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ABSTRACT


Background and Objective Milk production and cheese industries need to balance the genetic progress in milk yield and protein content with the need for improving milk coagulation properties and workability. Our objective was to determine how rapidly and to what extent Milk Clotting Properties MCP could be improved by using Embryo Transfer ET to increase the frequency of the -casein BB genotype and reducing A and E variants in an Italian Holstein herd with a low prevalence of the favorable genotype. Materials and Methods In a herd of 352 cows, with a relatively low distribution of the favorable -casein BB genotype 11.0 and poor milk clotting properties, -casein BB animals were superovulated 36 out of 39 and bred with SexedULTRATM sex-sorted semen of -casein BB bulls in order to improve milk workability and cheese yield. Forty-five embryo transfer sessions yielded 203 embryos, 108 pregnancies and 98 females, of which 89 calved and entered the first lactation. Results Milk composition and coagulation properties differed significantly among the groups considered p0.05 and were more favourable for cheese-making in the groups with a higher percentage of -casein BB animals whose tank and pool milk samples consistently showed greater p0.05 fat, protein, casein and -casein B content and improved clotting properties with lower p0.05 r and k20 and higher p0.05 a30. Conclusion In the relatively short period of the project, the embryo transfer program allowed the establishment of a herd whose milk has considerably improved composition and clotting properties.

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