Physiological and nutritional responses of steers infested with varying densities of Amblyomma americanum (Acari: Ixodidae).

The effects of varying densities of lone star tick, Amblyomma americanum (L.), on measured physiological parameters of beef cattle in a controlled environment was determined. Steers were infested with either 0, 20, 60, or 120 pairs of adult ticks. Heart rate, respiration, rectal temperature, fecal and urine excretions, and water and feed consumption were monitored daily. Blood samples were taken every 3rd d to measure cortisol, total proteins, urea nitrogen, and glucose levels. Hematocrits were also taken at each blood sampling. Results showed that A. americanum evoked elevated heart rates. The other measured physiological and nutritional responses of parasitized steers were similar to the control steers. These results suggest that tick densities were too low to cause physiological stress under the conditions used in this study. The methodology precluded detection of the parameters measured. A. americanum does not affect the parameters measured, or that fluctuating environmental parameters and varying host nutritional states may play major roles in modulating the effect of A. americanum infestations on cattle in nature.