Calving Ease EPDs
By Lance Bauer
In February 2017 Beefmaster Breeders United will introduce Calving Ease Direct (CED) and Calving Ease Maternal (CEM) Expected Progeny Differences (EPDs) in the next genetic evaluation. These new Beefmaster EPDs were approved by the BBU Board of Directors in October 2016 at the annual convention in Branson, Mo. So what are CED and CEM EPDs? And what do they mean? Let me explain.
A problem that many producers are concerned with is a cow’s ability to have a calf with no difficulty and no needed assistance. This can be especially important to producers who do not get to see their cattle on a daily basis and may have heifers calving without anyone watching. There are different factors that can cause dystocia, or a difficult birth, including the birth weight of the calf, the pelvic area of the cow or heifer, and whether or not the calf is presented normally at birth. Many times only one of these factors is used to try to prevent dystocia, and that is birth weight, either by looking at the animals individual birth weight or at birth weight EPDs. Single trait selecting for birth weight can lead to other issues such as slower growing and smaller animals, as well as decreasing the pelvic size in heifers and cows which leads to dystocia problems even when low birth weight bulls are used as sires. One way to keep from this single trait selection is to use calving ease EPDs. There are two different calving ease EPDs that are used, CED and CEM. These EPDs take into account the various different reasons for dystocia and can help select bulls that will produce calves with few issues of dystocia, as well as select bulls who will produce heifers that should have less issues with dystocia.
The calving ease EPDs take into account the birth weight, as well as the calving ease score that producers assign to heifers and cows at calving. The calving ease scores range from 1 to 11 with the scores of 1 thru 5 being associated with the presentation and ease of calving a live calf. In this scoring system a 1 is a natural unassisted birth, 2 the cow requires some assistance, 3 a mechanical device is used to pull the calf, 4 a caesarean section is performed, and 5 the calf is presented abnormally. These scores should be recorded at calving in order to make better predictions for the calving ease EPDs. Scores 1 thru 5 are the scores that are used to calculate the calving ease EPDs, scores 6-11 are excluded from the calculation since they deal with dead calves, aborted calves, cases where the cow died or the calf is a product of an ET program. The calving ease EPDs are done on the basis of a heifer calving at two years of age, since most calving issues tend to happen in these younger heifers.
The CED EPD is based on the calving ease score and birth weight and can be used to evaluate how a sire will impact calving ease in heifers calving at two years of age. For example, if bull A has a CED of +8 and bull B has a CED of +6 then it would be expected that bull A will produce 2% more unassisted births than bull B. It is beneficial to select bulls with a higher CED to help ensure more unassisted births. When mated to mature cows the difference between bull A and bull B would be expected to be less than the 2% calculated.
The CEM EPD is used to evaluate how a sire’s heifer offspring will calve at two years of age without difficulty. If bull C has a CEM of +5 and bull D has a CEM of +8 then it is expected that 3% more of the heifers produced by bull D will have calves unassisted, at two years of age, than bull C. Again, when selecting using CEM it is beneficial to use the bull with the higher value in order to produce more heifers that will calve unassisted at the age of two. The difference between daughters of different bulls will decrease over time as the cows mature and have more calves.
In the past focusing solely on birth weight was a way to pick bulls that would present less calving issues, but now with calving ease EPDs the weight of the birth weight and calving ease score are more properly balanced to include other factors that impact dystocia. Since both birth weight and calving ease score are used in the calculation, it is important that breeders submit both birth weight and calving ease score. When looking at these calving ease EPDs it is important to remember that birth weight is already factored into the EPD, so looking at birth weight again will place added emphasis on birth weight and take away some of the value of the calving ease score. When selecting bulls using calving ease scores it is important to remember that higher calving ease scores are more desirable than lower calving ease scores. This is unlike when selecting bulls using just birth weights, where lower birth weights are more desirable than higher birth weights. Both of these EPDs are very useful to the producer breeding heifers. The CED is useful in selecting a bull that should be able to be used on heifers without causing many calving issues. The CEM is useful in selecting bulls to produce heifers that will be retained for breeding purposes.