Progeny testing with auxiliary traits.

The problem of determining the breeding worth of a male on the basis of the phenotypic values of his female progeny is discussed. The use of one or more auxiliary traits in conjunction with the main trait for progeny testing seems to have an edge over the conventional method in which no auxiliary traits are used. A general expression for the accuracy of selection based on the progeny test is derived and a generalised sire index is proposed. Detailed numerical investigation with one auxiliary trait reveals that the accuracy of the progeny test in such a case is always increased. The maximum gain in accuracy is found when the phenotypic and additive genetic correlations between the main and the auxiliary traits are of opposite signs. The number of progeny required to attain a pre-assigned value of accuracy is determined for several cases. It is found that the use of auxiliary trait reduces this number resulting in decreased cost of the progeny testing programme. The effect of the number of auxiliary traits on the gain in accuracy is also studied under some simplified situations.