Effect of dietary lactose on gain, feed conversion, blood, bone and intestinal parameters in postweaning rats and swine.

Two trials were conducted to determine the effect of lactose on performance, bone integrity and certain blood constituents in postweaning rats and swine. The effect of lactose on calcium and phosphorus and percentage ash content of the small intestine was also determined. In both trials, average daily gains were not influenced by the feeding of diets containing 30% lactose. Feed conversion was depressed in both rats and pigs when 30% lactose was fed. Transitory diarrhea was observed in rats fed 30% lactose, but not in swine. In the rat trial, no significant differences due to treatment were observed for serum Ca of P, but a linear increase (P < .01) in alkaline phosphatase was observed as lactose increased in the diet. Analysis of blood constituents from multiple bleedings during the pig trial showed that in the first 2 weeks, alkaline phosphatase was increased (P < .01) in pigs fed lactose and slightly decreased in those not fed lactose. Lactose affected the change in serum Ca for 0 to 10 weeks (P < .05) as indicated by a marked reduction in serum Ca of pigs not fed lactose and a slight increase for those fed lactoss. Serum calcium decreased in the absence of lactose but increased in the presence of lactose (P < .05) in pigs fed .4% Ca diets. In both trials, breaking strength parameters (peak force and stress) were not affected by dietary lactose. Bones from pigs fed no lactose had a higher stress to strain ratio (P < .05) than those from pigs fed lactose. In the rat trial, stress to strain ratio was variable across all treatments. Percentage of bone ash increased (P < .01) as lactose increased in the diet. Dietary treatments did not affect the mineral content of specific gut segments.