DIVERGENT SELECTION FOR LONGEVITY IN BREEDING DOES

A divergent selection for functional longevity, based on genetic merit estimated through survival analysis techniques, was carried out in the INRA 1077 rabbit line. The experiment was carried out to estimate the efficiency of such a selection and to analyse the consequences on other reproduction traits. Given the herd management, length of productive life was measured as the number of artificial inseminations of rabbit does without any culling for infertility. A total of 48 males were progeny tested based on the longevity of ten daughters (5 in the INRA SAGA farm and 5 in the INRA EASM farm). Based on their estimated genetic merit, 5 “high longevity ” and 5 “low longevity ” males were selected and produced a new generation (5 sons/sire). These 48 males were similarly progeny tested to estimate the direct and correlated responses to selection. A significant difference in longevity (+0.92 AI i.e. 39 days) was observed between the two lines. The differences of survival between the 2 lines in the SAGA farm were mainly due to culling (26 % in the low line vs. 14 % in the high line) whereas the mortality was similar in the 2 lines. In the EASM farm, mortality and culling were both higher in the low line than in the high line (33 % vs. 15 % and 19 % vs. 7%, respectively). Except for the total number born which was higher in the low line, there was no difference between the two lines for reproduction traits recorded for each kindling. Nevertheless, because of the difference in the number of litters between the 2 lines, the sum of young rabbits born alive per doe and the sum of young rabbits weaned per doe were higher in the high line (+5 kits)