Physiological and immunological aspects of feed restriction and its beneficial impacts in fattening rabbits' productivity-an updated review.

Two feed restriction (FR) regimens are utilized with weaned rabbits including a quantitative FR (amount-limited feed or time-restricted admission to feed) and a qualitative FR (modulation of diet content especially protein and energy). The use of post-weaning FR may help in preventing post-weaning digestive disorders, stimulating compensating growth, improving feed efficiency, and decreasing carcass fat content. Interestingly, FR may contribute to changing meat's chemical composition and its physical quality attributes by regulating the morphological and biochemical characteristics of muscle fibers. Also, FR could enhance the gastrointestinal tract development, its histomorphology, and improve feed digestibility and absorption. Furthermore, FR regimens are involved in establishing gut microbial balance and enhancing the host immunological response. It might be concluded that post-weaning FR is involved in influencing the physiological and immunological aspects of growing rabbits. It might be documented that light to mild FR (i.e., 80-90% AL), early (i.e., at the first 2 weeks post-weaning), and relatively short in duration (i.e., for 2-3 weeks) had no negative effects on live body weight, while severing FR reduced live body weight in comparison with ad libitum rabbits.

A single introduction of wild rabbits triggered the biological invasion of Australia.

Biological invasions are a major cause of environmental and economic disruption. While ecological factors are key determinants of their success, the role of genetics has been more challenging to demonstrate. The colonization of Australia by the European rabbit is one of the most iconic and devastating biological invasions in recorded history. Here, we show that despite numerous introductions over a 70-y period, this invasion was triggered by a single release of a few animals that spread thousands of kilometers across the continent. We found genetic support for historical accounts that these were English rabbits imported in 1859 by a settler named Thomas Austin and traced the origin of the invasive population back to his birthplace in England. We also find evidence of additional introductions that established local populations but have not spread geographically. Combining genomic and historical data we show that, contrary to the earlier introductions, which consisted mostly of domestic animals, the invasive rabbits had wild ancestry. In New Zealand and Tasmania, rabbits also became a pest several decades after being introduced. We argue that the common denominator of these invasions was the arrival of a new genotype that was better adapted to the natural environment. These findings demonstrate how the genetic composition of invasive individuals can determine the success of an introduction and provide a mechanism by which multiple introductions can be required for a biological invasion.

Owner demographic factors are associated with suitable pet rabbit housing provision in the United Kingdom.

BACKGROUND: Rabbits are popular pets, but research into their welfare is limited. This study analysed the potential association(s) between the provision of suitable housing and owner demographic factors. METHODS: Data from 2017, 2018 and 2019 PDSA Animal Wellbeing (PAW) report surveys gave a sample of 1333 UK rabbit owners. Whether the rabbit housing was adequate or inadequate was ascertained by asking owners to indicate images of hutch and run size or indoor environment type that were similar to their own. The owner demographic factors collected included gender, education, household income and deprivation. Chi-squared tests and binary logistic regression (univariable and multivariable) were used to investigate factors associated with adequate/inadequate housing. RESULTS: One-third (31.2%) of rabbits lived in inadequate housing and half were housed alone (51.4%). Male owners were more likely to report providing inadequate housing than females (odds ratio [OR] = 1.795, 95% confidence interval [CI] 1.319-2.441, p < 0.001). Compared to owners over 55 years old, those aged 25-34 years were more likely to house their rabbits inadequately (OR = 2.050, 95% CI 1.286-3.267, p = 0.003). Owners with a household income below average were more likely to report providing inadequate housing compared to those with a household income above average (OR = 1.406, 95% CI 1.025-1.928, p = 0.035). CONCLUSION: The findings identify that inadequate rabbit housing is provided by owners of all ages, genders and deprivation levels but highlight some particular owner demographics that could be useful to target if resources are limited.

