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The Number of Proved Sons Necessary to Evaluate the Transmitting Ability of a Dairy Sire^1,2

West Virginia University, Morgantown

ABSTRACT

A total of 174 Holstein-Friesian sires with eight or more D.H.I.A.-proved sons was studied to determine the least number of proved sons necessary to estimate accurately the performance of those to be proved later. The results showed that the average butterfat production of the sons' daughters increased as more sons were proven, a tendency that also was reflected in greater daughters' fat difference as compared to their dams. This increase probably was due more to environmental than genetic causes.

Highly significant correlations (r = 0.46 to 0.62) indicated that the average butterfat production of the daughters of the first three or four sons was nearly as accurate as data on more sons in estimating the average butterfat production of the daughters of the next five or ten proved sons.

Similarly, the significant correlations (r=0.19 to 0.31) for the sons' daughters' average increase or decrease in butterfat production from their dams indicated that data on the first three or four proved sons were nearly as accurate as data on a larger number in predicting what might be expected from the next five or ten proved sons in this respect.

The correlations for per cent sons improving production were lower than those for fat level or fat difference. Figures on the first three or four sons were as accurate as data on a larger number of sons in predicting percentage of improvers in the next five or ten proved sons.

¹ The data in this paper are from a thesis submitted by the senior author to the Graduate School of West Virginia University in partial fulfillment of the degree of Master of Science, 1949.

² Published with the approval of the Director of the West Virginia Agricultural Experiment Station as Scientific Paper no. 415.

³ Now Cattaraugus County Agricultural Agent, Salamanca, New York.