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In some induced-ovulating species, beta nerve growth factor (β-NGF) has important roles in ovulation, though data for rabbits are still inconclusive. In this study we first synthesized functional recombinant β-NGF from rabbit tissue (rrβ-NGF) to address the following objectives: 1) to compare rabbit β-NGF amino acid sequence with those of other induced- or spontaneous-ovulating species; 2) to assess the effects of rrβ-NGF on rabbit sperm viability and motility, and 3) to examine the in vivo ovulation inducing effect of rrβ-NGF added to the seminal dose in rabbit does. The NGF gene in rabbit prostate tissue was sequenced by Rapid Amplification of cDNA Ends and annotated in GenBank (KX528686). Recombinant rβ-NGF was produced in CHO cells and purified by affinity chromatography. Once confirmed by Western blotting and mass spectrometry (MALDI-TOF) that the amino acid sequence of the recombinant protein corresponded to β-NGF, its functionality was validated in PC12 cells in a successful dose-response study over 8 days. The amino acid sequence of prostate rabbit NGF differed to that of other species mainly in its receptor binding sites. In all the spontaneous ovulating species examined, compared with rabbit, alanine and proline residues, which interact with the high-affinity receptor, were replaced by a serine. In rabbits, asparagine and methionine were substituted by lysine at the low-affinity receptor binding site. In time- and dose-response experiments, the in vitro addition of rrβ-NGF to the ejaculate did not affect sperm viability whereas sperm motility parameters were enhanced by the addition of 1 μg/mL of the neuropeptide. Addition of this same concentration of rrβ-NGF to the seminal dose administered via the intravaginal route in does induced ovulation with a delayed LH peak, leading to a plasma progesterone increase, gestation and delivery. Our findings suggest that rrβ-NGF could be a useful option for biotechnological and reproduction assisted techniques in rabb

This study reports the gene expression and immunolocalization of the low-affinity neurotrophin receptor, p75, in accessory glands (prostate and bulbourethral glands) and epididymis (caput and cauda) of male rabbits during sexual maturation. We showed that p75 was expressed in all tissues studied with similar mRNA levels during this period. However, it was differentially immunolocalized in bulbourethral glands and stereocilia of epididymis. These findings may be related with some remodeling processes in the accessory glands during sexual maturation, which could be associated with sperm maturation. The interaction of p75 with neurotrophins in rabbit male reproductive tract suggests the possible implication of this system in sexual maturation in rabbits.

This work attempts to confirm the effect of an enriched diet with n-3 polyunsaturated fatty acids (PUFA) trying to mitigate the reproductive performances issues such as low conception rate of primiparous rabbits. A total of 127 does were fed ad libitum throughout their two first cycles with two diets with different fat sources: mixed fat in the control and salmon oil in the enriched one, with 3.19 g/100 g (n=63 does) and 28.77 g/100 g (n=64 does) of n-3 of the total fatty acid, respectively. Feed intake was similar between groups ( P>0.05). Plasma progesterone concentration was higher in the enriched females than in control ones at 7 (30.9 ± 2.18 v. 23.9 ± 2.30 ng/ml, respectively; P= 0.029) and 14 (38.7 ± 2.18 v. 28.2 ± 2.30 ng/ml, respectively; P=0.001) days of first gestation. Considering both cycles, reproductive parameters of mothers (fertility, duration of gestation and prolificacy) and litter parameters (weight at parturition and weaning, mortality and average daily gain (ADG) of kits during lactation) were similar in both groups. However, individual measurements of neonates of enriched group improved 5.87%, 7.10% and 18.01% ( P 0.05), but embryo apoptosis rate was higher in control group than in enriched one (31.1 ± 4.56% v. 17.1 ± 3.87%, respectively; P < 0.05). In conclusion, dietary PUFA enrichment from the rearing and throughout two productive cycles improved plasma progesterone during pregnancy, fertility, milk fatty acid profile and neonates development of primiparous supporting the beneficial effect of n-3 PUFA supplementation in rabbit does.

