New Zealand White Research Articles

Initial results of the Hyperion IIDPET insert for simultaneous PET-MRI applied to atherosclerotic plaque imaging in New-Zealand white rabbits.

In preclinical research, in vivo imaging of mice and rats is more
common than any other animal species, since their physiopathology is very well-
known and many genetically altered disease models exist. Animal studies based on
small rodents are usually performed using dedicated preclinical imaging systems
with high spatial resolution. For studies that require animal models such as mini-
pigs or New-Zealand White (NZW) rabbits, imaging systems with larger bore
sizes are required. In case of hybrid imaging using Positron Emission Tomography
(PET) and Magnetic Resonance Imaging (MRI), clinical systems have to be used,
as these animal models do not typically fi t in preclinical simultaneous PET-MRI
scanners.
Approach. In this paper, we present initial imaging results obtained with the
Hyperion IID PET insert which can accommodate NZW rabbits when combined
with a large volume MRI RF coil. First, we developed a rabbit-sized image
quality phantom of comparable size to a NZW rabbit in order to evaluate the
PET imaging performance of the insert under high count rates. For this phantom,
radioactive spheres with inner diameters between 3.95 and 7.86 mm were visible
in a warm background with a tracer activity ratio of 4.1 to 1 and with a total
18-F activity in the phantom of 58MBq at measurement start. Second, we performed
simultaneous PET-MR imaging of atherosclerotic plaques in a rabbit in vivo using
a single injection containing 18-F-FDG for detection of infl ammatory activity,
and Gd-ESMA for visualization of the aortic vessel wall and plaques with MRI.
Main results. The fused PET-MR images reveal 18-F-FDG uptake within an
active plaques with plaque thicknesses in the sub-millimeter range. Histology
showed colocalization of 18-F-FDG uptake with macrophages in the aortic vessel wall lesions. 
Significance. Our initial results demonstrate that this PET insert
is a promising system for simultaneous high-resolution PET-MR atherosclerotic
plaque imaging studies in NZW rabbits.

Effectiveness and biocompatibility of a novel Schlemm’s canal microstent for glaucoma management

To evaluate the effectiveness and biocompatibility of Wistend, a novel Schlemm’s canal (SC) microstent made of Nitinol designed to improve aqueous humor outflow. New Zealand white (NZW) rabbits were divided into blank, sham-operated and Wistend groups. ICare® Tonovet Plus®, swept-source optical coherence tomography (SS-OCT), slit lamp biomicroscopy, retinal camera and scanning electron microscopy (SEM) were used for preoperative and postoperative observations. Hematoxylin and Eosin (H&E) tissue staining was adopted for biocompatibility. A significant difference in intraocular pressure (IOP) between the Wistend group and the control groups was observed during the six-month follow-up. SS-OCT identified arc line internal reflections within the SC in the anterior chamber angle. Conjunctival congestion and edema gradually diminished in the early stages. No corneal vascularization, no anterior chamber inflammatory response and no significant tissue reactions were noted in any groups. SEM showed the Wistend’s windows and orifices remained clear, encircled by minimal incidental ocular tissue and free from blockage. Histopathological examination revealed no discernible differences between the Wistend-implanted and sham-operated eyes. These in vivo studies demonstrate the effectiveness and biocompatibility of the microstent. Our findings suggest a promising potential for Wistend in significantly reducing IOP and effectively facilitating the outflow of aqueous humor.

Cerebral net uptake of lactate contributes to neurological injury after experimental cardiac arrest in rabbits

During focal ischemia, neurons can use lactate as an alternative source of energy through its oxidation into pyruvate by the lactate dehydrogenase (LDH). After cardiac arrest, the neurological consequences of this phenomenon are unknown. Experimental study. Experimental laboratory. Male New-Zealand rabbits. Animals were surgically instrumented and randomly divided into five groups receiving short infusion duration of either lactate or pyruvate or a pre-cardiac arrest infusion of oxamate (an inhibitor of the lactate dehydrogenase) or injection of fluorocitrate (an inhibitor of astrocytic tricarboxylic acid), or Saline (lactate, pyruvate, Oxa, FC and Control groups, respectively). After randomization, animals were submitted to 10 min of ventricular fibrillation and subsequent resuscitation. All animals were then either followed during 4 h, for the evaluation of the cerebral net uptake and concentrations of metabolites by microdialysis (n = 6 in each experimental group, n = 12 in control group), or during 48 h for the evaluation of their neurological outcome (n = 7 in each groups and n = 14 in control group). Cardiac arrest was associated with a dramatic increase in cerebral net uptake of lactate during 120 min after resuscitation, which was increased by lactate or pyruvate administration. This was associated with an increase in the mean neurological dysfunction score (66.7 ± 4.7, 79.0 ± 4.5 vs 57.7 ± 1.5 in Lactate, Pyruvate and Control group respectively) at 48 h after cardiac arrest. Oxamate and FC administration were associated with a lower lactate cerebral uptake after cardiac arrest and with an improvement of the neurological recovery (28.85 ± 9.4, 23.86 ± 6.2 vs 57.7 ± 1.5 in Oxa, FC and Control group respectively). After cardiac arrest, immediate isotonic lactate or pyruvate administration is deleterious. Pre-cardiac arrest LDH inhibition was potently neuroprotective in this setting.

