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

The aim of our studies was to determine, whether difference in GH alleles a ffect 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 o f Simmental (meat) and Holstein (milk) breeds at 90 d and 180 d of age usin g PCR, agarose gel electrophoresis and IRMA. The age-dependent increase in body mass, daily gain and plasma IGF-I concentration was observed in Simmen tal bulls. In Holstein bulls the age-dependent rise in plasma IGF-I was als o found, whilst Holstein bulls had significantly lover IGF-I level, than Si mmental bulls, The proportion of LL, VV and LV genotypes of GH in the rando mly selected herd of Simmental bulls was 0.25:0.20:0.55. Animals of VV geno type 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, sugge st that GH genotype may affect meat performance via IGF-I secretion.