The linear type trait genetic evaluations incorporate a multi-trait analysis. Multiple trait analysis increases the accuracy of the evaluations by considering the genetic correlations of the given linear trait with all other linear traits.

Genetic evaluations for linear type traits are reported by Holstein Association USA as Standard Transmitting Abilities, or STAs. STAs rank an animal based on its genetic merit relative to the average cow born in 2000 in standard units. Since the bulls being actively marketed by AI organizations have been heavily selected for production and type traits, the AI bull population has a higher STA average for most linear traits compared to cows born in 2000.

Linear type traits can help you breed a more profitable herd of Holsteins through selecting better bulls. Understanding linear type trait STAs can help you:

1. identify the most important traits
2. set realistic genetic goals for each trait
3. select a better group of mating sires
4. mate each cow to a complimentary bull
5. accumulate genetic gains across generations

Table 2 shows the average STAs of bulls coded ACTIVE or LIMITED. Classified cows born in 2000 represent the genetic base for these averages.

HERITABILITY OF TYPE TRAITS

The degree to which a bull or cow is able to genetically influence various characteristics in its offspring is measured by heritability. Faster genetic progress can be achieved for traits which are higher in heritability compared to traits which are lower in heritability. It is difficult to make much genetic progress through selection and mating unless a trait has a heritability of .10 or higher.

Table 3 contains estimates of heritability for linear traits currently summarized by the Holstein Association, USA.

Udder Composite is computed as the total of the STAs of these six udder traits times their respective relative herd life weight (listed above).

UDC = [(UD x .35)+(FU x .16)+(UH x .16)+(UW x .12)+(UC x .09)+(TP x .05 ) - (RP* x .070)]+0.15

Feet and Legs Composite

In January 1996, the Holstein Association USA introduced a greatly improved Feet and Legs Composite (FLC). Following extensive research, Holstein Association researchers added two new traits: the linear trait, Rear Legs - Rear View, and the major category, Feet and Legs Score. The new FLC is nearly three times more useful in explaining differences between cows for productive life - for every 1.0 STA increase in FLC you can expect a +0.3 month increase in productive life.

The FLC formula utilizes a 50:50 ratio of the three linear traits combined with the Feet and Legs Score. The three linear traits STAs are weighted:

.48 (Foot Angle) + .37 (Rear Legs – Rear View) – .15 (Rear Legs – Side View)

The overall Feet and Legs Composite is:

FLC = .5 (linear traits) + .5 (Feet and Legs Score)

Feet and legs are a primary concern of dairy farmers throughout the world. A survey recently completed by a leading dairy magazine found the FLC to be one of the five most important traits currently selected by dairy producers in the USA.

Selecting animals that transmit superior mobility, steeper foot angle, wider rear leg stance with little or no hock-in, and slightly straight rear legs (side view) will result in animals capable of longer productive life. The Feet and Legs Composite combines all four traits into one value that will help Holstein dairy farmers breed longer lasting, more profitable cows.

Body Size Composite Body Size

Composite is calculated from the four linear traits; stature, strength, body depth and rump width. The calculation is:

(.5 x Stature) + (.25 x Strength) + (.15 x Body Depth) + (.10 x Thurl Width)

Every 1 STA increase in body size equals a 24 pound increase in mature body weight. To put this in perspective, daughters of bulls that sire large cows (large positive evaluations for body size, +3.00) are expected to weigh 144 lb. more than those that sire small cows (large negative evaluations for body size, -3.00).