6459 A Novel Long-Acting GH Receptor Antagonist Optimizing Therapeutic Efficacy and Duration

Abstract Disclosure: C. Ku: None. C. Kang: None. J. Oh: None. E. Wang: None. H. Song: None. K. Park: None. B. Kim: None. K. Kim: None. S. You: None. S. Park: None. E. Lee: None. Background: Forty to sixty percent of acromegalic patients undergo medical treatment, utilizing somatostatin analogues, dopamine agonists, and GH receptor (GHR) antagonists. The GHR antagonist, pegvisomant exhibits the most robust efficacy in reducing IGF-1 levels in acromegalic patients. However, pegvisomant faces several clinical limitations, such as poor compliance due to the necessity of daily injections. This study aimed to develop a novel, long-acting fusion GHR antagonist with optimized therapeutic efficacy and duration. Method: Twelve mutant proteins with alterations in the C-terminal and N-terminal regions of GHR were generated to confirm the GHR binding affinity and inhibitory potency compared with pegvisomant, which was evaluated with STAT5b luciferase reporter assay. Several carriers were engineered into selected mutant GHRs to increase the therapeutic duration. For in vivo experiments, single or repetitive injection of GHR antagonists were applied to acromegalic mouse model (somatotroph specific Aip knock out (sAIPKO) mice). Pharmacokinetics (PK) and pharmacodynamics (PD) were evaluated in New Zealand White (NZW) rabbits. Result: Four out of the 12 GHR mutants exhibited higher affinity and stronger inhibitory potency toward human GHR when compared to pegvisomant. Specifically, three GHR mutants significantly reduced serum IGF-1 levels in sAIPKO mice following daily injections of 20 mg/kg for 7 days (52.3±6.0 to 5.9±1.3, 50.3±3.5 to 32.3±2.3, and 49.8±3.7 to 13.9±4.3 ng/mL; all p < 0.05). Among them, S4020N exhibited the lowest EC50 value for GHR binding affinity in in vitro analysis containing human GHR (0.594 nM) and mouse GHR (0.891 nM). Following fusion with each long-acting carrier, S4020N with the Fc carrier protein (ALT-B5) demonstrated the highest binding affinity and the strongest inhibitory potency toward human GHR, surpassing pegvisomant by 14 and 25 times, respectively. Administration of ALT-B5 (80 mg/kg) and pegvisomant (24 mg/kg) at a 3-day interval revealed the superior efficacy of ALT-B5 over pegvisomant (1879±219.4 vs. 3800±355.9 ng*hr/mL IGF-1 AUC for 5 days in ALT-B5 and pegvisomant, respectively; p < 0.01). In PK/PD studies, ALT-B5 was administered at doses of 3 mg/kg and 10 mg/kg in NZW rabbits, and PK/PD parameters were compared with the same molar concentration of pegvisomant. ALT-B5 exhibited the longest therapeutic duration and the highest efficacy compared to pegvisomant. Conclusion: ALT-B5 exhibited the longest duration and highest effectiveness in lowering IGF-1 levels. ALT-B5 emerges as a potential novel therapeutic option for acromegaly. Presentation: 6/1/2024

Development of a Preclinical Double Model of MandibularIrradiated Bone and Osteoradionecrosis in NewZealand Rabbits.

