the 3'-flanking region had the breed-dependent effect as well. These results suggest that SNPs analysed in this study are not causative mutations, but can be considered as markers of some other, still unrevealed genetic polymorphism that influences the physiological processes and phenotypic traits considered in this study.

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.

The objective of this study was to determine hepatic expression levels of GHR, IGF1R, IGF1 and IGF2 genes in young growing gilts at different developmental ages (60-210 days) in five pig breeds: Polish Large White (PLW), Polish Landrace (PL), Pulawska (Pul), Duroc (Dur) and Pietrain (Pie). We studied the differences among pig breeds as well as within each breed for pigs in different developmental ages. Obtained results revealed major differences among breeds in hepatic gene expression of porcine GHR, IGF1R, IGF1 and IGF2 genes in different developmental ages. The differences among breeds of GHR expression were significantly higher in PLW, PL at the age of 60, 90, 120 days as compared to Pul, Dur and Pie. In turn, the highest level of IGF1R expression was observed in PL at age of 150, 180 and 210 days, whereas in case of IGF1 the highest level was recorded in Pie gilts at the age of 60 and 90 days. Moreover trait associated study revealed highly significant correlations between hepatic expressions of IGF1R and IGF2 genes and carcass composition traits (P < 0.01) The results of study suggest that porcine GHR, IGF1R, IGF1 and IGF2 genes may be potential candidate genes for postnatal growth and carcass composition traits. Therefore, the implementation of the hepatic expression of GH/IGF genes into the pig breeding and gene assisted selection program in different pig breeds should be considered. However, further population wide study is needed to clarify the hepatic expression association with economic traits, such as body growth, meat quality and carcass composition traits.

Quality of semen of young boars of the breeds Pietrain and Duroc and their reciprocal crosses AbstractThe study concerned examination of 120 of young Pietrain and Duroc boars and hybrids descending from reciprocal crossing of those breeds. On 230 th , 250 th and 270 th day of their lives, their sperm was given a detailed examination. It is assessed that Pietrain boars gave ejaculates of the lowest volume, lowest mobility, and the lowest total number of spermatozoa. Semen of boars of this group had also the highest percentage of spermatozoa with major and minor morphological changes, and defected acrosome. Along with the age of boars (from 230 th to 270 th day of life) there was a significant improvement of quality of semen of all of the groups except the semen of Pietrain boars. We detected the positive effect of crossing especially in hybrids boars descending from mating of Duroc fathers and Pietrain mothers. Even during the first evaluation, they gave the semen of the highest total number of normal sperms, with normal acrosome, and with the highest value of osmotic resistance test and the lowest activity of AspAT in semen plasma. That proves the high quality of ejaculates of those hybrids comparing to the ejaculates of the boars of other groups -purebreds as well as hybrids of the opposite combination, i.e. descending from crossing of Pietrain fathers and Duroc mothers. This conclusion suggests to use Duroc fathers and Pietrain mothers in production of hybrid boars.