Effect of season and housing systems on various physio-behavioral attributes of local breed of rabbits (Oryctolagus cuniculus) in Southern Punjab, Pakistan / Efeito da estação e dos sistemas de alojamento em vários atributos fisiocomportamentais da raça local de coelhos (Oryctolagus cuniculus) no sul de Punjab, Paquistão

The present study was conducted to investigate the effect of season and various housing systems on behavioral i.e. sitting, standing, walking and physiological i.e. respiratory rate (RR), rectal temperature (RT), time of sexual libido (TSL) attributes of local breed of rabbits reared in Southern Punjab, Pakistan. Adult rabbits (n = 40) of 6 month to 1 year old were divided into two groups (n = 20 / group). Group I was placed under traditional colony system in the soil while group II was kept under modern cage system. Sitting and standing was significantly (p ≤ 0.05) higher during summer and winter respectively. The RR and RT were significantly (p ≤ 0.05) higher in summer as compared to other study seasons. Standing behavior was significantly (p ≤ 0.05) higher in caged rabbits as compared to colony-reared ones. Statistically higher (p ≤ 0.05) TSL value was observed in summer as compared to other three study seasons. From this study it is concluded that rabbit's behavioral and physiological traits are significantly affected by season and housing systems. We concluded that rabbits show better physio-behavioral performance in autumn and winter season while summer stress negatively affects physiology and behavior under caged-system. This study could contribute new aspects of behavioral and physiological processes in local breed of rabbits due to different seasons and housing systems.

O presente estudo foi conduzido para investigar o efeito da estação do ano e de vários sistemas de alojamento nos atributos comportamentais, isto é, sentar, levantar, andar e fisiológico, isto é, frequência respiratória (RR), temperatura retal (TR), tempo de libido sexual (TSL), atributos da raça local de coelhos criados no sul de Punjab, Paquistão. Coelhos adultos (n = 40) de 6 meses a 1 ano de idade foram divididos em dois grupos (n = 20 / grupo). O grupo I foi colocado sob o sistema de colônia tradicional no solo, enquanto o grupo II foi mantido sob o sistema moderno de gaiolas. Sentar e ficar em pé foi significativamente (p ≤ 0,05) maior durante o verão e inverno, respectivamente. O RR e o TR foram significativamente (p ≤ 0,05) maiores no verão, em comparação com as outras estações do estudo. O comportamento em pé foi significativamente (p ≤ 0,05) maior em coelhos engaiolados, em comparação com os criados em colônia. O valor de TSL estatisticamente maior (p ≤ 0,05) foi observado no verão, em comparação com outras três temporadas de estudo. A partir deste estudo, concluiu-se que os traços comportamentais e fisiológicos dos coelhos são significativamente afetados pela estação do ano e pelos sistemas de alojamento. Concluímos que os coelhos apresentam melhor desempenho fisiocomportamental no outono e inverno, enquanto o estresse do verão afeta negativamente a fisiologia e o comportamento em sistema enjaulado. Este estudo pode contribuir com novos aspectos dos processos comportamentais e fisiológicos em raças locais de coelhos devido às diferentes estações do ano e sistemas de alojamento.

Soursop juice enhanced seminal antioxidant defence and semen quality of rabbit bucks in extremely dry climatic condition of Southwestern Nigeria.

Heat induced stress associated with dry climatic conditions in the tropics does have adverse effects reproduction in rabbits, and this in-turn impacts negatively on the income of rabbit farmers. However, natural products might prove to be a reliable, safe and cheap remedy for ameliorating reproductive such anomalies in rabbits. The potential of soursop for mitigating heat induced reproductive deficiency in rabbit bucks was investigated during the peak of dry climatic conditions in southwestern Nigeria. Sixty mixed breed (New Zealand white x Chinchilla) adult rabbit bucks were allotted to five treatments of four replicates (3 bucks per replicate) each in a completely randomized design. Soursop (Annona muricata) fruit was processed into juice using standard procedures and was designated as soursop juice. The juice was administered orally daily per kg body weight (BW), 0.55ml/kgBW distilled water (control), 0.55 ml/kgBW soursop juice, 1.11 ml/kgBW soursop juice, 1.67 ml/kgBW soursop juice and 2.22 ml/kgBW soursop juice to designated treatments 1 to 5, respectively for 56 days. Semen samples were collected with an improvised artificial vagina on the 28th and 56th day of the study, semen quality and seminal oxidative status were evaluated using standard procedures. Results showed that rabbit buck exposed to heat stress had lower semen quality, seminal antioxidants and increased seminal lipid peroxidation. However, the consumption of soursop juice lowered lipid peroxidation and enhanced (p < 0.05) antioxidant production in the seminal fluid of heat-stressed bucks than bucks on control group. Bucks' semen quality and antioxidant status peaks in heat-stressed bucks gavaged 2.22 ml/kgBW soursop juice and gives 100% recovery from the effects of heat induced stress. It can be concluded that 2.22 ml/kgBW soursop juice administered for 56 days did enhance spermatozoa quality and mitigated lipid peroxidation by improving antioxidant capacity of male rabbits in a dose dependent manner on extremely dry climatic conditions.

