EXPLORE GENETIC DIVERSITY AT PEDIGREE LEVEL IN AN ITALIAN NATIVE MOUNTAIN HORSE BREED TO DEVELOP STRATEGIES FOR BREED PRESERVATION AND MANAGEMENT

Genetic diversity is a key factor for both adaptation and response to selection. The loss of genetic diversity not only causes a decrease in individual fitness, but it also has a dramatic negative effect on the population survivability in the long term. Bottlenecks, limited introgression and limited number of individuals that build the population can radically affect the rate of genetic diversity. This study aimed to explore the genetic diversity at pedigree level of the Bardigiano horse breed, which is a native breed from the Province of Parma, shaped for living in the mountain areas. The Bardigiano has excellent resilience, being well adapted to roughage diet, harsh climate and pasture conditions. In the 1977 the Bardigiano studbook was founded with the goal of improving the use of the Bardigiano for riding and draft purposes. Pedigree data contained 9,469 horses (3,416 alive) which were used to estimate population parameters using the software Endog 4.8. The completeness of pedigree information was investigated by using the complete generation equivalent (CGE) which was equal to 4.0 when considering all the animals in the pedigree and 5.2 when analysing only alive horses. Eight ancestors explained 50% of the genetic variability observed in the Bardigiano population, and the most influent one had an inbreeding coefficient of 0.25. The average inbreeding coefficient in the living population was 0.08. When considering only the last generation, the coefficient rose to 0.102. The effective population size (Ne) of the current population was 2,535. By contrast, when Ne was calculated including only animals that produced offspring, it decreased considerably to more than three times less than previously calculated. The Bardigiano still shows the pool of genetic diversity necessary to respond to selective pressures in the coming years. However, due to the observed increase in the inbreeding and the reduction of Ne when considering only breeding animals, we believe that breeding strategies to monitor genetic diversity are required. We thus suggest the use of Optimal Contribution Selection to control the rate of inbreeding while allowing response to selection.