This study investigated the effect of daily oral administration with allicin levels (0, 5 and 10 mg/kg of female body weight), 30 days pre‐insemination, on reproductive performance in vivo and in vitro, immunity, and oxidative stress of rabbit does under high ambient temperature. Niliparous NZW does (n = 105) were randomly divided into three groups (35 in each) treated with 0, 5 and 10 mg allicin dissolved in 2 ml distilled water, respectively, for 30 days pre‐insemination. At the end of treatment (30 days), does were artificially inseminated with fresh diluted semen of 20 fertile NZW bucks. Reproductive performance and ovulatory response parameters were determined. Serum biochemicals, enzyme activity, immunoglobulins (IgG and IgM) and antioxidant status were determined on day 30 of treatment. Serum progesterone and prolactin were determined pre‐insemination (30 days of treatment), on 15 days of pregnancy and 7 days post‐partum. Results showed that both allicin levels increased live litter size, and bunny viability rat and litter size at birth and weaning. Allicin levels increased ovulation rate and improved embryo quality. Number of total follicles decreased only with 10 mg allicin. Progesterone increased pre‐insemination, 15 days of pregnancy and 7 days post‐partum progesterone by allicin levels. Prolactin pre‐insemination and on day 7 post‐partum increased with 10 mg allicin. Serum total proteins, albumin, globulin, IgG and IgM increased, while glucose, aspartate and alanine aminotransaminases, and thiobarbituric acid reaction decreased by both allicin levels. In conclusion, the mechanism by which allicin administration 30 days pre‐insemination to improve the reproductive performance of rabbit does is based on that allicin can play an important role, as a natural exogenous antioxidant, increasing immune response and reducing lipid peroxidation.

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l‐Carnitine (LC) is considered to be a natural antioxidant agent that could be used to improve the efficiency of reproduction. However, the precise machinery of the effect of LC supplementation on frozen–thawed rabbit sperm has not been evaluated. Thus, the aim of this study was to evaluate the effect of the addition of LC to a freezing medium on parameters and ultrastructure changes in frozen–thawed rabbit sperm. Rabbit bucks (7 months of age) were involved, and semen was collected using the artificial vagina method. Pooled rabbit semen was cryopreserved in a tris yolk fructose extender without any supplement (LC0, control group) or with LC at levels of 1, 2 or 4 mM (LC1, LC2 and LC4, respectively). The samples were then loaded into 0.25‐ml straws and frozen over liquid nitrogen vapours before being plunged into the liquid nitrogen and stored at −196°C until evaluation. Data showed that the addition of LC significantly increased sperm motility, viability and membrane function, while sperm abnormalities decreased (p < .001). Sperm‐like apoptosis (early, late and necrosis spermatozoa) was lower in the LC4 group compared with the other groups. l‐Carnitine addition significantly enhanced the total antioxidant capacity and superoxide dismutase and glutathione peroxide activities and significantly reduced the protein carbonyl and malondialdehyde levels compared with the control group. Moreover, electron microscopy images demonstrated that LC addition (2 or 4 mM) preserved the acrosome and plasma membrane and protected the ultrastructure integrity of the cryopreserved spermatozoa in relation to the control group. Spermatozoa treated with LC exhibited higher mitochondria membrane potential (MMP) values compared with the control group. We conclude that the addition of LC (4 mM) to the freezing extender enhanced the quality, increased the antioxidant capabilities, preserved the ultrastructure integrity and reduced lipid and protein peroxidation as well as increased MMP activity of frozen–thawed rabbit sperm.

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Objective: The potentiality of extra virgin olive oil (EVOO), betaine (BET) and ginger (GIN), as a natural antioxidant, to reduce negative effects of heat stress on physiological responses, antioxidant capacity, semen quality and fertility of bucks under heat stress were investigated.Methods: Forty adult APRI line rabbit bucks were distributed randomly into four experimental treatments of ten rabbits each. The first treatment was fed the commercial pellet diet (CPD) without supplementation and served as a control. The other three treatments were fed CPD supplemented with EVOO (300 mg), BET (1000 mg) and GIN (200 mg) per kg diet for 3 consecutive months during the summer season.Results: Supplementation of EVOO, BET or GIN improved (p< 0.05) the sexual desire, progressive motility, vitality, intact acrosome and membrane integrity, sperm cell concentration, sperm outputs and fertility. Seminal plasma total proteins, globulin, total antioxidant capacity, glutathione and glutathione S-transferase, and initial fructose increased (p< 0.05), while total lipids, aspartate and alanine aminotransferases and malondialdehyde decreased (p< 0.05) compared with the control. In comparing the natural antioxidants treatments, GIN evoked the largest improvement. Conclusion:The inclusion of GIN (200 mg/kg diet) as a useful agent for improving the sexual desire, semen quality and oxidative stress of bucks. This may be a beneficial supplement for the management of rabbit bucks used in natural mating or artificial insemination.

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Exposing rabbits to some environmental stresses, particularly heat stress (HS) for long periods, affects their productivity, causing large economic losses (Ayyat, Al-Sagheer, Abd El-Latif, & Khalil, 2018). Under HS conditions, the changes in blood biochemicals and physiological parameters can potentially boost free radicals. These radicals may elevate the production of reactive oxygen species, ROS; resulting in lipid peroxidation, which induce cellular oxidative stress (OS); causing loss of animal welfare and productive ability

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