Populationsstruktur och genetisk analys av exteriöra egenskaper hos svensk ardenner

Sammanfattning: The purposes of this study were to estimate genetic and phenotypic parameters for conformation traits in Swedish Ardenner, a heavy draught horse, and to investigate the inbreeding status of the population. Additionally, a breeding scheme proposal was created, based on the results achieved in the study. The data studied were obtained from the Swedish Horse Board and from the Swedish Ardenner Association. The data included 1632 three-year-old horses, mainly mares, and 356 stallions, judged between 1986 and 2005 at conformation shows. The traits studied were type, head-neck-body, legs, walk and trot at hand, total score and height at withers. Additional traits studied for stallions were circumference of chest and cannon bone. To analyse the data an animal model was used. Heritability varied for three-year-olds between 0.09 and 0.35 and for stallions between 0.003 and 0.04. Heritability for height at withers was 0.72 and 0.11 for the three-year-olds and stallions, respectively. For stallions the heritabilities for circumference of chest and cannon bone were 0.09 and 0.26. The genetic correlations between the conformation traits were positive for three-year-olds and for the stallions the correlations varied between positive and negative values. For the inbreeding analysis the data included 16 387 horses, born between 1900 and 2004. The average coefficient of inbreeding for all horses with at least four generations (PEC >0.8) in their pedigree was 1.2 %. For horses born 2004 with PEC>0.8 the average coefficient was 1.66 %. The effective population size (Ne) was estimated to 227 animals in 2002, the inbreeding effective size (NeF) calculated for the period 1997-2004 was 550 horses and the variance effective populations size (NeV) was 184 horses. The variance effective population size was estimated for the period 1989-1996. The heritability and correlations of the three-year-old horses show a good opportunity to improve the conformation traits by selective breeding. The result of the calculations of inbreeding and effective population size indicate that the risk of problems caused by inbreeding presently is low in the Swedish Ardenner breed. The proposed breeding scheme suggests that more horses should be shown at the conformations shows. That is to prevent a too early selection and a risk to eliminate good horses before they got to show what they can. More horses should also do the performance test (draught test) in order to provide more information on the individual as well as to the progeny information of sires.