[Selection of laboratory rats for fertility components in synchronized estrus using Suisychron-Praemix. 1. Effects of...

The following results were obtained from experimental studies into effects of selection for fertility and into synchronised oestrus though eight generations of laboratory rats: -- The result of selection recordable from the population with selection only was better than that recorded from the population with selection and synchronised oestrus. This has been attributed to higher correlation between phenotype and genotype in the selection variant. -- Direct negative impact of synchronised oestrus on selection index was recorded from a population with random mating. -- The effects of synchronised oestrus regarding selection success were offset but not entirely ruled out by selection. -- Through the generations of both populations with synchronised oestrus the effects of synchronisation were lowered due to both physiological adaptation to Suisynchron application and contraselection with regard to suitability for synchronisation.