Rabbit Head Research Articles

Development of a novel SupraChoroidal-to-Optic-NervE (SCONE) drug delivery system

Purpose Targeted drug delivery to the optic nerve head may be useful in the preclinical study and later clinical management of optic neuropathies, however, there are no FDA-approved drug delivery systems to achieve this. The purpose of this work was to develop an optic nerve head drug delivery technique. Methods Different strategies to approach the optic nerve head were investigated, including standard intravitreal and retroorbital injections. A novel SupraChoroidal-to-Optic-NervE (SCONE) delivery was optimized by creating a sclerotomy and introducing a catheter into the suprachoroidal space. Under direct visualization, the catheter was guided to the optic nerve head. India ink was injected. The suprachoroidal approach was performed in New Zealand White rabbit eyes in vivo (25 animals total). Parameters, including microneedle size and design, catheter design, and catheter tip angle, were optimized ex vivo and in vivo. Results Out of the candidate optic nerve head approaches, intravitreal, retroorbital, and suprachoroidal approaches were able to localize India ink to within 2 mm of the optic nerve. The suprachoroidal approach was further investigated, and after optimization, was able to deposit India ink directly within the optic nerve head in up to 80% of attempts. In eyes with successful SCONE delivery, latency and amplitude of visual evoked potentials was not different than the naïve untreated eye. Conclusions SCONE delivery can be used for targeted drug delivery to the optic nerve head of rabbits without measurable toxicity measured anatomically or functionally. Successful development of this system may yield novel opportunities to study optic nerve head-specific drug delivery in animal models, and paradigm-shifting management strategies for treating optic neuropathies. Translational Relevance Here we demonstrate data on a new method for targeted delivery to the optic nerve head, addressing a significant unmet need in therapeutics for optic neuropathies.

Bismuth Chelate-Mediated Digital Subtraction Angiography.

Digital subtraction angiography (DSA) is considered the "gold standard" for the diagnosis of vascular diseases. However, the contrast agents used in DSA are limited to iodine (I)-based small molecules, which are unsuitable for patients with contraindications. Here, iodine-free DSA utilizing a bismuth (Bi) chelate, Bi-DTPA Dimeglumine, is proposed for vascular visualization for the first time. Bi-DTPA Dimeglumine possesses a simple synthesis process without the need for purification, large-scale production ability (over 200g in the lab), superior X-ray imaging capability, renal clearance capacity, and good biocompatibility. Bi-DTPA-enhanced DSA can clearly display the arteries of the rabbit's head and lower limbs, with a minimum vascular resolution of 0.5mm. The displayed integrity of terminal vessels by Bi-DTPA-enhanced DSA is superior to that of iopromide-enhanced DSA. In a rabbit model of thrombotic disease, Bi-DTPA Dimeglumine-enhanced DSA enables the detection of embolism and subsequent reevaluation of vascular conditions after recanalization therapy. This proposed iodine-free DSA provides a promising and universal approach for diagnosing vascular diseases.

Injectable 2D Material-Based Sensor Array for Minimally Invasive Neural Implants.

Intracranial implants for diagnosis and treatment of brain diseases have been developed over the past few decades. However, the platform of conventional implantable devices still relies on invasive probes and bulky sensors in conjunction with large-area craniotomy and provides only limited biometric information. Here, an implantable multi-modal sensor array that can be injected through a small hole in the skull and inherently spread out for conformal contact with the cortical surface is reported. The injectable sensor array, composed of graphene multi-channel electrodes for neural recording and electrical stimulation and MoS2-based sensors for monitoring intracranial temperature and pressure, is designed based on a mesh structure whose elasticrestoringforce enables the contracted device to spread out. It is demonstrated that the sensor array injected into a rabbit's head can detect epileptic discharges on the surface of the cortex and mitigate it by electrical stimulation while monitoring both intracranial temperature and pressure. This method providesgoodpotentialfor implanting a variety of functional devices via minimally invasive surgery.

