A 2-day-old 44-kg (97-lb) purebred female Holstein calf was evaluated for weakness, signs of depression, and inability to stand unsupported. Immediately after birth, the calf could stand and was tube fed with approximately 4 L of colostrum. Twenty-four hours after birth, the calf was standing and suckled its daily requirement of milk replacer, but 48 hours after birth, the calf was recumbent and only drank half of its 2-L morning milk replacer feeding. The owner had treated the calf with 100 mg of tulathromycin that morning. On initial examination, rectal temperature (39°C [101.5°F]) and heart rate (120 beats/min) were