What is an interim?
Interim EPDs are calculated on animals during the time period between the American Angus Association National Cattle Evaluations (NCE) that occur twice each year, once in June and again in December. An interim value is indicated by an "I" in front of the number. While admittedly low in accuracy, an interim value gives you a snapshot of the animal's value as a parent, and, thus, it provides a temporary selection-decision tool until the next NCE run in which enough information is available to calculate a true NCE EPD.

How is an NCE EPD different?
The EPDs from the biannual evaluations have no letter "I" preceding the EPD. These are calculated using all available performance data for a particular trait, accounting for relationships among animals.

The mixed model methodology behind the evaluations is complex. In the Spring 2005 NCE, approximately 4.5 million weaning weight records were evaluated to generate more than 5 million EPDs.

The EPDs resulting from this run have varying accuracies, depending on the amount of information (the animal's own record, progeny records, ancestral records, etc.) that contributes to each animal's predicted genetic value. To be included in the twice-a-year NCE runs, a nonparent animal must have a performance record that meets data requirements and is part of a valid contemporary group. (To be included weights must be submitted prior to the published cutoff date for an NCE run, so submit weights as soon as practical.)

Parent animals have progeny with performance records and are incorporated into the evaluations even if the parent does not have an individual record for the trait of interest. The evaluations to generate EPDs utilize many generations of pedigrees.

Interims using the calf's own performance
The best case is when interims have the calf's own record relative to its contemporaries included in the prediction. For example, a bull calf's adjusted 205-day weight relative to his contemporaries plays a role in calculating the interim weaning weight (WW) EPD. The calculations take into account the EPDs on the calf's sire and dam, too.

The Mendelian sampling effect predicts how the calf's own genetic value deviates from the average of his parents. This is the place where the calf's individual performance relative to his contemporaries plays a role. This interim would typically have an accuracy value of 0.20 to 0.30, depending on the trait.

Methodology behind the calculation of interims can be found in the Beef Improvement Federation Guidelines or at http://beefimprovement.org/guidelines.html (see Chapter 5: "National Cattle Evaluation").

Interim with pedigree only
In this case, only pedigree information, sometimes called a pedigree index, is involved in calculating the interim EPD. As an example, if a bull calf has no contemporaries and his parents have true NCE EPDs, then a pedigree-estimated EPD is computed as an average of the parental EPDs. The accuracy on the resulting interim is low, at 0.05.

Parents with interims
The most common answer to the question, "Why doesn't this animal have an EPD?" traces to the parents not having true NCE EPDs from the biannual evaluation. In many cases it is the dam that has interims. It is not possible to generate an interim EPD on an animal if one or both parents have interim EPDs without an individual weight record on the calf submitted in a proper contemporary group (at least two calves of the same sex, managed the same and weighed at the same time).

Once weights are turned in on the calves, the parents will become part of the NCE run (now having progeny), and the calf in question would have EPDs.

So, if a calf has no contemporary-group-defined weight, for example, and the dam has interims, then the calf's EPD for the trait will be missing.

Interims for ET calves
The individual weights on embryo transfer (ET) calves generally are not used in the interim EPD calculation. However, if the ET calves are raised by registered Angus recipient cows, in a contemporary group of ET calves also raised by registered Angus recipients, we are able to incorporate the individual ET calf data into the interim calculations and the NCE.

ET calves out of commercial recipient dams receive only a pedigree-estimated interim EPD with a 0.05 accuracy, since the EPD is just the average of the sire EPD and the donor dam EPD. If the donor dam has interims, the ET calf will have no EPD. (The donor dam would need to have a natural calf with performance data submitted in a proper group, and then she would have true EPDs generated during the next NCE.)

Interpreting interims
To summarize, let's say we identified a yearling bull on which we wanted more information. Doing an EPD/pedigree search online revealed the performance figures shown in Fig. 1. What can you tell from the bull's record?

First, his calving ease, birth weight and weaning weight are true NCE EPDs, and his individual records were available at the time of the last NCE.

The interim yearling weight (YW) EPD with an accuracy value of 0.36 indicates his yearling weight was turned in since the last NCE and is now reflected in his current interim. When the fall 2005 NCE is run in June, this EPD will lose its interim status and will be replaced by an NCE EPD. As more information on progeny is added, the accuracy value will increase. The same holds for the yearling height and scrotal circumference (SC) EPDs.

Interim EPDs are temporary in a sense. We expect the typical animal to progress toward NCE EPDs, either by way of its own record or progeny data entering into the twice-annual evaluations. The NCE EPDs take into account much more information than interims. Do not be shocked if the NCE EPD is not the same as the interim EPD.

Sometimes we invest too much confidence in an interim, as if we never expect change. EPDs change. Interim EPDs have low accuracies. Let's not forget that lower-accuracy animals are expected to have changes in their EPDs as more information becomes available on their genetic merit.

A calf with a pedigree-estimated interim EPD has a 0.05 accuracy associated with it. The animal's own performance is not included in the interim calculation. Even on interims that include the calf's own performance, the accuracies are still typically below 0.30. Utilize the possible-change tables available through the Association to help manage the interval of change expected on EPDs at a given accuracy level. Details on possible change associated with accuracy values are at www.angus.org/sireeval/accuracy.htm.

Also, don't be surprised to see bulls published in the Angus Sire Evaluation Report with a mixture of interim and NCE EPDs. It is a reflection of how much information was available to compute each EPD at the time the NCE was run.

Twins are a complication in genetic evaluations. Although they will receive an interim EPD, a twin will not enter the NCE runs until that twin has progeny incorporated into the analysis. Birth, weaning, milk and yearling interim epds will not be calculated using a twin's own weight. Twins will receive a pedigree index interim when possible.

    Fig. 1: Example of EPDs available online through EPD/pedigree search