Mature Height and Weight

Weight and height can be recorded on the cow at the time of weaning. Mature cow size is useful to match biological type to the environment where those cows are expected to perform.

Phenotype

Mature weight should be collected on an individual animal scale and should be recorded to the nearest pound. The weight should be collected on a high-quality digital or mechanical individual animal scale.

The weight should never be estimated and should be recorded to the nearest whole pound if possible. If recording the weight to the nearest whole pound is not feasible, then it can be acceptable to record the weight to the nearest 2-pound increment. Mature weight should never be recorded to the nearest five pound or other larger increment. Mature weight should never be estimated by averaging a group weight.

Mature height should be measured when the cow is standing on a flat surface with her hips level, and height is measured in inches. The measuring stick should be perpendicular to the ground with the height measured directly over the hooks. Heights can be converted to frame scores as shown here.

Both traits should be measured on all cows every year.

Adjusted Value

Mature weights should be adjusted for body condition score and age, and mature heights should be adjusted for age. Young females are still growing, meaning their weight and height are expected to change over time, and adjusting for age accounts for these changes.

Contempory Group

Because cows and calves are managed together, contemporary groups should be the same as those used for weaning weights. Contemporary groups include cows that calved around the same time, were managed together and had access to the same feed resources. Cows in the same contemporary group would have their weights and heights collected on the same day and at the same location.

Bull phenotypes are not useful for genetic evaluation because bulls are typically in very small contemporary groups.

Genetic Evaluation

The model for the mature weight (or height) should include direct additive genetic effects and permanent environmental effects because the traits are measured repeatedly on the same animal. The genetic correlations between mature weights at different ages have been estimated greater than 0.95 indicating mature weight can be considered as the same trait, no matter the age of the cow.

Usage

Mature weight and height provide an indication of cow feed costs as larger cows require more feed resources to maintain their body weight. Ideally, these traits should be incorporated into a selection index to account for differences in cow costs in combination with other economically relevant traits.