Review of genetic studies of susceptibility to facial eczema in sheep and dairy cattle

Figures & data

Figure 1.  Mean log_e[GGT] of calf groups, after dosing with the FE toxin sporidesmin and classified by the progeny-test status for FE susceptibility of their five ‘High’ (susceptible) Jersey sires or five ‘Low’ GGT (resistant) Jersey sires: results are summarised for the calves in log_e i.u./l units (with bars shown for the standard error of the difference) against days since the toxin challenge (from Morris et al. 1991a) (NB: Factor of ×1.75 between the mean log_e[GGT] values of High vs Low sire groups (74 calves)).

Figure 2.  Mean log_e[GGT] of calf groups, sired by Holstein–Friesian bulls that had been scored (performance tested) as weaned calves for response to FE susceptibility, or response to sporidesmin. Five such ‘High’ GGT and five ‘Low’ GGT bulls were selected for progeny testing for response to sporidesmin, alongside the progeny of eight untested/‘unselected’ Holstein–Friesian bulls. Results for progeny are shown in log_e i.u./l units (with bars for standard errors of means, shown in one direction) against days since the toxin challenge (from Morris et al. 1998).

Table 1 . Findings from different approaches used to identify causative FE genes and loci in the FE selection lines of Romney sheep. Locations are given in Ovis aries (OAR) chromosomes.

Experimental approach	Gene/locus	Chromosome location
Candidate genes	Catalase ABCG2	OAR15 OAR6
R×S QTL experiment^1	QTL (significant) QTL (suggestive) QTL (suggestive) QTL (suggestive) QTL (suggestive)	OAR3 OAR1 OAR8 OAR13 OAR15
Selection sweep studies^2	SNP (Peddrift) SNP (Peddrift) SNP (Peddrift)	OAR1 OAR11 OAR12
^1 FE-resistant×FE-susceptible (designated R×S) cross-bred rams were used to generate four half-sib families in this genome screen experiment to detect quantitative trait loci (QTL).
^2 Resistant and susceptible selection lines were used in selection sweep studies (Phua & Dodds 2011), with the ‘Peddrift’ analysis method of Dodds & McEwan (1997).

Table 2 . Genetic correlation (r _g) estimates (±standard errors) in dairy cattle between GGT and other potential indicators of liver injury (log transformations of enzyme levels or concentrations of metabolites, in blood) and heritability (h ²) estimates for these indicators (from Morris et al. 1998; Cullen et al. 2011).

Biochemical indicator	r g with GGT	h ^2
Glutamate dehydrogenase	0.93±0.03	0.33±0.05
Aspartate transaminase^1	1.00±0.04	0.28±0.09
5′-nucleotidase	1.00±0.01	0.23±0.12
Ferroxidase	Not significant	0.34±0.15
Bilirubin	0.92±0.14	0.12±0.06
Bile acids^2	0.94±0.07	0.50±0.26
^1 Also known as glutamate oxaloacetate transaminase.
^2 Jersey-sired animals only.

Morris , CA , Towers , NR , Smith , BL and Southey , BR . 1991a . Progeny testing bulls for susceptibility to facial eczema . New Zealand Journal of Agricultural Research , 34 : 413 – 417 . doi: 10.1080/00288233.1991.10417685

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Morris , CA , Burton , LJ , Towers , NR , Cullen , NG , Rendel , JM and Johnson , DL . 1998 . Genetics of susceptibility to facial eczema in Friesian and Jersey cattle . New Zealand Journal of Agricultural Research , 41 : 347 – 357 . doi: 10.1080/00288233.1998.9513319

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Phua , SH and Dodds , KG . 2011 . Different methods detected different loci involved in resistance to facial eczema disease of sheep . Proceedings of the Association for the Advancement of Animal Breeding & Genetics , 19 : 171 – 174 .

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Dodds , KG and McEwan , JC . 1997 . Calculating exact probabilities of allele frequency differences in divergent selection lines . Proceedings of the Association for the Advancement of Animal Breeding and Genetics , 12 : 556 – 560 .

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Cullen , NG , Morris , CA , Hickey , SM and Henderson , HV . 2011 . An update on genetic parameters for facial eczema susceptibility in New Zealand dairy cattle . Proceedings of the New Zealand Society of Animal Production , 71 : 117 – 121 .

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