J. Anim. Sci. 1998. 76:2040-2047
Received November 3, 1997
Accepted April 20, 1998
1 This project was funded by a grant from the National Cattleman's Beef Association -- Beef Quality Assurance Task Force, Englewood, CO.
2 To whom correspondence should be addressed: Phone: 970/491-5226; Fax: 970/491-0278; E-mail: firstname.lastname@example.org
Grandin (1992) and Smith et al. (1993) reported that the occurrence of dark cutting beef (DCB) is highest during very cold weather combined with precipitation, which increases the rate of body-heat loss and elicits shivering. The incidence of DCB is also high in very warm weather or when large fluctuations in temperature occur over short periods of time.
Hedrick et al. (1959), Grandin (1992), and Shackelford et al. (1994) reported that control of antemortem stress through proper management would be the most effective method to reduce the incidence of DCB.
Hedrick et al. (1959), Grandin (1992), and Smith et al. (1993) identified animal gender, biological type, use of growth promotants, and handling as potential contributors to an increased incidence of DCB. Therefore, the objective of this study was to use a large commercial database to identify and quantify management (biological type, implant type, and implant administration) and environmental factors that affect the incidence of DCB and to develop decision trees for use in the reduction of losses in carcass value as a result of DCB.
Data were compiled for the period between June 1, 1993, through July 31, 1996 (n = 15,439 pens of cattle), encompassing 2,672,223 total cattle, which produced 18,106 dark cutters, and equaling $4,024,058.50 in losses ($1.51 per steer, heifer, or spayed heifer harvested in this study) as a result of nonconformance (USDA-AMS, April 14, 1996).
|Feedyard||Percentage of dark cutters||95% Confidence interval|
Figure 1. Least squares means for the incidence of dark cutters within an individual pen for steers, heifers, and spayed heifers. Means lacking common superscript letters differ (P < .05).
|Item||LS Mean ± SE for DCb, %||No. of pens||Percentage of pens > 6% DCf|
|Reimplant given just before harvest|
Within steers, pens of cattle that were treated with implants containing androgens and estrogens (combination implants) as they entered the feedyard resulted in higher (P <.05) mean percentages of dark cutters per pen and a numerically higher proportion of pens that had a 6% or higher incidence of DCB than did steers treated solely with estrogen implants as they entered the feedyard. On-feed implants did not affect (P > .05) the mean percentage of dark cutters per pen within heifers (Table 2); however, heifers given an estrogenic implant as they entered the feedyard were associated with a numerically higher proportion of pens that produced a 6% or higher incidence level of DCB.
|Implantation Strategyc||No. of pens||LS Mean ± SE of % DCd||Pens > 6% DC %|
|Double Androgen/Androgen||6||.67yz ±.096||0|
|Androgen/Double Androgen||11||.26z ±.052||0|
Pens of steers that were reimplanted with combination implants (androgens and estrogens) as the final implant before harvest exhibited a higher (P < .05) incidence of dark cutters and a greater numerical proportion of pens with more than a 6% incidence rate of dark cutters than did pens of steers that were administered either androgen or estrogen implants as the final implant before harvest (Table 2). Additionally, steers that were reimplanted with androgen had a higher (P <.05) mean incidence of DCB per pen than steers reimplanted with estrogen. Intact heifers treated with estrogenic implants as the reimplant produced higher (P <.05) mean percentages of dark cutters per pen and a greater proportion of pens with a 6% or higher incidence level of dark cutters than pens of intact heifers that were treated with either androgen or combination (androgen and estrogen) implants as the final implant before harvest (Table 2).
Implantation strategies were constructed using the on-feed implant type and reimplant type, thus developing implantation strategies administered during the time on feed. Mean percentages of dark cutters per pen by implant strategy are reported in Table 3. Steers treated with combination on-feed implants, followed by combination reimplants, showed a higher (P <.05) mean percentage of dark cutters per pen and a higher percentage of pens over a 6% incidence level of DCB than either steers given a estrogen on-feed implant followed by a estrogen reimplant or given an estrogen on-feed implant followed by a combination (androgen and estrogen) reimplant. Implantation strategies using estrogen as the reimplant in heifers had a higher (P <.05) percentage of dark cutters per pen than strategies that used either combination or double androgen reimplantation treatment. Moreover, 8.3% of heifers treated with an estrogen on-feed implant followed by an estrogen reimplant before harvest had over a 6% incidence level of DCB.
As the duration between final implant and harvest increased (>100 d), mean percentages of dark cutters per pen declined (P < .05) across all genders and implant types, except for steers reimplanted with androgens and heifers administered estrogen as a reimplant before harvest (Table 4). Pens of steers implanted with androgens less than 100 d before harvest had lower (P <.05) mean percentages of dark cutters than pens of steers left on feed longer than 100 d from receiving the last implant. Overall, these data indicated that cattle tended to have a lower incidence of DCB per pen when the duration from reimplantation to harvest was longer than 100 d.
|Mean percentage of dark cutters per pen|
|Last Implant||< 100 db||> 100 d|
|Androgenc||.02z ±.021||.19wx ±.02|
|Combinationd||.32w ±..001||.17x ±..001|
|Estrogene||.09y ±.001||.07z ±.001|
|Androgen||.58u ±.001||.42v ±.001|
|Combination||1.74s ±.011||.50uv ±.003|
|Estrogen||.92t ±.002||.78t ±.002|
Figure 2. Least squares means for the incidence of dark cutters within an individual pen during periods of hot (>35°C), average, and high daily temperatures from 2 to 1 d before harvest for steers, heifers, and spayed heifers. Means lacking common superscript letters differ (P < .05).
