Disease & heat resistance

Genetic parameters for humoral response to Mycobacterium avium subspecies paratuberculosis in New Zealand dairy cattle

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Abstract

Johne's disease, also known as paratuberculosis, is caused by Mycobacterium avium subspecies paratuberculosis (MAP). In the absence of treatment and effective vaccines, genetic selection against the disease has potential to reduce the disease burden. There is limited or no information available on this in New Zealand dairy cattle. Thus, the present study was conducted to estimate the heritability of humoral response to paratuberculosis, measured by two commercial ELISA assays (IDEXX and iD.vet) and its correlation with the milk production traits such as milk (MY), fat (FY), and protein (PY) yields. Four dairy herds in the Manawatu region of New Zealand were sampled for milk during early summer or late autumn of 2022/23 production season. The animals were of different ages and breeds. The number of log-transformed ELISA scores used in the study were 930 for the IDEXX and iD.vet milk-based assays. Variance components were obtained using single-trait and bivariate animal models. The model for ELISA scores included the fixed effects of herd and lactation number (first to fifth and above) as class effects and days from calving to sampling, proportion of Holstein-Friesian and Holstein-Friesianà—Jersey heterosis as covariate and random effect of animal. The same model with days from calving to sampling replacing the lactation length was used for milk production traits. The analyses were performed using the Bayesian mixed model estimation using Markov Chain Monte Carlo (MCMC) sampling in the Julia-based JWAS package. Four independent chains with 2,50,000 iterations were used in the model, with the first 50,000 iterations discarded as burn-in and samples retained every 250 iterations. The results indicated that ELISA scores were heritable with a posterior mean and 95% highest posterior density (HPD) intervals of 0.25 (0.12-0.39) for iD.vet-milk and 0.34 (0.19-0.52) for Idexx-milk. While the estimates of phenotypic correlations of ELISA scores with milk production traits were negligible, the estimates of genetic correlations were unfavorable but low. The iD.vet ELISA assay had a genetic correlation with a posterior mean and 95% HPD intervals of 0.09 (-0.20, 0.36) with MY, 0.10 (-0.21, 0.37) with FY, and 0.10 (-0.20, 0.36) with PY. IDEXX ELISA had a genetic correlation of 0.13 (-0.14, 0.38), 0.10 (-0.18, 0.36) and 0.08 (-0.17, 0.34) with MY, FY and PY, respectively. In conclusion, this study suggests that antibody response to MAP may have a genetic component. However, additional longitudinal data and complementary phenotypes are required to better understand the genetic variation related to disease resilience. Further studies are also needed to clarify genetic associations with milk production traits and to assess the potential inclusion of ELISA-based traits in breeding objectives, as the HPD intervals of the estimated correlations did not rule out negligible genetic relationships.

Keywords: 2026

How to Cite:

Venkatesh, M., Dukkipati, V., Gupta, S., Udy, G., Laven, R. & Lopez-Villalobos, N., (2026) “Genetic parameters for humoral response to Mycobacterium avium subspecies paratuberculosis in New Zealand dairy cattle”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2285405. doi: https://doi.org/10.31274/wcgalp.23686

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