The accuracy of the reference - test results

The dissection trial performed in Belgium (05/02/2001 - 16/02/2001)

ir. Ongenae Ellen - University of Gent - Department of Animal Production

During the period 5-16th of February 2001, the third step in the dissection trial of WP1 was performed in Belgium. The two slaughterhouses chosen for the experiment were VACOM NV located in Lokeren, and Westvlees NV in Westrozebeke. Lokeren is situated centrally in Flanders, whereas Westrozebeke is a town in the western part of Flanders, close to the French border. Flanders is the main producing area of slaughterpigs (95%) in Belgium. The Belgian porc production is mainly (85%) based on crosses with Piétrain as a terminal sire and commercial hybrids, Belgian Landrace or Landrace Negative sows. About 10% of the Belgian slaughter pigs have been imported as piglet from the Netherlands and Germany.

Both abattoirs chosen for the experiment were private slaughterhouses. In Lokeren about half a million pigs is slaughtered anually at a chain speed of 300 pigs an hour. In Westvlees NV, the line operates at a speed of 450 pigs an hour, and they attain a yearly slaughternumber of 800 000 pigs. The slaughterprocedure in both abattoirs was quite analogous. The pigs arrived at the slaughterhouse during the day of slaughter and were allowed to rest for one or two hours. The animals were led to the stunning in small groups. Lokeren uses carbon dioxide for stunning, whereas in Westvlees the pigs were stunned electrically. After stunning the pigs were shackled and bled. From there they passed on to the scalding tank, the dehairing machine and the singeing oven. Organs were removed and carcasses splitted. After vets inspection, removal of the flare fat and weighing of the carcasses, they were measured with SKGII, PG200 and/or CGM. Normally the carcasses are further dressed after measuring, but for the sake of the experiment the selected carcasses were further left undamaged.

How did the selection of the carcasses take place ? The whole selection procedure could be split up in three steps. In a first step, a random selection of carcasses took place where the pigs came out of the dehairing machine. At random pigs were selected and put on a trolley, which transported the carcass to the Autofom. After the measurement, the pig was marked with an Autofom number and hooked back on the slaughterline. Between 100 and 150 carcasses were measured by the Autofom per day. Furtheron in the line the marked pigs were weighted and measured for backfat thickness with CGM or PG200. Based on these data, and taking into account the sex of the pig, a second selection was made. Pigs of different weights, fat thickness groups and sexes were thus selected. Selected pigs were marked with a blue rope. In a third selection step, the splitting errors and dressing procedure were evaluated. In this way 5 or 6 properly dressed carcasses meeting the criteria for fat thickness, weight and sex could be selected. Those carcasses were than chilled and transported to the dissection room, where they stayed overnight in a refrigerator.

The dissections took place in the experimental slaughterhouse of University in Melle. Before the dissection started the carcasses were digitally photographed and video taped. The 4 best carcasses were selected and each carcass half assigned to a butcher. The lenght of the carcasses from os pubis to the bottom of the atlas and from os pubis to the first rib was measured, as were the backfat thickness at 4 locations and leg muscle thickness. The carcasses were dissected according to the rules laid down by Mercus and Walstra. The carcass halves were first dissected into the main joints, which were then weighted individually. Subsequently, the ham, the loin, the leg and the belly were further dissected into muscles, bones and fat. Every part was weighted. The data were recorded onto a laptop and the software calculated directly the lean meat %. The lean meat % of the dissected halves varied between 48.3 and 76.9 %. The differences in lean meat % between butchers ranged from 0.01% to 3.08%.

The butchers were very skilful, and because they already had the experience from the two former dissection trials, the whole dissection trial went very fluently. The butchers also got along very well together, which was beneficial for the atmosphere in the group and the ongoing of the experiment. It can be concluded that the sampling and dissection were performed according to the general plan.