Associations between polymorphism localised in the third exon of the prolactin gene (PRL-RsaI) and milk production traits of Black-and-White and Jersey cattle were analysed. A total of 427 cows were included in the study. PCR-RFLP method was used. The frequencies of genotypes and alleles were as follows: 0.7107 -AA, 0.2851 -AB, 0.0042 -BB; 0.8533 -PRL A and 0.1467 -PRL B for Black-and-White cattle and 0.0919 -AA, 0.4324 -AB, 0.4757 -BB; 0.3081 -PRL A and 0.6919 -PRL B for Jersey cattle. Statistically significant differences between the breeds were observed in the frequencies of genotypes and alleles. Associations between PRL-RsaI polymorphism and milk production traits of Jersey cows and lack of associations with these traits in Black-andWhite cows were observed.

The aim of the study is to compare the content of nutrients, including selected macro- and micro-elements, in musculus semitendinosus and offal (liver, heart, kidneys, tongue, brain) derived from animals (calves, beef cattle, and lambs) that are fed and maintained in organic production conditions. The experimental material consisted of 60 animals: 20 calves, 20 beef cattle, and 20 lambs. This research was carried out using Limousin cattle and Ile de France sheep. From the obtained results, it is concluded that the physicochemical and nutrient composition varied significantly among the organs and species studied. Almost all byproducts are a rich source of trace elements, whose levels/amounts are usually much higher in byproducts such as offal than in muscular tissues. Also, for economic reasons (profitability), byproducts (offal) can be commercially sold for human and animal nutrition. Byproducts are processed and incorporated into many food products and provide competitive nutritional value for use by tissues and muscles (vitamins and elements).

Abstract. Associations between polymorphism localised in the six exon of PIT1 gene (PIT1-HinfI) and milk production traits of Black-and-White cattle were analysed. A total of 900 cows were included in the study. PCR-RFLP method was used. The frequencies of the genotypes and alleles were as follows: 0.054 for AA, 0.377 for AB and 0.569 for BB, and 0.243 for PIT1A and 0.757 – PIT1B. There were no associations between PIT1-HinfI polymorphism and milk production traits of the cows.

The insulin-like growth factor 1 (IGF-1) is considered to be a factor that mainly regulates growth, differentiation, and the maintenance of various function in numerous tissues through binding to a family of transmembrane tyrosine kinase receptors, signaling primarily through the insulin-like growth factor 1 receptor (IGF-1R) encoded by the IGF1R gene. The objectives of the present study were to estimate the allele and genotype frequencies of the IGF1R/MspI (silent mutation within exon 12) and the IGF1R/TaqI (within the 3′ untranslated region, 3′UTR) gene polymorphisms in beef cattle and to determine associations between these polymorphisms and growth traits. In a preliminary study on 310 Angus calves, association analyses with three production traits (birth weight, BWT; weaning weight adjusted to 210 days, WWT210; and average daily gain, ADG) were conducted. The GG genotype of the IGF1R/e12/MspI polymorphism was significantly associated (P ≤ 0.05) with a higher WWT210 (+5.06 kg) compared to the AG genotype. Polymorphism within the 3′UTR had no significant effect on growth traits. The effect of combined genotypes was also examined. At WWT210, calves with the GG/AA and GG/AG combinations were heavier than calves with the AG/AA and AG/AG combined genotypes (P ≤ 0.05). To our knowledge, this is the first report of a polymorphism within the coding region of the Bos taurus IGF1R gene.

The study was carried out on 658 Polish Holstein Friesian cows. A transversion of A→C in the P1 promoter region of bovine IGF1 gene at position 977 bp upstream from the start codon in exon 1 was identified using ACRS-PCR method. Reverse primer introduced an artificial TasI restriction site. Three genotypes (AA, AC, CC) were found in the analysed herd of dairy cows occurred with a frequency of 0.766, 0.213 and 0.021, respectively. In the presented study, the statistically significant differences between individuals of different IGF1/TasI genotypes were found in milk, fat and protein yield. In the 2nd and 3rd lactations, the cows carrying the CC genotype produced more milk than the AA individuals (P≤0.05). In the case of protein and fat yield, similar tendencies were observed.