The relationship between inbreeding and melanoma status (graded from 0 to 4) was analysed by various regression models. Analysed data referred to 296 grey Lipizzan horses originating from five state-owned studs (Austria, Croatia, Hungary, Slovakia and Slovenia) and with average inbreeding coefficient (F=0.107) calculated from extremely informative pedigrees (98% and 76% of horses had completely full pedigree in generation 10 and 20, respectively). In all regression models, in addition, the effects of stud (fixed) and age (covariate) were included. When all data were treated as one population, the estimates from linear and ancestral inbreeding models were not significant. Total inbreeding effect estimates (at F=0.125 and Fa=0.57) were 0.26 and 0.30 for the ancestral inbreeding and linear regression models, respectively. Heterogeneity among state-owned studs in inbreeding effects was also tested for both models and weak statistical significance was obtained for the interaction model with ancestral inbreeding (P=0.049). However, observed effect in the model with interaction was not consistent, did not yield in better model fitting and the obtained significance is probably just a statistical artefact. In general, although some indications about the relationship between ancestral inbreeding and melanoma were present, inbreeding does not appear to be a factor that substantially influences the expression of melanoma in Lipizzan horses.

Ancestral inbreeding; Inbreeding; Lipizzan horse; Melanoma

Published by University of Zagreb, Faculty of Agriculture, Zagreb, CROATIA
Sponsored by Ministry Science and Education of the Republic of Croatia