317
Can the effects of lactose on nursery pig performance and immune parameters be attributed to glucose, galactose, a combination of both, or sucrose?
To determine if lactose is effective as an energy substrate or benefits the immune system via the constituent monosaccharides, 96 crossbred nursery pigs (initial BW = 6.3 kg; d 21 to 23 postfarrowing) were allotted to 16 pens (4 pigs per pen; 4 pens per dietary treatment). The treatments were included in Phase 1 (d 0 to 14 postweaning) and Phase 2 (d 14 to 28 postweaning) diets. Diet 1 was a complex nursery diet supplemented with lactose (18% for phase 1 and 9% for phase 2, respectively); the other 3 diets were similar to diet 1 with 100% glucose, 50% glucose and 50% galactose, and 100% sucrose substituted for lactose, respectively. The nursery room was not cleaned after the previous experiment and the room temperature was maintained at 23 to 24 ˚C to induce an environmental stress. Data were analyzed as a completely randomized design using the MIXED procedure of SAS. Individual BW and feed disappearance were measured weekly from d 0 to 28. Blood samples were collected weekly for the determination of serum IgA, IgG, and haptoglobin concentrations. Overall, dietary treatments did not affect (P > 0.10) BW (average 15.31 kg; d 28), ADG (319 g), or G:F (687 g/kg). However, pigs fed glucose + galactose diet had greater (P < 0.05) ADFI than pigs fed the lactose diet in Phase 1 and 2 (247 vs. 210 g and 744 vs. 648 g, respectively). The ADFI (730 g) of pigs fed sucrose diet was greater (P < 0.05) compared to pigs fed the lactose diet (648 g) in Phase 2. There were no time × treatment interactions (P > 0.10) affecting circulating IgA, IgG, or haptoglobin. Serum IgA increased (P < 0.05) over time (d 0 to 28); whereas, IgG decreased (P < 0.05) from d 0 to 21. Haptoglobin had a 4-fold increase (P < 0.05) from d 0 to 7 and a 2.5-fold decrease (P < 0.05) from d 7 to 14. Pigs fed sucrose had greater (P < 0.05) IgA than pigs fed lactose and glucose + galactose diets, and tended to have greater (P < 0.10) IgA than pigs fed the glucose diet. There were no treatment effects (P> 0.10) on serum IgG or haptoglobin concentrations. In conclusion, when dietary lactose was substituted by the constituent monosaccharides (glucose and galactose), ADFI was increased in nursery pigs, although serum immune parameters were not affected.
Keywords: growth performance; lactose; nursery pigs