ARTHRITIS IN THE CARPAL JOINTS OF NORWEGIAN TROTTER - HERITABILITY, EFFECTS OF INBREEDING AND CONFORMATION

Carpal joint arthritis (carpitis) was diagnosed in a sample of 508 fou r year old Norwegian trotters born in 1980. The Norwegian trotter is a light Dole-horse, and prevalences of 10 and 27% were reported for bil ateral and overall carpitis, respectively. Corresponding underlying sc ale heritability estimates, based on data of 407 horses sired by 34 st allions, were 0.67 and 0.25. Significant effect of inbreeding on bilat eral carpitis was estimated on the same scale. The probability of the disease was, respectively, 6.7% and 12.3% among horses with lower or h igher inbreeding coefficient than average. The relationship between fa ults of conformation and variables of carpitis was examined by a logis tic regression procedure. On forelimbs, irregular values for calf knee s and anterior broken toe-axis were associated with an enhanced preval ence of bilateral carpitis, while corresponding values for calf knees, standing under, toeing out, anterior broken toe-axis and lower circum ference on cannon increased the overall carpitis probability.