Adding crude glycerin to nursery pig diet: Effect on nutrient digestibility, metabolic status, intestinal morphology and intestinal cytokine expression

The objective of this study was to determine the effect of crude glycerin (Gly) added to nursery pig diet on nutrient digestibility, the digestive and metabolic status, intestinal morphology and intestinal cytokine expression. A total of 18 male piglets (weaned at 23 days) were used. There were three dietary treatments that differed in the inclusion level of Gly (0, 9 and 18%). On day 14 of the experiment, the animals were weighed and plasma samples were collected before slaughtering. In addition urine, digesta content and intestinal tissues were sampled post mortem. No differences were observed among the tested diets as regards the coefficients of apparent ileal digestibility of DM and CP. The concentration of lactic acid decreased linearly (Po0.05) in the jejunum and ileum segments as the level of Gly increased, although the concentrations of volatile fatty acids in the cecum and colon were not affected. The plasma concentrations of glucose, fructosamine and IGF-1 were not affected. However, urinary glycerol concentrations increased (Po0.01) with increasing levels of Gly. In general, there were no differences in villus height, crypt depth, villus/crypt ratio or number of lymphocytes in the intestinal segments between the different treatments. Nevertheless, the control treatment produced a higher level of goblet cells in the ileum than either of the Gly treatments (Po0.01), while in the jejunum, the number of IgA-secreting cells in the 9% Gly group was higher (Po0.01) than in the control group. There were no differences among the experimental treatments concerning the gene expression of IL-10, IL-12 p40 and TNF-α. Gene expressions of TGF-β, IL-12 p35, IFN-γ and IFN-α were remained unaffected or increased, depending on the intestinal segment and level of Gly addition. In conclusion, the inclusion of Gly at 9 and 18% to the nursery pig diet did not affect nutrient digestibility or plasma metabolites but increased the levels of urinary glycerol, suggesting that metabolic pathways of glycerol utilization became saturated when high levels of Gly are used. In addition, the intestinal cell structure and intestinal cytokine expression might be affected when Gly is included in the feed.