Improving carcase traits
The requirement for carcases to meet market specifications has become increasingly important in the beef industry with producers aiming to optimise their abattoir and market compliance rates in order to maximise returns.
Visual appraisal can be challenging as it is difficult to accurately ‘see’ many of the carcase traits and selection on raw scans alone does not take into account any non-genetic factors such as age or nutrition. For example the majorityof bulls are selected according to looks, ‘fleshiness’, straight backline, and size that is often a refection of the animals age rather than the true genetic worth of the animal for growth and carcase.
Similar to growth traits, carcase traits are moderately heritable, which means that they respond well to genetic selection and animals can therefore be selected based on their objective genetic merit in order to improve the overall carcase characteristics of a herd.
BREEDPLAN calculates Estimated Breeding Values (EBVs) for carcase traits based on two main sources of information – live animal ultrasound scanning and abattoir carcase data. From these measurements, EBVs are available for the following traits:
- Carcase Weight
- Eye Muscle Area (EMA)
- Rib Fat
- Rump (P8) Fat
- Intramuscular Fat % (IMF %)
- Retail Beef Yield % (RBY %)
- Shear Force (trial EBV only)
Scanning performance data can be measured on animals between 300–800 days of age and the carcase EBVs (with the exception of carcase weight) are adjusted to a standard 300kg carcase.
The Carcase Weight EBVs are estimates of the genetic differences between animals in hot standard carcase weight (as defined by AUS-MEAT) at 650 days of age. For example, an animal with a Carcase Weight EBV of +20kg would be expected to produce progeny that have heavier slaughtered carcases at 650 days of age than an animal with a Carcase Weight EBV of +10kg.
The Eye Muscle Area EBV (EMA EBV) provides an estimate of genetic differences between animals in eye muscle area at the 12/13th rib site in a 300kg steer carcase. Larger, more positive EMA EBVs (measured in cm2) are generally more favourable.
Rib and Rump Fat EBVs are both measured in millimetres and are estimates of the genetic differences in fat depth between animals (adjusted to a 300kg steer carcase). Rib fat is measured at the 12/13th rib site and Rump or P8 fat is measured at the P8 rump site. Depending on your breeding/marketing objective, you may aim for either more positive or more negative Rib and Rump Fat EBVs. Some things to keep in mind when selecting animals based on their fat EBVs are:
- Stock with more positive fat EBVs are likely to produce progeny that are fatter or earlier maturing
- Stock with lower or more negative fat EBVs will tend to be leaner and higher yielding
- Increasing fat depth leads to a decrease in retail beef yield
- Market/abattoir specifications may stipulate a minimum fat depth, for example a minimum P8 fat depth of >5mm and rib fat depth of >3mm is required for MSA compliance
- Females with extremely low fat EBVs may be more difficult to get in calf
- Differences between Rib and Rump Fat EBVs can indicate differences in fat distribution among animals
Intramuscular Fat (IMF) EBVs indicate the difference in percentage (%) yield of marbling at the 12/13th rib site in a 300kg carcase. Higher IMF EBVs can contribute significantly to carcase value when selling to markets where marbling is important (e.g. Japanese B2/B3 market, restaurant trade, etc.). MSA marbling scores, along with other criteria, impact on which MSA boning group carcases align with.
Retail Beef Yield (RBY) EBVs are estimates of genetic differences in boned out retail beef percentage (%) yield in a 300kg steer carcase. Animals with larger, more positive RBY EBVs are expected to produce progeny that yield higher percentages of saleable beef in a 300kg carcase than animals with lower RBY EBVs.
Trial Shear Force EBVMs are estimates of genetic differences between animals in meat tenderness. They are calculated from gene marker information, flight time records and through objective abattoir measures for meat tenderness. Trial Shear Force EBVMs are expressed as the difference in kilograms of shear force that is required to pull a mechanical blade through a piece of cooked meat. Lower (more negative) Shear Force EBVMs indicate that less shear force is required to cut the meat and therefore it is more tender.
The availability of each these EBVs varies from breed to breed, however for most breeds there is information available that will allow you to make objective selection decisions based on estimates of the genetic potential of an animal for carcase traits. The emphasis that a commercial producer places on this information will be determined by the overall breeding objectives of the producer’s herd and the relative economic importance of carcase traits to other traits.
Where producers determine that carcase trait information is important to their breeding program and target market, they should be asking their bull suppliers to measure these traits and supply the objective data along with other information supplied on sale bulls.
Adapted from ‘Understanding Carcase EBVs’, BREEDPLAN Tip Sheet, BREEDPLAN International Beef Recording Scheme 2012.