What is a linear classification of beef cattle?
Phenotype traits are the basis of all modern evaluation systems and the usual basis for describing an animal. The linear classification is based on the dimensions of the different traits and expresses the value of the trait, not its desired occurrence.
Here is a closer look at the linear classification system developed in Denmark, which is used not only in Denmark but also in pure-bred beef cattle herds and bull stations in Sweden, Norway and Finland, and which is understood by many countries with high level beef breeding.
The exterior of beef cattle is evaluated on a linear scale on the basis of 19 traits. Each trait is rated in value 1-9. In addition, it is possible to describe deviations in the exterior traits by means of 50 deviation codes (errors), if they cannot be evaluated on the evaluation scale. These 19 traits and deviation codes (in case of deviations) are combined in the evaluation program into three composite traits – BODY, MUSCULARITY, FEET and HOOFS – which in turn are linked in the system as a common trait – TYPE. These 4 figures are corrected for cow´s body condition, calving interval, age of first calving, and number of calvings, and each individual trait is compared to the optimal average result within each breed. In the case of bulls, in addition to the four figures mentioned, the condition and age influence the score, the result of which is again compared to the statistical average within the breed. Selecting a breeding bull, the score should not be lower than 77 points.
Why linear classification?
- The evaluation is objective and independent of the number and time of cow lactations.
- Exterior traits are evaluated individually.
- Each linear trait describes each part of the body of an individual animal separately without influencing each other.
- Variation traits are detectable (variation in population).
- The breeding value of bulls on the basis of their exterior traits is descriptive.
- Economic value – a direct or indirect reference to the goal of breeding.
- Combined traits, such as legs and hoofs, are divided into several separate traits so that the advantages and disadvantages become clear.
- Linear evaluation increases the quality of the determination of the breeding value.
- The results can be helpful in developing breeding programmes.
- Linear evaluation is internationally known.
- The breeding value and the average total value estimated on the basis of the exterior traits of cows and bulls are based on the recording of linear traits by comparing them with statistical averages within the breed.
It is important to distinguish the breeding value and exterior value:
- Breeding value expresses the genetic value of an animal, including the traits it inherits to it´s offspring.
- The exterior value describes the appearance of the animal (what a “good” bovine looks like). And what level does the animal meet within the breed in terms of exterior for breeding goals.
Important breeding decisions should not be based solely on the breeding value of the animal.