KENNER SIMMENTAL RANCH Black 1/2 SimAngus Bulls (All Homo Polled)
UNDERSTANDING CALVING EASE, STAYABILITY & DOCILITY EPDS AND API & TI INDEXES BY ERIKA KENNER
EPDs are important to utilize when selecting bulls for your herd. It is the fairest way to compare animals across herds as it averages sire groups within contemporary groups and removes the environmental component. Actual data will only compare the animals within the herd they are raised and that environment may be entirely different than yours. In order to use EPDs most effectively, we need to understand what they measure and what data is included. The direct calving ease EPD (CED) measures the % of unassisted births when used on first calf heifers. American Simmental Association (ASA) recommends to use when selecting bulls for your heifers. CED EPD does not need to be as high when using on cows. I would even say it doesn’t need to be double digits when breeding cows. Don’t get me wrong, a live calf is always the goal, but there is a happy medium. We sell by the pound and still need these calves to grow. In northern ND, the small 60 lb calves struggle more to stay warm after birth than a heavier calf. Again, there is a happy medium. I’m not advocating for over 100-pound calves. The Indexes are included with the EPDs, but instead measure profit and are a combination of many EPDs plus they include inputs and outputs for each trait. The first Index is API. API stands for All Purpose Index meaning all the traits relevant when retaining a portion of the females in your herd. American Simmental Association has a nice chart that shows what is used to calculate API.
Many do not realize that the Docility EPD is not included in the indexes directly since there aren’t inputs associated with it. If cattle are culled for disposition after calving, then it’s included in the stayability portion, but docility is a trait where most will be culled prior to breeding. In my opinion, culling a sire group’s daughters for docility prior to breeding is an economic hit. That year of replacements is lost. Calving ease EPD is a major part of API in the Calf Survival portion of the pyramid. Since the CED of cow bulls will not be as high, the API of cow bulls often is not as high. But we can’t just breed for calving ease bulls. We still need performance. Cows should be able to have 7% of their body weight in a calf. Which means a 1400 lb cow can have a 98 lb calf and a 1200 lb cow can have an 84 lb calf. Granted, calving issues can cause reproductive problems in the cows later, so I am not an advocate of the extreme high birth weights either. Balance is key. Ranchers who are not retaining heifers from the herd and marketing the entire calf crop each year, need to pay more attention to the TI – Terminal Index. TI includes the EPDs and traits associated with growing calves to feed, finish and grade. This index also includes calf survival (CED) since we need live calves, but then it includes the growth traits and the carcass traits. We strive for balanced EPDs. We feel using the top 1% API EPD bulls is not necessary to be profitable. If the EPDs are balanced and the API is above average, that means profit to us. Sometimes extremes can cause problems and there are levels in each EPD where too much is not the answer. Too much milk for example and too much calving ease. There should be a point where it negatively affects the animal when it is too high. Is the highest calving ease bull truly the most profitable. Live calves are important, but so are pounds at weaning, structure, function and docility. We believe in EPDs and use them in our program. It is the only fair way to evaluate cattle across herds, but we need to understand how they are calculated. It is still important to evaluate the animals in the pen for feet and leg structure, udder quality of females, and dispositions. Every ranch is different and has different needs and managements. Some need extra calving ease because of their situation and are willing to give up the extra pounds. Understanding what they measure and how they are calculated is important.
Notice, the largest part is Stayability. Stayability EPD is the difference in probability of a sire’s daughters staying in the herd from after they calved as a 2-year-old until 6 years of age. Which means that anything culled from the herd prior to their first calf is not counted towards the EPD. If there are problems with a sire’s docility and most of the calves are wild, they are usually culled before breeding. Same thing with major feet and structure issues. There are bulls in the breed who have extremely high API and Stayability EPDs, yet have the lowest docility EPDs.
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