The effects of dietary supplementation with rumen-protected amino acids on the expression of several genes involved in the immune system of dairy sheep.

ABSTRACT

Amino acids might be a tool to transform animals from a pro- to an anti-inflammatory phenotype through the downregulation of several genes (TLR-4, NF-κB, TNFa, IL-1ß, IL-2, IL-6, IL-8, CCL-5 and CXCL-16) whose expression increases during inflammation. To examine this possibility, each of sixty Chios dairy sheep was assigned to one of the following five dietary treatments A basal diet (control group); B basal diet +6.0 g/head rumen-protected methionine (MetaSmart™ ); C basal diet +5.0 g/head rumen-protected lysine (LysiGEM™ ); D basal diet +6.0 g/head MetaSmart™  + 5.0 g/head LysiGEM™ ; and E basal diet +12.0 g/head MetaSmart™  + 5.0 g/head LysiGEM. The results showed a significant downregulation in the expression of the TLR-4 gene in both the macrophages and the neutrophils of ewes fed rumen-protected amino acids. Significantly lower mRNA transcript accumulation was also observed for the TNFa, IL-1ß and CXCL-16 genes in the macrophages and for the IL-1ß gene in the neutrophils of ewes supplemented with amino acids. The ewes that received dietary supplementation with rumen-protected lysine alone (C) had significantly lower CCL-5 transcript levels in their macrophages than the ewes fed the other supplemented diets. Diet D enhanced the mRNA expression of the IL-2 gene in ewe neutrophils. Negative correlations were found between a. TLR-4, TNFa, IL-1ß and CXCL-16 gene expression in macrophages and the milk fat and total solids content; b. CCL-5 gene expression in neutrophils and the milk yield and FCM(6%) ; and c. CXCL-16 gene expression and the milk protein content. Moreover, positive correlations were found between the BHBA concentration and the expression of the TLR-4 and CXCL-16 genes in macrophages. In conclusion, the rumen-protected amino acids improved sheep metabolism (as indicated by reduced blood BHBA and urea concentrations), milk chemical composition and immune system function.