Prevention of medication-related osteonecrosis of the jaw after tooth extraction by local administration of antibiotics and atelocollagen sponge: A preliminary study

Background/purposeMedication-related osteonecrosis of the jaw (MRONJ) often develops after extraction of a tooth with a local infection. Therefore, it is necessary to develop extraction methods that can prevent MRONJ. Before examining whether antibiotics and atelocollagen administered in the extraction socket can prevent the development of MRONJ after tooth extraction, this study was conducted to determine the appropriate antibiotics concentration and to conduct a clinical study with a small number of cases as a preliminary study. Materials and methodsFirst, a mixture of minocycline and atelocollagen at different concentrations was implanted into the bone cavity formed in the rabbit head, and the local minocycline concentration was measured after 24 and 48 h. Next, the incidences of MRONJ after tooth extraction in patients receiving high-dose antiresorptive agents were compared between the atelocollagen and atelocollagen/minocycline mixture groups. A group that did not undergo transplantation was also compared as a historical control. ResultsIn animal studies, a mixture of 10 mg/ml minocycline injected into collagen and implanted into the bone cavity showed sufficiently high antimicrobial concentrations, even after 48 h. Post-extraction MRONJ occurred in 3 of the 13 control groups (23.1%), 3 of the 13 atelocollagen groups (23.1%), and 1 of the 13 atelocollagen/minocycline groups (7.7%). ConclusionAtelocollagen functions as a carrier for retaining antibiotics for a certain period. Although this was a study with a limited number of cases, it suggested that the local administration of atelocollagen/minocycline in the extraction socket may reduce the risk of MRONJ following tooth extraction.

Стандартизированная модель огнестрельного проникающего ранения глаза без внутриглазного инородного тела (открытая травма глаза типа В)

The purpose of the work was to creation of a standardized model of a gunshot penetrating wound of the eye without an intraocular foreign body. The wound was inflicted by a specially made projectile. The shot was fired from an air rifle with modulated pumping of a compression pump. A set of shells (specially made and standard) was used, and they were weighed with laboratory analytical scales. The velocity of the projectiles was recorded with a ballistic chronograph. The parameters of the shot were previously worked out on a bar of ballistic plasticine, then on 11 heads of cadaver rabbits (22 eyes). 4 series of experiments were performed. We studied the flight speed of projectiles, the nature of their flight and the meeting with the target (plasticine, cadaver eyes). The nature of the eye injury (type of injury) was analyzed depending on the energy (based on speed and mass) and aerodynamic characteristics of the projectile. According to preliminary results, a decision was made to modernize the standard projectile. A projectile has been upgraded to meet external ballistic characteristics to create a standardized model of a gunshot penetrating wound to the eye without an intraocular foreign body. The specified wound parameters were as follows: the distance from the muzzle of the air rifle to the target was 30 cm. Shots were fired into the sclera projection area 2–3 mm from the limb. The parameters of the shot were as follows: the mass of the upgraded projectile was 0.54‒0.55 g, two pumps of the rifle's air pump. The parameters used provided a speed range of 40–46 m/s. In an experiment on laboratory animals, pathogenetic factors characteristic of a gunshot injury to the eye were reproduced. This made it possible in 100 % of cases to reproduce an injury simila to a gunshot penetrating injury to the eye without an intraocular foreign body (an open eye injury of type B). Keywords: pneumatic installation, standardized experimental model, gunshot open globe injury

Computed Tomographic Findings Secondary to Dental Pathologies: Comparison between Rabbits and Guinea Pigs.

(1) Background: dental pathologies are the most frequent reason for requesting a CT scan of the head in rabbits and guinea pigs. The study aimed to review head CT exams of both species to identify and characterize lesions secondary to dental disease. (2) Methods: head CT studies of 48 rabbits and 52 guinea pigs with dental pathologies were reviewed. (3) Results: dental abnormalities of mandibular teeth were the most represented, both in rabbits (81.2%) and guinea pigs (98%). The aggressive bone lesion associated with teeth was the more frequently observed bone lesion in rabbits' mandible and maxilla; in guinea pigs, the more frequent bone lesions were bulging around the roots of the teeth with focal lysis in the maxilla, and without focal lysis in the mandible. In the maxilla, the increased attenuation of nasal cavities (rhinitis) was the most frequently observed abnormality both in rabbits (60%) and guinea pigs (83.3%); the exophthalmos was more represented in rabbits (53.3%). In the mandible, the cavernous space-occupying lesion was more represented both in rabbits (92.3%) and guinea pigs (73.3%). (4) Conclusions: lesions secondary to dental pathologies were often observed both in rabbits and guinea pigs; CT examination has proven to be valuable in detecting secondary alterations in both species.

