The assessment of pre-slaughter and slaughter treatments of livestock by measurement of plasma constituents-A review of recent work.

The measurement of plasma constituents in a blood sample can provide information on the stress status of the animal. The interpretation of results obtained for constituents of blood samples collected at exsanguination must consider the effect of the slaughter process on the constituent. Both electrical and mechanical stunning methods can cause dramatic increases in catecholamine levels and minor increases in glucose levels. Thus, there are difficulties in the interpretation of catecholamine and, to a lesser extent, glucose, values in blood samples collected post-stunning. Cortisol levels appear to be unaffected by stunning methods and measurement of this constituent in post-slaughter blood samples has been used to assist in the evaluation of transport and abattoir treatments. Beta-hydroxybutyrate concentrations may assist in evaluating nutritional stress prior to slaughter while the limited evidence available suggests that beta-endorphin measurements will be of value in assessing pain and other stressors prior to slaughter. Adreno-corticotrophic hormone, calcium and magnesium, free fatty acids, glucose, lactate and thyroid hormones have all been used on occasions to assist in the evaluation of stress status. In some cases it was not possible to demonstrate a clear relationship between plasma constituents that indicate stress, and stress-related meat quality defects.