Abstract
A significant change in the methods of progeny-testing dairy sires in recent years has been the discarding of daughter-dam comparisons in favour 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 3 of which have large sire-proving routines in regular operation.