Influence of chitosan and Cissus quandrangularis coating on osseointegration in titanium implants in rabbits: A preclinical in vivo study

BackgroundTitanium (Ti) implants has been criticized for the tiring wait for osseointegration, often making the patient reconsider implant treatment. Surface treated Ti implants are emerging as a promising solution with superior osseointegration, early loading protocols and shortened period of edentulousness. The aim of this study is to assess the osseointegration of Ti surface coated with novel Cissus quandrangularis Chitosan Hydrogel (CqChH) compared to Commercially pure (Cp) implants. Methods24 Cp Ti implants were divided into 2 subgroups (n = 12). The test group consisted of Ti implants surface treated with the novel hydrogel and control group consisted of Cp Ti implants. 3 % CqChH was prepared and was coated on the Ti implants prior to placement in the femur and tibial heads of rabbits. Implant Stability Quotient (ISQ) was recorded at the 6th and 12th week. Animals were sacrificed and subjected to Removal Torque Quotient (RTQ). The samples were retrieved en bloc and stained for histopathologic analysis. The collected data was subjected to statistical analysis using Unpaired student t-Test. ResultsAt the end of 6th week CqChH coated implants did not show any statistically significant difference in both ISQ and RTQ values compared to Cp ones. However, at the end of the 12th week CqChH coated implants demonstrated significantly higher ISQ (73.91 ± 4.39) and RTQ (75.96 ± 14.10) compared to Cp ones. ConclusionsThis study demonstrated that the novel hydrogel coating applied to the implant's surface exhibited not only enhanced bone regeneration but also elicited a new bone formation.

Incidental Findings in Computed Tomography Examination of the Head in Rabbits and Guinea Pigs.

(1) Background: Rabbits and guinea pigs are popular pet animals and often undergo computed tomography (CT) examination for assessment of pathologies of the head. The goal of the study was to review CT examinations of the heads of rabbits and guinea pigs to identify and classify incidental findings. (2) Methods: 60 CT studies of the heads of rabbits and 65 of guinea pigs presented at 2 Institutions were reviewed and the indications for the study recorded. (3) Results: The presence of CT findings not directly related to the reason for the CT examination was present in 40/60 (66.7%) studies of rabbits and in 42/65 (64.4%) studies of guinea pigs. Most commonly, the incidental findings involved the ears, in 24/60 studies in rabbits and in 29/65 studies in guinea pigs. Incidental findings involved the nasal cavities, respectively, in 9 and 7 rabbits and guinea pigs. Soft tissue mineralization was present in 11 rabbits and 17 guinea pigs. (4) Conclusions: Based on the present study, incidental findings detected on CT studies are often present in rabbits and guinea pigs. Veterinarians should be aware of the possible clinical impact of these findings.

Enhancing STING activation by cyclic dinucleotide-manganese particles for systemic cancer immunotherapy.

2571 Background: Activating the innate immune pathway of stimulator of interferon genes (STING) can elicit potent anti-tumor immunity via the production of type-I interferons (IFN-I). However, cyclic-dinucleotide (CDN) STING agonists have undesirable pharmacological properties. Most CDNs in clinical development are administered intratumorally, thus precluding their applications in treating metastasis, hematologic malignancies, and hard-to-reach solid tumors. Here, we report the development of a new nanoparticle system for the systemic delivery of CDN STING agonists with potent efficacy, favorable pharmaceutical properties, and acceptable safety profiles. Methods: Nutritional metal ions play crucial roles in modulating immune pathways, which could potentially be used for enhancing STING activation. We screened different metal ions and found that manganese ion (Mn2+) achieved strong synergy with CDN STING agonists for inducing IFN-I production. We further developed a new nanoparticle system for co-delivery of Mn2+ and CDN for systemic cancer immunotherapy. Results: Mn2+ induced up to 77-fold enhancement in CDN-mediated STING activation. Mixing CDNs with Mn2+ resulted in the self-assembly of nanocrystals, and the lipid layer coating led to uniform nanoparticles. The resulting STING-activating CDN-Mn nanoparticle (SNP) given intravenously elicited IFN-I responses, attenuated the suppressive functions of myeloid cells, remodeled the immunosuppressive tumor microenvironment, and expanded CD8+ T cells for sustained tumor control. Intravenous SNP therapy resulted in robust anti-tumor efficacy in multiple murine tumor models, including a genetically engineered mouse model of MMTV-PyMT triple-negative breast cancer. We have also demonstrated the robust anti-tumor efficacy of SNP against VX2 head and neck squamous cell carcinomas (HNSCC) in New Zealand white rabbits. Mechanistically, the efficacy of intravenous SNP therapy was dependent on the host STING expression but independent of the tumor STING expression. In addition, the anti-tumor efficacy of SNP was decreased in mice lacking Ifnar1 or Ifngr1 expression in the B16F10 melanoma model, showing the crucial effects of IFN-I and IFN-II responses. Lastly, SNP was effectively uptaken by human PBMCs and elicited IFN-I responses when injected into fresh human tumor biopsies derived from HNSCC patients. Conclusions: SNP empowers highly effective systemic cancer immunotherapy via nanotechnology. It also underscores the potential of utilizing metal ions for immune-mediated disease treatment.

