Dr. Mark Thomas, Dairy Health Management, made a presentation on group housing at the Discover conference last week. He has walked in quite a number of preweaned group pens the past couple of years.
His insight was that when calves are fed ad lib. or free-choice milk or milk replacer (or rates of 8 liters or more a day with an automatic computer feeder) the pens require much more bedding than calves fed on more restricted milk rations. Rationale? More liquid in results in lots more urine out!
So, if you have group pens for preweaned calves that are on an intensive milk/milk replacer feeding program be aware that these pens will require more than the usual amount of bedding in order to keep the calves dry.