In the quest for ever-improving beef quality, scientists are taking a new look at an age-old challenge: dark cutters.
Those are the animals that get the B4 grade and discount, and exhibit the unsightly darker-red colour and associated toughness in the meat, along with reduced shelf life.
Dark cutting shows up more often during the hottest months, and has been on the rise overall recently. It’s no secret that it’s a stress-related condition, but there are some mysteries about the cause and effect. That prompted the Beef Cattle Research Council to fund a study by Heather Bruce at the University of Alberta. The project, which is nearing the halfway point, is a followup to one done under the first Beef Science Cluster, widening the scope of the work back from the processors to include feedlots. It marks the first research focus on dark cutters in at least a decade.
“We’ve had three really great feedlots to work with,” said Bruce, associate professor of carcass and meat science. “Fortunately, feedlots tend to keep records on grading, so we’ve been gathering data from them, as well as from Alberta Agriculture.”
Some physical characteristics may be useful in determining which animals are most at risk, she said.
“For instance, any animal that has eight to 10 millimetres of fat, and is most likely to grade AAA, they are least likely to dark cut. The AA are more at risk of dark cutting, but we’re still in the process of describing those animals more completely.”
The story behind what’s considered ‘classic dark cutters’ is fairly straightforward. The figures show they tend to happen in large numbers, and can often be traced back to circumstantial reasons, such as when a processing line goes down and the cattle are trucked away to be fed and then shipped back again.
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“That’s usually a recipe for dark cutters,” said Bruce. “And it’s nobody’s fault. Cattle just don’t do well with loading and unloading.”
Hot weather is another common trigger as animals need to keep eating and drinking to keep energy flowing to the muscles.
“Heat reduces the cattle’s appetite. They’re in an energy deficit because they’re not eating, and drawing on their muscle stores.”
Wet days are also rough.
“You’ll get 30 to 70 per cent dark cutting on the day, if animals get wet and shiver,” said Bruce, adding days with big temperature swings are also harder on cattle.
Both Beef Cattle Research Council studies have focused on three categories of cattle — regular AA, classic dark cutters, and what Bruce refers to as ‘atypical dark’ cutters. They’re ones with muscle pH levels under 6.0, and at times their colour returns to normal.
“We see them every day (at processors), and we don’t understand why they’re occurring. The classic dark cutters, with the pH over 6.0, we understand completely what’s happening there. The animals have experienced too many stressful situations, and you’ve just whittled down their reserves.”
The atypical group holds the biggest potential for improvement, she said.
“I definitely think some on-farm management could be tweaked in order to minimize the atypical population.”
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Bruce and her team are also looking at feedlot data to see if there’s more susceptibility in heifers compared to steers. That’s being compared to figures from a large Alberta abattoir as well.
Other aspects being studied include management tools, such as growth promotants and beta-agonists. The genetic factor is also being examined through DNA samples.
“We’ll look at the genetics of animals we consider to be extremes, to see if there are any particular genes that are going to stand out, particularly in the atypical group.”
Dark-cutting animals typically represent about two per cent of the total beef population in a year. So why the focus?
When Bruce first pitched her research idea, the industry cost was in the neighbourhood of $1.5 million annually.
“But it adds up every year, and also, to the producers who are affected, it’s devastating, because the animal’s worth goes from an A grade, to a cow grade’s worth, which is a pretty substantial drop in value.”
The hope is to find a way to identify animals most likely to cut dark, so they could be separated for some extra attention.
Once animals more susceptible to dark cutting can be better described, along with potential contributing behaviours, it will be up to feedlot operators and abattoirs to weigh the economic risks versus rewards of any actions. But the increasing attention on animal welfare is likely to play a role in the discussion.
“The industry is really focused on this, and has been very supportive of our research,” said Bruce. “We’ve learned a lot about dark cutters. Our work is trying to help every stage of the beef value chain to minimize the problem as much as possible, because it hurts everybody.”