THE EFFECTS OF LTF AND TNFα GENES ON MILK PRODUCTION ARE DEPENDENT ON LACTATION STATE

So far, a lot of studies have focused on the genetic background of bovine milk production traits and applied heritability models which assumed that the effects of individual genes add up in a simple way and remain unchanged throughout a cow’s life, independently of external and internal factors. The aim of this research study was to verify this assumption by checking if the effects of individual alleles of LTF (substitution C/T in exon 3) and TNFα (substitution T/C in intron 6) are variable and depend on a cow’s internal environment (physiological state). The genetic material used in the study was collected from black-and-white Holstein-Friesian cows kept in a single barn in Poland. Daily milk yield and percentage content of fat, protein and lactose were examined once a month on the basis of test-day milkings. The study results show that the effects of individual LTF and TNFα gene alleles vary throughout lactation, that is they depend on a cow’s physiological state.