PDGF-BB prevents destructive repair and promotes reparative osteogenesis of steroid-associated osteonecrosis of the femoral head in rabbits.

Destructive repair characterized by inadequate angiogenesis and osteogenesis is the main pathological progression in steroid-associated osteonecrosis of the femoral head (SONFH). Platelet-derived growth factor-BB (PDGF-BB) is an "angiogenesis and osteogenesis coupling" factor that has been used for the treatment of bone defects in clinic. This study was designed to analyze the ability of PDGF-BB for preventing destructive repair and promoting reparative osteogenesis in SONFH. Steroid-associated osteonecrosis (SAON) was induced and triggered destructive repair of the femoral head by repeated lipopolysaccharide (LPS) and methylprednisolone (MPS) injections in rabbits. At 2, 4, and 6 weeks after induction, recombinant human PDGF-BB, neutralizing PDGF-BB antibody, or saline was intramedullary injected into the proximal femora. At week 6 after SAON induction, the proximal femora were dissected for bone architecture and histological analysis. C3H10T1/2 cells and HUVECs were used for further mechanistic investigation. After PDGF-BB treatment, type H vessels and leptin receptor-positive (LepR+) mesenchymal stem cells (MSCs) increased in the affected femoral head, and more osteoblastic osteogenesis along the bone surfaces but scattered adipocytes in bone marrow tissue than that in the SAON group. PDGF-BB treatment prevented destructive repair progression and led to 50-70 % of osteonecrotic femoral heads undergoing reparative osteogenesis. In particular, we found that PDGF-BB could mediate MSC self-renewal and maintain their osteogenic potency by activating PDGFR/Akt/GSK3β/CERB signaling in the presence of steroids. Moreover, PDGF-BB also stabled the newly formed vascular tubes by recruiting MSCs for improving intraosseous vascular integration. PDGF-BB may be a candidate for the promotion of reparative osteogenesis in SONFH.

Anatomy of the rabbit inner ear using computed tomography and magnetic resonance imaging.

Anatomically, the inner ear is a highly complex organ of intricate design, composed of a bony labyrinth that encases the same-shaped membranous labyrinth. It is difficult to study the three-dimensional anatomy of the inner ear because the relevant structures are very small and embedded within the petrous temporal bone, one of the densest bones in the body. The current study aimed to provide a detailed anatomic reference for the normal anatomy of the rabbit's inner ear. As a study model, ten healthy adults New Zealand White rabbit heads were used. Six heads were used for macroscopic evaluation of the bony and membranous labyrinths. The remaining four heads were evaluated radiographically, where 3D images were generated of the bony and membranous labyrinths using data sets from computed tomography (CT) and magnetic resonance imaging (MRI), respectively. The anatomical structures were identified and labelled according to NominaAnatomicaVeterinaria (NAV). Our study revealed that CT and MRI are the optimal cross-sectional imaging modalities for investigating such tiny and often inaccessible inner ear structures. As high-quality scanners are not readily available to veterinarians, the CT and MRI images generated by this research were of lower quality; therefore, high-quality dissections were used to identify/support structures seen in these images. In conclusion, this study provides one of the first investigations that uses multislice CT scans and MRI to study the rabbit's inner ear and its correlation with the corresponding anatomical images. Both anatomical, CT and MRI images will serve as a reference for interpreting pathologies relative to the rabbit's inner ear.

The efficiency of genetically modified mesenchymal stromal cells combined with a functionally graded scaffold for bone regeneration in corticosteroid-induced osteonecrosis of the femoral head in rabbits.

