Leptospira interrogans serovar hardjo is not a major cause of bovine abortion in Victoria     

RJ. CHAPPEL  BD. MILLAR  B. ADLER †  J. HILL ‡  MJ. JEFFERS  RT. JONES  CJ. McCAUGHAN  LJ. MEAD  NW. SKILBECK 《Australian veterinary journal》1989,66(10):330-333

The aim of this study was to determine whether evidence could be obtained of foetal infection with Leptospira interrogans serovar hardjo in aborted foetuses collected from dairy farms. Material from 197 abortions occurring over a wide area of Victoria was collected over 3 years. None of 195 foetal kidney cultures or 7 cultures from membranes was positive for leptospiral organisms. Immunogold silver staining for leptospires was performed on sections of kidneys, lungs or heart from 156 foetuses, with negative results. Evidence of transient leptospiral infection in 11 of 123 foetuses was obtained by foetal heart blood serology. Two isolates of L. interrogans serovar hardjo were obtained from the urine of milking cows. These strains were examined by restriction endonuclease analysis and both were shown to be of the genotype Hardjobovis, as have been all Australian isolates studied so far. It appears that foetal infection with serovar hardjo is not associated with any substantial proportion of bovine abortions in Victoria, in contrast to the situation in Northern Ireland. The apparent absence from Victoria of the pathogenic genotype Hardjoprajitno is a possible explanation.  相似文献   

Surveillance for West Nile virus in British birds (2001 to 2006)     

Phipps LP  Duff JP  Holmes JP  Gough RE  McCracken F  McElhinney LM  Johnson N  Hughes L  Chantrey J  Pennycott T  Murray KO  Brown IH  Fooks AR 《The Veterinary record》2008,162(13):413-415

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Effects of different feed additives alone or in combination on broiler performance, gut microflora and ileal histology   总被引：1，自引：0，他引：1  

Owens B  Tucker L  Collins MA  McCracken KJ 《British poultry science》2008,49(2):202-212

1. The objectives of this experiment were to investigate the effects of different xylanases, alone or in combination with different organic acid and oligosaccharide sources, on bird performance, gut microflora and ileal histology. 2. Birds were given a diet based on a commercial formulation, which was split into 8 batches. Batch 1 contained the antibiotic growth promoter Avilamycin and acted as the positive control. To batch 2 the enzyme Allzyme PT was added and to batch 3 Allzyme PT was added with the organic acid and oligosaccharide mixture Avimos. To batch 4, Allzyme PT was added with the oligosaccharide mixture Biomos. To batch 5, yeast extract 2012 was added with the organic acid mixture Gustor and the enzyme xylanase XP20. To batch 6, yeast extract 2012 and feed acidifier Gustor were added as before, with the enzyme Avizyme 1300. Batches 7 and 8 both acted as negative experimental controls, with no added growth promoters. 3. A total of 64 birds were housed in individual wire cages in each of three consecutive experimental replicates (24 birds/treatment). Birds were fed ad libitum from 7 to 28 d and a 7-d excreta collection was carried out to determine apparent metabolisable energy (AME) content. 4. At 28 d, the birds were killed and viscosity of jejunal digesta supernatant and gizzard weight were determined. Samples were taken from the crop, ileum and caecum and analysed for viable presumptive lactic acid bacteria and coliforms. The overall microbial flora was determined using denaturing gradient gel electrophoresis of 16S ribosomal DNA followed by DNA sequence analysis in order to assign amplicons to a bacterial species. Ileal sections were also collected for histological analysis. 5. Total live weight gain (12%) and gain:feed (9%) were significantly improved for all diets containing additives, compared to the negative control diets. All diets containing xylanases gave significantly lower in vivo viscosity values than the positive and negative controls. Diet treatment significantly affected viable coliform numbers in the ileum and also viable lactobacilli in the ileum and caecum. A substantial proportion of the bacteria present in the GI tract (40%) belong to unknown species. No effects of diet treatment on histological measurements were observed in this study. 6. All the additive combinations studied were at least as effective as the antibiotic growth promoter and the results for Allzyme PT suggest that xylanase alone is as effective as any of the combinations studied.  相似文献   

Intrauterine infusion of BQ-610, an endothelin type A receptor antagonist, delays luteolysis in dairy heifers     

Keator CS  Schreiber DT  Hoagland TA  McCracken JA  Milvae RA 《Domestic animal endocrinology》2008,34(4):411-418

