Report for A2 Genotypes Now in Green Book

The American Jersey Cattle Association (AJCA) has compiled beta casein A2 and kappa casein genotypes from the August 2019 genetic evaluations in a new report carried in the online Jersey Genetic Summary, commonly called the Green Book. The list is not an official AJCA report, but rather, a single source of genotypes gathered through direct communication with marketing organizations or from their websites.

Genotypes for Active A.I., Foreign and Genomic Evaluated bulls can be found in the online Green Book.

List Content

The document is available in Excel and PDF formats. The following information for A-code, F-code and G-code bulls is included when it has been provided: registration name and number, NAAB code, beta casein A2, kappa casein and JPI. Beta casein is reported as A1A1, A1A2, A2B (a variant of A1A2) or A2A2. Kappa casein is reported as AA, AB, BB or BE.

Of the 526 bulls that were included on the list, 82% have genotypes for beta casein A2 and 79% have genotypes for kappa casein. Of those with beta casein A2 genotypes, 63% are A2A2, 18% are A1A2 and the balance are A1A1 or A2B. Of those with kappa casein genotypes, 68% are BB, 11% are AB and the balance are AA or BE.

More Information

Jersey breeders can genotype their cattle for A2 through the AJCA as an add-on to purchase of the 9K uLD (ultra-low density), 45K LD (low density) or HD (high density) chips or as a stand-alone test bundled as A2, beta lactoglobulin, kappa casein and beta casein AB. For prices, visit Look under the “Services” tab and then the “Genomics” tab.

Learn more about milk proteins and options for incorporating A2 in the breeding program by viewing a video (AJCA-NAJ A2 Milk Review) on the AJCA YouTube channel.