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Utilizing Both Part and Complete Daughter Records in Sire Evaluation

1961; Elsevier BV; Volume: 44; Issue: 11 Linguagem: Inglês

10.3168/jds.s0022-0302(61)90020-0

1529-9066

L.D. Van Vleck, Charles Henderson,

Folklore, Mythology, and Literature Studies

A three-stage program for evaluating sires used in artificial insemination is proposed.The first stage consists of acceptance or rejection of sires based on the part-lactation (5-too.)records of their daughters.The second stage utilizes both part records and complete records of other daughters.The third and final stage provides for evaluation dependent on complete records alone.Selection index equations are presented for estimating the breeding value of sires for these combinations of information.The correlations between estimated and true breeding value are given in an example which illustrates the additional knowledge available in evaluating sires when part records are utilized.For example, ten 5-mo.records have the expected correlation with true breeding value of 0.58, as opposed to 0.00 if only complete records are used; 20, 5-too.records, a correlation of 0.69 as opposed to 0.00; 20, 5-mo.and ten complete records~ 0.78 as opposed to 0.61; and ten 5-too.and 20 complete records, 0.79 as opposed to 0.74.The procedures used for sampling A.I. (artificial insemination) sires follow a familiar pattern.A young, untested bull is placed in service until enough cows are mated so that 40-50 daughters will eventually have records (in a central processing laboratory) available for evaluating the sire's breeding value for milk production.Then the sire is retired from service until a proof is completed.Recent research, Madden et al.(5), Searle (7), and VanVleck and Henderson (9), has shown the existence of high genetic relationships between individual monthly records and complete production records, and between cumulative monthly records (especially, five or more months in length) and complete records.These results have indicated the possibility of preliminary selection of A.I. sires on the basis of part records.In nearly all instances of sampling of young sires, a sizable number of 5-mo.daughter records would be available before any or only a few daughter lactations are completed.Intuitively, it would seem reasonable that sires with high genetic merit for milk production could be selected to return to service Oll the basis of 5-too.records of their daughters.Equally as intuitive would be culling of inferior sires.This reduction in generation interval could, in itself, increase the rate of genetic progress.If the average length of time from the sample inseminations until complete daughter records are centrally processed is 50 too., then the rate of genetic progress would be increased about 10%, if all the sire selection decisions are made on the basis of 5-mo.records, or about 5% if one-half the decisions are made on 5-too.records, over that accomplished by selection based entirely on complete records.This result requires that the accuracy of prediction is equal in both cases.The reduction in number of sires held out of service could de-l~eceived for publication