[Effect of prolonged consumption of lactose or hydrolyzed lactose in rats--nutritive efficiency and anatomical changes (author's transl)]

Growing rats receive for 270 days well-balanced diets with 40 p. 100 of lactose or industrial hydrolyzed lactose. Whey and ultrafiltration permeate are used in crude state or after enzymic lactose hydrolysis. In lactose diets the ingesta and the food efficiency are considerably reduced as well as the growth. The water intake is greatly increased. The dry mater digestibility is not modified by the lactose after an experiment of 7 months. Hydrolyzed lactose provokes all these phenomena but with a weaker intensity. In a zootechnical point of view the lactose hydrolysis reduces the detrimental properties of lactose. After 270 days animals having received lactose show a high hypertrophy of small intestine and caecum tissues as well as a small renal hypertropy (dry matter/100 g of living weight). Hydrolyzed lactose involves the comparable modifications but with a less extent. Numerous facts attributed to lactose molecule are partially imputable to galactose molecule mainly the increase of water consumption. Only the growth of bone tissue (femur) is provoked by the lactose molecule itself and not to its components. When the diet is well-balanced the presence of whey proteins does not seem to modify the lactose effects.