Spring 2008 North American Charolais Cattle Evaluation
On behalf of the American-International Charolais Association we are pleased to present the Spring 2008 Charolais Cattle Evaluation. Since 1998 the Canadian Charolais Association and the American-International Charolais Association have conducted joint genetic evaluations for Birth Weight, Weaning Weight, Yearling Weight and Maternal Milk. Genetic values in the form of Expected Progeny Differences (EPD) in this latest analysis represent the most accurate and comprehensive analysis of the North American Charolais breed. This joint analysis allows for the joint evaluation and comparison of Charolais cattle in Canada and the United States.
This genetic evaluation also includes Expected Progeny Differences for carcass merit, scrotal circumference and calving ease (direct and maternal). This edition of the 2007 Charolais Cattle Evaluation marks the first release of Expected Progeny Differences for direct and maternal calving ease EPD.
The carcass/ultrasound data base has grown significantly since the first carcass evaluation using ultrasound data in 2003 was published. Therefore, the University of Georgia re-evaluated the IMF/Marbling genetic correlation. Both bulls and heifers where ultrasound data has been reported to AICA and USDA Marbling Score using all data from slaughter cattle reported to AICA was used in the estimation of the genetic correlation. The genetic correlation has improved from 0.49 to 0.68. This marbling EPD in this genetic evaluation reflects these new changes.
The Carcass EPD do not represent a joint North American analysis with the Canadian Charolais Association. EPD for carcass merit is presented on a carcass basis for hot carcass weight (HCW), ribeye area (REA), fat thickness (FAT) and marbling (MARB). The carcass records for this genetic evaluation represents the combined efforts of breeders that have conducted their own structured sire evaluation program or submitted carcass data on non-replacement Charolais heifers and steers along with carcass data from the AICA Sire Evaluation Program (SEP). Also included in this analysis is ultrasound data on yearling heifers and bulls.
An EPD is currently the best estimate of an animals genetic worth given the information available for the analysis. Numerous studies using research herds and field records have validated the merit of an EPD as a selection tool to make directional change in beef herds for the traits evaluated. Research has further shown that even for young animals, an EPD can be as much as 9 times more accurate than a with-in herd ratio or weight. However, there are many traits that impact the profitability of the beef enterprise, not all of those traits are reported here in this analysis. Furthermore, proper management practices must be matched to your genetics to realize the best opportunity for profitability.
The production of this analysis involves the input of many people. First, the members of AICA and CCA have supplied the growth and carcass data along with the pedigree and birth information. The accuracy and quality of this analysis can only be as good as this data collectively. Secondly, the joint efforts and foresight of AICA and CCA to collect, compile, and cooperate in making this data available for the analysis. The American-International Charolais Association would like to acknowledge the dedication and cooperation of the Canadian Charolais Association for helping make this North American Charolais Cattle Evaluation a reality. And thirdly, Dr. Keith Bertrand and his professional staff at the University of Georgia for conducting the research, editing the data, and finally computing genetic values in the form of Expected Progeny Differences. Without the cumulative effort and dedication to the Charolais breed of all involved, this analysis would not be possible.
Forward
2008 North American Charolais Cattle Evaluation
Keith Bertrand, Del Little, Andra Nelson and Brett Middleton
University of Georgia, Athens
Sire genetic values in the form of Expected Progeny Differences (EPDs) in this summary are a result of the combined data from the American-International Charolais Association (AICA) and Canadian Charolais Association (CCA). North American Cattle Evaluation (NACE) represents a joint venture between two Charolais associations to provide the breeders of Charolais cattle with EPDs that can be used to evaluate and compare Charolais cattle for genetic merit (EPDs) on all Charolais cattle in Canada and the U.S. that have legitimate records or relatives with legitimate records with either of the associations. Thus, NACE is a direct result of the data collected through the performance and National Cattle Evaluation programs of both associations.
The genetic evaluation procedures use animal model technology to incorporate all available information into the prediction of an individual’s EPD. The information that may be available for an individual includes: 1) progeny; 2) relatives in the pedigree, particularly the sire and dam; 3) grand-progeny; and 4) the individual’s own record. An important aspect of the analysis procedure is that the superiority or inferiority of the individual’s mates are accounted for when progeny are available. This reduces, if not totally eliminates, any potential biases associated with specific matings of sires and dams. A second important aspect is the incorporation of genetic relationships among animals in the analysis procedure. Accounting for these relationships incorporates information on all ancestors and collateral relatives into the prediction of an animal’s EPD and also accounts for genetic trend. Adjusting for genetic trend allows for comparison of young and older animals.
