首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
OBJECTIVE: To compare incubation time and clinical signs of scrapie in codon 136/171 alanine-valine/glutamine-glutamine (AVQQ) experimentally inoculated sheep with that in sheep with the more common 136/171 AAQQ genotype. ANIMALS: 60 Suffolk sheep. PROCEDURE: Twenty-seven 171 QQ ewes purchased from 2 private flocks were bred with a 171 QQ Suffolk ram before being inoculated with a 20% solution of scrapie-positive brain homogenate (5 mL, PO) from sheep containing genotypes 136/154/171 AA/arginine-arginine (RR)/QQ, AVRRQQ, and VVRRQQ that had died of scrapie. Ewes had 33 lambs, which were inoculated in the same manner on the day of birth. RESULTS: All 16 genotype 136/154/171 AVRRQQ sheep that died of scrapie were 9 to 11 months of age; clinical signs lasted 1 day to 3 weeks with no wasting and only mild pruritus. The first AARRQQ sheep died with typical clinical signs of scrapie 27 months after inoculation, and 14 were still alive 37 to 42 months after inoculation. The 136/171 AVQQ sheep had minimal accumulation of modified cellular protein (PrP(SC)) as determined by immunohistochemical (IHC) staining within affected cells; thus the severity of clinical signs and time of death were not associated with brain lesions or the amount of PrP(SC) in brain TISSUE OF 136/154/171 AVRRQQ sheep as determined by IHC staining. CONCLUSIONS AND CLINICAL RELEVANCE: The rapid incubation time may have been influenced by the codon 136 genotype, a new unreported valine (V)-dependent strain of scrapie similar to strain SSBP/1, or the inoculum may have contained a traditional strain and a V-dependent or SSBP/1-like strain of scrapie.  相似文献   

2.
The PrP genotypes associated with natural scrapie in Ireland were determined and a comparison was made between genotypes found in scrapie-infected sheep and those found in healthy animals from scrapie-infected flocks. Seven PrP genotypes were identified in scrapie-infected animals: VV(136)RR(154)QQ(171),VA(136)RR(154)QQ(171),VA(136)RR(154)QR(171),VA(136)RR(154)QH(171),AA(136)RR(154)QQ(171),AA(136)RR(154)QH(171) and AA(136)RR(154)HH(171). Of 11 scrapie-infected flocks, 15 genotypes were identified in the healthy flock-mates. The genotypes identified in scrapie-affected animals were also all identified in healthy flock-mates. In 9 of the 11 flocks studied, the genotype frequencies among scrapie-infected animals were significantly different from those among healthy flock-mates. The results show that there is a significant risk of developing the clinical signs of scrapie associated with particular PrP genotypes in the Irish sheep population. The association between the V(136)R(154)Q(171) allele and scrapie was evident, as was the association between A(136)R(154)R(171) and resistance to developing the clinical signs of scrapie. The presence of the A(136)H(154)Q(171) allele in the flocks examined resulted in a decreased risk of developing scrapie compared to the presence of the A(136)R(154)Q(171).  相似文献   

3.
OBJECTIVE: To determine whether selection for the homozygous A136 R171 genotype that confers resistance to classic scrapie infection negatively affects production traits in sheep. ANIMALS: 996 commercial lambs obtained from 2 flocks at separate locations across 3 consecutive years. Procedures-Genotyping at codon 136 and 171 was performed by use of commercially available testing or a single-nucleotide polymorphism assay. Carcass data were collected without knowledge of genotype approximately 24 hours after slaughter by an experienced grader. The model to analyze associations between prion protein (PRNP) genotype and production traits was based on genotype, breed, or both as fixed effects and days on feed as a covariate. RESULTS: Average daily gain was significantly associated with only combined codons 136 and 171. In flock 1, weaning average daily gain was significantly greater in AA136 sheep than heterozygotes; the difference between QR171 and RR171 sheep, compared with QQ171 sheep, were not significant although QR171 and RR171 sheep had higher values. However, in flock 2, average daily gain was significantly greater in AV136 sheep than AA136 sheep and in QR171 sheep than QQ171 sheep. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggest there is an advantage for average daily gain in lambs with an arginine allele at codon 171, but there were no other genotype effects on production traits. Thus, selection for the resistant arginine allele at codon 171 to comply with USDA scrapie eradication guidelines should not be detrimental to lamb production in commercial flocks. Effects of codon 136 on average daily gain were ambiguous.  相似文献   

