Reduced Activity May Indicate Parasitism
Parasitism impacts grazing behavior. Parasitized animals reduce their intake of pasture. These changes are potential indicators of disease. The technology now exists to measure animal activity on pasture. Scientists are using the available technology to determine whether physical activity can be used to access the impact of gastro-intestinal parasites.
New Zealand researchers measured body weight, fecal egg count (FEC), and overall activity in two groups of Romney x Suffolk lambs. All lambs were given anthelmintics at the start of the experiment. Half the lambs (n=12) were given anthelmintics every 14 days. The other half (n=12) did not receive further treatment. After 42 days of grazing a contaminated pasture, the lambs were monitored for 4 days for physical activity with tri-axial accelerometers sensors mounted on ram breeding harnesses.
Anthelmintic treatment had an affect on FEC, but not body weight. An effect of treatment and lamb starting weight was found on overall activity, identifying a negative impact of sub-clinical parasitism on activity in heavier lambs. If a threshold for activity could be determined, it could serve as an early indicator of parasitism in sheep. It would be especially useful for sheep that are monitored remotely. Activity change without poor growth performance could be an indicator of resilience.