Calving ease is one of the many selection factors producers considers when purchasing a bull.

The following article was written by Alexis DeCorby—Livestock Feed and Extension Specialist, Ministry of Agriculture (Humboldt).

Bull buying season is just getting underway across the province. Calving ease is often a highly sought after trait, especially for producers who are breeding first calf heifers. Determining what qualifies a sire as “calving ease” can be challenging for producers. Often, I see producers rely on the actual birth weight as a selection factor. While birth weight certainly plays a role in calving ease, it’s important to understand that it is not the only factor. If you’ve been frustrated with your calving season in the past, understanding Expected Progeny Differences (EPDs) can help select a bull that may not leave you as disappointed.

EPDs are an estimate of how a sire will perform, relative to another sire in the same breed. By definition, the calving ease EPD is a percentage of unassisted births when a bull is bred to first calf heifers. Naturally, smaller calves tend to be born with ease. However, it is possible to have heavier calves that come out just as easily as a smaller calf. This comes down to how the calf is built. A smooth, long calf will weigh more, but will likely be born without issue. Conversely, a smaller, more ruggedly built calf may not come out as easily. So, while birth weight does contribute to calving ease, it is not the only factor. The shape of the calf is also important when considering calving ease.

Understanding that calving ease represents more than just the size of the calf at birth helps make the connection that relying on birth weight alone is not accurate. It is entirely possible for a bull that was born at 85 pounds to calve just as well or better than a bull that was born at 70 pounds. Among these reasons are that the 70-pound bull may have been out of a first calf heifer, or that he may be an outlier to what we expect.

Using the calving ease EPD is typically more beneficial that selecting on actual data, because it takes into account the animals genetic relatives, such as parents and siblings, and the animal’s own performance. The question then becomes; how much is too much? When thinking about calving ease it’s important to remember that what works for you may not work for your neighbor. Some producers select bulls with a score slightly above breed average or at breed average and have minimal difficulties. Other producers may prefer a bull that has a higher calving ease number.

Taking a look at your existing herd sire’s EPDs on a breed association website can give you a feel for how much calving ease you require. For example, if you’ve been buying bulls with breed average calving ease and are dissatisfied with the level of calving difficulty, it may be time to increase that number slightly.

While calving ease is an important factor, it’s important to continue to select on a balanced approach. You may be putting selection pressure on other traits, such as weaning weight if you only focus on calving ease. In addition, understand that EPDs are a selection tool. Structure and confirmation are still important factors to consider when buying your next bull.

The Saskatchewan Ministry of Agriculture has 10 regional offices across the province. To learn more about EPDs, or where your closest Ministry of Agriculture regional office is, contact the Agriculture Knowledge Centre at 1(866) 457-2377.

(Above photo credit: Beef Resource Council Canada)