Dietary origin and digestion of dietary nutrients in the preruminant calf

Milk-fed veal calves are mainly reared using liquid milk replacer, which is formulated from feedstuffs of animal and vegetable origins. The knowledge of their digestibility by the calf is necessary to optimize their use in animal nutrition. This literature review describes the different sources of proteins, lipids and carbohydrates used in liquid milk replacers and the mechanisms involved in the digestion of dietary proteins, lipids and carbohydrates. The digestibility coefficients for proteins, lipids and carbohydrates of feedstuffs of dairy origin (skim milk powder, whey powder and lactose) are higher than 90%. Nevertheless, the digestibility coefficients of vegetable feedstuffs (soy protein concentrate, potato protein concentrate and wheat gluten) are more variable and depend on the technological treatments they undergo. Nevertheless, these digestibility coefficients are high, which implies that the use of these vegetable feedstuffs is a good alternative to dairy feedstuffs when animals are older than one month.