HERITABILITIES OF MEASURES OF HOOVES AND THEIR RELATION TO OTHER TRAITS OF HOLSTEINS

Genetic and phenotypic variations of hoof measurements were related to milk and fat yields, days open from calving to conception, and surviv al to various ages. Data were from 5551 measures in the first four lac tations of 2972 Holstein cows in six herds over 15 yr. Estimates of he ritabilities for hoof angles by multivariate REML averaged .18 but ran ged from .03 to .39 by lactation. Similar averages for hoof lengths we re .25 (range .08 to .53) and .07 (range .02 to .16) for heel depth. H oof lengths had the highest phenotypic relationships with milk or fat yields and days open. Hoof angles of the first lactation were positive ly related to survival rates to various ages. For the second lactation , hoof lengths were the only useful predictors of survival. Days open, survival rate, and increase in age-adjusted milk yield from first to second lactation were favorably related to higher hoof angles and shor ter hoof lengths. Within a lactation, higher angles and shorter length s were undesirable for increased milk or fat yields. Genetic correlati ons of milk and fat yields with hoof angles were generally negative, b ut those for length were mostly positive. Genetically, days open decre ased as hoof angle increased; some differences occurred among lactatio ns. Longer hooves and deeper heels were positively related genetically to days open. Genetic correlations of hoof angles and heel depth with survival were positive, but those with hoof length tended to be negat ive.