Heritability estimates of tarsocrural osteochondrosis and palmar/plantar first phalanx osteochondral fragments in S tandardbred trotters

• Published in: Equine veterinary journal Vol. 46; no. 1; pp. 32 - 37
• Main Authors: Lykkjen, S., Olsen, H. F., Dolvik, N. I., Grøndahl, A. M., Røed, K. H., Klemetsdal, G.
• Format: Journal Article
• Language: English
• Published: 01-01-2014
• ISSN: 0425-1644; 2042-3306
• DOI: 10.1111/evj.12058

Summary
Reasons for performing study
The pathogenesis of osteochondrosis (
OC
) and palmar/plantar first phalanx osteochondral fragments (
POFs
) is multifactorial, but specific knowledge of heritability is limited.
Objectives
To improve the precision of heritability estimates and to estimate the genetic correlation between tarsocrural
OC
and
POFs
in Standardbred trotters. Further aims were to examine whether the prevalence of
OC
/
POFs
was different in the
A
merican and
F
rench lineages that have contributed to the
N
orwegian population, and if the prevalence was affected by heterozygosity.
Study design
Retrospective cohort study.
Methods
Categorical data on tarsocrural
OC
and
POFs
from 2 radiographic studies performed in 1989 and 2007/2008 (n = 1217) were analysed with sire threshold models that included 230 sires.
Results
Heritability of
OC
at the distal intermediate ridge of the tibia and/or the lateral trochlear ridge of the talus was estimated at 0.29 ± 0.15. For
OC
at the distal intermediate ridge of the tibia only, the estimate was 0.40 ± 0.17. Heritability of
POFs
in all 4 limbs was estimated at 0.23 ± 0.13; for metatarsophalangeal
POFs
this was 0.26 ± 0.13 and for medial metatarsophalangeal
POFs
0.32 ± 0.14. Estimates of genetic correlation between
OC
and
POFs
ranged from 0.68 ± 0.27 to 0.73 ± 0.28 but were not significantly different from a zero‐genetic correlation. Effects of lineages or heterozygosity were not observed.
Conclusions and potential relevance
This study confirmed a moderate to high heritability of tarsocrural
OC
and
POF
, providing further evidence of the heritable nature of these diseases. Examination of specific lesions yielded the highest heritability; therefore, breeding programmes and future genome‐analysis studies should focus on predilection sites rather than the entire disease complex.