Descriptive type classification data recorded by the HolsteinFriesian Association of America was compared to DHIA production data to determine which of the type subtraits were related to first lactation production, first calving interval, herd life, and lifetime milk and fat yields. Variables other than type traits were expressed as deviations from the contemporary average.
Heritabilities of type subtraits ranged from .00 to .45. First lactation milk and fat yields were approximately 30% heritable, whereas lifetime yields were only 11% heritable. Herd life was nearly 8% heritable, and the first calving interval had a heritability estimate of .04.
Means of first lactation and lifetime variables were computed by type subtrait and adjusted for effects of all other type traits. Linear and quadratic effects of final score, age and stage of lactation.when classified, and age at first calving were also removed through regression. Differences in herd life opportunity were removed from lifetime variables.
Adjusted means suggested that sloping rump was the only type subtrait related to a highly significant (P<.01) shortened first calving interval. Type subtraits related to high first lactation milk and fat yields included narrow front end, broken fore udder, udder floor too low, and tilted udder floor. However, broken fore udder was associated with shortened herd life and reduced lifetime yields. The other three type subtraits plus medium strength front end, sloping rump, bulgy fore udder, high and wide rear udder, and desirable teat size, shape, and placement had highly significant positive adjusted means for lifetime milk and fat production. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/74627 |
| Date | January 1978 |
| Creators | Honnette, John Everett |
| Contributors | Dairy Science |
| Publisher | Virginia Polytechnic Institute and State University |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | vii, 189 leaves, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 39901061 |
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