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Rabbit is an induced ovulatory species, so ovulation takes place after mating. Traditionally, exogenous and synthetic hormonal factors (administered by intramuscular and intravaginal route) such as GnRH and analogues, or different physical procedures (i.e. stimulation by intravaginal cannula) have been used to induce ovulation in females when artificial insemination is applied in rabbit farms. Restriction and public rejection of the use of hormones is leading to the study of the seminal plasma components with potential action on ovulation induction. The aim of the present review is to collect and summarise the strategies used in recent years to trigger ovulation and improve rabbit fertility management with respect to more animal-friendly manipulation methods. Furthermore, special attention has been paid to the use of a semen component (as endogen molecule) such as beta nerve growth factor (β-NGF) in male and female rabbit reproductive physiology. This neurotrophin and its receptors (TrKA and p75NTR) are abundantly distributed in both male and female rabbit reproductive tracts, and it seems to have an important physiological role in sperm maturation and behaviour (velocity, apoptosis and capacitation), as well as a modulatory factor of ovulation. Endogen β-NGF is diluted in the seminal doses with the extenders; hence it could be considered an innovative and alternative strategy to avoid the current exogenous (by intramuscular route) and stressful hormonal treatments used in ovulation induction. Their addition in seminal dose could be more physiological and improve animal welfare in rabbit farms.

Zona pellucida (ZP), the extracellular matrix sheltering mammalian oocytes and embryos, is composed by 3 to 4 proteins. The roles of the three proteins present in mice have been elucidated by KO models, but the function of the fourth component (ZP4), present in all other eutherian mammals studied so far, has remained elusive. Herein, we report that ZP4 ablation impairs fertility in female rabbits. Ovulation, fertilization and in vitro development to blastocyst were not affected by ZP4 ablation. However, in vivo development is severely impaired in embryos covered by a ZP4-devoided zona, suggesting a defective ZP protective capacity in the absence of ZP4. ZP4-null ZP was significantly thinner, more permeable, and exhibited a more disorganized and fenestrated structure. The evolutionary conservation of ZP4 in other mammals, including humans, suggests that the structural properties conferred by this protein are required to ensure proper embryo sheltering during in vivo preimplantation development.

To analyse the effect of pasture availability and genotype on innate immunological status,morphological organisation of lymphoid follicles, behaviour, performance and carcass and meat characteristics, 80 growing rabbits (40 Leprino of Viterbo and 40 New Zealand White, NZW) were reared in bicellular standard cages (control) or in a wired pen, provided with an external grass pasture (pasture). Blood samples and behaviour observations (10 rabbits per group) were performed at different ages (weaning, 49 and 89 d). At the end of the trial, 10 rabbits per group were slaughtered to study meat quality/composition and vermiform appendix structure. Leprino rabbits showed higher serum lysozyme values than NZW for all ages and rearing systems. Leprino rabbits showed the highest values in caged animals (29.6 and 32.4 mg/mL, respectively at 49 and 89 d of age), while NZW animals did so in the pen (2.2 and 0.00 g/mL, respectively at 49 and 89 d of age). Haemolytic Complement Assay increased with age in Leprino (43.7 vs. 48.6 and 51.2 μg/mL, respectively for cage and pen), but decreased in NZW (68.6 vs. 25.8 and 41.1 μg/mL, respectively for cage and pen). Plasma TBARs was always higher in Leprino rabbits (16.0 vs. 7.0 μmol malondialdehyde/L at 29 d of age; 17.9 vs. 8.0 μmol malondialdehyde/L at 49 d of age; 20.0 vs. 11.4 μmol malondialdehyde/L at 89 d of age), whereas plasma tocopherol showed an inverse trend (32.9 vs. 46.6 mg/L at 29 d of age; 32.5 vs. 44.4 mg/L at 49 d of age; 31.2 vs. 42.4 mg/L at 89 d of age). Mortality rate of Leprino rabbits was highest in the cage system, while mortality was highest in NZW housed in the pen. Productive performance, carcass traits and fatty acid composition of meat were strongly affected by genotype and rearing system. Regarding genotype effect, Leprino showed lower daily gains (31.9 and 29.6 vs. 44.2 and 40.0 g, respectively for cage and pen system), live (2563 and 2418 vs. 2902 and 2650, respectively for cage and pen system) and carcass weights (1561 and 1465 vs. 1763 and 1580, respectively for cage and pen system). Pasture availability improved the meat nutritional quality and, in particular, the n-6/n-3 ratio was optimal and the total tocopherol content was suitable to assure a good oxidative stability.

The major goal of animal production is to obtain abundant and healthy meat for consumers. Maternal food restriction (MFR) is often applied in farms to reduce production costs. However, the suitability of MFR in livestock animals is questionable, as this management may compromise maternal fitness due to a severe negative energetic balance and can induce Intrauterine Growth Restriction (IUGR) and prenatal programming in the offspring. Here, we sought to determine, using pregnant rabbits, the consequences of MFR on maternal endocrine and metabolic status and conceptus development. Pregnant dams were distributed into three groups: CONTROL (ad libitum feeding throughout the entire pregnancy; mean pregnancy length being around 31 days), UNDERFED (50% MFR during the entire pregnancy) and EARLY-UNDERFED (50% MFR only during the preimplantation period, Days 0-7). Maternal leptin concentrations and glycemic and lipid profiles were determined throughout pregnancy, whilst conceptus development was assessed ex-vivo at Day 28. Placental parameters were determined by macroscopic and histological evaluations and apoptotic assessments (TUNEL and Caspase-3). The main results of the study showed that, despite MFR altered maternal plasma lipid concentration (P