Source: Canadian Angus Association
It would be easier if we could assume that the highest EPDs (Expected Progeny Differences) are the best. Unfortunately, it isn’t that simple. Like most decisions, using EPDs for sire selection involves tradeoffs. For example, bulls with high growth EPDs may sire calves with a higher birth weight as well. And there may be other impacts on your operation to consider.
For example, when breeding heifers it is desirable to produce calves with lower birth weights, so a breeder may want to pay special attention to birth weight EPDs of prospective bulls. If all calves were sold as feeders, the milk EPD would generally not rate much attention. Yearling weight will be important if you want to ensure finished steers in the appropriate weight range.
It should also be kept in mind that reaction to selection can differ from trait to trait. This is because some traits have higher heritability than others, and are more easily passed to offspring. For instance growth traits such as weaning weight respond faster to selection, than reproductive traits such as age at first calving.
A balance of traits is required, and the perfect balance for you will depend on your climate, nutritional and economic environment, as well as the management goals you have set for your herd.
One way to select for several traits is to set minimum and maximum acceptable levels for each trait, and then choose sires that meet the criteria. Another method would be to rank all sires on each trait, then develop a weighted index which ranks each bull from one (most desirable) to five (least desirable) for each trait. The bull with the lowest total score would be your first choice.
A Sample Sire Summary Evaluation
|Bull||Birth Weight||Weaning Weight||Yearling Weight||Milk|
Producer 1 is looking for a sire that can be used on heifers; he wants a bull that will produce low birth weights and he wants to keep some heifer calves as replacements. Growth performance is not his first priority. The sire that fits his needs is sire D. He has a low birth weight EPD and above-average milk EPD.
Producer 2 has a sound breeding program; he is looking for a sire that will maintain performance and milking ability. He will select a bull that will increase growth performance and milk while maintaining calving ease. Sire B is his choice.
Producer 3 has a herd of above-average-frame cows and is not planning on keeping heifers as replacements. She is looking for a bull that will give her the most profit at weaning. Sire A will give her the best result in weaning weight. If heifers are kept as replacements, they will, on average, be inferior for maternal milk.
Producer 4 wants to maintain his calving performance and growth performance but would like to increase the milking ability in his females. Sire C is his choice.
EPDs are the most powerful genetic tool we have for selecting the best animals for your breeding program.
Commercial buyers rely on EPDs to make their purchasing decisions. Producers that do not have EPDs for their animals often lose out on selling their animals because of this. Buying an animal with EPDs provides a genetic snapshot of an animal’s breeding potential. While appearance and pedigree should be considered, EPDs allow a fair comparison of breeding value by removing environmental bias such as climate, feed and special management.
Depending on your target market, you can improve your herd by selecting for the right traits. Choosing a bull with high growth EPDs, in particular the weaning weight EPD, means more pounds at sale time. Looking at the EPDs of a prospective bull is essentially just as important as looking at specifications of an engine when buying farm machinery or vehicles.
To evaluate seedstock, use a combination of EPDs, pedigree and visual assessment. With EPDs, the concept of “intermediate optimums” works best. Selection for one trait or for extremes generally results in unexpected consequences due to genetic correlation. For example, intense selection for high yearling weight will also increase birth weight. Successful cattle breeding requires a thoughtful and balanced approach to optimize fertility, growth and carcass merit while improving profitability and efficiency. EPDs are the best tool we currently have to compare animals between herds and countries.
The quality of your EPDs also reflects the quality of data that comes into the office. Taking pride in your paperwork increases error-free data entry. Submitting your data on time or early eliminates the chances of receiving a Missing Data Report and your animals subsequently not getting EPDs due to non-compliance.