Carcass characteristics of steers sired by high marbling or high percent retail product bulls
by K. C. Davis, Research Associate, Animal and Range Sciences, Montana State University, Bozeman
Today's beef producer faces challenges on many different fronts. Producing a quality carcass to meet market demands is one. The presence or absence of fat, or marbling, in the carcass meets different consumer demands.
However, the same trait in the cowherd may have different affects on production. Because of this, Mike Tess, professor of animal science at Montana State University, initiated a study to document carcass traits and monitor production of dams sired by different types of sires.
Bulls with favorable EPD for different carcass traits were selected and bred to commercial Angus dams at a cooperator ranch. Heifer calves will be kept as replacement females and their performance as dams will be monitored. Carcass data from the steer calves will be collected and analyzed. The first calf crop was born in 2000 and this year's calves will be the final group of progeny from these matings. The first calving season for the heifers is this year.
As with all large animal research, data collection and analysis is a slow process. The carcass data from the first crop of steer calves has been collected and analyzed. Those results are presented here.
Data from these steer calves was collected during May of 2001. The calves are progeny of sires with high EPD for marbling or high EPD for percent retail product. There was also one sire with both high marbling and high percent retail product EPD. Additionally, some calves received implants of Revolar® while others were not implanted.
Calves were born at the Bair Ranch with an average calving date of March 25, 2000. Weaning was on Oct. 18, 2000 at an average age of 207 days. After weaning, calves were fed at the ranch for 45 days, and then moved to a feedlot for finishing. The animals were slaughtered at about 14 months of age. Measurements being reported are: birth weight, weaning weight, hot carcass weight, rib eye area, marbling score, back fat, calculated yield grade, and quality grade. The data were analyzed to detect differences due to the age of the calf, type of sire, and whether or not they received an implant.
The age of the calf at the time the data was collected did not account for any differences. The cows were bred by AI during a fairly short breeding season, so age differences should be minimal. There was no difference in birth weight among these calves. Average birth weight was 77 pounds. There were differences in weaning weight depending on the type of sire. Calves sired by high percent retail product bulls were heaviest at 550 pounds. Those sired by high marbling bulls averaged 538 pounds, which was not statistically different from those sired by retail product bulls. The calves from the bull identified as having high EPD for both traits were lightest (478 pounds) and this is where the difference was apparent.
Averages for the carcass traits are shown in the accompanying tables. The main differences in these carcasses were in the marbling scores and the quality grade. We looked at whether or not the combination of sire type and implant made a difference, but did not find this to be the case. Calves that received implants had heavier carcass weights, less marbling and lower quality grades.
Sires also had an effect on marbling scores and quality grade. Calves from percent retail product bulls had less marbling, with an average score of 4.4. The other sires averaged 5.3 to 5.9. As for quality grade, there were no prime carcasses from percent retail product bulls, while those sires identified as marbling bulls had an average of 16% prime carcasses. Half of the carcasses from percent retail product bulls graded select compared to 16% of the marbling carcasses. Choice+, choice and choice- percentages were similar, but the marbling sires produced better quality grades overall.
Because there were no differences in back fat and rib eye area, and little difference in hot carcass weight, the calculated yield grades showed no differences.
Continued collection and analysis of data will add
to the information being reported here. The first year's
data appears to show the use of EPD for carcass traits
can be useful for meeting specific market goals. Using
percent retail product sires showed results that were
similar to the use of implants. Marbling was achieved
without excessive waste fat and low yield grades. Sire
selection using carcass EPD could prove to be a valuable
production tool.
Carcass Trait Averages by Sire Type
| Sire Type | |||
|---|---|---|---|
| Trait | Marbling and %RP | Marbling | % RP |
| Carcass wt. | 665 | 683 | 689 |
| Ribeye, in | 10.6 | 10.5 | 10.8 |
| Marling | 5.9 | 5.3 | 4.4 |
| Backfat, in | .49 | .51 | .48 |
| Yield grade | 3.2 | 3.4 | 3.2 |
Quality Grade by Sire Type (percent)
| Sire Type | |||
|---|---|---|---|
| Qual. grade | Marbling and %RP | Marbling | % RP |
| PRIME | 20% | 16% | - |
| CHOICE+ | 40% | 11% | 9% |
| CHOICE | - | 19% | 15% |
| CHOICE- | 40% | 38% | 27% |
| SELECT | - | 16% | 49% |
Carcass Trait Averages by Implant Status
| Implant Treatment | ||
|---|---|---|
| Trait | Yes | No |
| Carcass wt., lb | 693 | 659 |
| Ribeye area, in | 10.7 | 10.6 |
| Marbling | 4.7 | 5.7 |
| Backfat, in | .49 | .48 |
| Yield grade | 3.3 | 3.2 |
Quality Grade by Implant Status
| Implant Treatment | ||
|---|---|---|
| Quality Grade | Yes | No |
| PRIME | 3% | 13% |
| CHOICE+ | 5% | 16% |
| CHOICE | 8% | 26% |
| CHOICE- | 38% | 26% |
| SELECT | 48% | 19% |