4.
The National Scrapie Plan (NSP) for Great Britain is a voluntary scheme that, through PrP genotype testing and restricted breeding, aims to reduce the risk of scrapie in the national sheep flock. To gauge the progress in member flocks and within breeds, the genotype profile of successive crops of ram lambs was monitored between 2002 and 2004. In each of the 11 most frequently sampled breeds, the proportion of ram lambs testing in the most resistant genotype category (NSP type 1: ARR/ARR) increased, and there was a reduction in the proportion of genotypes associated with the highest disease risk, that is X/VRQ, where X is an allele other than ARR. Changes in the proportion of ram lambs testing for ARR-heterozygous genotypes (NSP type 2: ARR/X, where X is not VRQ) appeared to be influenced by whether the sheep were hill breeds or non-hill breeds. In each of six frequently sampled hill breeds these genotypes expanded, in relative terms, whereas they declined in four of five prominent lowland/crossing breeds. The proportion of ram lambs that carried neither ARR nor VRQ (NSP type 3) declined consistently in the top 11 breeds, but there was little change in the ARR/VRQ genotype (NSP type 4). Among individual flocks that had ram lambs tested in all three years 2002 to 2004, the majority experienced an increase in the proportion testing ARR/ARR, and of those that had VRQ ram lambs in 2002, most recorded a decrease in their frequency by 2004.  相似文献   

5.
Sheep scrapie is a prion disease that requires interaction of exogenous prions with host prion protein (PrP) supporting prion formation. Disease is associated with deposition of a host-generated conformational variant of PrP, PrPsc, in a variety of tissues, including brain, resulting in fatal spongiform encephalopathy. Efficiency of PrPsc formation is determined by polymorphisms in the PrP-coding sequence. This article adds to previous data of natural sheep scrapie, concentrating on the effect of host genotype and age on PrPsc accumulation patterns during preclinical and clinical disease. Two entire scrapie-infected, predominantly Suffolk-cross, sheep flocks euthanized for regulatory purposes were genotyped and analyzed for PrPsc deposition in various tissues using single- and dual-label immunohistochemistry. Scrapie, as defined by PrPsc deposition, occurred in 13/80 sheep. Preclinical disease was evident in nearly 70% of infected sheep, ranging in age from 14 months to 7 years. PrPsc accumulated systemically in the nervous tissue, various lymphoid tissues, both alimentary tract related and non-alimentary tract related, and the placenta. Clinical neurological illness was always associated with spongiform encephalopathy and PrPsc deposition in the brain. Only 6 of 9 sheep with preclinical scrapie had PrPsc deposition in the brain but widespread PrPsc deposition in peripheral lymphoid tissue, supporting previous data showing peripheral PrPsc accumulation preceding deposition in the brain. PrPsc colocalized with a marker for follicular dendritic cells throughout the lymphoid system. PrPsc also accumulated in the peripheral nervous system, particularly the nervous supply of the gastrointestinal tract. Abundant PrPsc was evident in trophoblast cells of placentomes but not in the endometrium, myometrium, or associated nervous plexus. PrPsc deposits were not observed in the mammary parenchyma or bone marrow. Scrapie susceptibility was defined genetically by PrP codon 171: PrPsc deposition was restricted to PrP genotype AA136RR154QQ171 in 12/13 cases or AV136RR154QQ171 in 1/13 cases. The earliest accumulation was observed in the single VRQ/ARQ heterozygous animal, consistent with the reported high scrapie susceptibility and brief incubation period observed in breeds with predominance of the V136R154Q171 allele. Disease occurred within, as well as independent of, mother-daughter lines, suggesting both maternal and nonmaternal transmission in the flocks.  相似文献   

