By Dr. Gary W. Rogers
Introduction
Calving ease and stillbirth are economically important traits, and both have a significant impact on animal welfare. Geno has been calculating breeding values (BVs) for these traits for over 4 decades and these past BVs have helped Norwegian Red achieve outstanding calving ease and a very low frequency of stillbirths. To drive increased genetic improvement, we have a new model and approach for the genetic evaluation of these traits beginning in April 2023. This new model will provide more accurate BVs and even faster improvement in the coming years.
New model
We routinely calculate BVs for calving ease direct and for stillbirths direct. These direct traits are called service sire calving ease and service sire stillbirths in some populations because they reflect how the animals’ offspring (calves) will perform at birth. Many herds especially use calving ease direct BVs to eliminate some bulls from being used on maiden heifers. In addition, we also calculate BVs for maternal calving ease and for maternal stillbirths. The maternal traits are similar to what some populations call daughter calving ease and daughter stillbirths as they reflect calving performance in female offspring when they become mothers.
Previously the BVs for calving ease and stillbirths in Norwegian Red were calculated separately in what geneticists call single trait models. The new approach utilizes these traits in a multi-trait model so that data/information from one trait can influence the other trait BV. This new approach has advantages because the traits are moderate to highly genetically correlated. In addition, we now include calf size and gestation length in the same genetic evaluation model because calf size and gestation length are also correlated with calving ease and stillbirths and both traits have much higher heritability than calving ease and stillbirth. Most populations do not have calf size recorded but this trait in Norwegian Red now helps to improve the accuracy of BVs (especially calving ease).
The great benefit of the new model – increased accuracy of BVs
The benefits of the new model are increased accuracy for the BVs for both calving ease and stillbirths. Accuracy is especially improved for the young genomic selected sires. The increase in accuracy for calving ease direct averaged 12 percentage points and the increase in accuracy for stillbirths direct averaged 7.5 percentage points in young bulls so the new BVs on genomic selected young bulls will have better accuracy compared to the past. This will allow for more accurate sire selection and will result in improved genetic progress in customer herds.
Some changes in sire BVs
Most of the sire BVs for the calving ease and stillbirth traits changed by less than 5 points (12 points is 1 standard deviation in Norwegian Red BVs) but some bulls changed a bit more. Older sires with lots of calving ease and stillbirth data were not impacted very much by the model changes. Norwegian Red customers should also keep in mind that some bulls and families added information since the last proof run so this added data impacts BVs on some sires as well.
About calving ease in Norwegian Red
Norwegian Red has been a world-leading breed for calving ease and their low rate of stillbirths for decades. Due to the focus on these traits, the entire cattle population in Norway reports over 97% of calvings occur without significant difficulty or assistance, and under 4% of calves are stillborn. This is particularly important for block calving, grazing, and large herds that are focused on efficiency and animal welfare.
Take home message
Beginning with the April 2023 proof run, BVs for calving ease and stillbirths will have higher accuracy compared to the past. This will all for more accurate selection especially in young genomic sires and for faster genetic progress in these traits. Customers can have more confidence in calving ease and stillbirth BVs on young bulls compared to the past.
