Official type classification data recorded by the Holstein Friesian Association of America from January, 1967 to June, 1974 and DHIA production data recorded by the U.S. Department of Agriculture from January, 1960 to May, 1974 were evaluated as progeny tests to ascertain the relationship between body conformation and longevity and wearability of dairy cows. Data for 788 sires with at least 20 daughters in 10 herds with classification information and at least 30 daughters with production information was used.
Means for type and production were daughter final score 80.1, predicted difference milk (PDM) -136, lifetime production 55,919 lb., production per day of productive life (PDL) 44A lb/day, age at last calving (AGE) 60. 1 mo., and percentage completing four lactations, 48.4%.
Correlations between PDT and scorecard and descriptive traits were positive and highly significant (P < .01). Most of the relationships between PDM and type traits were negative and highly significant (P < .01) with the exception of dairy character which was positive ( .27). Longevity traits were lowly correlated with PDT and generally negative but were highly positively correlated with PDM. Correlations were low between longevity traits and descriptive and scorecard traits ranging from -.23 between PDL and rump to .21 between age and head.
Regression of type and production traits on longevity traits indicated that PDM was the best predictor of LTP (R² = .28) and PCT 4 (R² = .12); however, the combined descriptive traits are the best predictor of PDL (R² = .12) and AGE (R² = .10). The best type indicators of longevity appeared to be dairy character, mammary system, udder quality, udder support and floor, teat site and placement, stature, fore udder, and rump. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/74119 |
| Date | January 1976 |
| Creators | Catron, Samuel Morton |
| Contributors | Dairy Science (Genetics) |
| Publisher | Virginia Polytechnic Institute and State University |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | en_US |
| Detected Language | English |
| Type | Thesis, Text |
| Format | viii, 84, [4] leaves., application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 9249614 |
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