Surgical Stabilization of the Equine Cervical Spine

The Cloward technique for intervertebral fusion was utilized on 12 horses ranging from 3 months to 2 years of age. Of the 12 horses, 9 had been diagnosed as having equine cervical vertebral malformation (CVM) or "wobbles," and 3 were normal controls. A large hole was drilled from the ventral border of the vertebral bodies spanning the intervertebral disc and the vertebral end plates of the 2 articulating vertebrae. Frozen homologous bone dowels of slightly larger diameter from equine cadaver ilia were inserted in the holes. No adverse postoperative complication arose. Clinical improvement was seen in all horses with CVM. Three months postoperatively, partial or complete fusion was evident radiographically in 11 of the 12 horses. Necropsies were performed 3–6 months postoperatively to evaluate the quality of the fusion. Cadaver manipulation demonstrated reduced intervertebral movement at the operative site in all cases. The articulations of the equine cervical spine can be operatively fused by the Cloward technique, and surgically induced trauma is minimal. This technique can be used for stabilizing subluxations and may be applicable for treating fractures and osteolytic processes that have weakened vertebrae.     

Kinematics of the cervical spine of the adult horse

At least three types of movement, dorsoventral flexion and extension, axial rotation and lateral bending, were shown to occur at each of the intervertebral joints in the cervical spine. Between the first two cervical vertebrae the mean axial rotation was 107.5 degrees, which was 73 per cent of the total axial rotation of the cervical spine. The atlantooccipital joint rotated through a mean of 27 degrees, whereas the remaining cervical joints each had less than 3 degrees of rotatory movement. Dorsoventral flexion and extension were maximal at the atlantooccipital joint, which had an amplitude of 86.4 degrees and accounted for 32 per cent of the total dorsoventral movement of the cervical spine. Lateral bending was relatively more uniform along the length of the neck, with mean values ranging from 25 to 45 degrees for each joint except that between the first two cervical vertebrae, which had a mean of only 3.9 degrees of lateral bending.     

Anatomy of the vertebral column,ribs and sternum in orange rumped agouti (Dasyprocta leporina Linnaeus, 1758): Structural and Functional perspectives

The axial skeleton of orange rumped agouti, Dasyprocta leporina, was studied for better understanding of its locomotor behaviour. The bones from eight adult agoutis of both sexes were observed for their anatomical features and functional significance. The vertebral formula was found to be C₇T₁₂L₇S₅Cy_5–6. The well-developed occipital crest, caudally oriented prominent axis spine and well-developed transverse processes from C₃–C₇ indicated a highly flexible neck with greater sagittal mobility. Articular facets were horizontal in anterior series while oblique in the posterior series, which enabled them to perform both lateral and sagittal movements during locomotion. The caudally directed thoracic spines, T₁₂ as anticlinal vertebra and prominent mamillary process in the posterior series were suggestive of strong dorso-ventral flexion/extension and rotation. The robust lumbar vertebrae, well-developed transverse processes with cranio-ventral extension, were the feature for powerful sagittal/dorsoventral movement. The presence of spinous processes and well-developed transverse processes in all caudal vertebrae was an indication of a highly movable tail. The ribs were 13 pairs with first seven as sternal and six as asternal. They were laterally compressed in the anterior series as a cursorial adaptation. A strong muscular attachment to vertebrae provides this rodent speed, agility, dexterity and strength suitable for survival in food chain.     

Alternative classification and screening protocol for transitional lumbosacral vertebra in German shepherd dogs

Background

Lumbosacral transitional vertebra (LTV) is a common congenital and hereditary anomaly in many dog breeds. It predisposes to premature degeneration of the lumbosacral junction, and is a frequent cause of cauda equina syndrome, especially in German shepherd dogs. Ventrodorsal hip radiographs are most often used in diagnosis of LTV in screening programs. In this study, value of laterolateral lumbar spine radiographs as additions to ventrodorsal radiographs in diagnosis of LTV, and characteristics of LTV and the eighth lumbar vertebra (L8) in laterolateral radiographs were studied. Additionally, computed tomography (CT) features of different types of LTV were elucidated.

Methods

The ventrodorsal pelvic and laterolateral lumbar spine radiographs of 228 German shepherd dogs were evaluated for existence and type of LTV. Morphology of transverse processes was used in classification of LTV in ventrodorsal radiographs. The relative length of sixth (L6) and seventh (L7) vertebrae (L6/L7) was used in characterization of these vertebrae in laterolateral radiographs. CT studies were available for 16 dogs, and they were used for more detailed characterization of different types of LTV. Non-parametric χ² statistics, generalized logit model for multinomial data, and one-way analysis of variance was used for statistical analyses.