6.
Classical scrapie has proved to be a notoriously difficult disease to control due to a poor understanding of its natural history. The recognition of disease risk linkage to PrP genotype has offered the prospect of a disease control strategy, viz. genotyping and selective breeding, novel to veterinary medicine when first considered in the 1990s. The UK Spongiform Encephalopathy Advisory Committee recommended the exploitation of this approach in a voluntary, national programme to control classical scrapie and protect the public against food-borne exposure to bovine spongiform encephalopathy, should the national flock have been exposed via contaminated feed. The National Scrapie Plan for Great Britain was launched in 2001 and uptake has been widespread throughout the purebreeding sector of the sheep industry, with membership peaking at over 12 000 flocks in 2006. A total of 700 000 rams from 90 breeds have been genotyped. A comparison of ram lambs born in 2002 with those in 2006 shows evident changes in PrP genotype frequencies which are predicted to be associated with a reduction in disease risk. Various concerns have been raised regarding possible unintended consequences of widespread selection on PrP genotype, including impacts on other performance traits and possible effects on inbreeding and genetic diversity. To date, these concerns appear to be unfounded, as no consistent associations have been found with performance traits, nor are there likely to be any detectable impacts on inbreeding in mainstream breeds. Currently, semen banks have been implemented in Great Britain to store samples from animals of all common PrP genotypes, should these genotypes be required in the future. Various strategies to minimise future disease risks are discussed in the paper.  相似文献   

7.
In three flocks, 13 pure- and 1 crossbred German black headed mutton lambs were ascertained which had clinical signs of epidermolysis bullosa (EB). The three farmers reported of further 20 affected lambs with similar signs in their flocks in the past lambing seasons. The affected lambs were progeny of six rams and 17 ewes. Two rams and six ewes with affected offspring from two farms were used for a breeding trial. In the course of these experimental matings, 21 lambs were born, six of which were affected by EB. All lambs born in this trial underwent clinical and haematological examination and all the affected lambs had to be euthanised due to severe and progressing clinical symptoms. Clinical examinations in 20 affected lambs revealed shedding of claw horn, erosions and ulcers of skin and mucous membranes. Histopathology showed subepidermal splitting and blistering with intact basal keratinocytes. These findings together with the premature death of affected lambs within the first two months of life made a Herlitz type of junctional EB most likely. The results of the test matings demonstrated the genetic transmission and indicated an autosomal recessive mode of inheritance for this lethal condition.  相似文献   

8.
Genetic susceptibility to scrapie is associated with polymorphisms in three different codons of the ovine prion protein (PrP) gene (136, 154, 171). Studies of PrP genotypes linked to scrapie have revealed the resistance of homozygous PrPARR/PrPARR animals and the high risk of PrPVRQ/PrPVRQ and PrPvRQ/PrPARQ animals in scrapie-affected flocks. The selection of PrPARR/PrPARR genotypes may therefore provide a strategy for controlling clinical scrapie. The genotypes of 1361 German breeding sheep from 15 different breeds in northern Germany were determined. Apart from the wildtype allele PrPARQ, at least four mutually exclusive allelic variants were found. The greatest variability within the PrP gene was encountered in texel sheep, in which 14 PrP genotypes were found. In the important meat breeds, Suffolk, German whiteheaded mutton and German blackheaded mutton, the PrPARR allele was predominant, and in these breeds the breeding of scrapie-resistant pedigree flocks within four generations seems to be a feasible option. In the texel sheep, the German merino, the German milk and the German land sheep breeds, the frequency of the PrPARR allele was much lower, and in several breeds no homozygous rams were available for breeding purposes. In these breeds the breeding strategy would depend on the number of heterozygous rams available, but resistant pedigree flocks could be achieved within nine generations.  相似文献   