The developmental competence of in vitro maturation (IVM) oocytes can be enhanced by antioxidant agents. The present study investigated, for the first time in the rabbit model, the effect of adding a-tocopherol (0, 100, 200 and 400 mM) during IVM on putative transcripts involved in antioxidant defence (superoxide dismutase 2, mitochondrial (SOD2), glutathione peroxidase 1 (GPX1), catalase (CAT)), cell cycle regulation and apoptosis cascade (apoptosistumour protein 53 (TP53), caspase 3, apoptosis-related cysteine protease (CASP3)), cell cycle progression (cellular cycle V-Akt murine thymoma viral oncogene homologue 1 (AKT1)), cumulus expansion (gap junction protein, alpha 1, 43 kDa (GJA1) and prostaglandin-endoperoxide synthase 2 (prostaglandin G/H synthase and cyclo-oxygenase) (PTGS2)) and metabolism (glucose-6-phosphate dehydrogenase (G6PD)). Meiotic progression, mitochondrial reallocation, cumulus cell apoptosis and the developmental competence of oocytes after IVF were also assessed. Expression of SOD2, CAT, TP53, CASP3 and GJA1 was downregulated in cumulus–oocyte complexes (COCs) after IVM with 100 mM a-tocopherol compared with the group without the antioxidant. The apoptotic rate and the percentage of a non-migrated mitochondrial pattern were lower in COCs cultured with 100 mM a-tocopherol, consistent with better-quality oocytes. In fact, early embryo development was improved when 100 mM a-tocopherol was included in the IVM medium, but remained low compared with in vivomatured oocytes. In conclusion, the addition of 100 mM a-tocopherol to the maturation medium is a suitable approach to manage oxidative stress and apoptosis, as well as for increasing the in vitro developmental competence of rabbit oocytes.

The neurotrophin b-nerve growth factor (NGF) has been described as an important mediator of seminal plasma-induced ovulation in reflexive ovulators like camelids, but this action has not been evidenced in rabbits. In this study, the mRNA expression of NGF was analysed in rabbit male organs by PCR and in a purified basic fraction of seminal plasma by liquid chromatography mass spectrometry. Besides, the ovulatory response [ovulation rate (OR), corpora lutea number, LH peak and progesterone profile] of 27 rabbit does was recorded after injection with murine NGF, gonadoreline (GnRH) or saline solution (SS). An empty catheter was introduced through the vagina (n ¼ 4 animals per group) to simulate the nervous/mechanical stimulus of coitus. Molecular studies confirmed the expression of b-NGF mRNA in the prostate, seminal gland and testicles of male adult rabbits, and the presence of the protein in seminal plasma. For the in vivo experiment, all GnRH-group does exhibited a significantly higher OR (100%) compared to females treated with NGF (30%) and SS (25%), who showed significantly lower LH and progesterone concentrations at 120 min. However, in the non-vaginally stimulated animals, only the gonadoreline group ovulated properly, since no ovulation was recorded in the SS group, and only 17% of the NGF does ovulated; this was associated to a tendency to a higher rate of anovulatory haemorrhagic follicles. mRNA expression of NGF and its presence in seminal plasma evidence a role in rabbit reproduction. Nevertheless, murine NGF triggered some stimulatory effect in the females but not enough to elicit a significant ovulatory response.