Results

In all, 92 (40%) dogs had a LTV, the most common type being separation of first spinous process from the median crest of the sacrum in 62 dogs (67% of LTV). Eight dogs had eight lumbar vertebrae. Those dogs with LTV had longer L7 in relation to L6 than dogs with normal lumbosacral junctions. When L6/L7 decreased by 0.1 units, the proportion of dogs belonging to the group with L8 was 14-fold higher than in the group with normal lumbosacral junctions. L8 resembled first sacral vertebra (S1) in length and position and was therefore classified as one type of LTV. With CT it was shown that categorizing LTV, based on shape and visibility of transverse processes seen in ventrodorsal radiographs, could be misleading.

Conclusions

We suggest that L8 be included as a part of the LTV complex, and the laterolateral radiographs of the lumbar spine be considered as an addition to ventrodorsal projections in the screening protocols for LTV.     

Thoracic vertebral chordoma in a domestic ferret (Mustela putorius furo).

A castrated adult male 1.0-kg domestic ferret (Mustela putorius furo) was referred for evaluation of a mass of >5 mo duration that was associated with the thoracic spine. The ferret had motor dysfunction and no conscious proprioception or pain perception in either hind limb. Segmental reflexes were present. Survey radiography, myelography, and magnetic resonance imaging showed a mass involving the ninth and 10 thoracic vertebrae and compressing the spinal cord. Decompressive surgery was performed, but clinical signs persisted. A diagnosis of chordoma was made using histopathology and immunohistochemistry. This is the first reported case of a chordoma involving the thoracic vertebrae in a domestic ferret.     

Radiographic evaluation of congenital vertebral anomalies in Korean raccoon dogs (Nyctereutes procyonoides koreensis)

BackgroundThe normal vertebral anatomy of Korean raccoon dogs and their variants require research attention as a prerequisite for identifying pathologies and anomalies.ObjectivesThis retrospective study aimed at describing the vertebral formula and congenital vertebral anomalies in Korean raccoon dogs (Nyctereutes procyonoides koreensis).MethodsRadiographs of 82 raccoon dogs (42 males, 40 females) acquired from May 2013 to June 2020 in the Gangwon Wildlife Medical Rescue Center were reviewed to evaluate the cervical, thoracic, and lumbar vertebrae of the spine.ResultsNormal morphology of all vertebrae was observed in 50 of the 82 raccoon dogs, and the vertebral formula was cervical 7, thoracic 13, and lumbar 7. Congenital vertebral anomalies were found in 32 raccoon dogs: transitional vertebrae (TV) in 31 and block vertebrae in 2. Two raccoon dogs had 2 types of vertebral anomalies: one had TV and block vertebra, and the other had 2 types of TV. Twenty-nine raccoon dogs had thoracolumbar TV (TTV) and 3 had lumbosacral TV. TTV was morphologically classified into 4 different types: unilateral extra-rib in 5 raccoon dogs, bilateral extra-ribs in 14, bilateral elongated transverse processes in 4, and an asymmetric mixed formation of extra-rib with elongated transverse process in 6.ConclusionsThis study showed that TTV is common in Korean raccoon dogs, and that the vertebral formula is relatively diverse. The bilateral extra-ribs type TTV is the most common variant, which is almost similar to normal rib to be confused the radiographic evaluation.     

Paraparesis in a dwarf goat: clarification by means of magnetic resonance imaging

A 4-year old pygmy goat with chronic paraparesis of the hindlimbs was referred to the Ruminant Clinic of the University of Berne. The causative lesion was localized to the thoracolumbar spinal cord after a thorough clinical examination. Because a radiographic examination of the spine had not been diagnostic, magnetic resonance imaging (MRI) was performed. A mass compressing the spinal cord in the region of L2-L5 was detected. The goat was euthanized and autopsied, which allowed for the definitive diagnosis of lymphosarcoma. In addition to the changes in the lumbar area, further neoplastic masses were detected in the region of the thoracic vertebrae, near the thoracic aperture, on the lungs and on the pericardium. However, these processes had not yet caused clinical signs. MRI investigation allowed for the ante mortem diagnosis of an infiltrative mass in the spinal canal of this goat.     