Ginger root powder enhanced the growth productivity, digestibility, and antioxidative capacity to cope with the impacts of heat stress in rabbits.

Heat stress is the most significant environmental factor involved in the impairment of the health status of rabbits and lowering their productivity. Using medicinal feed additives is suggested to relieve heat stress-induced oxidative stress in rabbits. The study investigated the possible protective role of ginger root (Zingiber officinale) against heat stress in rabbits. Five week old rabbits were assigned randomly into four groups (48 rabbits each) and fed a basal diet supplemented with 0, 2.5, 5.0, and 7.5 g ginger powder/kg diet. The temperature and relative humidity inside the rabbitry units were kept at 33.0 ± 5.5 °C and 74.5 ± 4.5%, respectively, during 8 weeks fattening period. The results showed that rabbits that received the 7.5 g ginger powder/kg supplement had the highest final body weight. Rabbits that received different ginger powder levels recorded lower mortality values during the experimental period compared to that received the control diet, but the differences were not significant (5.0 vs. 10.0%, respectively). Rabbits fed 5.0 and 7.5 g ginger diet recorded the best food conversion ratio (P < 0.001). The weight of the carcass was significantly increased (P < 0.01) by supplementing ginger powder in diets. The digestibility of dry matter, organic matter, crude protein, and nitrogen free extracts nutrients was increased, but ether extract was significantly decreased (P < 0.001) by using ginger powder in diets. The detected blood metabolites displayed increased total protein but decreased triglycerides, total cholesterol, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) in rabbits treated with ginger. Rabbits fed 5.0 and 7.5 g ginger powder had the highest plasma total antioxidative capacity (TAC) and the lowest (P < 0.01) plasma malondialdehyde (MDA) concentration compared to those fed control diet. Conclusively, supplementing ginger powder up to a 5.0 g/kg diet for growing rabbits is recommended to improve the growth performance and enhanced viability under heat stress conditions.

Impact of Some Ions Administration on Sex Ratio and Ovarian Structures in Rabbits.

<b>Background and Objective:</b> The sex pre-selection for offspring before conception is desirable demand especially for the breeding program of farm animals. This study aimed to evaluate the preconception treatment of monovalent and divalent ions on the primary sex ratio, ovarian structures and serum minerals levels in New Zealand white rabbit does. <b>Materials and Methods:</b> Nine New Zealand white rabbits doe<i> </i>(5.4±0.61 months of age and 2.4±0.35 kg of body weight) were used. Rabbits in the 1^st group were given drinking water only (control). While the 2^nd and 3^rd groups were given 1% of (calcium and magnesium) and (sodium and potassium) in daily drinking water, respectively for 15 days before mating. The embryos of each group were individually collected after three days of mating for primary sex detection using SRY (Sex Determining Region Y) Polymerase Chain Reaction (PCR) assay. Mineral analyses for all studied animals were weekly detected in serum before and after mating. <b>Results:</b> The primary sex ratio for embryos of rabbits does receive (Na+K) produced more males (69.7%) while (Ca+Mg) administrated rabbits does produce more females (72.2%). The mineral treatment leads to a significant increase in the number of corpus luteum, total embryos, follicles bleeding and a significant decline in the count of large follicles. Also, there was no significant change in serum Na and Ca levels in the treated groups compared to the control. <b>Conclusion:</b> The preconception administration of Ca+Mg could produce more females while Na+K could produce more males without adverse side effects on serum minerals concentration.

Selection for environmental variance of litter size in rabbits involves genes in pathways controlling animal resilience.

