Effects of immunostimulators on growth performance and immune response in pigs weaned at 21 days of age

Abstract

One hundred and fifty pigs with an average body weight of 6.6 kg were allotted to treatment in a completely randomized block design. The treatments included: 1. Control (basal diet), 2, P-glycan (basal diet + 40 ppm peptidoglycan), 3. MOS (basal diet + 0.1% mannanoligosaccharides), 4. MG (basal diet + 0.4% β-glucan) and 5. NIS (basal diet + 300 ppm Nonspecific Immunostimulating Anionic Alkali Solution, rice bran was used as a carrier). Each treatment had 6 replicates with 5 pigs per replicate. Overall, although there were no significant differences in animal performance, pigs fed MOS showed better growth performance and feed efficiency than the other groups. Nutrients and amino acid digestibilities were improved during phase II (d 15 to 28 post-weaning) compared to phase I (d 0 to 14 post-weaning). During the entire experimental period, pigs fed control and other experimental diets increased T cytotoxic and suppressor cells (CD8+), which contrasted with the decline in T helper cells (CD4+) and granulocyte and monocyte proportions in week 3 after feeding (d 21) compared to week 1 after feeding (d 7). The decrease of T helper cells, granulocytes and monocytes between weeks 1 and 3 was higher in pigs fed diets supplemented with P-glycan, MOS, MG and NIS than in pigs fed the control diet. From d 15 to 28 post-weaning, the diarrhoea score was lower in pigs fed diets supplemented with any of the immunostimulators compared to phase I (d 0 to 14 after weaning), except for the NIS treatment. The diarrhoea symptom showed the largest improvement in the MOS group, but there was no statistically significant difference among all of the treatments. In conclusion, these data suggest that the inclusion of immunostimulators (peptidoglycan, mannanoligosaccharides, β-glucan and NIS) has no beneficial effect on growth performance, except for mannanoligosaccharides. But the use of some immunostimulators showed a potential for weaned pigs to increase body growth (mannanoligosaccharides), return quickly to a low-key immune system (mannaolisosaccharides, β-glucan and NIS), reduce mortality (β-glucan) and diarrhoea (mannanoligosaccharides).