Core decompression (CD) with mesenchymal stromal cells (MSCs) is an effective therapy for early-stage osteonecrosis of the femoral head (ONFH). Preconditioning of MSCs, using inflammatory mediators, is widely used in immunology and various cell therapies. We developed a three-dimensional printed functionally graded scaffold (FGS), made of β-TCP and PCL, for cell delivery at a specific location. The present study examined the efficacy of CD treatments with genetically modified (GM) MSCs over-expressing PDGF-BB (PDGF-MSCs) or GM MSCs co-over-expressing IL-4 and PDGF-BB and preconditioned for three days of exposure to lipopolysaccharide and tumor necrosis factor-alpha (IL-4-PDGF-pMSCs) using the FGS for treating steroid-induced ONFH in rabbits. We compared CD without cell-therapy, with IL-4-PDGF-pMSCs alone, and with FGS loaded with PDGF-MSCs or IL-4-PDGF-pMSCs. For the area inside the CD, the bone volume in the CD alone was higher than in both FGS groups. The IL-4-PDGF-pMSCs alone and FGS + PDGF-MSCs reduced the occurrence of empty lacunae and improved osteoclastogenesis. There was no significant difference in angiogenesis among the four groups. The combined effect of GM MSCs or pMSCs and the FGS was not superior to the effect of each alone. To establish an important adjunctive therapy for CD for early ONFH in the future, it is necessary and essential to develop an FGS that delivers biologics appropriately and provides structural and mechanical support.

Effect of Yang-Warming and Kidney-Tonifying Prescription on Expression of Osteogenic and Angiogenic Factors and H-Type Vascular Markers in Steroid-Induced Avascular Necrosis of Femoral Head in Rabbits

Effect of Yang-Warming and Kidney-Tonifying Prescription on Expression of Osteogenic and Angiogenic Factors and H-Type Vascular Markers in Steroid-Induced Avascular Necrosis of Femoral Head in Rabbits

Результаты экспериментального лечения кроликов с асептическим некрозом головки бедренной кости

The aim of the study was to cause aseptic necrosis of the femoral head in rabbits in an experiment by administering drugs that worsen blood supply in the femoral head and hip joint. The drugs were administered to rabbits distributed in two groups. X-ray, biochemical and morphological studies were carried out. Then a surgical operation was performed aimed at removing part of the femoral head by resection arthroplasty at different times before the restoration of limb functions.

Morphometric characterization of New Zealand white rabbit raised at different areas

The study aimed to morphometric characterization the New Zealand White (NZW) doe at three different areas. The materials used were 295 heads of NZW doe rabbits from 29 farms located at different areas. Twelve morphometric characteristics consist of body weight, eight body measurements, and three-body indices. Data analysis was performed by Mixed model, Pearson’s correlation, Principal component, and Canonical discriminant procedures. The most of parameters showed significant differences among areas. The heaviest body weight (4.71 kg) was observed in low-land and the lightest in medium land (3.54 kg). Most of the morphometric characters showed positive correlations with each other. Results of principal component show that the body indices of NZW doe raised in three different areas were similar. Canonical discriminant analysis showed that low-land was more favorable than high-land and medium land. In conclusion, The variation in size difference for morphometric characters of female New Zealand white rabbit could be explained by body index and thoracic index. The morphometric characteristics of New Zealand white doe raised in low-land area were superior to those raised in high-land and medium land areas.

A data compensation method for reducing impact of scalp dehydration in electrical impedance tomography

Electrical impedance tomography (EIT) has shown its potential in the monitoring of cerebral edema. It is found that scalp is also dehydrated when dehydration of brain tissue is conducted. Simultaneous dehydration of the brain tissue and scalp would greatly affect the image quality. To solve this problem, this work proposes a data compensation method which aims to reduce the influence of scalp dehydration on image reconstruction. Firstly, a rabbit head which is simulated by a three-layer elliptical model is established. The relationship between boundary measurement and dehydration degree in the case of simultaneous dehydration is investigated. Then a prior matrix representing variation of boundary voltage against degree of dehydration when only scalp is dehydrated is established. With the determination of dehydration degree and establishment of the prior information, it is able to reduce the impact of scalp dehydration on measured voltage data. To validate the performance of the proposed method, reconstruction of four different models when scalp and brain are simultaneously dehydrated is conducted. Image reconstruction is performed under noiseless condition and different noise level conditions. Also, reconstructed images under brain dehydration are given for comparison. The performance of the proposed method is also experimentally tested. The results show that the impact of scalp dehydration on image reconstruction can be effectively reduced with the proposed data compensation method. • A novel data compensation method and a simple L1 regularization method is proposed for accurate image reconstruction in EIT. • By analyzing boundary data measured from electrodes, dehydration degree is determined and a prior matrix is obtained. • In the case of simultaneous dehydration of scalp and brain, reconstruction quality is improved with the proposed method.

Optical Properties and Fluence Distribution in Rabbit Head Tissues at Selected Laser Wavelengths.

