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Why have we seen changes to Carcase Eye Muscle Area in the EBV to WBV change?

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Why have we seen changes to Carcase Eye Muscle Area in the EBV to WBV change?

With the transition from EBVs to WBVs, one of the more noticeable changes has occurred in the Carcase Eye Muscle Area (EMA) breeding value. Compared with most other traits, EMA has shown a larger degree of reranking between the previous EBV system and the new WBV evaluation. This is illustrated in Figure 1, where the correlation between EMA EBVs and EMA WBVs for 245 influential sires is 0.77, being still a strong relationship, but lower than for many other traits in the evaluation.

A key driver of this change is the update to the Wagyu data-driven genetic parameters used in the model. Under WBVs, EMA is now more strongly and positively correlated with growth traits, carcase weight and marbling score. These relationships are better aligned with what many producers observe in commercial carcase performance and aligned with correlations reported by Japanese researchers  in Japanese Black cattle (Oyama 2011 (82), Animal Science Journal pp367-373)  By updating the parameters on how EMA interacts genetically with these economically important traits, the evaluation now provides a more realistic picture of the way EMA contributes to overall carcase merit and allows for simultaneous gain in CWT, EMA and MS as the Japanese industry have achieved. Another major enhancement comes from removing the pre-adjustment of carcase traits to a standard carcase weight endpoint. In the past, raw EMA data was corrected to a standard 420 kg before entering the evaluation. Under the WBV system, EMA is modelled directly from the raw measurements, with non-genetic effects built into the model, allowing the evaluation to account for the genetic variation rather than relying on precorrections. For more on this change CLICK HERE

Together, these enhancements mean the WBV evaluation provides better and more biologically consistent genetic prediction of Carcase EMA. While this has resulted in some re‑ranking, breeders should have confidence that the new WBVs better reflect the underlying genetic merit for EMA in the Wagyu population.

Carcase EMA

Figure 1.  Carcase Eye Muscle Area EBV to WBV relationship for 245 influential Wagyu sires  

 

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