The Impact of Some Management Stressors on the Acute Phase Protein Haptoglobin in Beef Cattle

Abstract

Assessment of the response of cattle to stressors has previously relied on behavioural changes and physiological responses, in particular cortisol concentrations. This thesis examines the impact of some management practices on the acute phase protein, haptoglobin, in beef cattle. Haptoglobin is readily measured in plasma using a biochemical assay of the peroxidase activity generated by the binding of haptoglobin to haemoglobin. It was found that the accuracy of this method was reduced by haemolysis occurring at the time of blood sampling. The assay presented in this thesis used the peroxidase nature of the haemoglobin-haptoglobin complex in the presence of hydrogen peroxide to catalyse a redox reaction which results in a chromogen changing colour. The assay is highly repeatable (92%) and robust. A correction equation was developed to adjust estimated haptoglobin values for the effect of haemolysis caused at the time of blood collection. The correction equation incorporated measures of plasma haemoglobin concentration and endogenous peroxidase activity present in the sample. Two sites commonly used in cattle for collection of blood samples are the jugular vein and coccygeal vessels. The impact of blood collection site on haematological variables and haptoglobin was examined. Total white blood cell count, lymphocytes, basophils, red blood cells and platelets differed significantly (P<0.05) between the two sites. Basophil counts had a higher concentration in blood collected at the tail. The other variables that significantly differed were lower in the tail vessels compared to the jugular vein. Haptoglobin concentrations did not differ (P>0.05) between blood samples from the two sites. The effect of the production stressors; weaning, transport; intensive management; muscle biopsy and social re-grouping on haptoglobin were analysed.