Abstract

•* • * • asked by commercial poultry breed-ers is: How many breeding pens do I need to do a good job of breeding? The answer to this question would seem all the more pertinent at this time since Lerner and Dempster (1951) showed that nothing is gained, in fact something is lost, from a multiple shift scheme of sire testing, as compared to testing more thoroughly a single group of males. Thus, breeders with only a few breeding pens cannot expect to compensate for this apparent deficiency by using more males on those pens they do have available. On the other hand, the belief is apparently common among larger breeders that they are able to exert an enormous selection pressure because they have a large scale breeding operation with many breeding pens. Actually, the same percentage replacements are needed in a large flock as in a small one. Adding more pens to a breeding enter-prise can possibly affect breeding improve-ment four ways. First, more sires can be usgd., and hence a greater number of progeny tested sire and sire progeny groups will be available for selection. Sec-ond, J^er^jvill^^e^more ^ Jidl^jb__g>roup;s frorn ^ w^kh^Jajralv^elections can_bejnadg,.