BACKGROUND: Environmental variance (VE) is partially under genetic control, which means that the VE of individuals that share the same environment can differ because they have different genotypes. Previously, a divergent selection experiment for VE of litter size (LS) during 13 generations in rabbit yielded a successful response and revealed differences in resilience between the divergent lines. The aim of the current study was to identify signatures of selection in these divergent lines to better understand the molecular mechanisms and pathways that control VE of LS and animal resilience. Three methods (FST, ROH and varLD) were used to identify signatures of selection in a set of 473 genotypes from these rabbit lines (377) and a base population (96). A whole-genome sequencing (WGS) analysis was performed on 54 animals to detect genes with functional mutations. RESULTS: By combining signatures of selection and WGS data, we detected 373 genes with functional mutations in their transcription units, among which 111 had functions related to the immune system, stress response, reproduction and embryo development, and/or carbohydrate and lipid metabolism. The genes TTC23L, FBXL20, GHDC, ENSOCUG00000031631, SLC18A1, CD300LG, MC2R, and ENSOCUG00000006264 were particularly relevant, since each one carried a functional mutation that was fixed in one of the rabbit lines and absent in the other line. In the 3'UTR region of the MC2R and ENSOCUG00000006264 genes, we detected a novel insertion/deletion (INDEL) variant. CONCLUSIONS: Our findings provide further evidence in favour of VE as a measure of animal resilience. Signatures of selection were identified for VE of LS in genes that have a functional mutation in their transcription units and are mostly implicated in the immune response and stress response pathways. However, the real implications of these genes for VE and animal resilience will need to be assessed through functional analyses.

The effect of dietary supplementation with silkworm pupae meal on gastrointestinal function, nitrogen retention and blood biochemical parameters in rabbits.

BACKGROUND: The aim of this study was to determine the effect of dietary inclusion of silkworm pupae meal (SPM) on nutrient digestibility, nitrogen utilization, gastrointestinal physiology and blood biochemical parameters in rabbits. Thirty Termond White rabbits were divided into three groups: SBM - fed a diet containing 10% soybean meal (SBM), SPM5 - fed a diet containing 5% SBM and 5% SPM, and SPM10 - fed a diet containing 10% SPM. RESULTS: Nutrient digestibility and nitrogen retention decreased with increasing SPM inclusion levels in rabbit diets. The dietary inclusion of SPM caused a significant increase in the stomach pH. Group SPM10 rabbits were characterized by the highest cecal tissue and digesta weights. The lowest cecal pH was noted in group SPM5. The relative weights of colonic tissue and digesta tended to increase with increasing levels of SPM. The total and intracellular activity of bacterial α-galactosidase decreased significantly in both SPM groups. The replacement of SBM with SPM led to a decrease in the activity of bacterial ß-glucuronidase in the cecal digesta. The intracellular activity of bacterial α-arabinofuranosidase increased, and its release rate decreased in the cecum of rabbits in SPM groups. The extracellular activity of bacterial ß-xylosidase in the cecal digesta tended to decrease in group SPM10. The highest extracellular and intracellular activity of bacterial ß-cellobiosidase in the cecal digesta was noted in the SPM5 treatment. The lowest and the highest activity of bacterial N-acetyl-ß-D-glucosaminidase (NAGase) was observed in groups SBM and SPM10. The SPM10 treatment contributed to a decrease in the cecal concentrations of butyric, iso-valeric and valeric acids. The lowest total concentration of putrefactive short-chain fatty acids (PSCFAs) was observed in group SPM10. The cecal concentration of propionic acid tended to increase in group SPM5, whereas the cecal concentration of iso-butyric acid tended to decrease in group SPM10. The colonic concentration of iso-valeric acid was lowest in group SPM5. SPM treatments resulted in a significant increase in plasma albumin concentration. Plasma urea concentration was significantly higher in group SPM10 than in SBM and SPM5. CONCLUSIONS: The results of this study suggest that rabbit diets can be supplemented with SPM at up to 5%.

Computational biomechanical modelling of the rabbit cranium during mastication.

