Capítulo 2 Agentes y tipos de mercado de gas en Colombia
4. Bibliografía
2. 5.1 Past payment method
Prior to the 1 980's payment for lamb carcasses within New Zealand was based on carcass weight alone. This would have meant that farmer's main objectives would have been to produce the heaviest possible lambs irrespective of their fatness or the distribution of cut weights within the carcass. The main reason this method was used was because fat levels in lambs were not considered important. However, feed back from the United Kingdom, the main export destination at the time, suggested that New Zealand lamb was too fat (pers. comm. Patricia Johnson). This encouraged research into the area of fatness in lambs and the concept of using GR, "total tissue thickness between the surface of a lamb carcass and the rib at the point 1 1 cm from the midline in the region of the 1 th rib" (Kirton, 1 989), as a measurement of carcass fatness.
2. 5. 2 Current payment method
From 1 983 a new export lamb carcass grading system was used to grade carcasses; this system was based on the weight and GR of the carcass (Kirton et al., 1 985). With this
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grading system it
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optimal for farmers to produce heavy lean lambs as apposed to heavy fat lambs, which would have been acceptable prior to 1 983. The price paid to farmers per kilogram of carcass weight changes between years as can be seen in Figure 2.3 . The per-kilogram price is determined every month by the processing plant and is dependent on many factors including market demands and processing costs (Bray,Two Review c; � 450 � 400 �
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-� 0 ; "iij 1 00 � � ·;: D. Yea r SeriesFigure 2.3 : Prices paid to the farmer per kilogram of carcass weight over the past ten years
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There is an averaging effect seen through the use of this payment option. Within a carcass grade, such as PM where GR ranges from 7mrn up to and including 1 2 mm and carcass weights range from 1 3 to 1 6kg, there will be thousands of carcasses within these limits. Of these carcasses the ones that are at the upper end of the scale will produce more money for the processor than the ones at the lower end. However, farmers will not be rewarded for generating more profitable lambs as they will be paid on the average of all the lambs within the grade. On the other hand farmers producing animals at the lower end of the grade will be paid more than the carcass is worth. So in essence the farmers producing the better lambs are compensating for the farmers producing the smaller lambs.
The proportion of the variation seen in the composition (total muscle, fat, and bone) of lamb carcasses that is accounted for by GR and HCW (hot carcass weight) is low, with values of over 50% to 70% for fat and bone, and 26% to 47% for muscle ( Kirton et al. , 1 985). For this reason more accurate methods of predicting carcass composition are required to ensure that farmers are accurately rewarded for the lambs they produce, to encourage the production of lambs that meet the requirements of overseas markets. 2. 5.3 Future payment methods
It has been suggested that lamb payment options are to be changed in the future. Two l ikely scenarios are the use of image scanning to determine carcass composition and payment on the weight of individual cuts.
2.5.3.1 Payment based o n the weight of individual cuts
With this payment method farmers are paid on the weights of the individual cuts as
opposed to the carcass weight and GR measurements. Each cut will be priced differentially with some cuts, such as the frenched rack, having a higher value than other cuts. The value of the cuts will reflect the market values and will therefore change accordingly. This approach will allow the processor to send market signals to the farmer so they can produce lambs that fit the specifications required. I f higher prices are paid for certain cuts then farmers will strive to produce animals that have increased weights in those cuts, which will result in the farmer receiving more income, and processors obtaining carcasses that are more desirable. Progressive Meats ltd is currently updating their processing plant to enable farmers to be paid on the weights of individual cuts (pers. comm. Craig H ickson).
2. 5.3.2 Payment based o n image scanning metho ds
Image scanning is used to determine the muscle, fat and bone content of the carcass. Two methods of image scanning have been developed, the use of DXA/DEXA (dual energy x-ray absorptiometry) and VIAscan®.
The principle behind the DXA scanning system is tha measurements of fat and lean are determined by the greater attenuation of X-rays by lean (water and protein) than by fat (Mitchell et al. , 1 997). These measurements are taken at different sites of the carcass that do not overlie bone (as the X-ray is greatly attenuated by bone) (C larke et al. , 1 999;
Mitchell et al., 1 997).
The VIAscan® system uses a co lour video camera, and a computer that analyses the images obtained from the camera (Ross, 2005). A photograph of the carcass is taken as it passes the camera on the chain, from this photograph the computer derives the expected yield (of lean meat) from the colour and shape of the carcass (Chalmers, 2003) . This system gives objective measurements on the final cut conformation, and boned out meat yield, in addition to measuring carcass weight and GR (Anon, 2003) . The VIAscan® has an accuracy of 94-96% for predicting expected yield from the photograph (Chalmers, 2003) . The VIAscan® system is currently being implemented into Alliance meat company processing plants (Chalmers, 2003) .
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The basis of both the image scanning and the weight of cuts payment method is for farmers to produce carcasses with improved cut distribution that contain a large amount of muscle and little fat. This requirement for leaner carcasses has come from a change in consumer perceptions whereby leaner cuts are more acceptable than fatter cuts (Johnson et al., 2002).