Radiotherapy (RT) plays a crucial role in head and neck (HN) cancer treatment. Nevertheless, it can lead to serious and challenging adverse events such as osteoradionecrosis (ORN). A preclinical rabbit model of irradiated bone and ORN is herein proposed, with the aim to develop a viable model to be exploited for investigating new therapeutic approaches. Nine New Zealand white rabbits were irradiated using a single beam positioned to the left of the mandible and directed perpendicular to the left mandible. A 10 × 10 mm2 region of interest (ROI) located below the first molar tooth on the left side was identified and irradiated with 7 Gy each fraction, once every 2 days, for five fractions. Dose distributions demonstrated that the corresponding ROI on the contralateral (right) mandibular side received approximately 5 Gy each fraction, thus bilateral irradiation of the mandible was achieved. ROIs were categorized as ROIH on the left side receiving the high dose and ROIL on the right side receiving the low dose. Rabbits were followed up clinically and imaged monthly. After 4 months, the irradiated bone was excised, and histological examination of ROIs was performed. Radiological signs suggestive for ORN were detected in the entire population (100%) 16 weeks after irradiation on ROIH, which consisted of cortical erosion and loss of trabeculae. ROIL did not show any radiological evidence of bone damage. Histologically, both sides showed comparable signs of injury, with marked reduction in osteocyte count and increase in empty lacunae count. A preclinical double model was successfully developed. The side receiving the higher dose showed radiological and histological signs of bone damage, resulting in an ORN model. Whereas the contralateral side, receiving the lower dose, presented with histological damage only and a normal radiological appearance. This work describes the creation of a double model, an ORN and irradiated bone model, for further study using this animal species.

The Ocular Penetration and Intraocular Pressure Lowering Effect of Topical Acetaminophen in the New Zealand White Rabbit.

Purpose: Emerging data suggest that acetaminophen lowers intraocular pressure (IOP) and has the potential to be repurposed as pharmacotherapy to treat open-angle glaucoma. However, pharmacokinetic data are lacking. This study aims to describe the pharmacokinetics of topical acetaminophen and its metabolite [N-arachidonoylaminophenol (AM404)] when administered individually and in combination, and to determine its effect on IOP in the ocular normotensive adult New Zealand White Rabbit (NZWR). Methods: A randomized control trial was conducted using topical 1% acetaminophen and 1% AM404. The study was divided into two sub-studies using both paired-eye and two-eye designs. Results: The mean [95% confidence interval of the mean (95% CI)] concentration of acetaminophen detected in the aqueous humor (AH) was 4.09 ppm (3.18-5.00) at 2 h and 0.92 ppm (0.60-1.24) at 4 h after an immediate dose of topical acetaminophen. The integral IOP, defined as the integral of IOP change from baseline over time, was -5.1 mmHg⋅h (95% CI: -10 to 0.41) for control,-7.5 mmHg⋅h (95% CI: -14 to -1.1) for half-hourly acetaminophen, and -4.4 mmHg⋅h (95% CI: -14 to 5.5) for hourly acetaminophen over a 4-h period. When comparing topical acetaminophen with AM404 dosed half-hourly over a 4-h period, the integral IOP was -2.3 mmHg⋅h (95% CI: -5.9 to 1.3) for control,-2.0 mmHg⋅h (95% CI: -5.6 to 1.7) for AM404, -1.7 mmHg⋅h (95% CI: -4.5 to 1.2) for acetaminophen, and -3.2 mmHg⋅h (95% CI: -5.4 to -0.96) for acetaminophen/AM404 combined. Conclusions: Acetaminophen, but not its metabolite AM404, penetrated the multilayered cornea via passive diffusion in a dose-dependent fashion. There was a nonsignificant tendency to cause a lowering of IOP over the 4-h dosing period with higher AH concentrations of acetaminophen. Topical AM404 did not show a significant IOP-lowering effect.

Impact of Silver Nanoparticles (Ag-NPs) as a Dietary Supplement on Growth Performance, Carcass Traits, Blood Metabolites, Digestive Enzymes, and Cecal Microbiota of Growing Rabbits

Abstract The present study investigated the impact of silver nanoparticles (Ag-NPs) on growth performance, carcass traits, liver and kidney functions, immunity and antioxidant indicators, digestive enzymes, and cecum bacteriology of growing rabbits. One hundred 5-week-old New Zealand White (NZW) male rabbits were randomly divided into 5 equal groups and fed for 8 weeks on the basal diet only or on the basal diet supplemented with different levels of Ag-NPs (0.25, 0.50, 0.75, or 1.00 mg/kg diet). Animals in each group were randomly distributed in 10 cages (replicates), with two rabbits each. Different dietary concentrations of Ag-NPs significantly increased live body weight (LBW) and feed conversion ratio (FCR). Also, body weight gain (BWG) increased dramatically during all experimental periods except 11–13 weeks of age. Levels of 0.25 and 1 mg of Ag-NPs/kg diet showed the highest increase in LBW, BWG, and FCR. All studied carcass traits, except liver %, were not affected by Ag-NPs levels. Rabbits fed diet supplemented with 1 mg Ag-NPs had the highest liver %. Serum total protein, albumin, and globulin levels were increased (P<0.05) in groups treated with 0.25 and 0.75 mg Ag-NPs. In contrast, serum values of aspartate transaminase (AST) and alanine transaminase (ALT), urea and creatinine were significantly reduced with the supplementation of Ag-NPs up to 0.75 mg/kg diet. The immunoglobulins M, G, and A (IgM, IgG, and IgA), complement 3 (C3) and lysozyme activity were improved with the inclusion of nano-silver in the rabbit feeds, particularly at the level of 0.25 mg Ag-NPs/kg feed. The inclusion of Ag-NPs in rabbit diets at different concentrations increased the total antioxidant capacity and the activities of superoxide dismutase, catalase, and glutathione peroxidase. Growing rabbits fed on diets supplemented with Ag-NPs had higher levels of digestive enzymes than the control group. The addition of Ag-NPs reduced the load of E. coli, Salmonella spp. and coliform in the rabbit cecum. Overall, the inclusion of 0.25–1 mg Ag-NPs/kg to NZW rabbit diets has shown beneficial effects on health and performance.

