Interrelationships between breed, growth hormone genotype, plasma IGF-I level and meat Performance in bulls of different ages (short communication)

Abstract. The aim of our studies was to determine, whether difference in GH alleles affect growth Performance in cows and whether these effects may be mediated by IGF-I. The presence of L (leucine-rich) and V (valine-rich) alleles of GH, plasma IGF-I level and changes in body mass were analyzed in 84 bulls of Simmental (meat) and Holstein (milk) breeds at 90 d and 180 d of age using PCR, agarose gel electrophoresis and IRMA The agedependent increase in body mass, daily gain and plasma IGF-I concentration was observed in Simmental bulls. In Holstein bulls the age-dependent rise in plasma IGF-I was also found, whilst Holstein bulls had significantly lover IGF-I level, than Simmental bulls. The proportion of LL, VV and LV genotypes of GH in the randomly selected herd of Simmental bulls was 0.25:0.20:0.55. Animals of VV genotype had lower body mass, daily gain and plasma IGF-I level, than bulls of LL and LV genotypes, whilst no differences in these indexes between LL and LV genotypes were found.

The observed association of growth rate, GH genotype and IGF-I level, suggest that GH genotype may affect meat Performance via IGF-I secretion.