9.
The objectives for this study were to 1) determine the relationship between sexual performance class and lambs sired in a competitive mating environment, and 2) determine whether the male-oriented ram test is valid. Fifteen 2- to 3-yr-old whitefaced rams classified as female-oriented, with high or low sexual performance, or classified as male-oriented were used in a multiple-sire breeding arrangement. Five groups of approximately 200 ewes each were exposed for 21 d to 3 rams per group consisting of 1 ram from each class. Rams were blocked for sexual class, and those with close genetic relationship were assigned to different pens. Genomic DNA was prepared from blood collected from 15 rams, 934 ewes, and 1,757 lambs. Up to 4 microsatellite markers were used to determine a lamb's sire. Of 884 ewes with identifiable lambs (known sires), 178 ewes had single lambs, 408 had multiples sired by 1 ram, and 298 had multiples sired by more than 1 ram. The sexual partner preference test used to identify male-oriented rams did not absolutely reflect their sexual performance during competitive breeding. In contrast to only mounting and servicing males in preference tests before breeding, male-oriented rams sired 480 lambs from 330 ewes. Serving capacity tests predicted sexual performance of high and low sexual performance rams. High performance rams impregnated more ewes (499 vs. 258; P < 0.05) and sired more lambs (756 vs. 357; P < 0.05) than did low performance rams, respectively. Low performance and male-oriented rams did not differ for ewes impregnated or lambs sired. We conclude that 1) sexual partner preference tests used to classify male-oriented rams were not absolute in reflecting their breeding performance in a competitive breeding environment; 2) serving capacity tests predicted that high performance rams would breed more ewes than low performance rams and sire more lambs than either low performance or male-oriented rams; and 3) under the conditions of this study, low performance and male-oriented rams did not have an adverse impact on the overall breeding outcome. Combined, low performance and male-oriented rams sired 81 more lambs than did high performance rams, but this required twice as many rams to obtain approximately equal breeding results. Therefore, we suggest that serving capacity tests should be used to select high performance rams, reduce number of rams with marginal sexual performance, and make decisions on ram numbers needed.  相似文献   

10.
Scrapie is one of several transmissible spongiform encephalopathies of livestock. Disease susceptibility is linked to polymorphisms in the normal prion protein gene that encodes the mammalian prion precursor. Codon 171 of this gene is a major determinant of scrapie susceptibility. Selection for arginine (R) at codon 171 is encouraged by the USDA to decrease the incidence of scrapie. Objectives of this study were to determine the frequency of R allele variants at codon 171 in a sample of sheep from five breeds (Columbia, Hampshire, Rambouillet, Suffolk, and Targhee) and western white-faced commercial ewes and to determine whether the R allele is associated with ewe and lamb production traits. Genotyping was performed on 532 ewes and 901 lambs from the University of Wyoming flock, in addition to 820 rams from 52 sheep producers from Wyoming and surrounding areas, using a DNA mismatch assay that discriminated the R allele from others at codon 171. Genotyping was performed by DNA sequencing on 127 rams representing all breeds, except Hampshire from the USDA Sheep Experiment Station at Dubois, ID. The 171R allele was found in all five breeds and in the commercial western white-faced ewes. Genotype frequencies varied (P < 0.001) by breed in ewe and ram populations. Influence of R-allele frequency on ewe lambing records and individual lamb records was analyzed for Columbia (62, 161, 121), Hampshire (89, 193, 162), Rambouillet (87, 179, 133), Suffolk (67, 178, 161), and commercial sheep (227, 463, 324) for numbers of ewes, total number of ewe production records, and individual lamb records, respectively. Suffolk ewes without the R allele (non-R/non-R) gave birth to more (P or= 0.08) by ewe genotype. Lamb birth and weaning weights were not influenced (P >or= 0.12) by lamb genotype in any of the breeds or in the commercial flock. In this population, ultimate lamb production was only influenced by genotype at codon 171 in the Suffolk flock.  相似文献   

11.
Scrapie is a naturally occurring fatal neurodegenerative disease of sheep and goats. This study documents incubation periods, pathologic findings, and distribution of abnormal prion proteins (PrP(Sc)) by immunohistochemistry in tissues of genetically susceptible sheep inoculated with US sheep scrapie agent. Four-month-old Suffolk lambs (QQ at codon 171) were inoculated by 1 of 3 different routes (nasal, peritoneal, and conjunctival) with an inoculum (No. 13-7) consisting of a pool of scrapie-affected sheep brains. Except for 3 sheep, all inoculated animals were euthanized when advanced clinical signs of scrapie were observed between 19 and 46 months postinoculation (MPI). Spongiform lesions in the brains and labeling of PrP(Sc) in central nervous system and lymphoid tissues were present in these sheep. One intranasally inoculated sheep euthanized at 12 MPI had presence of PrP(Sc) that was confined to the pharyngeal tonsil. These results indicate that the upper respiratory tract, specifically the pharyngeal tonsil, may serve as a portal of entry for prion protein in scrapie-infected environments.  相似文献   

