Variation in Toll-like Receptor Genes and Susceptibility to Clinical Mastitis in Holstein cows

Thursday, July 24, 2014: 8:30 AM
3501A (Kansas City Convention Center)
Christopher M Seabury , Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University System, College Station, TX
Klibs N Galvao , Department of Large Animal Clinical Sciences and D. H. Barron Reproductive and Perinatal Biology Research Program, College of Veterinary Medicine, University of Florida, Gainesville, FL
Kevin Lager , Iowa State University, Extension and Outreach, Ames, IA
Pablo J Pinedo , Texas A&M AgriLife Research, Amarillo, TX
Abstract Text:

Toll-like receptor proteins (TLRs) recognize conserved pathogen-associated molecular patterns (PAMPS) and initiate signaling pathways that coordinate the innate immune response. The primary objective of this study was to investigate potential associations between bovine single nucleotide polymorphisms (SNPs) and insertion-deletion (indel) mutations occurring in 7 bovine TLR genes (TLRs 1, 2, 4, 5, 6, 9, and 10) and clinical mastitis (CM) in dairy cows.  Clinical mastitis cases were diagnosed by herd personnel in the milking parlor if milk from one or more quarters was abnormal in color, viscosity, or consistency, with or without accompanying heat, pain, redness, or swelling of the quarter, or with generalized illness, and all treatments were recorded in the on-farm software. Cows were considered as cases if they had at least two CM episodes in the current lactation with the first case occurring within the first 100 days after calving. Cows were included in the control group if they had no CM events during the complete lactation. Each case was matched with 3 control herd-mates in the same parity and with a calving date within 2 months relative to the case cow. The final study population consisted of 686 Holstein cows (269 primiparae; 417 multiparae) in three farms located in Florida and Texas, including 510 cases and 176 controls. Custom allele-specific genotyping assays derived from multiple bovine TLR sequencing studies were utilized. Genotypes for 110 loci (SNPs and indels) that are known to be variable in domestic cattle were determined, resulting in 46 monomorphic loci and 64 loci with two alleles.  Collectively, 35 loci did not meet our case-control inclusion criterion for minor allele frequency (MAF ≥ 0.10).  The association between specific TLR genotypes and CM was evaluated by logistic regression with evaluation and correction for potentially confounding variables including: year and season of calving; parity; ME 305 day milk yield; and farm. Overall, five SNPs (TLR2, TLR9) produced uncorrected P-values ≤ 0.05 with respect to CM; four of these SNP associations (3 inTLR2, 1 in TLR9) endured corrections for multiple testing (P-values ≤ 0.05). Several confounding variables including year and season of calving, and milk yield remained significant after correction for multiple testing.  Our analysis of these data suggests that naturally occurring bovine TLR2 and TLR9 variation may potentially elicit tangible effects on udder health in Holstein cows.

Keywords: Mastitis, toll-like receptors, candidate gene