Abstract
Abstract The New Zealand Dairy Board, in organising the genetic improvement of dairy cattle, has the objective of maximising net income per farm. For given farm conditions this is achieved by maximising net income per cow. Because of the problems associated with measuring net income for each cow, selection has been based on milkfat production per cow, but other traits are monitored to prevent their deterioration. The genetic studies of dairy cattle in New Zealand are summarised. Evidence of genetic progress in milkfat per cow is reviewed. The evidence includes a controlled experiment conducted at the Ruakura No. 2 dairy farm, the comparison of Premier Sires Service (PSS) progeny with the progeny of other bulls in tested herds, and a comparison between short- and long-term users of PSS using marker bull techniques. Evidence that genetic improvement per cow in milkfat production is being accompanied by improved productive efficiency is found from a comparison of 507 paired herds.
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