Thirty-one batch- or continuous-flow milk pasteurizers used on commercial dairy and custom calf-feeding operations were surveyed. One sample of raw waste milk (RWM) immediately prior to onfarm pasteurization and one sample of pasteurized waste milk (PWM) immediately after on-farm pasteurization from daily waste milk pools were evaluated. The RWM and PWM samples were evaluated for nutrient composition, microbiological profile, alkaline phosphatase activity, and antibiotic residues. Percentages of fat (2.79 to 4.70), protein (2.89 to 5.10), and lactose (3.78 to 4.80) in PWM were highly variable between operations, resulting in a wide range of metabolizable energy (4.75 to 6.61 Mcal/ kg) contents in PWM. Thirteen percent (n = 4) of on-farm pasteurizers did not denature alkaline phosphatase, indicating incomplete pasteurization. On-farm pasteurization of waste milk reduced (P