There were no differences in loin IMF between Merino
and various crossbred types with a mean level of 4.8%
(Hopkins et al., 2005c). However Díaz et al. (2005) showed
variation in IMF between breeds for loins, but the comparison
was confounded by differences in production systems.
There were some differences in IMF between 5 genotypes
(Merino, BLM and first and second cross types with sires
having different breeding values for growth and muscling)
in a rigorous study in which the animals were run together
and slaughtered at 4 ages from 4 to 22 months (McPhee
et al., 2008). The BLM had the highest IMF across both ewes
and wethers and the highest increases in IMF between 14
and 22 months.