Cervical and Thoracic Vertebral Malformation ("Weak Neck") in Colombia Lambs

The purpose of this study is to describe a developmental defect of the caudal cervical and cranial thoracic vertebrae in 11 purebred Colombia lambs. The lambs were either affected at birth, or developed the condition within the first 18 days of age. Cervicothoracic kyphosis, with a compensatory cervical lordosis and ataxia were common; 8 lambs had abnormal head posture, characterized by inability to lift the head from the ground. One lamb had rigid head and neck, and had to move the entire body to look to the left or right. Neurological signs included ataxia, tetraparesis, diminished conscious proprioception, and increased patellar and triceps reflexes. One lamb had inspiratory stridor because of compression of the trachea in the area overlying the abnormal vertebrae (cervical vertebrae 6 [C6] and 7 [C7]). Radiographic and pathological abnormalities included malalignment and malarticulation of the caudal cervical and cranial thoracic spine, rounded cranioventral margins in the bodies of vertebrae C7 and T1, wedging of the intervertebral disc spaces between C6 and T1 vertebrae, and hypoplasia of the dens. Pathological changes in the soft tissues included hypoplasia of the cervical epaxial and hypaxial musculature, with associated focal areas of myodegeneration. Mild Wallerian axonal degeneration, compatible with a mild cord compression syndrome, was found in 3 lambs in the cervicothoracic spinal cord adjacent to the vertebral anomalies. The concentrations of copper and selenium in blood, plasma, or tissues were normal in 10 of 11 lambs. All but one of the lambs in which pedigree information was provided were genetically related. Siblings born as twins to 5 of the affected lambs were normal, but both lambs from one twin pregnancy were affected. Owners reported that breeding stock had been shared among the ranches. Because of the close familial relationships of the affected lambs, the condition is suspected to have a hereditary basis.     

Relationship between spinal biomechanics and pathological changes in the equine thoracolumbar spine

The relationship between spinal biomechanics and pathological changes occurring in functionally normal equine thoracolumbar spines was studied in 23 horses. Ventrolateral vertebral body osteophytes occurred in 36 per cent of the spines. The majority occurred between the 10th and 17th thoracic vertebrae with the largest being found between the 11th and 13th thoracic vertebrae, the region of the thoracic spine where the greatest amount of lateral bending and axial rotation occurs. Impingement of the dorsal spinous processes was detected in 86 per cent of the spines with most lesions occurring between the 13th and 18th thoracic vertebrae. The severity of occurrence of impingement did not appear to be related to regional spinal mobility. Degeneration of intervertebral discs was observed in three of four specimens that were sectioned sagittally. It occurred in the first thoracic and the lumbosacral intervertebral discs and appeared to be related to the increased dorsoventral mobility and the increased disc thickness of these joints. The characteristic distribution of fractures of the thoracolumbar spine is discussed with respect to the biomechanics of the spine.     

Mapping of Split-Line Pattern and Cartilage Thickness of Selected Donor and Recipient Sites for Autologous Osteochondral Transplantation in the Canine Stifle Joint

Objective— To characterize donor and recipient sites for autologous osteochondral transplantation in the canine stifle joint with respect to split-line pattern and cartilage thickness.
Study Design— In vitro study.
Sample Population— Stifle joints (n=30) of dogs >20 kg.
Methods— Collagen network orientation of the hyaline cartilage coverage of the distal femur was assessed using split-line technique (n=10). Cartilage thickness was measured radiographically on osteochondral plugs harvested at the abaxial and axial surfaces of the femoropatellar joint (n=15), the most proximal abaxial aspect of the medial condyle (CO; n=5) and at both femoral condyles (n=15).
Results— Cartilage within the femoropatellar joint and both femoral condyles had mostly transversely orientated pattern of split-lines. Abaxial to the femoropatellar joint split-lines were absent. All donor sites had significantly thinner cartilage than the medial condyle (CM). Only the distal trochlea had cartilage thickness comparable to the lateral condyle (CL). The thinnest cartilage was found abaxial to the femoropatellar joint followed by CO, which was ∼2–3 times thinner than the cartilage at both condyles.
Conclusions— None of the investigated donor sites provided transplants of comparable cartilage thickness to CM. Transplants from within the femoropatellar joint should be harvested in priority as they reach cartilage morphology comparable to CL.
Clinical Relevance— Adjusting for cartilage thickness and split-line pattern may improve long-term outcome after autologous osteochondral transplantation. But surface curvature and donor-site morbidity have to be considered as well when choosing the most suitable donor site.     

