Influence of hog lice, Haematopinus suis, on blood components, behavior, weight gain and feed efficiency of pigs.

Blood components, behavior, weight gain and feed efficiency were studied in 40 weaner pigs infested with lice and 40 left uninfested (controls). Packed cell volumes and concentrations of hemoglobin, serum proteins, leukocytes, serum globulins, and serum albumins increased significantly in both groups. Eosinophil concentrations increased and neutrophil concentrations decreased in the infested group but not in the controls. There was a significant increase in erythrocyte concentrations in the control group while the infested group's erythrocyte concentrations decreased at the middle of the experiment. Blood of infested and uninfested pigs showed no significant differences from pre-infestation values in sedimentation rates and concentrations of fibrinogen, basophils, and monocytes. Control pigs spent more time at feeders and more time active while not at feeders. Nevertheless, average daily gains (ADG) and feed efficiencies (FE) of the two groups were not significantly different. When ADG and FE were grouped by severity of Haematopinus suis infestation, pigs with more H. suis had higher ADG and better FE than pigs with fewer or no lice. The results suggest that a decrease in activity by infested pigs allows them to save energy which is then available for growth.