Genetic assessment of litter size, body weight, carcass traits and gene expression profiles in exotic and indigenous rabbit breeds: a study on New Zealand White, Californian, and Gabali rabbits in Egypt

Rabbits are essential for commercial meat production due to their efficient growth and productivity, breeds like New Zealand White (NZW), Californian (CAL), and Gabali (GAB) rabbits offer unique genetic traits in litter, growth, and carcass traits. This study aimed to evaluate heritability (h2), genetic and phenotypic correlations (rg and rp) for litter size, body weight and carcass traits across California (CAL), New Zealand white (NZW) and Gabali (GA) rabbits. Along with exploring gene expression profiles of TBC1D1, NPY, AGRP, POMC, Leptin, GH, GHR, IGF-1, CAA, GPR, ACC, CPT1, FAS, and CART in the brain, liver, and meat tissues of different rabbit breeds. The breed genotype had a significant impact on litter size (LS), litter weight (LW), body weight at 12 weeks (BW12), and daily weight gain (DWG) traits. NZW rabbits displayed superior performance in terms of litter size and litter weight, while CAL rabbits recorded the highest values for BW12 and DWG. Heritability estimates (h2) were generally low for litter size (ranging from 0.05 to 0.12) and medium for body weight (ranging from 0.16 to 0.31). Both genetic (rg) and phenotypic (rp) correlations for litter size were positive and moderate (ranging from 0.08 to 0.48), while correlations for body weight ranged from 0.21 to 0.58. Additionally, CAL rabbits exhibited higher carcass traits compared to NZW and GA rabbits. In terms of breed-specific gene expression patterns, New Zealand White (NZW) rabbits displayed the highest expression levels of key genes related to energy metabolism (TBC1D1), appetite regulation (NPY, AGRP, POMC), nutrient transport (CAA), and G protein-coupled receptors (GPR) in both brain and liver tissues. Californian (CAL) rabbits exhibited superior gene expression of the ACC gene in brain tissue and GH, GHR, and IGF-1 genes in brain and meat tissues. Gabali (GAB) rabbits demonstrated the highest expression levels of TBC1D1, NPY, AGRP, GPR, and ACC genes in meat tissues. These breed-specific gene expression differences, combined with genetic evaluation efforts, have the potential to enhance reproductive and productive performance in rabbits, offering valuable insights for rabbit breeding programs and genetic selection.

A Case Study on Sarcocystis in Laboratory Rabbit

Sarcocystosis spp. was diagnosed in Newzealand white rabbit which was brought for the purpose of experiment. The rabbit was brought from the local market and rearing in group in cage and feed locally available grasses. No any clinical signs were observed infected rabbit. The physiological along with biochemical and hematological test were performed. At necropsy and tissue harvest, a gross lesion was not observed in heart. During histo-pathological observation, an oval round shape along with longitudinal shape cyst was observed in the myocardium.

Association of single nucleotide polymorphisms in Neuropeptide Y (NPY) and Phosphoglycerate Mutase 2 (PGAM2) genes with growth traits in rabbits

