PHYSIOLOGICAL-RESPONSES OF BEEF-CATTLE TO GULF-COAST TICK (ACARI, IXODIDAE) INFESTATIONS

Nine yearling crossbred beef steers, Bos taurus L., were used to exami ne physiological responses to Gulf Coast tick, Amblyomma maculatum Koc h, infestation. Steers were stanchioned indoors in individual environm entally controlled rooms. On day 0, each animal received 0, 25, or 75 pairs of ticks. Physiological variables measured daily were feed intak e, heart rates, rectal temperatures, and respiration rates. Blood samp les were collected from each animal on days 7, 21, and 42 for serum co nstituent analysis. To monitor metabolic hormone status, intensive blo od samples were collected hourly for 6 h on days 21 and 42. Throughout the treatment period, feed intake values were similar among treatment s resulting in comparable body weight at the end of the trial. Heart r ates and rectal temperatures were unaffected, however, respiration rat es of steers infested with 25 pairs of ticks were higher than the othe r treatment groups. Treatment effects were detected in uric acid conce ntrations on day 7 in steers infested with 75 pairs of ticks. Treatmen t effects were detected in total, direct and indirect bilirubin, gamma -glutamyl transpeptidase, and aspartate amino transferase concentratio ns. Likewise, creatine kinase concentrations were higher in the tick-i nfested steers on day 7. Elevated white blood cell counts were observe d in tick-infested steers. All other serum components were similar and were within their normal ranges. Serum insulin, prolactin, growth hor mone, and cortisol concentrations were unaffected by tick infestations . Gulf coast tick infestation resulted in altered blood composition in dicative of infection caused by tick feeding habits.