Variance components for susceptibility to Mycobacterium bovis infection in dairy and beef cattle

Abstract

BackgroundInfection of livestock with bovine tuberculosis (bTB; Mycobacterium bovis) is of major economical concern in many countries; approximately 15 000 to 20 000 cattle are infected per year in Ireland. The objective of this study was to quantify the genetic variation for bTB susceptibility in Irish dairy and beef cattle.MethodsA total of 105 914 cow, 56 904 heifer and 21 872 steer single intra-dermal comparative tuberculin test records (i.e., binary trait) collected from the years 2001 to 2010 from dairy and beef herds were included in the analysis. Only animal level data pertaining to periods of herd bTB infection were retained. Variance components for bTB were estimated using animal linear and threshold mixed models and co-variances were estimated using sire linear mixed models.ResultsUsing a linear model, the heritability for susceptibility to bTB in the entire dataset was 0.11 and ranged from 0.08 (heifers in dairy herds) to 0.19 (heifers in beef herds) among the sub-populations investigated. Differences in susceptibility to bTB between breeds were clearly evident. Estimates of genetic correlations for bTB susceptibility between animal types (i.e., cows, heifers, steers) were all positive (0.10 to 0.64), yet different from one. Furthermore, genetic correlations for bTB susceptibility between environments that differed in herd prevalence of bTB ranged from 0.06 to 0.86 and were all different from one.ConclusionsGenetic trends for bTB susceptibility observed in this study suggest a slight increase in genetic susceptibility to bTB in recent years. Since bTB is of economic importance and because all animals are routinely tested at least once annually in Ireland and some other countries, the presence of genetic variation for bTB susceptibility suggests that bTB susceptibility should be included in a national breeding program to halt possible deterioration in genetic susceptibility to bTB infection.

Genomic regions underlying susceptibility to bovine tuberculosis in Holstein-Friesian cattle

“…We found that heritability for bTB susceptibility was moderately high in this population and therefore selection for resistance is a feasible strategy to reduce the incidence of bTB nationwide. Other studies [12–16] corroborate these findings. Tsairidou et al [13] and Bermingham et al [19], respectively reported polygenic heritabilities of 0.23 and 0.21 for susceptibility to bTB, which were similar to the estimate for phenotype 1 in our study, based on positive skin test reactors with positive post mortem examination results.…”

“…Most of earlier research on bTB was mainly focused on environmental risk factors for bTB infection [9–11], whilst limited attention was given towards identifying possible genetic factors in the bovine host. However, it was not until recently that genetic studies established the presence of between animal variation in dairy and beef cattle susceptibility to the disease with heritability estimates ranging between 0.09 and 0.23 [12–16]. Furthermore, some genome-wide association (GWA) and regional heritability mapping (RHM) analyses aiming at identifying Quantitative Trait Loci (QTL) underlying cattle susceptibility to bTB have been undertaken.…”

Risk factors for failure to detect bovine tuberculosis in cattle from infected herds across Northern Ireland (2004–2010)

“…Finally, dairy breeds may have different levels of genetic resistance to M. bovis relative to beef herds (Allen et al, 2010;Richardson et al, 2014).…”

Genetic relationships between claw health traits of dairy cows in different parities, lactation stages, and herds with different claw disorder frequencies

“…In high-frequency herds, cows are more likely to express their resistance to claw disorders. Richardson et al (2014) found a higher heritability for susceptibility to bovine tuberculosis (bTB) for herds with a higher bTB prevalence. Furthermore, Richardson et al (2014) found genetic correlations different from unity for susceptibility to bTB between environments that differed in bTB herd prevalence.…”

“…Richardson et al (2014) found a higher heritability for susceptibility to bovine tuberculosis (bTB) for herds with a higher bTB prevalence. Furthermore, Richardson et al (2014) found genetic correlations different from unity for susceptibility to bTB between environments that differed in bTB herd prevalence. Calus et al (2006) found similar results for SCS across herds with different mean bulk tank SCS.…”