This is particularly noticeable with young pigs during the transition phase. During this period a piglet's body is totally dedicated to animal protein and energy sources coming from sows' milk. What we want to do is transition the piglet's system from animal protein and energy to plant protein and energy. At weaning, the piglet's body has not developed adequate amounts of enzymes for plant starch digestion or stomach acid for plant protein digestion. Through the introduction of highly digestible plant material blended with highly digestible animal source protein and energy, two things are accomplished.
Growth can continue, since the pig's body can deal with animal source protein and energy.
Secondly, the pig must develop sufficient enzymes and stomach acid to deal with the presence of plant material in the diet. In a warm, dry, sanitary environment, appropriate digestion of plant material can occur within 10 days. Once transition occurs, a higher amount of plant material can be added in a step-wise fashion until no animal protein sources are necessary. Economics often dictates when animal protein such as herring meal will be removed from the ration. The step-wise approach is taken so as not to overwhelm the developing amounts of stomach acid that is vital in several ways.