Higher growth rates and sustained growth through weaning
According to various studies (Meale et al. 2015, amongst others), weaning calves gradually by reducing the amount of milk fed over time, instead of doing so abruptly, helps calves maintain higher growth rates during weaning. By experiencing less of a growth dip, calves weaned gradually have a better chance at continuing the high growth rates achieved prior to weaning after the transition, especially when fed higher planes of nutrition.
Transitioning from milk to solid feed needs time
Indeed, the transition from primarily milk and liquid feed to solid feed should take place as gradually as possible. As Trouw Nutrition's researcher Dr Harma Berends puts it, "The change from digesting milk to the fermentation of roughage and concentrates in the rumen is a major step. Rumen development needs time and a gradual approach. If rations are changed too quickly, the animal suffers stress, intestinal damage, and the so-called weaning dip in growth. That can be prevented by gradually reducing the amount of milk supplied." Weaning needs time which using a step-down process allows for. Weaning calves gradually also reduces weaning stress. As their bodies are going through a transition in the way they work to digest nutrients, it can be quite taxing on their systems. Allowing time for their systems to adjust gradually, reduces systemic and other types of stress.
Smoothness of transition is also key
Many researchers agree that the smoothness of the transition during weaning is absolutely essential. Dr Ajmal Khan, Senior Scientist at AgResearch, New Zealand, emphasizes this point. He concludes that a smooth transition from liquid to solid feed allows calves to consume and digest sufficient solid feed to support growth both during and after weaning. The smoother the transition, the better able calves are to handle it, with the least detrimental effect on their health, and with the highest potentially positive effect on their future performance.