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Two NSW DPI/MLA reports provide insights into the economics of cattle in commercial herds that are heterozygous for myostatin mutations. Myostatin mutations such as F94L found in French Pure and high French content Limousins are associated with, among other things, higher meat yield, higher proportion of preferred cuts of meat, and leaner, more tender meat.
NSW DPI Economic Research Report No. 42 observed "that meat yield contributes around 80% to profit while meat quality contributes only 20% on a per carcase basis", and that the use of a Limousin bull over commercial Angus cows increased gross margins per cow by nearly 8% when compared with a self-replacing Angus herd. These premiums were higher than other breeding systems studied. The report's review of different breeding systems included various combinations of heterozygous and homozygous parents. It noted the difficulty in sourcing bulls homozygous for the myostatin mutation found in Angus and the inconsistencies arising from the inheritance of myostatin mutations from heterozygous parents.
The MLA's final report on the NSW DPI study, published in February 2012, although focused primarily on the extreme myostatin mutation found at low frequency in Angus cattle, and which also leads to excessive muscling found in Belgian Blue cattle, contains fact sheets (Appendices 2 and 3) with information of relevance to Limousin marketing and promotion. Of particular interest is the observation that visual selection for muscling is effective and can be conducted without the need for EBVs. Visual selection for muscling does not negatively affect other important traits such as growth, reproduction and meat quality, and has a positive effect on feedlot efficiency.
The reports indicate that a one unit increase in muscle score generated a 6.1% increase in gross margin per breeding cow, and a two unit increase in muscle score increased the gross margin by 17.7%. A Limousin bull homozygous for F94L should achieve at least a one unit increase in muscle score in progeny of British breed cows as well as providing additional benefits gained from hybrid vigour. By comparison, a typical heterozygous Lim-Flex bull would achieve an increase in muscle score in only 50% of the progeny of Angus cows, which would also have lower hybrid vigour.
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