Wagyu were originally draft animals used in cultivation, so they were selected for physical endurance. This selection favoured animals with more intra-muscular fat cells - marbling - which provided a readily available energy source. Japanese Wagyu derive from native Asian cattle, which were infused with British and European breeds in the late 1800's. Although the breed was closed to outside breed lines in 1910, regional isolation has produced a number of different lines with varying conformation.
It is important to recognise that the variation of conformation within the Wagyu breed is greater than the variation across British and European breeds. The three major black strains were evolved due to regional geographic isolation in Japan. These breeding differences have produced a Japanese national herd which comprises 90% black cattle with the remainder being red.
Tajiri or Tajima
Originating from the Hyogo prefecture, these black cattle were originally used to pull carts and ploughs so the developed larger forequarters and lighter hindquarters. They are generally smaller framed with slower growth rates, but produce excellent meat quality with large eye muscle and superior marbling. They are thought to be ideal for the production of F1 cattle for slaughter. The Tajima bloodlines are generally regarded as producing the best quality meat in all of Japan.
Fujiyoshi or Shimane
From the Okayama prefecture are medium framed cattle with average growth rates and good meat quality.
Tottori or Kedaka
From the Tottori prefecture were originally pack animals in the grain industry, so they are larger animals with straight, strong back lines and generally good growth rates. However, their meat quality is variable. Best strain for milking ability. Combinations of all 3 lines are often used for Fullblood meat production.
Kochi and Kumamoto
The red lines, Kochi and Kumamoto, have been strongly influenced by Korean and European breeds, particularly Simmental. It is critical for Wagyu breeders to understand the characteristics of each line when cross breeding to produce higher quality Wagyu beef.
The production of Wagyu beef in Japan is highly regulated and progeny testing is mandatory. Only the very best proven genetics are kept for breeding. Realising the value of their unique product, the Japanese Government banned the export of Wagyu and declared them a national treasure. However in 1976, four bulls were exported to the United States and Wagyu were graded up from the American cow herd and was the beginning of a two decade window of Japanese genetics entering North America and filtering through to Australia and the rest of the world to today where Wagyu genetics exist on every continent even though actual numbers remain relatively low in comparison to the more popular beef breeds.