The Japanese word Wagyu translates to the English word cattle. There are different strains, or breeds, of Wagyu; Akaushi is one that has a high propensity to marble. Judging by the way Wagyu look, moo and marble (they ain’t Bos indicus cattle) it appears that the cattle brought onto the islands of Japan during the 2nd century were indigenous to Europe (Bos Taurus). Further when Japanese Wagyu were actively cross-bred during the late 19th and early 20th centuries it was to established British beef breeds and to 2 European dairy breeds. On average the better a breed milks & the higher the butter-fat content of the milk, the better it marbles. Oklahoma State University has an excellent page on livestock breeds. Wagyu get a lot of press, but all high eating quality beef production has British breeds at their foundation. British breeds are comparatively early maturing, produce ample milk, have a moderately high propensity to marble, display beef cattle type conformation and yield portion control size steaks. Angus (both red and black, they were once one breed), Hereford and Shorthorn are the prominent British breeds. Shorthorn carcasses tend to be “barky,’ carrying a thick layer of subcutaneous fat. Grain-finished Wagyu marble profusely at a young/tender age, but also normally display a thick layer of cover fat.
About 100 years ago the Angus and Shorthorn breeds were crossed in Australia, then line-bred to create the Murray Grey breed of beef cattle. Breeding Murray Grey cows to pure bred Angus sires in order to produce F1 cross-bred brood cows; then breeding those F1 cows to a terminal Hereford sires more fully exploits hybrid vigor for efficient-moderately high quality beef production. Smaller cows are less expensive to maintain for crossing to a slightly larger terminal sire to produce fast gaining offspring. This 3 breed system is close to the classic black baldy, but Murray Grey cows are substantially less costly then trendy Angus cows (Hereford is often larger than Angus). Such a production program is an optimal compromise between super marbled young Wygyu and least cost European Continental beef breeds production.
Thank you for the resource information, but good knowledge sources are readily available all over the internet. The harder part is compiling bits of knowledge into currently actionable wisdom. Please feel free to post relevant content (via comments) to P. & B. E posts.