Australian sire selection in crossbreeding is largely predicated by feedlot buyers, specifying in reference to carcass summaries as recorded in feedlot carcass databases. Derived from these databases, early, largely anecdotal Wagyu sire ranking information relates mainly to this XB production, using high Tajima (Hyogo) strain bloodline sires,. High Tajima strain specification is based on the traditional prefecture/trait relationships mentioned above – Tajima is strongly identified with marbling performance (but relatively low growth). So Australian XB specification of high Tajima sires has effectively become a ‘default setting’ for marbling. Within the specification, any reduced progeny growth possibility in the XB joining is theoretically addressed by dam (often Angus) genetics.
In implementing this ‘default selection’ to Tajima bloodlines, and for most of the entire history of Australian Wagyu production, the feedlot livestock buyers who ‘advise’ XB producers on sire selection have consistently specified sons of the same first generation Tajima sires. This long-standing specification of a short sire list is supported by science supporting consistent levels of marbling heritability in Wagyu, but fails both to recognize that identical heritability factors apply to all Japanese Blacks – not just Tajima sons; and that NOT all high Tajima sons are high marbling. In the event, lower-Tajima sires are rarely considered and in this scenario there can be little or no genetic progress in XB Wagyu breeding driven from the sire side.
An informal survey of major Australian feedlots and live exporters in late 2013 revealed that most continue to mandate a high Tajima son specification for XB suppliers – some seeking as high as 75% Tajima content in XB producer sire specifications. And there are no industry-wide or publically reviewed independent genetic development programs in Australian Wagyu XB production to challenge the ‘traditional specification’, despite the overall economic dominance of this sector in the local Wagyu industry.
As a result, breeding of F1 sires to the generic feedlot buyer specification is a ‘no brainer’: simply put ‘feedlot approved’ first generation 100% Tajima sires over FB dams sired by another consistently specified high Tajima sire – for a 75% or higher Tajima calf crop in which males are destined to become F1 paddock sires. These prospective F1 sires are usually approved on pedigree paperwork alone, so no additional selection tools are required.
Only in Hyogo is selection to a single prefectural bloodline so rigidly enforced, and no further discussion of predictive tools for XB Wagyu is currently necessary in the Australian context.