Focus on Carcase Conformation

A significant proportion of lambs presented for slaughter do not meet the target specification due to them being overfat or poorly conformed. Selecting rams with superior EBVs for carcase attributes can increase flock returns.

How is carcase conformation measured?

Muscle and fat depth across the loin are measured using ultrasound as lambs reach 5 months old (21 weeks). Computed Tomography (CT) enables even more accurate measures of muscle and fat yields to be collected on the live animal.

Which EBVs are important?

Muscle Depth EBV (mm)
An assessment of muscling across the loin that provides a good prediction of total lean meat yield.

Interpretation:

A ram with an EBV of +2mm is expected to produce lambs with an extra 1mm of eye muscle depth compared to a ram with an EBV of 0.

Fat Depth EBV (mm)
Negative values indicate the potential to produce leaner carcases or carcases that can be taken to heavier weights.

Interpretation:

A ram with an EBV of –1mm is expected to produce lambs with 0.5mm less fat cross the loin compared to lambs sired by a ram with an EBV of 0.

Abattoir kill sheets and price grids indicate how much emphasis to place on carcase traits.

A ram’s fat depth EBV will influence how quickly lambs can be finished. In extensive systems where quick finishing is important, it may be desirable to select a ram with a slightly positive fat depth EBV.

Research has shown that selecting leaner breeding lines is not detrimental to ewe or lamb survival.

Muscle and fat depth EBVs can be used to enhance carcase grades for fat class and conformation.