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

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Abstract
From 3 to 77 days of age, male Holstein calves (6/group) were fed the following rations: 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 11 wk calves were sacrificed; small intestines were removed, separated from contents, and analyzed for lactase activities. Responses in blood glucose to ingestion of lactose were also determined at biweekly intervals. Lactase activity (mg glucose released/g intestinal protein) in the proximal 3rd of the small intestine averaged to 876, 1399, 1881 and 2012 for the respective treatments. Greater differences between treatments were noted for total lactase due to a direct relationship between dietary lactose and g of intestinal protein. Efficiency of gain was poorest and incidence of diarrhea highest for calves in group 4. Increases in blood glucose due to lactose ingestion were also greatest for calves in group 4 (particularly at 9 and 11 wk).