Genome-wide association study in colostrum reveals QTL on BTA21 for IgG and IgM natural antibodies in Swedish dairy cattle

Cordero Solorzano, Juan; Wensman, J.J.; Tråvén, M.; Arts, J.A.J.; Parmentier, H.K.; Bovenhuis, H.; Koning, Dirk Jan De


Colostrum with sufficient antibodies is essential for the newborn calf,
as it requires this passive immunity to survive until weaning. High
variation in the amount of colostrum antibodies in Swedish dairy cows
has been reported, with a large proportion having low antibody levels.
Natural antibodies (NAb) are produced without any antigenic stimulation
and target self-antigens and pathogen-associated molecular patterns
(PAMPs). Our objective was to estimate genetic parameters and detect
quantitative trait loci (QTL) for 2 NAb isotypes (IgG, IgM) in colostrum
binding keyhole limpet hemocyanin (KLH) and muramyl dipeptide
(MDP). Three experimental farms were included in the study, 1719
colostrum samples from 1313 cows between 1 to 6 parities, calving from
January 2015 to April 2017 were collected. 70% of the animals were
Swedish Red and 30% Swedish Holstein. Antibodies were measured
from colostrum using indirect ELISAs. To estimate genetic parameters, a
linear mixed model with repeated measures (different calvings from the
same cow) was run using ASReml 4, correcting for cow parity number,
time from calving to colostrum sampling and breed, including herdyear-
season of calving and sample storage plate as random effects. An
imputed 50K SNP array from a LD 7K array was used for the Genomewide
association study (GWAS), running the same model but including
the SNP genotype as a fixed effect. Heritabilities for colostrum NAbs
ranged from 0.15 to 0.27, with a permanent environment effect for IgG
isotypes accounting for 30% of the variance and for IgM ranging from
15 to 19%. Genetic correlations between IgG and IgM ranged from
0.1 to 0.4. The GWAS revealed one QTL on BTA3 for IgM (KLH and
MDP), the latter comprised of 7 SNPs (−log10(P) = 4.4), 2 significant
and 5 suggestive, ranging from 80 to 105 Mbp and another QTL on
BTA7 for IgG (KLH and MDP) consisting of 3 SNPs (−log10(P) =
4.1), from 85 to 113 Mbp. Our results suggest that natural antibodies
can potentially provide an effective tool to improve colostrum quality using genetic selection