Although a functional relationship between bone structure and mastication has been shown in some regions of the rabbit skull, the biomechanics of the whole cranium during mastication have yet to be fully explored. In terms of cranial biomechanics, the rabbit is a particularly interesting species due to its uniquely fenestrated rostrum, the mechanical function of which is debated. In addition, the rabbit processes food through incisor and molar biting within a single bite cycle, and the potential influence of these bite modes on skull biomechanics remains unknown. This study combined the in silico methods of multi-body dynamics and finite element analysis to compute musculoskeletal forces associated with a range of incisor and molar biting, and to predict the associated strains. The results show that the majority of the cranium, including the fenestrated rostrum, transmits masticatory strains. The peak strains generated over all bites were found to be attributed to both incisor and molar biting. This could be a consequence of a skull shape adapted to promote an even strain distribution for a combination of infrequent incisor bites and cyclic molar bites. However, some regions, such as the supraorbital process, experienced low peak strain for all masticatory loads considered, suggesting such regions are not designed to resist masticatory forces.

Amelioration of sperm fertilizability, thyroid activity, oxidative stress, and inflammatory cytokines in rabbit bucks treated with phytogenic extracts.

This study investigated the beneficial effect of phytogenic extracts on semen quality, reproductive hormones, thyroid activity, immunity, hepatic antioxidant activity, and fertility in rabbit bucks. We divided 70 bucks into seven groups (10 in each). Group 1 was fed a basal diet (control); groups 2, 3, and 4 were fed the control diet with 30, 60, and 90 mg/kg of turmeric, respectively; and groups 5, 6, and 7 were fed the control diet with 50, 75, and 100 mg/kg of garlic extract, respectively, for 8 weeks. Rectal and skin temperatures decreased, while follicle-stimulating hormone, luteinizing hormone, triiodothyronine, thyroxine, testosterone, immunoglobulin M, tumor necrosis factor-alpha, and interleukin-6 in blood serum and glutathione peroxidase in the liver increased in all groups (p < .05). Garlic extract (100 mg/kg diet) increased adenosine triphosphate and glutathione in the liver tissues. All treatments significantly increased net semen volume, percentages of progressive motility, livability, curled tail, and intact acrosomes of spermatozoa, sperm cell concentration, and outputs of total and motile spermatozoa, while significantly decreased percentage of sperm abnormality. In conclusion, dietary supplementation of turmeric or garlic extract can be used as a suitable tool for enhancing the hepatic antioxidant activity, immunity, and semen quality in rabbit bucks.

Clinical tolerance of dexamethasone in New Zealand white rabbits.

Rabbits have been a popular pet and research species world-wide. In many clinical and research situations, controlling inflammation is necessary for the health of these animals. One of the first drugs commonly employed in veterinary medicine to suppress inflammatory responses is corticosteroids. Unfortunately, steroid use in rabbits is not universally accepted as they are perceived, based on their potent immunosuppressant activity, to negatively impact quality of life. This is may be due, in part, to the lack of well-developed dosing protocols in these animals. This study evaluated the impact of a 5-day IM dexamethasone (Dex, 0.5 mg/kg) protocol on the immunity and clinical health of the New Zealand rabbit. Through two experiments separated by a 10-day washout period, experiment 1 comprised 5-days of dosing with bleedings on day 0, 3, 5 and 7, where experiment 2 consisted of 5-days of dosing with bleedings on day 0, 3 and 5. Animals were monitored twice daily for changes in clinical health. Hematology, T cell subset phenotype, leukocyte cell cycle, histopathology, phagocytosis and oxidative formation were evaluated. Consistent with other species, 5-day dosing with Dex suppressed leukocytes, in particular the T cells (p ≤ 0.003). Interestingly, rabbits failed to show any adverse clinical signs throughout the entire study. This would imply that a 5-day IM Dex (0.5 mg/kg) dosing protocol is well tolerated by New Zealand white rabbits and could be used in rabbits suffering from inflammatory conditions or disease as long as the animal's immune status is closely monitored.

Effects of Cisapride, Buprenorphine, and Their Combination on Gastrointestinal Transit in New Zealand White Rabbits.