A third aspect of the analysis procedure is the use of a multiple trait model that analyzed birth weight, 205-day weaning weight,160-day post-weaning gain, and scrotal circumference simultaneously. The yearling weight EPD that is reported is the combination of the 205-day weaning weight and the 160-day post-weaning gain. Use of the multiple trait model helps to correct any bias that can be caused by the loss of records between weaning and yearling due to culling at weaning and helps to correct potential bias in the birth weight EPD due to possible mistakes or inaccuracies in the reporting of birth weights. Basically, the genetic relationships between the four traits help to provide information that can be used to adjust the EPDs for those traits that have missing or misreported information. The heritabilities used for birth weight, weaning weight, milk, post-weaning gain and scrotal circumference were .49, .25, .14, .31, and .31, respectively. The genetic correlations between birth weight/weaning weight, birth weight/postweaning gain, and weaning weight/postweaning gain were .47, .22, and .49, respectively. The genetic correlation between 205-day weaning weight and milk was -.32.
All the sire, dam and non-parent (young animals) EPDs that result from this analysis can be directly compared for their potential to transmit genes to their progeny. For example, if two Charolais bulls have weaning weight EPDs of +20 and -10 lbs., respectively, and if they were bred to cows with similar genetic merit and the result calves were raised in the same environment, then the expected difference between the average weights of the two groups of calves would be 30 lbs. (20 minus -10). The milk EPD is expressed in pounds of weaned calf and provides information on the resulting weaning weight difference between the grandprogeny of two bulls based on the milk provided by the bulls’ daughters. Therefore, if two bulls differ in their milk EPDs by 40 lbs., the average weaning weights of their grandprogeny would be expected to differ by 40 lbs., provided that the weaning weight EPDs of the bulls grandprogeny were similar and they were raised in similar environments.
The effects of contemporary group environments are adjusted out in the analysis procedure. This results in the EPDs being computed as though all animals were in one large contemporary group. This is the reason EPDs are comparable across herds and contemporary groups. The proper identification of the contemporary groups is of critical importance to the overall accuracy of the analysis. Contemporary groups are defined as 1) animals of the same sex, 2) animals of similar ages (usually not more than 90-day spread in birth dates), and 3) animals managed together and given equal opportunity to perform (same pasture, same feedlot, same weigh dates, etc.). Most inaccuracies in genetic evaluation programs can be traced back to improper identification of contemporary groups or erroneous records. Breeders must provide the association with the necessary information so that contemporary groups can be formed correctly.
The reliability of the EPDs are reflected in the accuracy value. Accuracy values range from 0 to 1.0, with values close to 1.0 being more accurate. The accuracy is a reflection of the distribution and number of progeny of an animal, the amount of pedigree information available and the existence of a performance record on the animal. The higher the accuracy, the smaller the amount of change to be expected in the EPD with the addition of new information. Breeders should use the EPDs to decide whether a bull is to be selected for use in their breeding program and then use the accuracy value to determine how extensively to use the bull. Sires with large numbers of progeny are the most accurately evaluated individuals. Research indicates that EPDs computed for young bulls not yet producing progeny are far more accurate for across herd selection than either ratios or actual weights.
There has been a temptation among purebred and commercial producers to use breed specific sire summaries to compare sires of different breeds. The users of NACE must realize that the EPDs generated from this joint analysis can be used to only compare Charolais cattle in Canada and the U.S. Thus, a 10 lb. EPD for sires of another breed is not the same as a 10 lb. EPD for a sire that is evaluated as a part of NACE. The program is designed to help breeders find Charolais bulls across Canada and the U.S. that could be useful in their breeding program.
This joint analysis was possible because AICA and CCA have developed strong performance programs. It is important to the cattle industry that Charolais breeders in Canada and the U.S. continue to support strong performance programs. The Charolais NACE program will help to insure that the best Charolais germ plasm is identified and available for use throughout the cattle industry in Canada and the U.S.
