Beef Quality Corner - "Dark Cutters"
Livestock Update, March 1998
Bill R. McKinnon, Animal and Poultry Sciences, Virginia Tech
Dark cutting beef refers to muscle tissue that fails to turn the typical cherry red when exposed to air. With dark cutter the muscle remains dark (ranging from dark red to almost black) when the carcass is ribbed. A depletion of glycogen stores in the muscle results in dark cutting beef. Glycogen is the source of carbohydrate energy for use by the muscles. The pH level is also higher than normal in dark cutting beef. Consumers associate dark beef with meat from old animal, toughness, and poor flavor. Additionally, dark cutting beef has poor storage properties and shortened shelf life.
According to the 1995 National Beef Quality Audit 2.7% of the audited carcasses were classified as dark cutters. Dark cutting carcasses are discounted within the USDA beef quality grades. Packers routinely must lower the price of dark carcasses 20% to 40% and market them to alternative outlets. The most recent quality audit calculated that dark cutters cost the industry $6.08 per head on every fed steer and heifer slaughtered.
Dark cutting beef is most often associated with preslaughter stress. Environment factors such as extreme cold, rain or heat along with weather fluctuations can lead to temporary glycogen depletions. Cattle which become excitable during sorting, hauling, penning and overcrowding can be candidates for dark cutting. Holding cattle off feed for one to two days can also lead to dark cutting beef. Heifers that have been showing estrus just prior to slaughter can have a high incidence of dark cutters. Since many heifers are fed MGA to prevent heifers from coming into heat, heifers held off feed too long before slaughter can result in a high percentage of those heifers coming into heat with the accompanying dark cutter problem. Overaggressive or misuse of growth promotant implants have also be implicated with dark cutters.
The cost to the industry of dark cutters is borne by each segment. The cattle feeder receives approximately $.50 per cwt. less for each finished cattle because of lowered carcass value. The problem of dark cutters also costs feeder cattle producers close to $1 per cwt. on a 6-weight steer.
The cow calf operator can address the dark cutter issue by selection against excitable breeding cattle. Easily excitable cattle tend to be stressed during the marketing process. Research work has also demonstrated that nervous cattle tend to have a slower rate of growth.
The cattle feeder would seem to have the most control over minimizing the incidence of dark cutters. The feeder should do all that is possible to expedite the movement of cattle from the feedlot to the point of slaughter, especially heifers on MGA. Quiet handling of the cattle to reduce excitement is also critical. Avoiding the mixing of cattle from different pens at shipment time should also tend to reduce the problem. Cattle feeders should also adopt a growth implant plan that uses specific implant products according to the manufacturers' directions and avoids their over aggressive use.