Due to their effective analgesic properties, opioids are worthy of consideration for pain management in rabbits. However, this class of drugs causes undesirable effects including reduced gastrointestinal (GI) motility, reduced fecal output, and delays GI transit times and thus increases the risk of GI stasis. The risk of stasis discourages the use of opioids in rabbits, which could affect animal welfare. Gastroprokinetic agents such as cisapride are effective in promoting gastric emptying in many species, but whether this effect occurs in rabbits is unknown. This study assessed the efficacy of cisapride when administered as a single agent and in combination with buprenorphine in rabbits; efficacy was assessed by measuring GI transit times, fecal output, body weight, and food and water intake. Female New Zealand White rabbits (n = 10) were studied in a crossover, randomized design and received either vehicle and buprenorphine, cisapride and saline, cisapride and buprenorphine, or vehicle and saline (control) every 8 h for 2 d. Rabbits were anesthetized and administered radio-opaque, barium-filled spheres via orogastric tube. Feces was assessed via radiography for detection of the barium-spheres to determine GI transit time. GI transit time was significantly longer in buprenorphine groups than in control groups, regardless of the use of cisapride. Fecal output and food and water intake were lower for buprenorphine groups than control groups. Cisapride did not significantly alter GI transit, fecal output, or food and water intake. In addition, treatment group did not significantly affect body weight. In conclusion, buprenorphine treatment (0.03 mg/kg TID) prolonged GI transit time and reduced fecal output and food and water consumption in rabbits. Coadministration of buprenorphine and cisapride (0.5 mg/kg) did not ameliorate these effects, and the administration of cisapride at this dose did not appear to affect GI motility in female rabbits.

Evaluation of dextran for rabbit sperm cryopreservation: Effect on frozen-thawed rabbit sperm quality variables and reproductive performance.

Effects were analysed of dextran supplementation to Me2SO and acetamide rabbit semen freezing extenders on quality characteristics of rabbit spermatozoa and reproductive performance. The final concentration of cryoprotectants in pooled semen samples was 12.4 % Me2SO for the A extenders, 10.7 % Me2SO and 2.9 % acetamide for the D extenders and 8.9 % Me2SO and 2.9 % acetamide in F extenders, with a supplementation of 1.7 % sucrose in all cases. There was not inclusion of dextran in the A0, D0, F0; while 5 % dextran was included in A5, D5, F5 and 10 % dextran in A10, D10 and F10 extenders. Sperm motility and viability rates were similar with use of the different extenders. Acrosome integrity after the freeze-thawing processes, however, was markedly greater when there was dextran supplementation of D and F extenders. Prolificacy was affected by extender composition. When there was artificial insemination (AI) using semen cryopreserved in the A extenders, number of kits born was similar to when there was AI with fresh semen when there was inclusion of 5% dextran for cryopreservation, while there was no effect on prolificacy when there was cryopreservation of semen using the D and F extenders. In conclusion, dextran supplementation of extenders containing Me2SO and acetamide resulted in greater acrosome integrity. Furthermore, when there was AI using sperm preserved in cryo-diluents containing an intermediate concentration of Me2SO, combined with inclusion of 5 % dextran, there was a marked beneficial effect on rabbit doe reproductive performance.

Rabbit Elastase Aneurysm: Imaging and Histology Correlates for Inflammation and Healing.

OBJECTIVE: Aneurysmal subarachnoid hemorrhage remains a devastating event with poorly understood pathophysiology. Previous studies have suggested that aneurysm wall inflammation may play a part in the development and potential rupture of aneurysms. The rabbit elastase aneurysm model is a well-established model, which produces aneurysms closely mimicking human cerebral aneurysms in flow dynamics and histopathology. The primary aim of this study was to correlate inflammatory changes after aneurysm formation using sequential vessel wall imaging with histopathologic analysis. A secondary aim was to evaluate the potential effect of gender and anti-inflammatory treatment with aspirin on this inflammatory response. METHODS: Twenty-seven New Zealand rabbits underwent surgery to create an aneurysm using elastase infusion at the right common carotid artery origin. Vessel wall imaging and histopathologic analysis was obtained at different time points after aneurysm creation. The rabbits were also randomized by gender and to treatment groups with or without aspirin. RESULTS: Histopathologic analysis revealed 3 distinct phases after aneurysm formation. These phases were an initial inflammatory phase, followed by a regeneration phase, and finally a connective tissue deposition phase. Vessel wall imaging demonstrated 2 distinct imaging patterns. No appreciable differences were seen in histology or imaging when comparing gender or treatment with aspirin. CONCLUSIONS: Inflammatory changes induced by the rabbit elastase aneurysm model can be correlated with histopathologic findings and observed on noninvasive vessel wall imaging. This may provide a method to study the inflammatory pathway as it pertains to aneurysmal development and subsequent rupture.

