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Tenderness Versus Feed Efficiency

10 November 2009

Studies carried out by the Beef Cooperative Research Centre looks at the performance of high feed efficient cattle and how this effects the tenderness of meat.

Improving profitability is one of the main aims of any beef producer. To stay in the game, costs need to be reduced and output increased. While many producers have focused on increasing growth rates and improving the fertility of their herd, little emphasis is placed on reducing inputs. That is until now. A Beef CRC project, run at a commercial feedlot, has proved high feed efficient cattle can reduce feed costs by up to 80 dollars per head.

But there are some tradeoffs. In scientific circles, feed efficiency has been on the radar for more than 40 years. Beef geneticists at Trangie research station in central west New South Wales have some of the most comprehensive research on feed efficiency of beef cattle in the world. So when Beef CRC scientists wanted to evaluate the benefit of using steers bred from high, intermediate and low efficient parents in a commercial feedlot environment, it made sense that cattle from Trangie were used.

Professor John Thompson from the University of New England said there is a reluctance among feedlots to buy feed efficient cattle despite them being one group which could benefit most. He said it’s a simple case of the chicken and the egg. “High efficient cattle (those cattle which eat less than their contemporaries for the same weight and growth rate) just aren’t produced in large numbers, so lot feeders can’t access them easily.”

“If they can’t buy them easily, they don’t see the immediate benefit of them in their system and hence don’t put pressure on industry to produce high efficient cattle,” Professor Thompson said. That is one of the reasons why the trial was set up. “We wanted to break the nexus and prove to feedlots there was an economic benefit of having feed efficient cattle in their yards.”

“If we could do that, feedlots may be more interested in demanding these animals from producers,” he said. The trial involved 208 Angus yearling steers which were divided into high feed efficient (HE), medium feed efficient (ME) and low feed efficient (LE) groups. They were fed a normal feedlot ration for about 220 days in a commercial feedlot. At induction, the majority of the steers averaged between 410 and 470 kilograms. At slaughter, the majority averaged between 670 and 750 kilograms.

Professor Thompson said the cattle performed as expected with the HE cattle eating less but having the same rate of gain as the LE animals.

“On current feed prices of about $300 per tonne, it means a cost saving of about $80 per head over the 220 days,” said Professor Thompson. “Obviously if the cattle were fed for less time the savings would be scaled back, but it’s still a substantial saving.”

After 220 days in the feedlot, the cattle were then slaughtered. Meat samples were taken and evaluated for a range of meat quality traits, including tenderness. Beef CRC PhD student, David Lines said the cube roll was collected and portions aged for either one day or seven days. Samples were then measured for shear force and compression. Shear force is a mechanical measure of how much force it takes to cut through a piece of cooked meat. It can be likened to the pressure required to bite through a piece of steak.

Mr Lines said the results indicate less feed efficient cattle tend to have a small advantage in terms of eating quality. “After one day of aging, there was a 0.4 kilogram difference in shear force between the HE and LE animals,” said Mr Lines. “It took 3.5 kilograms to cut though the samples from the HE animals, whereas it only took 3.1 kilograms to cut through the samples from the LE cattle.”

After seven days of aging differences in shear force between the two lines had decreased, but the HE animals were still 0.2 kilograms higher in shear force. “The samples from the LE cattle still tended to be more tender than those samples from the HE cattle,” said Mr Lines. Overall the difference would equate to about half a dozen eating quality points on the MSA scale.

“The measures of shear force are still in the acceptable range for tenderness. This means that consumers would probably not be able to tell the difference in tenderness between aged meat from the HE and LE cattle.” Mr Lines said when the animals were graded there was also a noticeable difference in fat cover between the high and low lines. “The LE animals finished with about 5mm more rib fat on the carcass than the HE steers,” said Mr Lines.

Professor Thompson said the decision about whether to produce leaner cuts or more tender meat depends on what producers are being paid for. “It’s all a balance. The thing you have to keep in mind is that you may get more cuts, and it might cost less to produce those cuts, but there is a tendency to produce tougher meat,” he said.

Mr Lines said they don’t know why HE animals rated tougher in the shear force experiments. However, one hypothesis is that there may be a difference in the calpain system. Calpains are the principle enzymes which help break down skeletal muscle protein in the body, which affects the rate of aging in the meat.

Calpastatin is a natural inhibitor of calpains. If calpastatin activity is higher following slaughter it reduces the ability of the calpains to break down the protein bonds within the muscle fibres, therefore making the meat less tender. “We wanted to see whether the high and low lines of cattle have more or less calpastatin activity,” said Mr Lines. “The results show a trend for greater calpastatin activity in the HE animals. This, along with differences in fat cover, may explain the tenderness results.”

Dr Hutton Oddy, Senior Research Fellow within the School of Environmental and Rural Science at University of New England said the feedlot industry won’t readily use HE cattle until there are sufficient numbers for them to access easily.

“This research has proved that HE cattle can save money on feed. But until there are more HE cattle available in the marketplace and they are readily identified as such, uptake by industry will continue to be low,” Dr Oddy said.

November 2009

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