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Calm cattle have a dark side, researchers find

Beef Central, 19/11/2012

Peter McGilchristThe findings of a recent study conducted by Murdoch University researchers has challenged the long-held belief within the beef industry that flighty or stirry cattle are at a higher risk of producing dark, less tender and drier meat.

Working in conjunction with the WA Department of Agriculture and Food and Tammin (WA) feedlot operator Ivan Rogers’ Kylagh Cattle Co, two researchers found that calm cattle were not exempt from the issue of dark cutting.

Dark cutting is a complex problem caused by low muscle energy (glycogen) at the time of slaughter.

Depletion of glycogen during the pre-slaughter period is controlled by many factors, one of which is the animal's temperament.

Temperament affects how agitated cattle become and how much adrenalin they release during handling, and therefore, in theory, how much muscle energy they deplete between leaving the farm and slaughter.

The syndrome in beef carcases produces meat which is dark in colour and lacking in tenderness and juiciness, which also spoils quickly.

Dark cutting affected 3.6 percent of more than two million carcases graded by Meat Standards Australia in the 2011/12 financial year, costing the beef industry millions of dollars.

In their study, Dr Peter McGilchrist, a post-doctorate researcher, and Stephanie Coombes, an honours student from Murdoch's School of Veterinary and Biomedical Sciences, measured the temperament of 648 commercial lotfed cattle, mostly British and Euro based, using flight speed, an electronic measure of how quickly an animal exits a weighing chute. Their project was funded by the Australian Meat Processors Corporation.

Flightier animals will exit at a faster speed while quiet animals move more slowly. Their results showed that as flight speed increased, muscle glycogen concentration in the loin muscle at the time of slaughter also increased. This indicates that the cattle which had higher flight speeds were in fact at a lower risk of producing dark cutting carcases in this study.

Only two per cent of the cattle in the study were graded as dark cutters (pH greater than 5.7 and/or meat colour score of four or higher), and these carcases were evenly distributed across the range of flights speeds measured.

"Even though calm cattle certainly have their production benefits, they are not exempt from the issue of dark cutting," Ms Coombes said.

In many different studies around the world, calmer cattle have been shown to have higher growth rates and more tender meat than flighty animals.

The owner of Kylagh Cattle Co and feedlot, Ivan Rogers, said flighty cattle posed a danger to their handlers, consistently went onto feed slower, took longer to reach slaughter weight, had a higher morbidity rate and generally performed more poorly than calm cattle in the feedlot environment. "They also have the potential to upset calm cattle, which is why we always try to purchase quiet, well-handled animals," he said.

Dr Peter McGilchristDr McGilchrist suggested that producers needed to continue to cull flighty cattle and minimise variation in temperament across a herd, but also to habituate their quiet cattle to change.

He said that producers and processors also needed to ensure that calm cattle are treated with as much care during the pre-slaughter period as their more reactive counterparts.

"The employment of common practices like yard weaning not only provide the benefit of improved handling ease, but also provide the opportunity to desensitise cattle to potential stressors, such as being mustered or drafted," Dr McGilchrist said.

"All cattle also need to be exposed to changes in their environment, so that during the pre-slaughter period, they don't become as stressed and agitated."

Dr McGilchrist added that the effect of temperament was not completely understood and that further research was needed to unravel the interactions between animal temperament and energy metabolism during the pre-slaughter period. 

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