Linear Appraisal

The Linear Appraisal System assumes that physical traits that we see in any particular animal are an expression of the genetic background of that animal. If five does out of 5 different dams are sired by one buck and all have wider rumps than their dams, we begin to conclude that the width of rump of those does is a particular trait thrown by that one buck. By assigning numerical linear values, we can use mathematical methods to summarize the influence of genetics on particular traits, across broad populations of animals to determine the influence of any particular sire.

Linear Appraisal is an artificial method to more accurately describe physical traits by using a numerical value between 1 and 50 to represent the degree of biological extremes of that trait.

We know that if we measured the rump width of 1000 does, that we could calculate an average rump width by totaling all of those measurements and dividing by 1000. If the average doe had a 7" wide rump, and we assigned a mid-range score of 25 to that rump width, then the rump that is wider at 9" would be assigned a score of 45 and a rump that in narrower at 5" would be assigned a score of 15. Likewise, a doe of average strength would have a strength score of 25, while an extremely strong doe is assigned a strength score of 45 and an extremely frail doe would have a score of 15 for strength. And so it goes for 13 basic physical traits of dairy goats.

Linear Appraisal actually consists of 3 parts:

•     An evaluation of 13 traits on a linear scale
•     A coding of particular traits that do not fit a linear scale appraisal system
•     An evaluation of the overall quality of an animal in each of 4 categories;

1. General Appearance
2. Dairy Character
3. Body Capacity
4. Mammary System

             based on the following categories of quality:

•     E = Excellent @ 90% or greater
•     V = Very Good @ 85-89%
•     + = Good Plus @ 80-84%
•     A = Acceptable @ 70-79%    
•     F = Fair @ 60-69%
•     P = Poor @ 59% or less

A Final Numerical Score is calculated, based on the scoring of the animal in the 4 categories and the relative percentage value of each category.

1. General Appearance = 35% of the Final Score
2. Dairy Character = 20% of the Final Score
3. Body Capacity = 10% of the Final Score
4. Mammary System = 35% of the Final Score