Cervical spondylomyelopathy (wobbler syndrome) in the Boerboel

The Boerboel is a South African large-breed dog resembling a Bullmastiff. The records of Onderstepoort Veterinary Academic Hospital were searched for dogs that had presented, between 1998 and 2003, with symptoms indicative of wobbler syndrome and had undergone survey radiographic and myelographic studies. Ten cases fitted the inclusion criteria. Dogs presented within the first 2 years of life, often with acute onset of symptoms. All presented with pelvic limb and 6 with concomitant thoracic limb ataxia or paresis. Treatment varied and included none (4), prednisolone (2), and dorsal laminectomy (2). Two dogs were euthanased at the time of diagnosis. The breed appears to be affected with a form of spondylomyelopathy that comprises bony malformation of cervical and/or thoracic vertebrae. In 8 dogs, malformations were evident on survey radiographs and were characterised by enlarged, irregular articular facets and associated medial deviation of the pedicles. These changes resulted in axial compression of the spinal cord best seen on ventrodorsal or dorsoventral myelographic studies. Multiple vertebrae were affected in some dogs and lesions were not confined to the caudal area of the cervical spine. Three dogs were alive and without symptoms at follow-up. Four were euthanased as a result of the disease and 1 died as a result of post-operative complications. Two additional dogs presenting with wobbler clinical signs are also described. One had medial deviation of the T5 and T6 caudal pedicles and 1 dog suffered from multiple cervical articular facet synovial cysts.     

Vertebral stabilisation for cervical spondylopathy using a screw and washer technique

A transvertebral screw and interbody washer technique was used to stabilise the vertebrae and maintain the intervertebral space in 34 adult dobermann pinschers with cervical spondylopathy. The long term success of the procedure was 50 per cent. Pre-operatively three dogs were considered mildly ataxic, 16 moderately ataxic, 13 severely ataxic and two non-ambulatory. Thirty dogs had radiographic changes of calcified disc, vertebral malalignment or narrow intervertebral disc space and all dogs had myelographic abnormalities in the caudal cervical spine. Vertebral malalignment and narrow intervertebral space correlated closely with myelographic cord compression. However, compressive lesions were not identified in 11 cases on plain films. Follow-up was available on 30 dogs of which 25 showed neurological improvement. This was temporary in 10 cases which were destroyed two weeks to three years following surgery.     

Pathological Changes Associated with Vitamin C Deficiency in Walleyes

Abstract

Walleyes Stizostedion vitreum were fed three experimental diets containing 0, 96, and 190 mg vitamin C/kg for 20 weeks. Retarded growth, increased mortality, and clinical signs of vitamin C deficiency were seen only in the group fed the vitamin-C-free diet. Skeletal deformities, primarily lordosis, were evident in 76% of this group. Pathological changes associated with vitamin C deficiency in walleyes included twisted cartilage of gill filaments and extreme dislocation of vertebrae. Vertebral lesions included focal hemorrhage, compressed spinal cord, and displacement of adjacent kidney and skeletal muscle. Breaking of the isthmus, a clinical sign not previously described for vitamin-C-deficient fish, was the cause of death in 27% of walleyes fed the vitaminC-free diet. Hemorrhagic fins, skin, and eyes were seen occasionally. A diet that was not supplemented with vitamin C but that contained 96 mg vitamin C/kg was adequate for normal growth and prevention of vitamin-deficiency signs in walleye.     

Vertebral mineral density measured by dual-energy X-ray absorptiometry (DEXA) in a group of healthy Italian boxer dogs

We studied the feasibility of using dual-energy X-ray absorptiometry (DEXA) to obtain reference bone density values in relation to age, gender and body weight in growing and young adult Italian boxer dogs. The study was performed on eight animals (three males and five females) at 7, 12 and 18 months of age. Animals were carefully examined and blood samples were collected from each dog to detect any sign of metabolic and/or endocrine disease. Each subject underwent radiographs to evaluate growth of the spine and hip. One female was not considered in the statistical model because of the development of grade 4 spondylosis deformans during the study period. All animals were serially scanned using DEXA; the region of interest was the whole spine T12-L2, while the subregions of interest were the four vertebrae (T12-T13-L1-L2) within the scanned spine. Statistical analysis was performed separately for each region of interest. Age had the strongest relationship with bone density (P < 0.001). Gender effect on spinal mineral density was not significant while vertebral site effect was highly significant. Average bone mineral density (BMD) +/- SD for the whole spine trait was 0.862 +/- 0.108 g/cm2 while average BMD +/- SD for subregions of interest ranged from 0.836 +/- 0.141 g/cm2 for T12 to 0.928 +/- 0.119 g/cm2 for L2. Estimated reference BMD values at 7, 12 and 18 months of age for each vertebral site in males and females are provided.     

