This time of year many producers are busy sorting through bull sale catalogues and buying next year’s herdsires. One extremely useful tool that is often overlooked (or even disparaged) in this process is the use of EPD or expected progeny differences.
The primary advantage of EPD over adjusted weights for the commercial cattle producers is that it allows the objective assessment of the genetic merit of animals across herds within the breed of interest. In essence it removes the effect of management when comparing animals. When buying a bull, you are not buying the performance of that bull, rather you are buying the performance of his calves.
EPD are expressed in the units by which the trait is measured in offspring. They are comparable within breed as being the “difference” between progeny of sires when used across similar groups of cows. For example, if two Angus sires have weaning weight EPD of 35 and 45 respectively, then when used on the same group of cows, we would expect the calves of the second sire to be 10 pounds heavier at weaning due to his genetics when compared to the first sire (45-35 = 10). Depending on your ranching operation this may mean 460 versus 450 pound calves or it may mean 860 versus 850 pound calves. What the EPD expresses is the difference.
This method of expression is fast and easy to understand, and it also creates problems. Because many genetic providers use EPD in their marketing efforts, often the “bigger is better” mentality sets in. If a 40 for a trait is good, then a 70 must be better does not represent an effective way to use EPD. This is perhaps the primary reason that you may hear remarks about “EPD don’t work”. When used in the context of a decision based on clear goals, they work very well.
Let me give you an example using milk. A producer from a relatively low rainfall area buys a bull with a very high milk EPD of 36 pounds. When he retains heifers out of the sire he notices that they milk well and wean heavy calves. In year two he also notices that several of the heifers come in open, they eat a lot and they struggle to maintain the body condition that the heifers from some of his lower milk sires are producing. This is a case of bigger is better overstepping the environmental boundaries of the production system. In order to support that level of milk production additional resources must be deployed and additional costs incurred. The 36 Milk EPD sire may work very well for a producer in a production environment with fewer limitations such as weather.
Another argument you will hear is that “EPD are not accurate”. Each EPD is associated with an accuracy value. This is a poorly named item. The accuracy value ranges from 0.00 to 1.00 and reflects the amount of information used in formulating the EPD. For a proven AI sire with hundreds of calves reported the accuracy value will approach 1. For most yearling and two year old sires it will be somewhere around 0.30. This does not mean that the EPD is 30 percent accurate, it simply shows the relative amount of information used in calculating the EPD (the bull’s own record and pedigree information) and that the EPD has potential to change if more calves are reported. The EPD is still a more accurate reflection of the DNA the bull contains than any adjusted weight or index.
Clear goals are the only way to effectively use EPD to make better decisions. If an “average” cow of a particular breed works well for you, then maternal sires need “average” EPD. If you need to push the envelope for growth, then a high growth EPD sire makes sense. Each breed posts very good information on their websites or will readily answer a phone call and provide information on their EPD systems. As well, there are more EPD available than listed in the table below. These tend to be the more common EPD, but there are also EPD for traits such as cow size, longevity, heifer pregnancy rate, etc. This information is available from the breed you are
interested in using. It should be noted that not all breeds are contained in the table, however the information represents the seven most used populations of beef cattle in Canada. Some breeds may not have EPD available and in this case adjusted weights and indexes are useful within the context of the operation where they were collected. The EPD averages shown are based on the current population, as this is where most commercial producers are buying sires from (yearlings and two year olds).
Once a producer starts to pay attention to EPD, they will find combinations that work well for them. The trick at this point is to simply buy more sires with a similar EPD or genetic profile.
6 COMMON MISTAKES WHENUSING EPD
Not Using EPD
Unfortunately for whatever reason, many producers do not use EPD in their selection decisions. EPD are a useful tool that can increase the rate of progress in a herd and reduce risk. EPD can be used to compare relative genetic merit of animals across herds. They should not be intimidating and are relatively easy to understand with a little bit of practice. Comparing Across Breeds EPD cannot be directly compared across breeds. Each breed calculates its genetic evaluation with their own data and their own genetic model. Knowledge of the general characteristics of a breed is important to put the EPD into context. For example, the average Limousin will have much greater carcass yield and less marbling than the average Angus. The characteristics of the breed and application of the sire (eg: producing replacements) should be considered.
Bigger is Better
There is no bigger tragedy than taking this approach. Optimum is always better. Often, an average size animal (or even smaller) may be a better fit for a production system. Average milk is often plenty or even too much. A slightly above average birth weight may create no calving problems and lead to more marketable pounds in the fall. If a sire passes a semen test, a large scrotal EPD is not a necessity. Each operation is unique and bigger may be better for some traits, but certainly not all. Many superior sires are overlooked because of this fallacy. Too Much Milk
This one deserves special mention simply because replacement females with milk that is too high for the environmental and management conditions cost more to feed, have shorter productive lives, and often exchange fertility for milk production. In an environment that can support it, milk is good. Just be aware if you are selecting cattle for your environment or if you are altering your management to fit your cows.
Calving Ease for Cows
All too often sires for use strictly on cows are selected for extremely low birth weight or well above average calving ease. While this may come into balance with production of replacements, it represents a terrific cost and loss of income for feeder calf production. Low birthweight, high growth sires tend to attract a premium price. Because of genetic relationships, high calving ease sires also tend to have less growth. Depending upon the cowherd, most mature cows can handle some additional birth weight and most ranches can benefit from the resulting increase in saleable pounds of calf. These sires with more growth and slightly higher birthweights also tend to sell for much less than the “curve-bender” sires.
Not using current EPD
EPD are typically released by a breed association every six months. It is important to try to use the most current evaluation (Spring 2009) since it represents both the most up to date data available, and also the most current science. Breeds spend a lot of time and money on developing their genetic evaluations to serve the industry and the most recent evaluation will represent the most current and correct available science.
I would encourage you to examine the EPD on your sires. At the very least it will help you to identify the genetics that are or are not working for you. When used in the context of a plan, EPD are a powerful tool for ranch management.