Computers create a fairer carcass grading system

Introducing computerised classification of lamb carcasses to abattoirs would improve objectivity and help eliminate the long standing misconception that some classifiers are more lenient than others.

And current trial work being undertaken in Welsh Country Foods’ Gaerwen abattoir on a video image analysis (VIA) system is showing great promise.

MLC’s Kim Matthews told delegates at last week’s Langford Food Industry conference, Bristol, that the real value of classification was the ability to predict meat yield and match carcasses to market requirements.

“In this sense, objective grading systems, such as VIA are the best option.”

Explaining the principles of VIA, Mr Matthews said the system worked by taking digital photographs of carcasses and analysing those photographs by a series of formulae to decide on classification.

At present the trial is being used in two ways, firstly to establish prediction equations for conformation and fat class and secondly to demonstrate the ability of VIA to predict meat yield, using an example cutting specification.

But variations in the way abattoirs present lambs means there is a significant amount of trial work to be done, he said.

“Lamb carcasses are presented in up to six different ways, with three different leg suspension methods – crossed, together or standard gambrel – and two shoulder presentations – banded and unbanded.

“Each of these presentation methods changes how the carcass looks when hung up.

This has the potential to confuse VIA, unless the system is able to recognise the same carcass presented in a number of different ways.”

To overcome this issue each of the 700 carcasses used in the trial have been presented to the system six times, with roughly equal numbers of carcasses presented for each classification.

“Following development of prediction equations a panel of three experts classified 800 carcasses selected as a representative sample of the UK distribution of conformation and fat classes.

All 800 carcasses were then presented to VIA by each of the six presentation options.”

This trial work should lead to a set of prediction equations which can be programmed into the system for future application across all UK plants opting for VIA.

“Provided agreement with existing standards can be demonstrated, VIA will offer advantages in terms of objectivity and consistency in carcass classification.”

And it also has the potential to improve producer’s ability to meet market specification, said NSA chief executive Peter Morris.

“When meat yield is measured and paid for then there could be a big difference in how well farmers respond to market signals.”

Mike Tempest of Livestock and Meat Commission, Northern Ireland, agreed, suggesting assessing meat yield and the relevant distribution of meat throughout carcasses would offer huge opportunities to reward producers for what they produce.

But for meat yield assessments to be fully beneficial there is a need for standardisation in trim levels applied at the butchery level, said Mr Matthews.

“How carcasses are trimmed and cut after the slaughter line affects the yield of saleable meat coming from a carcass.”

And Mr Matthews admitted the information would only be of value when it was passed back to farmers.

“There may be difficulties when farmers sell liveweight, communication back to farmers via buyers is essential.”

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