Genetic improvement of local rabbit breeds using modern approaches such as marker-assisted selection requires accurate and precise information about marker‒trait associations in animals with different genetic backgrounds. Therefore, this study was designed to estimate the association between two mutations located in the Neuropeptide Y (NPY, g.1778G > C) and Phosphoglycerate Mutase 2 (PGAM2, c.195 C > T) genes in New Zealand White (NZW), Baladi (BR), and V-line rabbits. The first mutation was genotyped using high-resolution melting, and the second mutation was genotyped using the PCR-RFLP method. The results revealed significant associations between the NPY mutation and body weight at 10 (V-line) and 12 weeks of age (NZW, BR, and V-line), body weight gain (BWG) from 10 to 12 weeks of age (BR), BWG from 6 to 12 weeks of age (NZW, BR, and V-line), average daily gain (NZW, BR, and V-line, and BR), growth rate (GR) from 8 to10 weeks (V-line), 10 to 12 weeks (BR), and GR from 6 to 12 weeks of age (BR, and V-line). The PGAM2 mutation was associated with body weight at 10 (V-line) and 12 (NZW, and V-line) weeks of age, with significant positive additive effects at 12 weeks of age in all breeds, and was associated with BWG from 8 to 10 and 10 to 12 in BR, and BWG from 6 to 12 weeks of age (NZW, and BR), and average daily gain (NZW, and BR), and was associated with GR form 8 to 10 weeks (BR), from10 to 12 weeks (BR, and V-line) and from 6 to 12 weeks (BR). The results highlighted the importance of the two mutations in growth development, and the possibility of considering them as candidate genes for late growth in rabbits.

Comparison of the Effect of Different Treatment Doses of Intrastromal Vancomycin in a Rabbit Model of Methicillin-Resistant Staphylococcus Aureus (MRSA) Keratitis

ABSTRACT Purpose To compare the effect of different doses of vancomycin on a rabbit model of MRSA keratitis. Methods Twenty-four eyes of 24 New-Zealand White rabbits were included in the study. MRSA keratitis was applied to 24 left eyes of 24 New Zealand rabbits. Twenty-four hours after MRSA inoculation; 0.5 mg/0.1 mL, 1 mg/0.1 mL, and 2 mg/0.1 mL and balanced salt solution were administered to 6 rabbits in 4 groups, respectively. Results The effect of different doses of vancomycin on reducing bacterial load was found to be statistically significant when each was compared to the control group (p = 0.006). When comparing the dosages with each other, no superiority was shown (p = 0.297, p = 0.749, p = 0.262 respectively). There was a significant increase in the posttreatment total clinical score in the control and 2 mg/0.1 mL groups compared to the pretreatment score (p = 0.001, p = 0.001 respectively). Conclusion It is emphasized that necessary treatment can be achieved by administering less antibiotic (0.5 mg/0.1 mL) to the corneal intrastromal area.

Safety and tolerability of pooled human immune globulins after topical ophthalmic administration in New Zealand White rabbits

Purpose To evaluate the safety and tolerability of pooled human immune globulins, Flebogamma® 5% DIF and Flebogamma® 10% DIF, administered by topical ophthalmic instillation to New Zealand White (NZW) rabbits. Methods Male NZW rabbits were used in this study. In the acute single dose tolerability study, rabbits (n = 12) received a single topical dose of Flebogamma® 5% DIF. In the two-week repeated-dose tolerability study, rabbits (n = 5 for each group) were administered either Flebogamma® 5% DIF or Flebogamma® 10% DIF by topical bilateral administration four times daily (q.i.d.) between 8 am and 6 pm for a period of two weeks. Full ophthalmic examinations were conducted to evaluate ocular tolerability at baseline, Day 7, and Day 14. Results In the acute single dose study, mild hyperaemia was observed in 1 out of 4 eyes at each 4 h and 24 h post-instillation of Flebogamma® 5% DIF. In the repeated dose study, no ocular signs were detected after q.i.d. topical instillation of Flebogamma® 5% DIF, while Flebogamma® 10% DIF resulted in mild hyperaemia in 8 out of 10 eyes on Day 7, and 5 out of 10 eyes on Day 14. No positive corneal fluorescein staining was detected. Schirmer tear test results were unremarkable. No other ocular signs were observed. Administration of immune globulins had no effect on intraocular pressure. Conclusions Flebogamma® 5% DIF and Flebogamma® 10% DIF were well-tolerated by NZW rabbits following single and repeat dose topical ophthalmic administration, supporting the future development of topical pooled human immune globulins for the treatment of ocular surface disease.

Evaluation of genetic diversity within different rabbit (Oryctolagus cuniculus) genotypes utilizing start codon targeted (SCoT) and inter-simple sequence repeat (ISSR) molecular markers

