Injury Thresholds and Production Loss Functions for the Lone Star Tick, Amblyomma americanum (Acari: Ixodidae), on Pastured, Preweaner Beef Cattle, Bos taurus

Production loss (decreased average daily gain [ADG]) in preweaner beef cattle, Bos taurus (L.), is a logarithmic function of the number of feeding female lone star ticks, Amblyomma americanum (L.) (In X). In 1982, Ŷ, the estimated change in ADG (kg) in tick-infested calves was Ŷ = 0.1342 − 0.0582(ln X). In 1983, Ŷ = 0.5107 − 0.1671(In X). Threshold values for production loss were 10 and 21 female A. americanum in 1982 and 1983, respectively. Slopes of the regression functions fitted to data in both years were not significantly different. The fitted production loss function for data from both years combined, Ŷ = 0.2810 − 0.103(In X), estimated an injury threshold of 15 feeding female A. americanum per calf.