@article{hahn_mcdaniel_wilk_1984, title={GENETIC AND ENVIRONMENTAL VARIATION OF HOOF CHARACTERISTICS OF HOLSTEIN CATTLE}, volume={67}, ISSN={["0022-0302"]}, DOI={10.3168/jds.S0022-0302(84)81664-1}, abstractNote={Genetic and environmental components of variation of hoof measurements were ascertained from 257 Holstein heifers and 1051 cows in eight herds in North Carolina. Angles and lengths of both claws, heel depth, and base area of the hoof were measured on both right feet for four herds. Angles, lengths, and heel depths were measured only on the right rear foot for four other herds. Heritabilities combined across all lactations were .30 or above but for individual lactations were as low as .12. Number of sires ranged from 16 to 40 for individual lactations. Average repeatabilities among measurements in same lactation were mostly above .40. Age affected all hoof measurements in heifers. Herd effects had a large impact on hoof measurements. Averages for hoof angles by ages ranged from 42 degrees to 45 degrees and from 60 to 70 mm for hoof length. Ratio of length to angle ranged from 1.36 to 1.68, heel depth from 34 to 44 mm, and base areas of hoof from 93 to 103 cm2. Lengths of medial and lateral claws for front and rear feet increased with advancing age. Medial front and lateral rear claws were longer than respective opposing claws.}, number={12}, journal={JOURNAL OF DAIRY SCIENCE}, author={HAHN, MV and MCDANIEL, BT and WILK, JC}, year={1984}, pages={2986–2998} }
 @article{hahn_1980, title={Studies of genetic and environmental characteristics of hooves of dairy cattle}, volume={40}, number={10}, journal={Dissertation Abstracts International. B, Sciences and Engineering}, author={Hahn, M. V.}, year={1980}, pages={4578} }