Senescent cells in rabbit, nutria and chinchilla testes-Results from histochemical and immunohistochemical studies.

Rabbit, nutria and chinchilla testes were evaluated to compare testicular cellular senescence. There were no major species-specific differences in structure of either seminiferous tubules or interstitial tissue. There, however, were occasional abnormalities in seminiferous tubule structure with there being multinucleated and exfoliated cells present in rabbit testes. Furthermore, there were seminiferous tubules without a lumen that were filled with premeiotic/meiotic cells in nutria; and tubules with vacuolization with there being no post-meiotic cells in chinchillas. There were no differences in distribution or content of acids, total proteins and polysaccharides in the testis of any of the three species. Results using comparative immunohistochemistry procedures indicated the testes contained a few senescent cells in seminiferous tubules with typical morphology and there was a large number of senescent cells in seminiferous tubules of nutrias and chinchillas that had an abnormal structure (P <0.001). Compared to rabbit testes, in which there was the least number of senescent cells in seminiferous tubules, there was a greater abundance of senescence markers in both nutria and chinchilla testes (P < 0.05; P < 0.001, respectively). Furthermore, there were small abundances of caspase 3 and LC3 in the testes of all species. In chinchilla testes, there was a lesser concentration of cholesterol (P < 0.001) and testosterone compared with the other species. Cellular senescence in testes, therefore, can be assessed by detection of morpho-functional disorders of the testis of the three species evaluated in the present study.

Aspergillus awamori positively impacts the growth performance, nutrient digestibility, antioxidative activity and immune responses of growing rabbits.

In this study, we explored the effects of dietary administration of Aspergillus awamori on the growth, intestinal histomorphology, immune parameters and antioxidant enzyme activity of growing rabbits. The rabbits of 5 weeks of age (body weight, 855 ± 5.53 g) were allotted into four groups (12 rabbits per group) and fed four experimental diets enriched with A. awamori at 0, 50, 100 and 150 mg per kg diet for 8 weeks. After the feeding trial, an equal number of male APRI rabbits (3 months old; 4 groups, 5 rabbits per group) were housed in metabolism cages and fed the test diets for 14 days for the digestibility trial. All A. awamori-enriched diets induced a significant increase in the average body weight and weight gain of rabbits and significantly decreased the feed conversion ratio. In rabbits fed with A. awamori at 100 or 150 mg per kg diet, protein, lipid and fibber digestibility coefficients significantly increased compared with the control group. Intestinal villi measurements (length and thickness) were also enhanced in all rabbits fed with A. awamori. Adding A. awamori as a food supplement generally did not affect rabbit haematology and blood biochemistry values; however, at 150 mg per kg diet, it significantly increased the levels of haemoglobin and total protein, as well as red blood cell count. Furthermore, all enriched diets significantly increased rabbits' phagocytic activity and their phagocytic index. Rabbits fed with A. awamori also showed decreased malondialdehyde but increased catalase activity. In conclusion, A. awamori administered as feed supplement at 100-150 mg per kg of growing rabbits' diet enhances their growth, intestinal health and nutrient digestibility, and it raises the levels of their immune and antioxidative responses.

High temperature impairs rabbit viability, feed consumption, growth and fecundity: examination of endocrine mechanisms.

