Beef Cattle Live Animal Assessments

3.6 Live animal assessments

3.6.1 Assessment of muscularity

Linear scoring is a technique which allows a systematic description of an animal’s morphology. Linear scoring reveals part of the animal’s economic value and, if the scored traits are heritable, part of its genetic value. Economic and environmental conditions vary over time and between countries so the economic importance of each scored trait may differ depending on the circumstances. The specific relative importance has to be determined by the responsible breeding organisations.

As well as the description of a single animal, data from linear scorings are used for genetic evaluation of dairy, dual purpose and specialised beef breeds.

Many breeders, breed societies and those in the AI industry use linear scoring in routinely performed animal recording. In beef breeds linear scoring of muscle shape is particularly important as an indicator of saleable beef yield per animal, and thus is an indispensable part of the beef recording system.

To meet the need for an efficient world wide, genetic exchange, international comparison of breeds, and demand for more comparability of individual cattle between countries, procedures for linear scoring of muscularity should be harmonised. This need is best served by an internationally recognised set of recommendations.

The following recommendation may help organisations design a linear scoring system for beef performance recording which suits their market conditions, and which may lead to more homogeneous and comparable scores between different countries.

The present recommendation refers only to linear scoring of muscularity, which is usually part of a complete integrated scoring system within breed. It does not deal with the full spectrum of linear scoring. A complete linear scoring system for a given breed often includes further items such as skeletal traits, udder, legs etc.

The following recommendation may be used both for dual-purpose breeds as well as for specialised beef breeds. Linear scoring can be conducted on any category of animals, such as male and female calves, heifers, cows, bulls and steers.

3.6.2 Recommended approach to be taken in organising Linear Scoring

Linear scoring has the following characteristics:

Linear scoring has the following characteristics:

1. Linear scoring is a systematic description of an animal’s morphology.
2. It is usual for a linear scoring scheme to takes several anatomical sites into account.
3. The anatomical sites must be precisely defined.
4. Within one single anatomical site, linear scoring provides a description of the biological extremes and a number of intermediates.
5. The scores represent an ordinal scale, which should allow for sufficient discrimination in the degree of expression of the linear trait.
6. The extremes and the intermediates are ordered according to the degree of expression of the trait. For example, thin and thick, long and short etc.
7. A high or a low score has no particular meaning and it is not necessarily desirable or undesirable.
8. By convention one of the extremes receives the score ‘1’; the other levels receive a number in ascending order which describes the expression of the trait.
9. A scale from 1-9 points is recommended for most traits.
10. Where the range of biological extremes is large in the population of animals under consideration, (e.g. double muscling or an across breed recording scheme) the scale may need to be extended. A 1 to 15-point scale is recommended in such circumstances.
11. The scoring system should be consistent across contemporary groups, i.e. breeds/breed groups.
12. Linear scoring should if possible be conducted on animals which belong to the same category in terms of sex and age.
13. For each category of animals, the scoring scale for muscle shape should be the same.
14. Scoring for muscularity relates to muscle shape only.

The traits which should, as a minimum, be taken into account in a muscularity linear scoring scheme are:

1. Shoulder width.
2. Loin width.
3. Rump length.
4. Rump width.
5. Thighs width.
6. Thighs depth.
7. Thighs inside.
8. Thighs rounding.

The following is a graphical representation of the linear muscular anatomical sites.

File:Type scoring diagram.pdf

3.6.3 Requirements for linear scoring

All factors accounting for any non-genetic variance should be recorded., e. g.

1. Scorer’s identification.
2. Scoring date/time.
3. Management group.
4. Nutritional status etc.

All information should be recorded in accordance with ICAR recommendations where they apply.

Within contemporary group (e.g. animals of one scoring season within farm) all animals of the same category should be scored according to the standard of the appropriate category.

In order to prevent any pre-adjustments by the scorer, it is necessary that no information other than the animal’s identification should be provided when scoring. No other information, particularly in relation to the ancestors of the animal, or its age should be available.

Linear scoring requires well trained technicians. The practical and theoretical knowledge of the scorer should be tested after receiving appropriate training. The training should allow the scorer to:

1. Make full use of the scale within the category of animals being recorded.
2. Attain a minimum level of repeatability within scorer.
3. Attain a minimum level of repeatability across scorer.

If possible, a routine regional rotation of the scorers is recommended as this facilitates and improves the statistical evaluation of data from linear scoring in different herds by giving a better estimation of the scorer’s effect.

The responsible breeding organisation should establish a routine supervision procedure for the scorers. The competency of all scorers should be monitored and training should be provided annually or more often if necessary.