The question I received was about the ideal temperature at which to feed acidified milk replacer to young dairy heifer calves. 
The producer is set up with multiple pens. They have insulated boxes for each pen with a heater in each box for cold weather (it is a naturally-ventilated cold barn in New York State). The barrel in each box is wrapped with a thermostatically-controlled heating unit. Each box contains eight nipple feeding stations.
Fresh milk replacer is prepared twice daily and added to barrels at each pen as needed. The entire feeding system is taken apart between groups, barrel scrubbed and new tubes, check valves and nipples installed.
Now, the question. At what final temperature should the milk replacer be mixed and at what temperature should the heating units be set?