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.
Scanning performance data can be measured on animals between 300–800 days of age. Bulls are most commonly scanned, although it is recommended that stud breeders also scan their heifers as this provides valuable data for marbling as they mature earlier than males. It is also useful for stud breeders to scan their steers as this will provide information for their sires and dams.
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. Larger, more positive Carcase Weight EBVs are usually more favourable. Although this EBV should not be confused with yield. Carcase Weight EBV is an indication of the animal’s carcase weight and not an indication of its yielding percentage.
Eye Muscle Area (EMA) EBVs provides an estimate of genetic differences between animals in eye muscle area at the 12/13th rib site in a standard weight steer carcase. Larger, more positive EMA EBVs (measured in cm2) are generally more favourable.
Rib Fat EBVs (measured in millimetres) are estimates of the genetic differences in fat depth at the 12/13th rib site between animals in a standard weight steer carcase. Either a more positive or more negative Rib Fat EBV may be favourable depending on your breeding objectives relating to the finishing ability of your animals.
Rump Fat EBVs (measured in millimetres) are estimates of the genetic differences between animals in fat depth at the P8 rump site in a standard weight steer carcase. As with Rib Fat EBVs a more positive or negative Rump Fat EBV may be more favourable depending on your breeding objectives
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
- 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 standard weight steer 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 standard weight steer carcase. Animals with larger, more positive RBY EBVs are expected to produce progeny that yield higher percentages of saleable beef in a standard weight steer carcase than animals with lower RBY EBVs.
Shear Force EBVs 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. Shear Force EBVs 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 EBVs 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 (PDF, 224KB), BREEDPLAN International Beef Recording Scheme 2012.
Further information
BREEDPLAN
Website: www.breedplan.une.edu.au
Ph: (02) 6773 3555
Email: breedplan@abri.une.edu.au
Tropical Beef Technology Services
Website: www.tbts.une.edu.au
Ph: (07) 4927 6066
Email: office@tbts.une.edu.au