Using EPD For Selection
Cattle Evaluations use the term Expected Progeny Differences (EPD) to express genetic transmitting ability of a sire for the various traits listed. An EPD is a prediction of how future progeny of a sire are expected to perform in a particular trait relative to other sires in the analysis. The key word is “difference”. The EPD itself does not imply “good” or “bad” performance. But rather, the EPD gives a prediction of the average difference to expect in the performance of a sire’s progeny relative to other sires in the same analysis.
The EPD for a given trait on each animal in the analysis is compared to every other animal in the analysis. The EPD is reported as a plus or minus value in the unit which the trait is measured.
Each EPD reported is accompanied with an Accuracy (ACC) value. ACC is a measure of reliability regarding the EPD evaluation for a performance trait. Accuracy is reported as a decimal number between zero and one: large values indicate greater accuracy and more certainty the EPD will show little change as additional progeny information is obtained.
Birth Weight EPD (BW) The expected difference in average birth weight (pounds) of progeny. Birth weight reflects prenatal growth.
Calving Ease Direct (CE) is expressed as a difference in percentage of unassisted births in first calf heifers. A higher value indicates greater calving ease. It predicts the average difference in unassisted births with which a sire's calves will be born when bred to first-calf heifers.
Calving Ease Maternal (MCE) is expressed as a difference in percentage of unassisted births in first calf daughters. A higher value indicates greater calving ease. It predicts the average difference in unassisted births with which a sire's daughters will calve as first-calf heifers when compared to daughters of other sires.
Weaning Weight EPD (WWT) The expected difference in average weaning weight of calves. The evaluation reflects the genetic influence on pre-weaning growth rate.
Yearling Weight EPD (YWT) The expected difference in average yearling weight of progeny. The evaluation reflects genetic influence on both pre-weaning and post-weaning growth rate.
Maternal Milk EPD (MAT) The genetic ability of a sire’s or dam’s daughters to express in pounds of weaning weight in her calves due to her maternal ability through mothering instinct and milk.
Total Maternal EPD (TOTMAT) A value to predict the weaning weight performance of calves from a animal’s daughters due to genetics for growth and maternal ability. Total Maternal is calculated by adding ½ the WWT EPD to the Maternal Milk EPD.
Scrotal Circumference EPD (SC) The expected difference in scrotal circumference (expressed in centimeters) of a bull’s or dam’s male offspring at yearling compared to progeny of all other animals evaluated. Research has also indicated a relationship between increased SC EPD and decreased age at puberty for daughters.
Carcass records are adjusted to an age constant endpoint. Therefore selection based on any or all of the carcass merit EPD are comparable among cattle at the same age endpoint. For example selection based on increased EPD for carcass weight will result in heavier carcass weights than those animals with lower EPD for carcass weights when the cattle are harvested at the same age.
Carcass Weight EPD (HCW) Expected progeny differences for Carcass Weight is a predictor of pounds of retail product at a constant age endpoint. Selection for increased values should result in heavier carcasses, while selection for decreased values should result in lighter carcass weights at the same age endpoint. Carcass Weight EPD are expressed in pounds and is a predictor of the differences in hot carcass weight between parents progeny at an age constant endpoint.
Ribeye Area EPD (REA) Ribeye area is measured from a cross-sectional area of the longissimus dorsi muscle at the 12th rib. Ribeye area is a major component of the USDA yield grade equation and selection for increased ribeye area should result in larger ribeyes and lower yield grades between animals with the same carcass weight. Ribeye area has a positive relationship with weight, the larger the animal the larger the ribeye area. Ribeye Area EPD are expressed in square inches and is a predictor of differences in ribeye area between parents progeny at a constant age endpoint.
Fat Thickness EPD (FAT) Fat thickness is measured at the 12th rib and is the primary component to the USDA Yield Grade equation. Fat thickness has a negative relationship to cutability; therefore, selection base on decreased fat thickness should result in lower yield grades and leaner cattle given the same age endpoint. Fat Thickness EPD are expressed in inches and are a predictor of differences in fat thickness between parent’s progeny at an age constant endpoint.
