Auswirkungen intensiven Wachstums auf Konstitutionsmerkmale in einer Mäuse-Auszuchtpopulation: Ein Vergleich von Lebensleistungsdaten der G 89/90 der 90er Jahre mit denen der G 8/9 der 60er Jahre

Abstract. Title of the paper: Effects of intensive growth on constitutional traits in a mouse outbred stock: comparison of life Performance results of G 89/90 in the 90,h with results of G 8/9 in the 60,h
Laboratory animal populations are characterised among other things by traits of their breeding Performance. The value of information of these traits is increasing with the amount per breeder of proofed litter Performances and is maximum, when it is possible to keep the animals over the time of reproduction- and lactation end until their natural end of lifetime.

The result ofa comparison of generations that is each done with 100 female breeders is that it was not possible to keep the mouse outbred stock on the same level of Performance (Constitution) within its meanwhile more than 40 years of breeding-history. The obviously all deciding trait is the animals' body weight (composition?), that has been increasing over more than 20% from a more intensive young animals' development up to over all Steps of old animals' ages. Higher fertility (litter size, litter interval with homogeneous first mating age in 49 days) and higher lactation Performance (litter weight development) are linked with such a shortened productive time that live Performance of the G 8/9 are not reached anymore. The age of live has decreased as well (78 in comparison to 100%). The breeding strategy has moreover stayed the same over the years. Therefore the supposed „improvements" in the environment, especially the mouse's nutrition, and the out of this following genotypeenvironment- interaction have to be seen as the main cause of the change of traits of the population. These common valid and therefore also for the agricultural productive livestock applying results emphasize, that by intensifying the especially growing and younger animals' nutrition, a shortening effect of the productive time and the lifetime has to be accepted.