Abstract. This work aimed at studying the genetic diversity among different rabbit genotypes reared in Egypt by two different molecular markers (start codon targeted, SCoT, and inter-simple sequence repeat, ISSR) to improve breeding strategies. Five different groups of rabbits were used Gabali (Gab), New Zealand white (NZW), Californian (Cal), Rex, and Papillon (Pap). DNA was extracted and analyzed using SCoT and ISSR-PCR, and the obtained fragments were analyzed. Six SCoT primers scored 60 bands with 78.33 % polymorphism; primer SCoT 6 was the most polymorphic marker with 92.31 % polymorphism, while SCoT 5 was the lowest with 60 %. A dendrogram based on SCoT-PCR revealed that the Rex breed was the most genetically different. Seven ISSR primers gained 56 bands in total with 49.762 % polymorphism. ISSR 4 was the most polymorphic primer that detected 75 % of polymorphism, while ISSR 6 was not able to detect any polymorphism. It was suggested that the SCoT markers may be more effective than ISSR for differentiating and identifying the genetic variations within investigated breeds. Also, the usage of molecular markers of SCoT and ISSR may be more proper for calculating genetic diversity and common ancestry among tested rabbit breeds. Furthermore, evaluating genetic variability is important for enhancing existing breeds' adaptation to ecological alterations and crucial for preservation or breeding purposes.

Comparing Intradermal (ID) Rabies Vaccination with Conventional IM Regimen on Humoral Response of New Zealand White Rabbits for the Production of Animal-Derived Polyclonal Antibodies.

In developing countries, it is imperative to implement cost-effective strategies for animal humoral response development in the production of antiserum. This study compared the effect of immunization regimens on the humoral immune response of New Zealand White (NZW) rabbits (N = 24) using cell culture rabies vaccine (CCRV) through intradermal (ID) and traditional intramuscular (IM) routes. The rabbits were divided into three experimental groups: (a) IPC-R2 with a two-site one-week regimen; (b) TRC-R3 with a two-site twenty-eight-day regimen; and (c) Alternate-R4 with a four-site one-week regimen. These regimens were then compared to the standard IM schedule of five doses of rabies vaccine administered at days 0, 3, 7, 14, and 28 in control group R-1. The results were evaluated at days 14 and 35 postvaccination using rabies-specific Platelia II™ ELISA kit method. The results showed a better response to the ID regimen than the IM route regarding immunogenicity and volume consumption of the vaccine. The three selected ID regimes showed significantly higher mean titer values than the control IM regimen group R-1 (p < 0.001). The study aims to explore simple immunization strategies to enhance the RV-specific antibody titers for immunization donor animals. This method would produce polyclonal antibodies and strengthen local production of polyclonal antibodies in Pakistan to deal with vaccine and rabies immunoglobulin (RIG) shortage, thus providing effective postexposure prophylaxis (PEP) for better control of rabies in developing countries.

Prediction of body weights from linear body parameters of rabbit genotypes in the humid tropics

This study aimed to determine the association between body weight and linear body parameters in rabbits. A total of 93 kittens generated from crosses of New Zealand White (NZW) x NZW, Chinchilla (CHA) x CHA, NZW x CHA, and CHA x NZW genotypes of rabbit in a nested classification of a Completely Randomized Design were used for this study. Data on body circumference weight (BW) and linear body parameters namely, body length (BL), ear length (EL), heart girth (HG), head-to-shoulder (HS), length of hind limb (LHB), length of forelimb (LFB), tail length (TL) and thigh girth (TG) were taken bi-weekly from weeks 2 to 12. The regression procedure used was a stepwise multiple regression using the backward elimination method. The body weight was regressed on linear body parameters using the stepwise multiple regression procedure in SPSS software. The result showed that the regressions of body weight on linear body parameters are all positive and highly significant (p&lt;0.01; 0.05) except for CHA x CHA in week 2. The values of the coefficient of determination (R2) ranged from 26 - 91% in NZW x NZW, 85 - 98% in NZW x CHA, 1 - 88% in CHA x CHA, and 92 - 99% in CHA x NZW. CHA x NZW had the highest R2 value of 94, 99, 94, 97, and 96% in weeks 2, 4, 6, 8 and 12, respectively. NZW x CHA also had a similar R2 value of 94, 96, and 98% in weeks 2, 8 and 10, respectively. For predicting body weight at weeks 2 and 4, LFB and TG were good predictors of body weight for NZW x NZW mating type while at weeks 6 and 10, LFB was a good predictor of body weight. Also, BL and HS proved to be the best predictors of body weight for NZW x CHA mating type. For CHA x CHA, HG and TG were good predictors of body weight while in CHA x NZW, BL was a good predictor of body weight at these periods except for weeks 10 and 12. This suggests that body weight increases with an increase in linear body measurements. Except CHA x CHA in weeks 2 and 12, all the multiple regression equations were significant; all the parameters had R2 values above 60% which shows that the linear model was a perfect fit. Hence, BL can be predicted with accuracy using CHA x NZW cross to facilitate the selection of rabbits for body weight-related purposes.