The aim of the present study was to examine the effect of high ambient temperature on rabbit feed consumption, growth, viability, and fecundity, as well as the morphology and endocrine function of gonadal and adrenal cells. Adult does and their offspring were kept at either a comfortable (20°C; control) or high (36°C) temperature throughout pregnancy and up until weaning of pups. Doe mortality and fecundity, and plasma concentrations of hormones were evaluated. In addition, granulosa cells were cultured with and without FSH to assess progesterone production. In the offspring, we assessed mortality, total feed consumption, feed efficiency, growth, plasma hormone concentrations, as well as the microstructure in ovarian granulosa cells, testicular Leydig cells, and adrenocortical cells. We observed greater mortality of both adult animals and offspring at the higher ambient temperature compared with the control. The higher ambient temperature suppressed feed consumption, feed efficiency, and growth of pups. Adult and young females exposed to a high temperature had lower circulating concentrations of progesterone, but not of estradiol, compared with controls. Young males exposed to a high ambient temperature had greater circulating concentrations of testosterone, but not progesterone, compared with controls. High ambient temperature reduced circulating IGF-I concentrations in all the animals. Corticosterone level was increased in plasma of young but not of adult animals. Granulosa cells isolated from the ovaries of does subjected to high temperatures released less progesterone, and they had poorer response to the stimulatory action of FSH than the cells from control does. High temperatures induced fragmentation of nucleoli in ovarian granulosa cells, but they did not alter the state of other organelles in ovarian, testicular, or adrenocortical cells. A negative influence of high temperature on rabbit feed consumption, growth, viability, and fecundity was observed. Taken together, these changes could be due to a decrease in IGF-I and/or progesterone secretion, destruction of ovarian cell nucleoli, and/or impaired ovarian cell response to FSH.

Effect of ovarian stimulation by different gonadotrophin treatments on in vivo and in vitro reproductive efficiency of rabbit does under high ambient temperature.

Non-lactating multiparous NZW rabbit does (n = 227) were used in two experiments. In the 1st experiment (n = 87), does were i.m. injected with 0.1-ml saline/doe in day 0 (control, n = 29). Other does were injected with 25 IU equine chorionic gonadotrophin (eCG), followed by 0.2-ml gonadotrophin-releasing hormone (GnRH, n = 29) or 75 IU human chorionic gonadotrophin (hCG, n = 29) per doe 48 h later. After 60 h of day 0, does in all groups were artificially inseminated (AI). In the 2nd experiment, does (n = 140) were mated (AI) after synchronization of estrus/ovulation with 25 IU eCG, and 75 IU hCG 48 h later. On day 5 post-AI, does were injected with saline (control), 75 IU hCG, 0.2 ml GnRH, or 25 IU eCG per doe. Injection of eCG with GnRH or hCG pre-AI significantly increased corpora lutea number, ovulation rate, total number/doe and recovery rate of embryos, viable embryos, hatched blastocysts, in vivo reproductive parameters, and concentration of progesterone and progesterone/estradiol 17-ß ratio. Injection of eCG on day 5 post-AI significantly improved large and total follicle number, and in vivo reproductive efficiency. The corpora lutea number and impantation sites were significantly increased in the hCG and eCG groups. Fetal loss rate significantly increased only in the GnRH group. Under high ambient temperature, administration of eCG with hCG or GnRH injection pre-AI could be synchronized estrus/ovulation for improving in vivo and in vitro embryo production. In addition, pregnancy outcomes could be enhanced in rabbit does induced to ovulation by a single eCG or hCG dose on day 5 post-AI.

Sarcomere length non-uniformities dictate force production along the descending limb of the force-length relation.

The force-length relation is one of the most defining features of muscle contraction, and yet a topic of debate in the literature. The sliding filament theory predicts that the force produced by muscle fibres is proportional to the degree of overlap between myosin and actin filaments, producing a linear descending limb of the active force-length relation. However, several studies have shown forces that are larger than predicted, especially at long sarcomere lengths (SLs). Studies have been conducted with muscle fibres, preparations containing thousands of sarcomeres that make measurements of individual SL challenging. The aim of this study was to evaluate force production and sarcomere dynamics in isolated myofibrils and single sarcomeres from the rabbit psoas muscle to enhance our understanding of the theoretically predicted force-length relation. Contractions at varying SLs along the plateau (SL = 2.25-2.39 µm) and the descending limb (SL > 2.39 µm) of the force-length relation were induced in sarcomeres and myofibrils, and different modes of force measurements were used. Our results show that when forces are measured in single sarcomeres, the experimental force-length relation follows theoretical predictions. When forces are measured in myofibrils with large SL dispersions, there is an extension of the plateau and forces elevated above the predicted levels along the descending limb. We also found an increase in SL non-uniformity and slowed rates of force production at long lengths in myofibrils but not in single sarcomere preparations. We conclude that the deviation of the descending limb of the force-length relation is correlated with the degree of SL non-uniformity and slowed force development.