12.
This paper compares the dinical signs, histopathology, detection of PrPSc protein and PrP genetics of the transmission of BSE to sheep and goats, with the effects of the transmission of natural scrapie from a brain homogenate from a single sheep. After intracerebral and oral inoculations there were similarities in the clinical signs due to the two sources of infection, but there were differences in pathology at the end stage of disease and in the genotypes of the sheep which succumbed to the challenges. The incubation period of BSE was associated with the sheep PrP codon 171 genotype, but the natural scrapie source, despite inducing disease only in known susceptible genotypes, showed no clear association with PrP genotype.  相似文献   

13.
From April 2005, member states of the European Union were required to implement a compulsory breeding programme for resistance to transmissible spongiform encephalopathies (TSEs) in sheep as part of measures to eradicate TSEs from national flocks. In this paper, we assessed the impact of four different breeding strategies on prion protein (PrP) genotype frequencies using a mathematical model which describes in detail gene flow in the British sheep flock. These strategies ranged from the minimum requirements laid down in by EU legislation to compulsory implementation of the current National Scrapie Plan for Great Britain (NSP) ram genotyping scheme. All four strategies were predicted to substantially reduce the frequency of the VRQ allele, which is associated with the highest risk of scrapie, although schemes with more stringent requirements produced a larger reduction. However, there were marked differences in the impact of the strategies on the frequency of other PrP alleles. In particular, restrictions beyond those required by EU legislation were necessary to change the frequency of other PrP alleles substantially. Consequently, a breeding programme which aims to reduce the risk to human health by reducing the frequency of the ARQ allele (associated with the highest risk of BSE in sheep) must place restrictions on ARQ-bearing animals. Similarly, a programme which seeks to increase the frequency of the ARR allele (associated with the lowest risk of TSE) must favour ARR-bearing animals.  相似文献   

14.
Testicles from rams in flocks experiencing ram epididymitis in Idaho and eastern Oregon were cultured. Twenty-six breeding rams from 6 flocks were cultured and only Brucella ovis was isolated. Virgin rams (65) harbored numerous species of small fastidious gram-negative rods, including Actinobacillus actinomycetemcomitans, Haemophilus spp, Moraxella spp, and Pasteurella spp. Thus, there appeared to be 2 separate disease entities, dependent on sexual experience of the animal.  相似文献   

15.
One hundred twenty-nine sheep with scrapie were identified from 20 flocks in which scrapie previously had been confirmed. Physical and neurologic examinations were performed on all animals. Videotape recordings were made and reviewed to assess gait. These procedures were repeated in 46 sheep at 2- to 3-week intervals until recumbency or inappetence necessitated euthanasia. Confirmation of scrapie was made by histopathologic and immunohistochemical examinations of brain tissue. The clinical signs most frequently recorded in the 129 animals on initial presentation were hindlimb ataxia (71%), head tremor (61%), altered mental status (57%), positive nibble reflex (51%), crouching posture (51%), teeth grinding (44%), low head carriage (38%), body condition score (BCS) < 1.5 (38%), and conscious proprioceptive deficits of the hindlimbs (36%). Progression of the disease was characterized by an increase in the frequency and severity of ataxia, weakness and hypermetria of the hindlimbs, a decreasing sway response, a decreasing extensor response to thoracolumbar pressure, and a reduction in the BCS. No effect of farm of origin on the clinical presentation could be shown. The presence of a nibble reflex was strongly associated (P < .0005) with prion protein (PrP) genotypes AA136RR154QH171 and AA136RR154QQ171. Logistic regression modeling of groups with associated clinical signs showed that animals with a crouching posture (odds ratio [OR], 20.036) and an abnormal yield to thoracolumbar pressure (OR, 7.117) were at increased risk of ataxia. Pruritus (OR, 0.168) was negatively associated with ataxia. Pruritus (OR, 4.974) and teeth grinding (OR, 4.279) were associated with a positive nibble reflex.  相似文献   

