Lactation curves for renneting suitability of monozygous twin cows with different milk protein variants

Renneting ability is regarded as a main parameter for the cheesemaking suit ability of milk. Variants of kappa -casein and beta -lactoglobulin influenc e renneting time, gelation time and curd firmness differently but significa ntly. A number of papers deals with these aspects. What was actually not or iginally shown are laction curves for these parameters. Effects of the mont hs of lactation were previously obtained in studies of different cows in di fferent months of lactation. This paper presents lactation curves of three pairs of monozygous twin cows from the experimental farm at Schaedtbek with the genotypes BB/AA, AA/BB and AB/AB for kappa -casein and beta -lactoglob ulin, respectively. The results for weekly means indicate the advantage of the BB genotype for kappa -casein in all three parameters even though the b eta -lactoglobulin locus with the alleles AA was contradictory. The largest day-to-day variation was measured for curd firmness which was independent of the casein content. The year curves for the herd milk, including also th e twin pairs, vary less than expected. They indicate that e.g. for manageme nt purposes it suffices to measure cheesemaking suitability parameters four times per month to attain adequate accuracy.