Part Lactations. III. Progeny Testing with Part Lactation Records

Journal of Dairy Science (Impact Factor: 2.55). 05/1961; 44(5):921-927. DOI: 10.3168/jds.S0022-0302(61)89833-0

ABSTRACT Analyses of monthly records of artificially-bred cows indicate that under New Zealand conditions records accumulated up to a specified test day early in lactation are suitable for progeny testing. Heritability slightly exceeds that for lactation yield and the genetic correlation between the part record and lactation yield exceeds 0.90. As a result, the rate of progress in improving additive genetic merit for lactation yield when selecting on part records differs very little from when selecting on lactation yield. Approximately 40, 60, and 80 daughters in sire proofs using part records give the same information about lactation yield as a proof using lactation yield on 30, 40, and 50 daughters, respectively. Proofs evaluated on both kinds of records for the same group of sires were highly correlated and the part lactation proofs were just as repeatable as those based on lactation yields.

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    ABSTRACT: A significant change in the methods of progeny-testing dairy sires in recent years has been the discarding of daughter-dam comparisons in favor of comparing daughters with their herd-mates. These involve comparing records of daughters with those of their herd-mates made in the same year, and as such are often referred to as contemporary comparisons, or sometimes as stable-mate comparisons. They were first used on a widespread scale in New Zealand in 1950, with refinements added in 1957. They were introduced in Great Britain in 1954 and were also being used in New York State at about the same time. This paper discusses some of the underlying principles of progeny-testing based on such contemporary comparisons, and presents details of the methods used in these places, all three of which have large sire-proving routines in regular operation.
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