Yearling Weight

Yearling weight is a measure of post-weaning growth reported in pounds.

Phenotype

Yearling weight measurements should be taken between 320-440 days of age. Suggested time between weaning and yearling weight measurement is 160 days. It is important to not take the yearling weight measurement too closely to the weaning weight to allow for more post-weaning growth and a more accurate measure of the yearling weight trait.

Proper measurement procedures are also important. An accurate scale should always be used. The yearling weight measurement is taken and reported in pounds.

Adjusted Value

Adjusted 365-day weights are used to adjust for age of dam and actual age of calf at weighing. Age of dam is known to have an impact on calf weights and each calf is not going to be exactly a year old when the yearling weight measurement is taken, so an adjustment is used. Age of dam is accounted for in the Adj 205-day Wt. The equation used is shown below:

$Adj\,365-day\,Wt\,=\,{\frac {Yearling\,Wt\,-\,Weaning\,Wt}{Number\,of\,days\,between\,weights}}\,\times \,160\,+\,Adj\,205-day\,Wt$

Contemporary Group

A contemporary group is a group of cattle that are similar in their age, sex, and breed composition and have been managed similarly. Management includes feeding, health treatments, and environment. All cattle in a contemporary group have their yearling weights taken on the same day.

Genetic Evaluation

The adjusted yearling weight is used to calculate the yearling weight EPD. The YW EPD predicts the amount of yearling growth (lbs) that will be transmitted to offspring. It is a reflection of both pre-weaning and post-weaning growth for that animal. There are not as many yearling weight records as there are weaning weight records because once the animal reaches the feedlot, yearling weights are often not reported. Some breed associations account for missing yearling weights by using a multiple-trait model for the yearling weight EPD. This multiple-trait model utilizes genetic correlations between birth, weaning, and yearling weights to calculate yearling weight EPDs. Multiple-trait models help avoid selection bias caused by culling lightweight calves from herds before yearling weights are reported. Yearling weight is also sometimes used as an indicator trait for other EPDs such as Mature Weight.

In genetic evaluation, yearling weight is commonly fit as post-weaning gain. The resulting reported yearling weight EPD is the sum of the weaning weight EPD and the post-weaning gain EPD. Because weaning weight and yearling weight have a part-whole relationship, fitting post-weaning gain instead of yearling weight improves the condition of the model equations to be solved. This is a result of both, a lower genetic correlation between post-weaning gain and the other traits (e.g. weaning and birth weight), and not needing to include a maternal effect for yearling weight.

Usage

Yearling weight is an important trait for producers who plan on retaining ownership and feeding out calves. The greater the YW EPD, the more growth potential that animal has to pass to its offspring. Higher growth rates can mean fewer days on feed and lower input costs to reach market weights. Yearling weight measurements may not be as important for those producers who sell their calves directly after weaning. However, producers who purchase weaned calves may be interested in the genetic growth potential the calves have to offer.

References

1. Bormann, J.M., 2010. Data Collection and Interpretation. Beef Sire Selection Manual. Pages 21-23. http://www.nbcec.org/producers/sire_selection/chapter7.pdf. 16 April 2019.

2. American Angus Association. 2019. Adjusted 365 Day Yearling Weight. https://www.angus.org/Performance/AHIR/PerfLinks.aspx. 16 April 2019.