SEQUENTIAL IN-VIVO MEASUREMENTS OF BODY-COMPOSITION OF CALVES EXPOSEDTO NATURAL INFECTION WITH GASTROINTESTINAL NEMATODES

Sequential in vivo measurements of total body water, exchangeable sodi um and exchangeable potassium, made by radioisotopic dilution techniqu es, were used to determine changes in body composition in calves expos ed to natural infections with gastrointestinal nematodes during their first grazing season. Two groups of calves were studied, one of which received a sustained release anthelmintic bolus at turn out. Over the grazing season the bolus-treated calves showed a significantly improve d pattern of bodyweight gain, compared with the untreated control calv es. There were also significant increases in both total body water and exchangeable potassium, as a percentage of the bodyweight, in the bol us calves compared with the controls. These findings indicated that bo dy protein as a percentage of bodyweight was increased in the bolus an imals. The bolus-treated calves also had significantly lower serum pep sinogen concentrations, faecal egg counts and worm burdens.