Stocker strategies that enhance carcass quality -

Due to the current price of grains and harvested forages, cattle are entering the feedlot at heavier weights, indicating that post-weaning management programs are being used to decrease the number of days cattle spend in the feedyard.

Clint Krehbiel

Understanding how these post-weaning nutrition and management programs impact carcass growth and development is becoming increasingly important.

Because an estimated 76 percent of the yearly calf crop enters a backgrounding or stocker program prior to finishing, there is tremendous opportunity to improve carcass quality attributes by influencing marbling development during the stocker phase of production.

Marbling deposition is a lifetime event, and therefore stocker programs that vary in forage quantity and quality and result in varying cattle growth rates likely have an impact on marbling deposition.

Maintaining animal health is essential for promoting high carcass quality. Morbidity due to bovine respiratory disease (BRD) or parasite load can have long-term negative effects on marbling score.

Data shows that fat deposition in cattle is the most directly affected by BRD; however, decreased growth and anorexia also occurs, as evidenced by decreased hot carcass weight.

It may be possible to achieve similar carcass weight for animals treated for BRD, although animals would need to be sorted by number of times treated and fed for additional days during the finishing phase.

Other than in chronically infected cattle, this would indicate that BRD constraints on growth are relieved with time on feed.

However, the trend for decreased marbling score with increased number of treatments suggests that quality of carcasses may not fully recover even with increased days on feed.

Internal parasites in cattle have been shown to decrease carcass quality. The percentage of USDA choice carcasses was lower, and the percentage of USDA select carcasses was greater for steers not dewormed on pasture or in the feedlot compared to treatment groups that were dewormed.

For the complete grazing-finishing system, feedlot deworming of previously non-dewormed steers produced a net benefit of $30.61 per steer on a carcass-adjusted basis, while feedlot deworming of dewormed steers produced a net benefit of $11.07.

Therefore, there are clear economic benefits to deworming grazing steers on pasture – and to deworming yearling steers entering the feedlot from summer pasture.

Research shows early-weaned calves placed directly on a finishing diet had greater marbling scores compared with calves that were normal weaned with or without creep feed.

These data suggest that an increase in starch intake early in an animal’s life may begin to initiate marbling development and improve final carcass quality.

Further research suggests that if normal-weaned calves can sustain their growth curve without additional supplementation, then creep feeding won’t increase quality grade.

However, if the calves are growing below their growth potential due to inadequate nutrition, then creep feeding or early weaning should help their ability to grade.

Even though early-weaned calves generally have lower average daily gains in the finishing phase than yearlings, they are consuming excess calories early in life above their requirement for normal growth, which may explain the increased marbling compared with normal-weaned calves.

Energy supplementation of heavyweight yearling stocker cattle could be beneficial for enhancing final marbling score of cattle.

Research showed a breakpoint bodyweight of 830 pounds, at which intramuscular fat begins to increase. Applying this concept to previous studies indicated that energy supplementation to heavier stocker cattle increased total energy intake and marbling deposition was increased.

Further research is necessary to validate the concept that providing an energy supplement to heavyweight yearling stocker cattle could improve marbling scores.

Rate of gain during the stocker phase and placement weight can influence marbling score. A meta-analysis of 29 trials evaluated the relationships of rate of gain during the stocker/backgrounding phase and initial bodyweight at the start of finishing with carcass characteristics.

Marbling scores can be improved by making cattle bigger through increasing rate of gain during the stocker phase, increasing initial finishing bodyweight and increasing hot carcass weight at harvest.

However, “making cattle bigger” may also increase 12th-rib fat thickness and yield grade, resulting in little improvement in the marbling:rib-fat ratio.

In contrast, 12th-rib fat-adjusted marbling score (i.e., improved ratio of marbling to rib fat) might be improved by using low to moderate rates of gain for longer grazing periods during the stocker phase to increase initial finishing bodyweight and 12th-rib fat-adjusted hot carcass weight.

Growth-promoting implants increase weight gains of beef cattle by 10 to 20 percent and are one of the most profitable management tools available to beef producers.

However, use of anabolic implants has been shown to have a negative impact on quality grade. A review of the literature suggests that any combination of implanting steers during the production cycle that includes a late-finishing implant (75 days prior to harvest) can decrease quality grade compared to non-implanted controls.

However, any combination of implants that eliminates the late-finishing implant does not significantly decrease quality grade compared to non-implanted steers even if the combination includes suckling, growing and early-finishing implants.

Therefore, it appears that administration of implants close to the end of the finishing phase can have a greater negative impact on quality grade, whereas administration of implants during the stocker phase has little influence on quality grade even if cattle are to be implanted early in the finishing phase.

Heritability estimates shown in the literature indicate that carcass traits will respond well to selection, and that it may be possible to select for increased growth within a breed without negatively impacting marbling score or percentage retail product.

Therefore, the potential exists for DNA-assisted selection to maintain or increase muscle growth (ribeye area), while at the same time improving carcass quality (marbling score).

In conclusion, no one factor solely contributes to carcass quality, but numerous factors interact to have an effect.

Calf health, nutrition and management (e.g., implant strategy) prior to and during feedlot finishing can have an impact on carcass quality.

It is important to maintain the genetic potential of calves to express growth performance and carcass quality through health management programs and implant strategies during the stocker phase.

Marbling scores can be improved by making cattle bigger through increasing rate of gain during the stocker phase, initial finishing BW and carcass weight.

However, this will also increase rib fat thickness and yield grade, resulting in little improvement in marbling-to-rib fat ratio.

In contrast, rib fat-adjusted marbling score (i.e., improved ratio of marbling to rib fat) can be improved by using low to moderate rates of gain for longer grazing periods during the stocker phase to increase initial finishing bodyweight and rib fat-adjusted carcass weight.

Finally, the potential exists for DNA-assisted selection to maintain or increase muscle growth (ribeye area), while at the same time improving carcass quality (marbling score).