Association of variants in anti-bacterial TLR with health, milk utility and reproductive traits in Czech Simmental cattle

Abstract

Screening was performed in Czech Red Pied (Czech Simmental) cattle for the association of the sequence variants in the anti-bacterial series of TLR genes (TLR1, -2, -4, -5 and -6) with 12 - phenotypic traits comprising milk fat percentage, fat yield, protein percentage and protein yield, total milk yield, somatic cell score, udder health index, milkability, lactation persistency, incidence of cystic ovaries, early reproductive disorders, calving ease, maternal calving ease, production longevity, and calf vitality index. Gene variants were discovered by hybrid resequencing using WGS with Hiseq X-Ten technology and amplicon panel with PacBio RSII.

Found polymorphisms were genotyped in 164 bulls using primer extension assays. Associations were detected using one-way ANOVA with subsequent Benjamini-Hochberg tests.

Limited or no association with udder health and milk utility traits were observed for 30 polymorphisms tested, in contrast to the expectation. On the other hand, associations were observed between variants in all TLRs and reproductive traits, namely for incidence of cystic ovaries and index of early disorders.

Two variants of TLR4 and one of TLR5 were associated with calving ease. Two SNPs in TLR4 were associated with production longevity.

The association of rs43578094 in TLR4 with calf vitality index might reflect perinatal risks. Only three SNPs in TLR5 were associated with milk production traits.

The presumed causality was corroborated by supporting evidence. The shared pattern of associations for TLR1, -2 and -6 can be explained by the interaction of the products in TLR1/TLR2 and TLR6/TLR2 heterodimers.

There is a good positional match with the known QTLs for calving ease, namely, (#1681 on chr. 6, #43837 on chr. 8 and #48258 on chr. 16, with TLR1/TLR6, TLR4 and TLR5, respectively. Consistently, the effects of non-immune functions of TLRs on reproductive traits are documented in model species.