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Losses of both product quality and quantity during the critical pre-slaughter period are inevitable. These losses are the result of social, environmental and nutritional stresses imposed on the animal between the farm/feedlot and the abattoir knocking box. Clearly, in the interests of animal welfare and beef quality, our primary aim is to develop appropriate management strategies to minimise pre ~ slaughter stress.
Some examples of these strategies include:
* utilisation of skilled and experienced stock handlers and transporters;
* education of cattle to handling and transport;
* non-mixing of unfamiliar groups of cattle in lairage;
* utilisation of direct consignment when selling of cattle;
* provision of lairage pens with suitable space and water
* resting of cattle on arrival (minimum of four to six hours);
* provision of nutritional supplements when required (for example, after excessive periods of time off feed).
Apart from bruising, another significant meat quality defect that occurs as the result of severe stress is the condition known as dark cutting. Dark cutting beef is the result of significant losses in muscle glycogen reserves brought about by the animal's response to stress. As the name implies, the meat is very dark in appearance and is characterised by a high ultimate pH (that is, > 5.9), reduced shelf life and increased toughness (especially between pH 5.9-6.2).
Whilst this condition represents the extreme response to stress, the CRC Meat Science team has been focusing on how meat quality can be influenced through more subtle variations in the way cattle are managed pre-slaughter.
Two different pre-slaughter management treatments were investigated in a joint CRC/MRC experiment involving 60 Bos indicus crossbred steers that had been lotfed for approximately 70 days. Half the group were trucked to the abattoir five days prior to slaughter and fed on the same ration as that received in the feedlot (non-fasted group). The remainder was handled according to normal industry practice where they were trucked to the abattoir the day before slaughter and fasted overnight (fasted group). Both groups were slaughtered on the same day. Within each group, three low voltage stimulation (LVS) treatments were applied (no stimulation , that is, 0 seconds, 1 0 seconds and 40 seconds of stimulation). The striploins were collected after overnight chilling and aged for 1 and 14 days. Objective measurements of tenderness (shear force) and trained taste panel assessments were recorded on the striploins.
The results (Table 1) revealed a significant interaction between the pre-slaughter treatments and the post-slaughter electrical stimulation treatments on both shear force and panel tenderness scores. There were minimal differences in tenderness in the response to electrical stimulation in the non-fasted group. For the fasted group however, there was a clear response to electrical stimulation. Differences in the rate of pH decline were also observed between the two pre - slaughter groups, which we believe largely explains the differences in the response to low voltage electrical stimulation.
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