Journal of Animal Science

Heritability and repeatability of insect bite hypersensitivity in Dutch Shetland breeding mares

A. Schurink, E. M. van Grevenhof, B. J. Ducro and J. A. M. van Arendonk

Abstarc :

Insect bite hypersensitivity (IBH) is a seasonal recurrent allergicreaction of horses to the bites of certain Culicoides spp. andis found throughout the world. The aim of our study was to estimatethe heritability and repeatability of IBH in the Dutch Shetlandpony population. A total of 7,924 IBH scores on 6,073 mareswere collected during foal inspections in 2003, 2005, and 2006.Mares were scored for clinical symptoms of IBH from June untilFebruary by 16 inspectors. Of all mares, 74.4% (n = 4,520) hada single observation, 20.7% (n = 1,255) had 2 observations,and 4.9% (n = 298) had 3 observations in different years. Theoverall mean IBH prevalence was 8.8%. Heritability was 0.08(SE = 0.02) on the observed binary scale and 0.24 (SE = 0.06)on the underlying continuous scale. Repeatability was 0.30 (SE= 0.02) and indicates that including repeated observations ofthe clinical symptoms of IBH will improve the accuracy of breedingvalues for IBH. We conclude that IBH, based on clinical symptoms,is a heritable trait in the Dutch Shetland pony population.Therefore, the IBH prevalence in this population can be decreasedby selection.

Key Word :
heritability, horse, insect bite hypersensitivity, repeatability

Volume 87, Number 2, February 2009