EX VIVO COMPUTED TOMOGRAPHIC EVALUATION OF MORPHOLOGY VARIATIONS IN EQUINE CERVICAL VERTEBRAE

Diagnostic imaging is one of the pillars in the clinical workup of horses with clinical signs of cervical spinal disease. An improved awareness of morphologic variations in equine cervical vertebrae would be helpful for interpreting findings. The aim of this anatomic study was to describe CT variations in left–right symmetry and morphology of the cervical and cervicothoracic vertebrae in a sample of horses. Postmortem CT examinations of the cervical spine for horses without congenital growth disorders were prospectively and retrospectively recruited. A total of 78 horses (27 foals, 51 mature horses) were evaluated. Twenty‐six horses (33.3%) had homologous changes in which a transposition of the caudal part of the transverse process (caudal ventral tubercle) of C6 toward the ventral aspect of the transverse process of C7 was present (n = 10 bilateral, n = 12 unilateral left‐sided, n = 4 unilateral right‐sided). There was one horse with occipito‐atlantal malformation, two horses with rudimentary first ribs bilaterally, and one horse with bilateral transverse processes at Th1, representing homeotic (transitional) vertebral changes. Chi‐square tests identified no significant differences in the number of conformational variations between the group of mature horses with or without clinical signs (P = 0.81) or between the group of mature horses and the group of foals (P = 0.72). Findings indicated that, in this sample of horses, the most frequently identified variations were homologous variations (transposition of the caudal part of the transverse process of C6–C7) in the caudal equine cervical vertebral column. Homeotic (transitional) variations at the cervicothoracic vertebral column were less common.     

MRI has limited agreement with CT in the evaluation of vertebral fractures of the canine trauma patient

Complete assessment of vertebral trauma in dogs currently requires CT and MRI for evaluation of the osseous and soft tissue structures that contribute to vertebral stability. Some studies in people have suggested that MRI may be sensitive and specific at detecting vertebral fractures making this potentially a single modality that could be used in spinal trauma evaluation. This study aimed to assess the ability for observers to evaluate vertebral fractures using MRI when compared to CT, which was used as the reference standard. Twenty‐nine dogs with previously diagnosed acute vertebral fractures and four dogs with no vertebral fracture that had undergone sequential CT and MRI were included into the study. One hundred twenty‐eight vertebrae were evaluated for the presence of fractures. Imaging studies were read by two observers blinded to the history. While both observers had similarly high sensitivity and specificity for simple detection of any fractured vertebrae, interobserver agreement was only moderate (κ = 0.584). When evaluations were specifically limited to detection of structurally unstable fractured vertebrae both observers showed improved specificity and interobserver agreement became substantial (κ = 0.650). Complete agreement for exact fracture location between MRI and CT results was only achieved in 14.3‐32.6% of fractured vertebra with up to 79% of fractures being missed in some vertebral structures. This suggests that although MRI may be able to detect the presence of fractured vertebrae, it is not able to replace CT for the complete evaluation of the traumatized spine and documentation of fracture morphology.     

Total vertebrectomy for stabilisation of chronic spinal lumbar luxation in a paraplegic dog without nociception

An adult male crossbred dog was referred with a history of a road traffic accident that took place 1 month earlier. Neurological examination revealed paraplegia with absent nociception in the pelvic limbs. On epaxial palpation, significant curvature of the anatomical axis of the spine between the third and fourth lumbar vertebrae was observed, with the presence of a bone end almost piercing the dog's skin. Survey radiographs of the lumbar spine revealed severe dislocation between L3 and L4 vertebrae. During surgery, the spinal cord was not visible between the dislocated segments. Because of difficulties in reducing the lumbar luxation during surgery, vertebrectomy and vertebral shortening were performed. After alignment between vertebrae L3 and L5, eight cortical orthopaedic screws and bone cement were used for fixation. After 30 days, the dog started to use a wheelchair and was considered by its owner to have a good quality of life with no evidence of pain. To the authors’ knowledge, this is the first case of severe luxation treated by total vertebrectomy and spine shortening in a dog. This surgery can be considered as an option in the management of severe spine luxation when the spinal cord is physically transected.     

