Lactose, sucrose, and molasses in simple and complex diets for nursery pigs

Two experiments were conducted to determine the effects of lactose, sucrose, and molasses in simple and complex diets for nursery pigs. In Experiment 1, 210 weaned pigs (4.6 kg) were used in a 30-day growth assay. Treatments included complex diets with 100 g crystalline lactose/kg, and 50% or 100% of the lactose replaced with sucrose or molasses. Overall, replacing lactose with sucrose or molasses did not affect weight gain, feed intake, or efficiency of feed utilization. Surprisingly, diets with molasses supported greater overall weight gain than diets with sucrose (P<0.05), because of reduced performance when lactose was totally replaced with sucrose (sucrose versus molasses at 50% versus 100% replacement of lactose, P<0.01). In Experiment 2, 180 weaned pigs (6.4 kg) were used in a 30-day growth assay. Treatments were arranged in a 2×3 factorial design with diet complexity (simple or complex) and added sugar (none, lactose, or sucrose) as main effects. Complex diets supported greater performance (P<0.05) during the first 10 days post-weaning compared with simple diets, but performance was equal during the last part of the experiment. Apparent digestibilities of dry matter and nitrogen on day 10 were greater (P<0.05) in pigs fed complex diets versus simple diets, but they were not affected by sugar additions. Furthermore, addition of either simple sugar improved feed utilization (P<0.01) regardless of diet complexity throughout the experimental period, whereas sucrose tended to be as effective as lactose (P=0.07). In conclusion, sucrose and molasses effectively replaced lactose, supporting comparable performance in nursery pigs.