Impact of the mare colostral immunoglobulins on the expression of TLR3, TLR4, and TLR7 in foals

Colostrum contains substances such as hormones, enzymes, polyamides, nucleic acid derivatives, and amino acid derivatives and also includes immunomodulating substances, proline-rich polypeptides, immunoglobulins (Ig) as well as bacteriostatic compounds. The aim of the study was to evaluate the impact of colostral Ig on the level of expression of selected Toll-like receptor genes (TLR3, TLR4, and TLR7). The experiments were conducted on 25 Polish Pony foals. Blood samples were collected according to the following scheme: before first suckling, at the 1st, 3rd, 5th, 10th, 20th, and 30th, day of age. Colostrum was obtained before the first suckling, 24 hr, and 3 days after the delivery. Gene expression analyses were performed on Illumina Eco using a commercial kit TaqMan®MGB probes. The quality of colostrum was assessed via refractometer and BRIX value. The total Ig level was calculated from the spectrophotometric method. IgG levels were measured using ELISA assay. The quality of colostrum significantly correlated with TLR4 and TLR7 expression. Foals that ingested colostrum with low Ig content displayed a higher level of TLR4 gene expression, while in the case of TLR7 the opposite trend was shown. This result indicates that colostrum may play an important role in shaping the mechanisms of building the immune system's response to bacterial pathogens.