Effects of a lignin-rich fibre diet on productive, reproductive and endocrine parameters in nulliparous rabbit does

In rabbits, modifications in dietary composition may be associated with reproductive benefits. However, the influence of nutrition on ovarian function and embryo development is poorly known in this species. The goal of this work was to study the short-term effects of feeding high-fibre diets with different levels of lignin during the rearing period on productive, endocrine and reproductive parameters of nulliparous rabbit does. A total of 95 New Zealand × California 11-week-old nulliparous white rabbits were randomly allocated in two experimental groups fed ad libitum fibre-rich diets with a high lignin content (HL group: NDF 49.6% of DM, LAD 15.8% of DM; n = 48) or a standard lignin content (SL group: NDF 40.9% of DM, LAD 4.9% of DM; n = 47). All animals were artificially inseminated (AI) at 16 weeks of age. Daily feed intake and live body weight (LBW) were recorded during the rearing period. Conception rate and prolificacy were also determined. In addition, in ten animals of each group, body composition, serum estradiol 17β (E2), progesterone (P4) and leptin levels, as well as reproductive parameters including ovary weight, follicular population, ovulation rate, in vitro oocyte maturation (IVM), blastocyst recovery rate and in vitro embryo development were studied at AI time. Animals fed the HL diet had a significantly higher feed intake until the first AI (P < 0.003) and during the first pregnancy (P < 0.03). At 16 weeks of age, animals fed the HL diet had a lower content of lipids (P < 0.05) and crude energy (P < 0.05) than those fed the SL diet, but average LBW of does, ovary weight, and ovulation rate per doe were similar between HL and SL treatments. No significant differences were found in P4 levels. However, the HL group had elevated E2 serum levels (P < 0.003) compared to those fed with the SL diet, whereas antral follicular population was similar between groups. Both nuclear and cytoplasmic IVM measured as metaphase II and cortical granule migration rates were also similar between both groups. In addition, no differences in blastocyst recovery rate or in prolificacy were found. However, mean serum leptin levels (P < 0.05), in vitro embryo development (P < 0.03), and fertility rate (P < 0.02) were higher in the SL group compared to the HL group. In conclusion, the HL diet enhanced feed intake of does, but reduced serum leptin levels at AI time, in vitro embryo survival and conception rate.