Does stress in livestock affect quality of meat?

A couple invited my family for lunch last weekend. As expected, only my wife and I were available because the children are back to school. The same case applied to the hosts.

But what struck me most was that the lunch was a perfect replica of the Christmas and New Year delicacies!

Noticing my salient bafflement, the lady of the house offered an explanation saying: "We stuffed a lot of meat in our fringe and so much is still hanging around. Surprisingly, some of it is getting bad while other meats are well preserved. As a public health professional, could you offer us an expert explanation for this?"

I had the following story to tell our hosts: -

Quality of meat depends not only on how disease-free an animal was before slaughter. It also relies on the emotional state of the animal before slaughter.

The meat is nutritionally alright but is less delicious and has a shorter shelf life.

Animals meant for slaughter should be stress-free if we want to get quality meet that keeps longer in our refrigerators.

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HEART PUMP

The reason is that, a stressed and tired animal’s body is depleted of glycogen (an energy-giving sugar). Because of this, during slaughter the animal will not expel out all blood in its body when its neck is severed because it did not have enough energy to make the heart pump desperately like that of a less stressed animal.

Secondly, it is important to note that since blood carries oxygen and food in it, these two components provide the right environment for growth of microorganisms that cause faster decomposition of the meat.

On the other hand, a carcass whose live animal had depleted its glycogen reserves, is less acidic (lactic acid) on its surface making the meat a good medium for bacterial growth, hence rotting of the meat that if consumed could cause severe food poisoning.

"But how would one identify meat from an animal that was stressed before slaughter," they asked me.

On close observation of a carcass, the surface tends to be wet or appear to take longer to dry if the animal was stressed before slaughter.

The joints and muscles of the carcass also do not stiffen if it was unhappy before death. Moreover, a carcass of frightened or stressed animals show signs of imperfect bleeding (blood is visible on the surface of the carcass).

So what should we do to avoid stress in animals before slaughter? Before transportation, horned animals must be separated from those without horns to keep conflict on freight at bay. They should be handled with kindness at all stages before slaughter.

Before slaughter, animals should be given a 24-hour rest to reduce stress and should be given a lot of water in order to reduce bacteria in the gut.

Butchers should avoid feeding animals just before slaughter so as to reduce amounts of dung generated at the killing floor.

My observation is actually supported by a study that was conducted in Norway last year and whose report was published last week.

The Scandinavian researchers established that stress in livestock actually affects quality of meat as regards tenderness, perishability and colour.

A project conducted by the Norwegian Veterinary Institute investigated how distance from the farm to the slaughterhouse affects animal welfare and meat quality. In the past decade, many slaughterhouses have closed down for various reasons.

"Consumers demand increasingly cheaper food, so efforts are made to cut costs in every step of livestock production. Unfortunately this is unfavourable for animals. For this, animals are subjected to long hauls and in many rural areas these rides are on narrow, curvy, bumpy roads, which are stressful for livestock," the report explains.

Little research has been conducted to date regarding how livestock stress influences the health-giving qualities of meat.

"As long as the stress factors are limited to transport and butchering, there are no reasons to think this affects nutrition," says Laila Aass, a researcher at the Department of Animal and Aquaculture Sciences at the Norwegian University of Life Sciences at _s (UMB).

"If an animal is mistreated, causing for example infections, it’s reasonable that this can affect nutritional content," she says.

Laila Aass explains that stressed cattle yield Dark, Firm and Dry (DFD)-meat.

"It affects perishability," says Aass.

DFD is caused by the muscles of the animals being depleted of their stored muscle energy prior to slaughtering, which hinders a natural decrease in pH level after the animal dies.

She says it is easy to see this in meat, and it is sorted out at the slaughterhouse.

Aass explains that DFD-meat cannot be utilised for beef destined for the older and ageing people, but it can be used for products that are salted, smoked or heat-treated, such as smoked sausages.

Eli Gjerlaug-Enger an animal husbandry researcher at the cooperative for Norwegian pork producers, Norsvin, and who took part in the research says one of the aims of her trade is the elimination of tension in animals.

"The animals that yield prime meat quality are the ones that have not been subjected to stress," she said.

One of the main causes of stress, she says, is poor handling and long distance of transportation.

Whereas in Kenya there is no regulation to safeguard animals from this, Norwegian regulations limit the duration of this transportation to a maximum of eight hours. Yet in special circumstances this can be extended to 11 hours.