7 May 1999


Improving lamb slaughter

returns could be one way of

helping your sheep enterprise

stay in business. MLC sheep

scientist Jenny Anderson

looks at ways to improve

lamb carcass quality

FAST-GROWING lambs produced cheaply, efficiently and in good health will help producers stay profitable.

We also need to keep ewes that produce sufficient numbers of lambs without compromising their health status and fertility.

Efficiency is important in todays world so work out how much it costs to produce one kg of lamb and compare it to current lamb prices.

It may be that you need to re-examine your cost structure but always keep abreast of new technology within the industry and embrace quality assurance and traceability within your system.

The advantage of development initiatives, such as the Welsh Sheep Strategy, the Highlands and Islands Sheep Strategy, Sire Reference Schemes and group breeding schemes to source better quality sheep.

Recorded information

Firstly, buy sheep that have background information and recording data. You wouldnt buy a car or tractor by colour alone, you would check its engine capacity, fuel type and service history first.

Some producers think that genetic improvement is short-term. This is wrong. It is permanent, sustainable and accumulates over the years. Research at the Scottish Agricultural College proves this, showing lambs that are genetically leaner produce leaner carcasses, regardless of the way they are fed.

Because of the structure of the British sheep industry this is a critical finding, as lambs in terminal sire flocks are typically reared on high quality diets and are selected for breeding on their physical performance.

But in commercial flocks, crossbred lambs are finished at grass. So its important that sheep which perform well from concentrate feeding must also perform well at grass.

Otherwise, selecting terminal sire sheep for leanness would have no benefits for the commercial lamb producer.

The SAC trial revealed that on three different feed treatments, high index lambs had a 20% lean to fat ratio advantage compared with low index lambs.

And so we know that buying terminal sire sheep with high-index scores will improve lamb carcass quality.

Killing out percentages

It is common to hear producers complain about lamb killing out percentages. However, to know killing out percentages are wrong you have to weigh each animal before going to slaughter.

Many good flockmasters do this as it allows them to work out gross margins and collect basic carcass information which can be used as a benchmark to improve on each year.

But weight can be affected by other factors, such as the accuracy of your weigh scales and the cleanliness of your sheep.

Muddy belly wool can account for over 2kg extra weight. Also, long fleeced lambs will weigh differently to shorter-fleeced or shorn lambs.

What animals are fed on before they are sent to slaughter will affect killing out percentages as well. For example, sheep fed on concentrates tend to have less gut fill than grass or forage fed sheep.

Animals slaughtered after lairage without feed for 24 hours will be two to five percent different in liveweight to those with a full belly.

It is common to hear athletes excuse their heavy weight by stating that muscle weighs more than fat. It is true, it does, and more heavily muscled sheep will have higher killing out percentages than their lightly muscled contemporaries.

This means there are large breed differences, which work currently undertaken at SAC using its computer tomography (CT) scanning machine, is looking to assess.

Saleable meat yield

Saleable meat yield is calculated by dividing the amount of meat obtained by the carcass weight and multiplying it by 100. Again this is affected by different factors such as fatness.

A lamb of fat class 2 will produce more lean than a 4L. The amount of muscle on the animal naturally affects the saleable meat yield. So the more muscle, the more meat yield.

Whether the meat is sold on or off the bone makes a lot of difference to saleable meat yield, while conformation doesnt. More important is the muscularity of the animal.

This is because conformation is the structure of the sheep and includes bone, muscle and fat. Normally leaner animals do not have as good conformation.

Many beef producers found that once the beef on the bone ban was enforced, conformation did not matter, as once meat is removed from the bone all that was left is muscle.

This is why muscle depth is so important in genetic improvement. Improving muscle depth, a measurable trait, increases muscularity and saleable meat yield.

The MLC are currently promoting Quick Lamb to attract the younger consumer to buy lamb. It seems that the modern consumer prefers quick, easy lamb, ready prepared and off the bone. So are you producing what the market requires? &#42


&#8226 Use breeding schemes.

&#8226 Improve muscularity.

&#8226 Produce what market wants.

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