Marbling Score (MARB) Marbling is a subjective measure of the amount of intramuscular fat in the ribeye muscle. Marbling score is the primary component of USDA Quality grade and selection for increased Marbling Score EPD should result in cattle with higher quality grades at the same age endpoints. Marbling score has a small genetic correlation with fat, therefore producers may select for increased marbling score EPD while not changing external fat thickness when cattle are harvested at the same age-constant endpoint. Marbling EPD is a prediction of the differences in the USDA subjective marbling score between parent’s progeny at an age constant endpoint. Marbling is expressed in the same units as the USDA Marbling Score (see table below), see the accompanying table for USDA Marbling Score in the Carcass Section.
| Quality Grade |
Amount of Marbling |
Numerical Score |
| Prime + |
Abundant |
10.0 — 10.9 |
| Prime |
Moderately Abundant |
9.0 — 9.9 |
| Prime - |
Slightly Abundant |
8.0 — 8.9 |
| Choice + |
Moderate |
7.0 — 7.9 |
| Choice |
Modest |
6.0 — 6.9 |
| Choice - |
Small |
5.0 — 5.9 |
| Select |
Slight |
4.0 — 4.9 |
| Standard |
Traces |
3.0 — 3.9 |
| Standard |
Practically Devoid |
2.0 — 2.9 |
| Utility |
Devoid |
1.0 — 1.9 |
Heritabilities and Genetic Correlations
Heritibility may be defined as the proportion of the observed phenotypic variation that is due to genetic variation. For example, when analyzing a group of Charolais calves from the same sire, one would expect some variation in the weaning weights. Since weaning weight is 25 percent heritable, 25 percent of the observed variation is attributable to genetics while the remaining 75 percent of the observed variation is due to environmental influences.
Traits with low heritability estimates are influenced more by environment than by genetics, thus genetic progress from selection may be slow. Traits with low heritability respond greater to the effects of crossbreeding. Since heritibility is already an integral part of the EPD calculation, EPD reflect actual differences and require no adjustment.
Click here to download the Heritability and Genetic Correlations Tables.
ACcuracy
Accuracy values give us an indication of how close our estimates are to an animal’s true genetic value. Accuracy values are extremely useful to breeders in determining the reliability of an EPD. An accuracy value can range from 0.0 to 1.0, depending on the amount of information that is known about an animal for any one of the reported traits. As the amount of information included in the analysis of a trait for an animal increases, the accuracy value for that trait increases accordingly.Table 1 shows the standard error of prediction (possible change value for an EPD) at various levels of accuracy for the traits reported. You will notice that as accuracy level increases, the possible change value decreases. Still, an EPD can change from year to year even though it may have a high level of accuracy. The point to remember is that the expected change of an EPD with a high ACC is correspondingly less than those of an EPD with a lower ACC value.
The possible change of identical EPD, given different levels of accuracy can be seen in the example. Two sires have YWT EPD of +30, but different ACC values. This figure illustrates the possible range within where the true genetic value is. Sire A has an ACC of .40 with a possible change value of 23 pounds, and Sire B has an ACC of .80 with a possible change value of 8.5 pounds.
As additional information is reported and accuracy levels increase, we would expect the EPD to stay within the range of the possible change value.
Even though both sires have an EPD of +30 pounds for yearling weight; Sire B has a higher reliability that his true genetic value is within the narrower range of 21.5 to 38.5 (30 ± 8.5).
The ACC of a given EPD can help determine the amount of risk a breeder is willing to take in his breeding decisions. Let us compare the sires in the example again. Which sire is more desirable for your breeding program? The sire with the high ACC is more predictable, but the amount of genetic change that can be made is correspondingly limited as well. Sire A has the same YWT EPD, but his true genetic value may be beyond that of Sire B. Therefore Sire A could possibly increase the amount of genetic progress made, but he is also more of a risk because his true genetic value falls within a wider range.
Click here to download the Possible Change Table.
Possible Change Values
Accuracy values help determine the amount of risk associated with genetic repeatability, but they are not foolproof. Click on the link above to view the possible change values of an EPD with a given accuracy value (ACC). Approximately 70 percent of the time the EPD will not deviate outside of these parameters.
Genetic Trend
This chart lists the genetic trend of the North American Charolais breed for birth weight, calving ease, weaning weight, yearling weight, maternal milk, maternal calving ease and scrotal circumference. the chart also lists the genetic trend of the US Charolais breed for hot carcass weight, ribeye area, rib fat thickness and marbling for most recent years.
Click here to download the Genetic Trend Tables.
EPD Distribution Tables
Click here to download the EPD Distribution Tables.
Percentile Rank Tables
Click here to download the Percentile Rank Tables.
Phenotypic Trend Tables
Click here to download the Phenotypic Trend Tables.
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