Journal or Book Title
Journal of Dairy Science
Daughters of sires selected on Predicted Difference milk of first lactations (yield) were compared with daughters of sires selected on an udder index from among artificial insemination bulls with less than 10% of their daughters culled and with a Predicted Difference fat-corrected milk greater than 181 kg (merit). On latest proofs yield bulls were 425 kg higher than merit bulls for Predicted Differences of first lactations, whereas merit bulls had an average Predicted Difference Type, which was 1 point higher than yield bulls. Data were from first calving interval.
Yield daughters produced 685 and 51 kg more milk and solids-not-fat but were .28% and .12% lower in fat and protein percentages than merit daughters. Energy intake of the ad libitum mix rations was nearly identical, but gross feed efficiency was significantly higher (.73 vs. .69) for yield daughters. Mammary conformation score was significantly higher for the merit group. A significantly higher number of merit daughters were coded acceptable for descriptive udder traits in the udder index. Net income per day was significantly higher for the yield group than for the merit group ($.25 vs. $.15). Much of this difference was due to the higher expense associated with a 21 day longer calving interval of merit heifers.
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Pearson, R. E.; Miller, R. H.; Smith, J. W.; Fulton, L. A.; Rothschild, Max F.; Balaine, D. S.; and Coffey, E. M., "Single and Multiple Trait Sire Selection. First Lactation Milk Yield and Composition, Conformation, Feed Intake, Efficiency, and Net Income" (1981). Animal Science Publications. 331.