Effect of dietary nutrients on osteochondrosis lesions and cartilage properties in pigs

OBJECTIVE: To evaluate dietary ingredients involved in cartilage and bone metabolism and their influence on osteochondrosis lesions in swine. ANIMALS: 80 crossbred gilts (mean initial weight, 39 kg). PROCEDURES: Pigs (10 pigs/treatment) were fed a corn-soybean meal basal (control) diet or the basal diet supplemented with additional minerals (copper and manganese or silicon), amino acids (proline and glycine; a combination of leucine, isoleucine, and valine; or methionine and threonine), or fatty acids (provided by fish oil) for 84 days. Pigs were then slaughtered and the distal portion of the left femur was collected for determination of osteochondrosis lesions at the femoral condyle. After evaluation of external joint surfaces, the distal portion of the femur was sectioned to evaluate lesions in the growth plate and articular cartilage. Additionally, a cartilage specimen was obtained from the patella for analysis. RESULTS: Pigs fed diets containing high amounts of methionine and threonine or the diet containing all additional ingredients had significantly lower total severity scores, compared with scores for pigs fed the control diet or a diet supplemented with fish oil. Pigs fed diets containing additional proline and glycine, copper and manganese, methionine and threonine, or all additional ingredients had significantly lower overall scores, compared with scores for pigs fed the control diet or a diet supplemented with fish oil. CONCLUSIONS AND CLINICAL RELEVANCE: Dietary manipulation decreased the severity of osteochondrosis lesions, compared with results for pigs fed a control diet. However, additional research on optimal concentrations and combinations of dietary components is needed.     

富马酸亚铁对虹鳟幼鱼生长性能、血液生化指标及微量元素含量的影响

本试验旨在研究富马酸亚铁对虹鳟幼鱼生长性能、血液生化指标及微量元素含量的影响。选择初始体重为（８９．２±０．２）ｇ的虹鳟幼鱼 ３６０尾,随机分成 ６组,每组 ３个重复,每个重复 ２０尾鱼,分别饲喂添加富马酸亚铁 ０、２０、４０、８０、１６０、４８０ｍｇ／ｋｇ（以铁计）的试验饲料,各组分别为 Ｄ０、Ｄ２０、Ｄ４０、Ｄ８０、Ｄ１６０和 Ｄ４８０组,Ｄ０组为对照组。各组铁实测含量分别为 ６２．６、７９．５、９９．６、１３９．３、２１５．２、５３８．４ｍｇ／ｋｇ,试验期６０ｄ。结果表明：１）饲料中不同铁水平对虹鳟幼鱼生长性能无显著影响（Ｐ＞０．０５）。２）血红蛋白含量和红细胞数量呈现先上升后平稳的趋势;各组血细胞比容无显著差异（Ｐ＞０．０５）。３）各组全鱼、脊椎骨和肌肉铁含量随着饲料中铁水平的升高而升高,肝脏铁含量呈现先上升后平稳的趋势;各组全鱼锌含量无显著差异（Ｐ＞０．０５）,Ｄ０组脊椎骨和肌肉锌含量显著高于其他各组（Ｐ＜０．０５）,Ｄ０和 Ｄ２０组肝脏锌含量显著高于其他各组（Ｐ＜０．０５）;全鱼铜含量随饲料铁含量的升高而升高,各组脊椎骨铜含量无显著差异（Ｐ＞０．０５）,Ｄ０组肌肉铜含量显著低于其他各组（Ｐ＜０．０５）。４）Ｄ０组血清溶菌酶活性显著低于 Ｄ２０、Ｄ４０、Ｄ８０和 Ｄ１６０组（Ｐ＜０．０５）,但与 Ｄ４８０组无显著差异（Ｐ＞０．０５）;过氧化氢酶活性呈现先上升后下降趋势,Ｄ４０组最高。由此可见,本试验条件下,以富马酸亚铁作为铁源,通过折线模型分析发现,以血红蛋白含量和肝脏铁含量为评价指标的虹鳟幼鱼对饲料中铁需要量分别为 ９９．８和 １００．４ｍｇ／ｋｇ。