Heritability of jumping ability and height of pony breeds in France

Heritability of jumping ability in competition and height were calculated in three breeds of ponies: Poney Francais de Selle (PFS), Connemara (CO) and New-Forest (NF). Results from 1996 to 1999 were used: 2,295,867 ranks in 64,880 events of which 261,077 were in specific pony competitions. A bi-variate analysis was performed for rank and height within each breed separately, i.e. on 2688 (PFS), 2014 (CO) and 671 (NF) ponies. Other results were used as comparison to estimate the level of the event. Ranks were analysed on the relative placing of an underlying performance. Two models were applied: with and without an effect of the height of the pony category. Estimated heritabilities of height were 0.72 (PFS), 0.47 (CO) and 0.34 (NF). Estimated heritabilities of the underlying variable responsible for ranks were 0.05 and 0.06 (PFS), 0.10 and 0.13 (CO), 0.19 and 0.16 (NF), respectively, for the two models. Effect of height represented a quarter of phenotypic deviation between adjacent categories. Estimated genetic correlations were 0.20 and 0.12 (PFS), 0.16 and 0.13 (CO), 0.11 and 0.07 (NF), respectively, for the two models. This suggests an important effect of size on the overall competitive ability of ponies but not for each breed in a homogeneous height category. (C) 2004 Elsevier B.V. All rights reserved.