16.
The objective of this study was to develop a reliable Taqman 5' Nuclease Assay for genotyping sheep for scrapie susceptibility. The sheep prion gene contains 2 single nucleotide polymorphisms (SNPs) that may mediate resistance to classical scrapie, one at codon 136, alanine (A) or valine (V), and another at codon 171, arginine (R) or glutamine (Q). The R allele appears to confer resistance to classical scrapie, with the AA(136) RR(171) genotype the most resistant to scrapie and QR(171) only rarely infected in the US sheep population. The Assays by Design protocol was used for development of probes and primers for codon 136 and Primer Express for codon 171. Commercially available kits were used to isolate genomic DNA from blood or muscle. For validation, 70 SNP determinations for each codon were compared to commercial testing with an error rate of less than 1%. Then, 935 samples from blood (n = 818) and muscle (n = 117) were tested for both codons with 928 successful determinations and only 7 samples (<1% of total samples) that needed repeating. Genotypes were AA QQ (n = 102; 11.0%), AV QQ (n = 28; 3.0%), AA QR (n = 396; 42.7%), AV QR (n = 54; 5.8%), and AA RR (n = 348; 37.5%). Thus, 86% of the sheep tested (n = 798) contained R at codon 171 and were expected to be scrapie-resistant. This new Taqman 5' Nuclease SNP genotyping assay is accurate, easy to perform, and useful in the study of classical scrapie in sheep and its prevention through selective breeding programs to eliminate highly susceptible animals.  相似文献   

17.
A breeding soundness evaluation was conducted on 824 Colorado range rams. These rams were determined to be free from epididymitis via testicular palpation. Semen evaluation included microscopic observation for the presence of WBC. Of the 824 rams, 15.5% failed the breeding soundness evaluation on the basis of the semen evaluation: 10.6% had WBC in the semen and 4.9% had poor sperm morphology. The prevalence of Brucella ovis isolation varied from 0% to 16.2% within flocks. The prevalence of subclinical B ovis infection was 10% in the control flocks. Brucella ovis was isolated from 71.9% of the rams that had WBC in their semen. From this study, it appeared that palpation and vaccination may be inadequate for control of ram epididymitis.  相似文献   

18.
In 1999, among 164 randomly selected Dutch sheep farmers, a questionnaire was carried out to estimate the prevalence of myiasis in sheep and to investigate factors associated with the occurrence of myiasis. The total number of sheep and/or lambs on the reference date 1 August 1999 was 12,200: 5243 ewes, 225 rams, 3393 ewe- and 3339 ram lambs. On 86 (52.4%) of the farms 349 (2.9%) of all sheep and/or lambs contracted myiasis, of which two died. Myiasis was seen significantly more frequently on farms with over 25 ewes compared to smaller farms. Cases of myiasis were detected from April to September, with a peak (47.1%) in August. Occurrence of myiasis was most frequently associated with hot and humid weather and was mainly observed (69.1%) in the area around the tail.Ewes and ewe lambs had significantly more myiasis when compared with rams and ram lambs. There was no relationship with tail docking, with breed, with the time of shearing, with the kind of soil (clay, sand, etc.), with the environment (bush, trees, water, etc.), with the type of treatment (pour on, dipping, spraying), the used insecticides (synthetic pyrethro?ds, diazinon, cyromazin, etc.), the number of preventive treatments, the time of treatment or the number of observations on the herd (once a day, once a week, etc.).  相似文献   

19.
绵羊痒病的发生和易感性可受绵羊朊蛋白等位基因密码子136,154和171多态性的影响。利用SSCP电泳和非变性聚丙烯酰胺凝胶结合的方法对10只健康绵羊的朊蛋白等位基因154,171两个多态性位点进行检测,发现8只纯合子羊基因型为154RR171QQ,2只杂合子羊基因型为154RR171HR。表明该方法可以应用于此等位基因多态性的研究中。  相似文献   

20.
Actinobacillus seminis was isolated from the semen of five rams on four farms. Four of the rams had abnormal semen and three were also infertile. The isolates of A seminis showed similar phenotypic profiles and electrophoretic protein patterns to the type strain of A seminis but were distinct from Histophilus ovis previously isolated from rams with epididymitis in Scotland. The infection appeared to be subclinical but two of the five rams had palpable abnormalities of their testes. Three rams were treated with antibiotics but the infection persisted. No gross lesions were found in the genitalia of two of three rams examined post mortem but one had necrotic abscesses in the testes and epididymis. A seminis was isolated from the seminal vesicles and epididymis of one ram without gross lesions but not from the genitalia of the other two. On one farm the infection in a recently purchased ram led to the detection of another case as a result of the bacteriological screening of 11 stock rams not in contact with the initial case. These five subclinical cases, which included a supposedly healthy stock ram, suggest that A seminis infection may be widespread and should be considered in cases of infertility.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号