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The present study in rabbits compared, in the first experiment, the effect of two commonly used oocyte ages, 13 h and 17 h after ovulation induction treatment, on the technical efficiency of somatic nuclear transfer steps, using fresh cumulus cells as nuclear donors. Recently ovulated metaphase II oocytes (13 h) showed higher fusion (13 h: 83% vs 17 h: 67%, p < 0.05) and in vitro development rates than in vivo slightly aged metaphase II oocytes (morula, 13 h: 74% vs 17 h: 25%, p < 0.05; blastocyst, 13 h: 16% vs 17 h: 8%; p < 0.05). In contrast, activation rate was higher in the 17 h group (13 h: 45% vs 17 h: 67%; p < 0.05). In a second experiment, using recently ovulated oocytes (13 h) as recipients, two donor cell types (from primary cultures of either cumulus cells or fetal fibroblasts) were tested to evaluate their effects on the efficiencies of the different technical steps of somatic nuclear transfer procedure. A better fusion rate was obtained when fetal fibroblasts were used as nuclear donors (cumulus cells: 45% vs fetal fibroblasts: 67%, p < 0.05). No statistically significant differences were detected in cleavage rate regardless of the cell type used (cumulus cells: 44% vs fetal fibroblasts: 60%, p > 0.05). However, in vitro development to morula (cumulus cells: 41% vs fetal fibroblasts: 14%, p < 0.05) and to blastocyst stage (cumulus cells: 27% vs fetal fibroblasts: 3%, p < 0.05) were different between cell types.

Summary Litter size traits of a maternal line of meat rabbits, line H, founded by selecting on hyperprolificacy, were studied to check its prolificacy. Due to health problems related to the putting together of animals with different origins and to the genetic heterogeneity of the commercial population from which the new line (line H) was founded, line H was compared to the best maternal line available (line V) and with crossbred does (A × V) of high litter size. The comparison took place on four farms and involved 858 females. The analysis of litter size traits showed that line H had superior prolificacy compared with crossbred females and the average of line V and crossbred females, which was around 0.5–0.8 young (p < 0.05). The contrasts between line H and line V were always favourable to line H, by around 0.5 pups, but were not significant (p = 0.06). The differences between the two lines, however, changed with parity order: they were null for first and second parity but reached values of one young and even more for superior parity orders. The differences in prolificacy did not have consequences on the fertility of the females as there were no differences in kindling interval for the animals studied. It can be concluded that hyperprolific selection has been successful in rabbits, and the new line could play an important role as a maternal line in rabbit production for meat. Zusammenfassung Leistung fruchtbarer Kaninchenlinien. I. Wurfgrößenmerkale, Wurfgrößenmerkale der maternalen Linie H von Mastkaninchen, selektiert auf hohe Fruchtbarkeit, wurden überprüft. Aufgrund hygienischer Bedenken bei Zusammengühren kommerzieller Herkünfte konnte sie nur mit der verfüfbaren Mutterlinie V vergliche werden sowie mit entsprechenden Kreuzungen (A × V). Die Untersuchung umfaßte 858 Muttertiere auf 4 Betrieben. Wurfgröße von H war Kreuzungen und Linie V um ca. 0.5 bis 0.8 Junge überlegen. Kontraste mit Linie V bgünstigten immer Linie H, um ca. 0.5 Junge. (p < 0.06). Die Linienunterschiede änderten sich mit Wurffolge ‐ null bei ersten bis au 1 bei späten Würfen. Die Fruchtbarkeit war durch größere Würfe nicht beeinträchtigt, das Zwischenwurfintervall änderte sich nicht. Selektion auf Wurfgröße ist bei Kaninchen erfolgreich und die neue Linie sollte in der Kaninchenmast eine wichtige Rolle spielen. Resumen Se estudiaron los caracteres de prolificidad en una nueva IRnea de conejo de carne fundada aplicando un esquema de selección por hiperprolificidad. La nueva línea (línea H) se comparó con dos tipos de animales de prolificidad superior a la población a partir de la cuál se fundó (línea V y hembra cruzada A×V). El experimento se realizò en cuatro granjas e involucró a 858 hembras. El análisis de la prolificidad indica que la línea H fue superior en 0.5–0.8 gazapos al cruce A×V y al promedio de la línea V con la hembra cruzada. Los contrastes entre la línea H y la línea V fueron siempre favorables a la línea H, en torno a 0.5 gazapos, aunque no resultaron significativos (p = 0.06). Al analizar la prolificidad en función del or...