4.2. Optimal milk feeding
Voluntary intake as high as 5–6 l of milk in one meal did not cause milk to enter the rumen. This does not mean that we can recommend feeding milk meals of that size to dairy calves on a daily basis. The test meals were offered as single meals on three separate occasions, and we did not test how much the calves would have drunk if offered this amount three times a day. Neither were the long-term effects of large meals investigated. However, it has been found elsewhere that feeding milk ad libitum [9] or in large quantities [27] results in higher growth rates without compromising health or reducing solid feed intake after weaning. For instance, in a study by de Passillé et al. [12], calves were allowed to suckle twice daily. The amount drunk by the calves increased from 6.5 kg per day in week 1 to 12.5 kg per day in week 9, indicating large milk meals without adverse effects. Also, in the study by Appleby et al. [10], the average size of the calves' first milk meal of the day was 4.7 l (range 1.7–8.0 l) with favourable outcomes. Our results support these findings by showing that the abomasum has a large ability for distension and that voluntary intake does not cause milk to enter the rumen.