Genetic Characterization of Myf5 and POU1F1 Genes in Different Egyptian Local Rabbit Breeds and Their Association with Growth Traits

Genetic characterization and its association with quantitative traits in local breeds are important tools for the genetic improvement and sustainable management of animal genetic resources. Myogenic regulatory factor 5 (MYf5) and POU class 1 homeobox 1 (POU1F1) are candidate genes which play important roles in growth and development of mammals. The present study aims to detect the genetic diversity of the MYf5 and POU1F1 genes in four local Egyptian rabbit breeds and their association with growth traits, using PCR-restriction enzyme (PCR–RFLP), PCR-single-strand conformational polymorphism (PCR–SSCP), and direct sequencing techniques. The results showed that MYF5 exon 1 was observed with two genotypes in Baladi Black (BB), Gabali (GB) and New Zealand White (NZW) breeds while APRI-line (APRI) presented one genotype. The genetic diversity of Myf5 exon 2 between breeds showed two genotypes in APRI compared to three in NZW and four genotypes in BB and GB breeds. The genetic diversity of the POU1F1 gene (intron 5 and partial cds) in different rabbit breeds was two genotypes in NZW and three genotypes in BB, GB, and APRI breeds with different frequencies for each genotype. Based on the statistically significant difference between genes genotypes and growth weight, the results suggested that the genotypes of Myf5 exon 2 (1 and 2) of the BB breed, Myf5 exon 2 genotype 2 of the APRI breed, and genotype 1 of Myf5 exon 1 and genotype 1 of POU1F1 of the NZW breed compared to genotypes for each gene can be considered candidate molecular markers associated with the improvement of growth traits in these breeds.

The feasibility of partial replacement of berseem hay by spent mushroom (Pleurotus osteratus) substrate in rabbit diets on growth performance, digestibility, caecum fermentation, and economic efficiency

ABSTRACTNowadays, agricultural by-product disposal is a major concern. The mushroom by-products could be used as an alternative feed source in rabbit diets. Therefore, partial replacement of berseem hay (BH) with spent mushroom substrate (SMS) was conducted in four experimental groups as follows: 0, 20, 40, and 60% of SMS. Forty weaned New Zealand White (NZW) rabbits at 6th weeks of age with an initial body weight of 520.25 ± 70.01 g were fed the experimental diet for 8 weeks. The results showed that ash content and cell wall constituents in SMS were higher than in BH, while the other nutrient compounds in SMS were lower than in BH. Dietary SMS at a level of 60% increased the final body weight (p = 0.05) and feed conversion ratio (p ≤ 0.05). However, average daily gain and total feed intake were not affected by treatments. The replacement of SMS at levels of 40 and 60% significantly improved nutrient digestibility and total digestible nutrient value. SMS 60% decreased (p = 0.040) faecal N and improved (p = 0.006) retained nitrogen. The SMS replacement increased caecum length (p = 0.001), and full and empty caecum weight (p = 0.001 and 0.021, respectively) compared to the control. The SMS inclusion caused a decrease (p = 0.021 and 0.007) in the pH and NH3-N concentrations, respectively. Total VFA, acetic acid, butyric acid, and propionic acid proportions increased with the dietary inclusion of SMS in a level-dependent manner. Using SMS as a replacement for BH in growing rabbit diets reduced the total feed cost, and consequently improved net revenue, economic efficiency, and relative economic efficiency.

Rice gluten meal as a substitute for soybean meal in the diets for growing rabbits

ABSTRACT The impacts of different dietary levels of rice gluten meal (RGM) on growth performance, digestibility, carcass characteristics, and blood traits of growing New Zealand White (NZW) rabbits were studied. One hundred and twenty, 6 weeks old weaned male rabbits (body weight; 682 [g] ± 23) were randomly allotted into four groups. The control diet contained 160 [g/kg] soybean meal (SBM), while the other three diets were obtained by replacing 40, 80, and 120 [g/kg] SBM with RGM (RGM40, RGM80, and RGM120, respectively). The results showed that RGM contained higher levels of dry matter (DM), crude protein (CP), ether extract (EE), ash, and gross energy than SBM. RGM contained a high level of arginine followed by leucine and valine as essential amino acids and high levels of glutamic, aspartic acid, and alanine as non-essential amino acids. The obtained results showed that the final body weight of rabbits fed diets containing 40, 80, and 120 [g/kg] RGM was higher than those fed the control diet. The daily weight gain of rabbits fed RGM diets increased (p < 0.05) by 10.50%, 6.50%, and 10.00%, respectively, compared to the control group. Rabbits fed RGM80 showed the highest (p < 0.05) digestibility of DM, organic matter (OM), EE, neutral detergent fibre (NDF), and acid detergent fibre (ADF) compared to the other tested levels. Rabbits fed RGM120 had the highest (p < 0.05) digestible energy (DE) and digestible crude protein (DCP) values. RGM inclusion levels of 40 and 80 [g/kg] increased (p < 0.05) plasma total protein and albumin compared to the control group. Rabbits fed a diet containing RGM40 had the highest (p < 0.05) globulin level. The highest (p < 0.05) plasma urea concentration level was measured in the rabbit group fed the RGM120 diet. Conclusively, RGM could be a valuable ingredient for growing rabbits, as at all the tested levels improved growth performance, digestibility, and nutritional values.