The accurate estimation of skin and skull optical properties over a wide wavelength range of laser radiation has great importance in optogenetics and other related applications. In the present work, using the Kubelka–Munk model, finite-element solution of the diffusion equation, inverse adding-doubling (IAD), and Monte-Carlo simulation, we estimated the refractive index, absorption and scattering coefficients, penetration depth, and the optical fluence distribution in rabbit head tissues ex vivo, after dividing the heads into three types of tissues with an average thickness of skin of 1.1 mm, skull of 1 mm, and brain of 3 mm. The total diffuse reflectance and transmittance were measured using a single integrating sphere optical setup for laser radiation of 532, 660, 785, and 980 nm. The calculated optical properties were then applied to the diffusion equation to compute the optical fluence rate distribution at the boundary of the samples using the finite element method. Monte-Carlo simulation was implemented for estimating the optical fluence distribution through a model containing the three tissue layers. The scattering coefficient decreased at longer wavelengths, leading to an increase in optical fluence inside the tissue samples, indicating a higher penetration depth, especially at 980 nm. In general, the obtained results show good agreement with relevant literature.

Effects of methacrylic anhydride gelatin hydrogel loaded with silver and recombinant human basic fibroblast growth factor on deep partial-thickness burn wounds in rabbits

Effects of methacrylic anhydride gelatin hydrogel loaded with silver and recombinant human basic fibroblast growth factor on deep partial-thickness burn wounds in rabbits

Copper-Lithium-Doped Nanohydroxyapatite Modulates Mesenchymal Stem Cells Homing to Treat Glucocorticoids-Related Osteonecrosis of the Femoral Head.

In situ tissue regeneration has been demonstrated to promote bone repair. To identify a better approach for treating osteonecrosis of the femoral head (ONFH), we prepared scaffolds using copper-lithium-doped nanohydroxyapatite (Cu-Li-nHA), which has the potential to modulate mesenchymal stem cells (MSCs) homing. The scaffold was fabricated using the gas foaming method and the migration, angiogenesis, and osteogenesis activities of MSCs were detected using Transwell assays, tube formation assays, alkaline phosphatase and alizarin red S staining, respectively. We then implanted the Cu-Li-nHA scaffold into the femoral heads of ONFH rabbits, and CFSE labeled exogenous MSCs were injected intravenously to verify cell homing. The repair effect was subsequently examined using micro-CT and histological analysis in vivo. The results showed that Cu-Li-nHA significantly promoted MSCs migration and homing by upregulating the HIF-1α/SDF-1 pathway. The Cu-Li-nHA group showed optimal osteogenesis and angiogenesis and greater improvements in new bone formation in ONFH rabbits. To summarize, Cu-Li-nHA promoted homing and induced the osteogenic differentiation of MSCs, thereby enhancing bone regeneration during ONFH repair. Thus, Cu-Li-nHA implantation may serve as a potential therapeutic strategy for ONFH in the future.

The effect of vitamins A and D on the protein balance in the body of young rabbits

In feed for farm animals, the most expensive component is protein. To increase the intensity of its metabolism, fat-soluble vitamins are included in the feed of herbivorous animals. The effect of vitamins A and D on the balance of protein (nitrogen) in the body of young rabbits was studied by classical methods in a series of exchange (balance) experiments in the Department of Fur Animal Husbandry and Rabbit Breeding of the V. A. Afanasyev Scientific Research Institute of Fur Farming and Rabbit Breeding. From 12 heads of young rabbits of the Soviet Chinchilla breed at the age of 45 days, 3 groups of 4 heads each were formed according to the principle of analogues. Rabbits of the 1st - control group received full-fledged granular mixed feed (PGK) without additives, vitamin A was added to the mixed feed of rabbits of the 2nd group at the rate of 500 IU per 100 g, vitamin D was added to the mixed feed of the 3rd group at the rate of 150 IU per 100 g of mixed feed. As a result of three balance experiments, it was found that the groups practically did not differ in the amount of digested nitrogen. The excretion of nitrogen in the urine was stable, without significant differences in the groups. Thus, the addition of synthetic vitamins A and D to the diet does not affect the intensity of protein metabolism in young rabbits. The indicator of daily nitrogen deposition in rabbits aged 45-74 days is quite stable, on average 1.5 g per head. The percentage of nitrogen deposition to the accepted one is on average 49.55. The deposition of nitrogen in the body of young rabbits to the digested nitrogen of the diet is quite high – 76.5%, which indicates the rational use of protein by rabbits for plastic needs.