The Genetic Relationships Between Intramuscular Fat Measured in Four Different Lamb Muscles

Intramuscular fat percentage (IMF) is a key determinant of eating quality in red meat. Measures of IMF from the short loin muscle (M. longissimus lumborum, LL) are currently used as selection criteria in Sheep Genetics eating quality indexes. To understand how routine selection on the short loin impacts IMF across the whole carcase, this pilot study examines IMF data collected from three additional muscles from the fore quarter (Muscularis supraspinatus, SS) and hind quarter (Musculus semimembranosus, SM; Muscularis semitendinosus, ST) of the carcase. The heritability of IMF was relatively high and consistent across the SS, LL and ST muscles, and lower in the SM. The genetic correlation estimate between IMF measured in the different muscles were all positive, ranging from 0.49 ± 0.13 to 0.97 ± 0.10. Therefore, IMF measurements from the short loin, which is currently being used as selection criteria for eating quality, will be a useful indicator for IMF across muscles from other parts of the carcase. Further, the genetic selection to increase IMF in one muscle should result in an increase in IMF in the other muscles, although at differing rates.