Performance Article Series: Part 2 Weight Traits
By Lance Bauer, Director of Breed Improvement & Western Field Representative
The traits of birth weight, weaning weight and yearling weight are all economically important to cattlemen. Birth weight is one of the leading causes of dystocia in cattle and can cause the loss of cow and/or calf. This leads many cow-calf producers to look for bulls with low birth weights. The majority of calves in the United States are also sold at weaning and are sold by the pound, so weaning heavy weaning weights are important to these producers. Other producers will retain ownership of calves through the feed yard and yearling weight can be an indicator of how well they will perform there. By measuring these weights on your cattle and recording the weights with the BBU registry system, you provide more information for the calculation of EPDs.
Birth weights are the first weights that should be recorded and should be taken within 24 hours of the calf being born. There are different ways to take the birth weight including traditional scales or a weight tape. Scales are the most accurate way to take weights. The weight tapes tend to underestimate the weight of larger calves and overestimate the weight of lighter calves. The manner in weighing the calves should remain constant throughout the calving season. The weight of the calf will then be adjusted for the age of the dam, once it is recorded in the BBU registry system.
Weaning weights should be recorded at weaning time, which is approximately 205 days of age or seven months of age. In order for BBU to include weaning weights in the genetic evaluation they need to be recorded between 140 and 270 days of age for an animal. This means that if you have a 90 day calving season and you wean calves when the majority of them are 205 days old, then they should all fit into the age window for weaning weight. Weaning weights are adjusted using the age of the dam, as well as the age of the calf, at the time of weaning. The standard for the age of the dam is five years old and adjustments are made on differences from five years old. The adjustment formula that is used is not the standard linear formula for adjusted weaning weight, but a non-linear formula that is based on BBU data and allows for the calculation of a weaning weight without having to assign a birth weight to animals that do not have a birth weight recorded. Recorded weaning weights with contemporary groups of larger than one animal and fit within the age range will be included in the genetic evaluation for the calculation of EPDs.
The next weight to measure is yearling weight and it should be measured around 365 days or one year of age. For yearling weights to be included in the genetic evaluation they need to be taken between 320 and 430 days of age. Yearling weights are also adjusted using the age of the dam, as well as the age of the animal, at the time of weighing. A five year old cow is the standard for the adjustment of yearling weight, and again it is a non-linear adjustment. Animals that are in contemporary groups of more than one animal and fit within the age range will be included in the genetic evaluation.
Recording these weights is important for the Beefmaster breed and allows the association to utilize more data in our genetic evaluations to calculate EPDs. EPDs are important because they allow both purebred breeders and commercial breeders to compare animals throughout the breed and animals that are raised in different environments. The EPDs for these weight traits are economically important traits that are included in the calculations of $T and $M, which are very helpful tools in the selection of animals. There will be more articles in this series that cover more about performance, such as what a contemporary group is and what EPDs are. The next article will focus on calving ease scoring, udder and teat scoring, as well as mature cow weights.