HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Lush, J. L. Articles by Arnold, F. Search for Related Content PubMed Articles by Lush, J. L. Articles by Arnold, F.

Effects which Selection of Dams may have on Sire Indexes^*

ABSTRACT

Several studies (1, 2, 3, 4, 5, 8) have shown that when the mates of a bull are divided into a high group and a low group on the basis of their own records, the average difference between the daughters of the two groups is less than half the difference between the two groups of dams. For example in Edwards' study (3) where the mates of each of 23 bulls were divided into a high half and a low half on the basis of the mate's own milk record, the low half averaged 7,513 and the high half 10,369, a difference of 2,856 pounds. But the daughters of these two groups averaged 7,835 and 8,427, a difference of only 592 pounds, which is barely one-fifth the difference between the two groups of dams.

If offspring were always mid-way between the phenotypes of their parents regardless of how the parents were selected, or if the offspring deviated individually from that only in a random way, the average difference between two groups of daughters by the same sire would tend to be half as large as the average difference between their darns (9).

^* Journal Paper No. J-866 of the Iowa Agricultural Experiment Station, Ames, Iowa. Project No. 317.