Acute and sub-chronic toxicological profile of Musa cavendishii (Musaceae) Lamb peel extracts in New Zealand rabbit

Musa cavendishii (banana) peel is a waste product of human daily consumable fruit used traditionally in the management of ulceration and scar. This study evaluates the toxic effects of its peel in New-Zealand rabbits after topical administration. Acute and sub-chronic toxicity study of the peel extracts were carried out in 116 randomly selected rabbits using methods described by Organization of Economic Corporation and Development (OECD) 402 (2017) and 410 (2018), respectively. Changes in body and relative organ weight, hematology, serum liver and renal enzyme were investigated. Vital body organs were also processed for histopathology to observe any alteration from normal architecture. No mortality was observed during the acute toxicity with no changes in body and relative organ weight of the organs tested when compared with the control. After 28 days of topical administration of the extracts, even at the highest dose (1500 mg/kg) of the aqueous extract, the histoarchitexture of the skin’s epidermis and dermis, and other biochemical markers of the rabbits were normal. However, mild adipocyte infiltration, glandular hyperplasia and distortions in the renal parameters were seen in the hexane, ethylacetate and methanol extracts portions at the highest dose (1500 mg/kg) after 28 days topical administration. The study indicates that M. cavendishii peel is not capable of causing toxic effects in rabbits. However, it’s prolong use at higher doses may result in some harmful effects.

A double-crosslinked nanocellulose-reinforced dexamethasone-loaded collagen hydrogel for corneal application and sustained anti-inflammatory activity

In cases of blinding disease or trauma, hydrogels have been proposed as scaffolds for corneal regeneration and vehicles for ocular drug delivery. Restoration of corneal transparency, augmenting a thin cornea and postoperative drug delivery are particularly challenging in resource-limited regions where drug availability and patient compliance may be suboptimal. Here, we report a bioengineered hydrogel based on porcine skin collagen as an alternative to human donor corneal tissue for applications where long-term stability of the hydrogel is required. The hydrogel is reinforced with cellulose nanofibers extracted from the Ciona intestinalis sea invertebrate followed by double chemical and photochemical crosslinking. The hydrogel is additionally loaded with dexamethasone to provide sustained anti-inflammatory activity. The reinforced double-crosslinked hydrogel after drug loading maintained high optical transparency with significantly improved mechanical characteristics compared to non-reinforced hydrogels, while supporting a gradual sustained drug release for 60 days in vitro. Dexamethasone, after exposure to crosslinking and sterilization procedures used in hydrogel production, inhibited tube formation and cell migration of TNFα-stimulated vascular endothelial cells. The drug-loaded hydrogels suppressed key pro-inflammatory cytokines CCL2 and CXCL5 in TNFα-stimulated human corneal epithelial cells. Eight weeks after intra-stromal implantation in the cornea of 12 New-Zealand white rabbits subjected to an inflammatory suture stimulus, the dexamethasone-releasing hydrogels suppressed TNFα, MMP-9, and leukocyte and fibroblast cell invasion, resulting in reduced corneal haze, sustained corneal thickness and stromal morphology, and reduced overall vessel invasion. This collagen-nanocellulose double-crosslinked hydrogel can be implanted to treat corneal stromal disease while suppressing inflammation and maintaining transparency after corneal transplantation. Statement of significanceTo treat blinding diseases, hydrogel scaffolds have been proposed to facilitate corneal restoration and ocular drug delivery. Here, we improve on a clinically tested collagen-based scaffold to improve mechanical robustness and enzymatic resistance by incorporating sustainably sourced nanocellulose and dual chemical-photochemical crosslinking to reinforce the scaffold, while simultaneously achieving sustained release of an incorporated anti-inflammatory drug, dexamethasone. Evaluated in the context of a corneal disease model with inflammation, the drug-releasing nanocellulose-reinforced collagen scaffold maintained the cornea's transparency and resisted degradation while suppressing inflammation postoperatively. This biomaterial could therefore potentially be applied in a wider range of sight-threatening diseases, overcoming suboptimal administration of postoperative medications to maintain hydrogel integrity and good vision.