Effect of Level of Lactose upon Lactase Concentrations in the Small Intestines of Young Calves

Abstract

Varying amounts of lactose were fed to 24 male Holstein calves (six per group) from 3 to 77 days of age. Rations were: 1) Hay-grain (after weaning from whole milk at 5 wk); 2) whole milk; 3) whole milk plus 5% lactose (on a milk weight basis); and 4) whole milk plus 15% lactose. At biweekly intervals animals were fasted 14 hr and blood glucose responses to ingestion of lactose (2 g/lb body weight) were determined. Calves were sacrificed at 11 wk, small intestines were removed, separated from contents, and divided into three equal-length sections for determination of lactase activities.Total digestible nutrients required per pound of gain and incidence of diarrhea were highest for calves on high lactose (Group 4). Increases in blood glucose resulting from lactose ingestion were also greater for this group (particularly at 9 and 11 wk). Lactase activity (mg glucose released/g intestinal protein) in the proximal third of the small intestine amounted to 876, 1,399, 1,881, and 2,012 for the respective treatments. Even greater differences among treatments were noted for total lactase due to the direct relationship between dietary lactose and intestinal tissue protein.