|Item||Temp.b > 0°C,
Prec.c < 5.0 mm
|Temp. > 0°C,
Prec. > 5.0 mm
|Temp. < 0°C,
Prec. < 5.0 mm
|Temp. < 0°C,
Prec. > 5.0 mm
|Steers||.07z ±.001||.04z ±.002||.06z ±.001||.08z ±.002|
|Heifers||.39yz ±.001||.21z ±.001||.46y ±.005||.50y ±.001|
|Spayed Heifers||.13z ±.001||.33yz ±.001||.27yz ±.006||.02z ±.068|
Temperature fluctuations at 1, 2, and 3 d before harvest are presented in Table 6. Twenty-four hours before harvest, when the absolute difference between the daily high and low temperature was greater than 5.6°C, the incidence of dark cutters within steers was higher (P < .05) than in periods when the absolute difference between the daily high and low temperature was less than 5.6°C. At both 2 and 3 d before harvest, when daily temperature fluctuations were above 5.6°C, heifers showed a higher (P < .05) mean incidence of dark cutters per pen, which indicated that large temperature changes over a short period of time (1 to 3 d) induce stress and increase the incidence of dark cutters.
|1 db||2 d||3 d|
|< 5.6°Cc||.03z ±.001||.03y ±.002||.04z ±.002|
|> 5.6°C||.07y ±.001||.07y ±.001||.07z ±.001|
|< 5.6°Cc||.30x ±.004||.12y ±.006||.21y ±.005|
|> 5.6°C||.39x ±.001||.40x ±.001||.40x ±.001|
Factors in this study that had the greatest influence on the incidence of dark cutters seemed to be gender and the aggressive use of growth promotants. It was clear that heifers present a higher inherent risk of becoming dark cutters than do steers or spayed heifers. Studies by Fleming and Luebke (1981), Voisinet et al. (1997a), and Voisinet et al. (1997b) all found that females had a more excitable temperament and that fearfiilness was greatest in nulliparous females. Additionally, Voisinet et al. (1997) found that heifers had a higher (P < .05) incidence of 'borderline" dark cutters. This could explain why females, especially those given exogenous estrogen, in the present study seemed to be much more susceptible to dark cutting epidemics (pens > 6% DCB). Flemming and Luebke (1981) associated this behavior with the fact that estrogen secretion in parous females is lower than estrogen secretion in nulliparous females, which were found to be more excitable.
Implants have been under suspicion for promoting carcass quality defects since their introduction (Grandin, 1992). Because implants modify growth curves, rates of gain, and nutrient requirements of beef cattle through hormonal changes, adding other sources of stress to hormonal shifts ultimately could increase the risk of dark cutters. Administering combination (androgen and estrogen) implants to steers and estrogen implants to heifers, especially as reimplants before harvest, seemed to inflate the manifestation of stress and ultimately lead to an increase in the incidence of dark cutters.
Environmental factors also played a role in the occurrence of dark cutters. These results paralleled reports by Smith et al. (1993) and Grandin (1992), who reported higher incidences of dark cutters during periods of adverse weather conditions. Management decisions should include environmental factors that could be encountered at the time of harvest, such as extremely hot or cold weather or large temperature fluctuations, and cattle should be managed accordingly to reduce the risk of incurring DCB.
The factors evaluated in this study all additively increased the risk of incurring dark cutters and must be comanaged to optimize these findings. Taking into account all of the factors found to influence the occurrence of dark cutters, decision trees were developed for steers and heifers that present the risk of incurring dark cutters out of 1,000 cattle given specific production factors (Figures 3 and 4). These flow diagrams provide a quick reference for quantifying the risks associated with gender and implantation decisions and the impact that hot (>35°C) weather has on the occurrence of dark cutters. For instance, high risk takers that feed steers would utilize a combination onfeed implant followed with a combination reimplant before harvest. In addition to aggressive use of growth promotants, the time period from reimplant to harvest would be less than 100 d. This management scheme would increase the risk of incurring dark cutters from .8 per 1,000 steers shipped to 13 per 1,000 steers shipped. Furthermore, this could be compounded if the average maximum temperature 2 d to 1 d before harvest is above 35°C; the risk is again increased by 3 per 1,000 steers shipped, totaling a risk of incurring dark cutters of 16 per 1,000 steers shipped (a 20-fold increase in risk). Even though it is an apparently low-percentage risk (1.6%), real economic losses will continue to mount, potentially 20-fold greater than if the incidence of DCB is minimized.
Figure 3. Management guidelines that indicate the risk of incurring dark cutters per 1,000 steers shipped under individual management schemes. The hierarchy utilized agender, bimplant strategy, cdays from final implant to harvest, and daverage maximum daily temperature 2 to 1 d before harvest.
Figure 4. Management guidelines that indicate the risk of incurring dark cutters per 1,000 heifers shipped under individual management schemes. The hierarchy utilized agender, bfinal implant, cdays from final implant to harvest, and daverage maximum daily temperature 2 to 1 d before harvest.
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