The aim of the present study was to evaluate the productive, endocrine, and metabolic responses as well as oxidative stress of rabbit does and their offspring when fed a diet supplemented with n -3 PUFA during their first productive cycle. To this aim, a total of 105 rabbit does were fed ad libitum from d 60 to 172 of age 2 isoenergetic and isoproteic diets dif - fering in fatty acid composition. The control diet ( n = 52 does) contained 45.9 g/kg of n -3 of the total fatty acids and the enriched diet ( n = 53 does) contained 149.2 g/kg of n -3 of the total fatty acids. Both experi - mental groups had similar feed intake during rearing, pregnancy, and lactation. The enrichment of diet had no effect on ultrasonographic assessment of does on d 9 and 16 of pregnancy, with an embryonic vesicle number and fetus and placenta size similar between groups ( P > 0.05). Even though there were no major effects ( P > 0.05) on fertility, duration of gestation, and number born alive and stillborn kits at parturition, live kits from enriched does were longer (71.6 ± 2.42 vs. 79.5 ± 2.13 mm; P < 0.05) and tended to be heavier (42.5 ± 3.94 vs. 50.8 ± 3.47 g; P = 0.07) than those from control does ( P < 0.05). The 2 groups had similar milk production and mortality values during lacta - tion; consequently, there were no differences between diets in ADG, litter weight, and number of weaned kits ( P > 0.05). In enriched does, higher plasma leptin and estradiol concentrations than in control does ( P < 0.05) were observed. In addition, enriched females also had lower total and high-density lipoprotein cho - lesterol (HDL-c) than control females during lactation ( P < 0.05). Regarding offspring, the enrichment of diet with PUFA caused a hyperlipidemic status (greater values of plasma triglycerides, total cholesterol, and HDL-c; P < 0.05) at 1 d postpartum (dpp), compared with the control group, that disappeared at 32 dpp. Supplemented does before parturition and their off - spring at 1 dpp

The present study evaluated the effectiveness of sildenafil citrate (SC) to improve placental and fetal growth in a diet-induced rabbit model of intrauterine growth restriction (IUGR). Pregnant rabbits were fed either ad libitum (Group C) or restricted to 50% of dietary requirements (Group R) or restricted and treated with SC (Group SC). The treatment with SC improved placental development by increasing vascularity and vessel hypertrophy in the decidua. The assessment of feto–placental haemodynamics showed higher resistance and pulsatility indices at the middle cerebral artery (MCA) in fetuses treated with SC when compared with Group R, which had increased systolic peak and time-averaged mean velocities at the MCA. Furthermore, fetuses in the SC group had significantly higher biparietal and thoracic diameters and longer crown–rump lengths than fetuses in Group R. Hence, the SC group had a reduced IUGR rate and a higher kit size at birth compared with Group R. In conclusion, SC may provide potential benefits in pregnancies with placental insufficiency and IUGR, partially counteracting the negative effects of food restriction on placental development and fetal growth. However, the present study also found evidence of a possible blood overflow in the brain that warrants further investigation.

El conejo ibicenco o conill pagès d’Eivissa es una población originaria de esta isla que actualmente presenta un escaso número de efectivos, ya que está siendo desplazada por otras razas con mayores rendimientos productivos. La conservación de este tipo de poblaciones precisa de la creación de bancos de germoplasma, con lo que es necesario establecer primeramente sus características reproductivas. Por ello, el objetivo del presente trabajo ha sido caracterizar algunos parámetros reproductivos de hembras ibicencas y compararlos con el cruce comercial de California x Neozelandés blanco, que es el habitualmente utilizado en cunicultura para producción. La fertilidad obtenida fue similar en ambos grupos, siendo de un 76,8% y de un 81,3% para las conejas híbridas e ibicencas, respectivamente. La prolificidad, el peso de la camada a 21 días de vida, la producción de leche, el número de gazapos destetados, el peso de la camada al destete y su ganancia media diaria fue superior en los cruces comerciales que en la población ibicenca, presentando ésta última una mayor duración de la gestación y un mayor peso individual al destete. Los ibicencos tardaron un par de días más en alcanzar el peso de sacrificio que los híbridos comerciales, puesto que su ganancia media diaria fue menor y el índice de conversión fue siempre superior, salvo en la última semana que disminuyó y se equiparó al de los híbridos. Respecto a los parámetros endocrinos, tanto las concentraciones de LH como las de progesterona post-ovulación fueron superiores para las hembras híbridas comerciales. finalmente, los datos de caracterización de la respuesta ovárica muestran que las hembras de cruce comercial presentaron un mayor número de folículos preovulatorios y de oocitos por ovario, así como un mayor número de cuerpos lúteos y embriones recuperados, que presentaron además una mayor velocidad de desarrollo embrionario, que las ibicencas. Por tanto, se ha comprobado experimentalmente que el conejo ibicenco, al