Three separate in vivo experiments were conducted to evaluate the putative role of endothelin-1 (ET-1) during luteal regression in heifers. In Experiment 1, a single intraluteal injection of 500 μg BQ-610 [(N,N-hexamethylene) carbamoyl-Leu-d-Trp (CHO)-d-Trp], a highly specific endothelin A (ET_A) receptor antagonist, did not diminish the decline in plasma progesterone following a single exogenous injection of 25 mg prostaglandin F2 alpha (PGF₂) administered at midcycle of the estrous cycle. In Experiment 2, six intrauterine infusions of 500 μg BQ-610 given every 12 h on days 16–18 delayed spontaneous luteolysis, as evidenced by an extended elevation (P = 0.054) of plasma progesterone concentration. In Experiment 3, heifers were administered six intrauterine infusions of BQ-610 or saline on days 16–19, and peripheral blood samples were collected from day 11 to 16 (before infusion), hourly on days 16–19 (during infusion), and on days 20–25 (after infusion). BQ-610 treated heifers had markedly higher (P < 0.0001) levels of plasma progesterone compared with saline controls, and this effect was most notable during the infusion period (treatment by period interaction; P ≤ 0.05). Heifers infused with BQ-610 also had higher progesterone levels on day 21 (treatment by time interaction; P ≤ 0.05). Mean plasma concentrations of 13,14-dihydro-15-keto-PGF₂ (PGFM), the primary metabolite of PGF₂, were measured in the samples collected hourly and were not different (P ≥ 0.05) between treatments. These results indicate that the in vivo antagonism of the ET_A receptor can delay functional luteolysis, and supports the theory that ET-1 regulates luteal function in ruminants.  相似文献   

Ovarian Responses, Hormonal Profiles and Embryo Yields in Anoestrous Ewes Superovulated with Folltropin®-V after Pretreatment with Medroxyprogesterone Acetate-releasing Vaginal Sponges and a Single Dose of Oestradiol-17β     

PM Bartlewski  BD Alexander  NC Rawlings  DMW Barrett  WA King 《Reproduction in domestic animals》2008,43(3):299-307

In ruminants, superovulatory treatments started at the time of follicular wave emergence result in greater and less variable ovulatory responses and embryo yields compared with the treatments begun in the presence of a large growing antral follicle(s) from the previous waves. The progesterone–oestradiol treatment is routinely used for follicular wave synchronization in cattle. The main objective of this study was to characterize the ovarian responses, hormonal profiles and in vivo embryo production in anoestrous Rideau Arcott ewes (May‐June), which were superovulated after pretreatment with medroxyprogesterone acetate (MAP)‐releasing intravaginal sponges and a single dose of oestradiol‐17β (E₂‐17β). Six days after insertion of MAP sponges, eight ewes were given an i.m. injection of 350 μg of E₂‐17β (E₂‐17β‐treated ewes); 10 ewes were given an i.m. injection of vehicle (control ewes). Multiple‐dose Folltropin®‐V treatment, followed by the bolus injection of GnRH (50 μg i.m.), began 6 days after E₂‐17β/vehicle injection. Transrectal ovarian ultrasonography revealed that: (i) the interval between E₂‐17β/vehicle injection and regression of all follicles ≥5 to 3 mm in diameter was shorter (p < 0.01; 2.6 ± 0.4 vs 4.8 ± 0.6 days respectively); and (ii) the interval between injection and emergence of the next follicular wave was longer (p < 0.05; 5.4 ± 0.3 vs 1.2 ± 0.4 days, respectively) in E₂‐17β‐treated than in control ewes. During the 6 days after injection, the mean FSH peak concentration and basal FSH concentration were lower (p < 0.01) in E₂‐17β‐treated ewes. The mean ovulation rate and the number of recovered embryos did not differ (p > 0.05) between the two groups of ewes. However, the number of luteinized unovulated follicles per ewe, and the variability in the number of luteal structures and overall embryo yield were less (p < 0.05) in E₂‐17β‐treated compared with control ewes. In conclusion, the MAP–E₂‐17β pretreatment significantly reduced the variability in ovarian responses and embryo yields, without affecting the embryo production in superovulated anoestrous ewes.  相似文献   

Management effects on C accumulation and loss in soils of the southern Appalachian Piedmont of Georgia   总被引：1，自引：0，他引：1  

Paul F. Hendrix  Alan J. Franzluebbers  Daniel V. McCracken 《Soil & Tillage Research》1998,47(3-4):245-251

Soil conservation management practices can impact on soil C storage. Long- and short-term data sets from three research sites were used to assess effects of management on C content of soils on the southern Appalachian Piedmont of Georgia. Intensive cultivation resulted in no observable change in total C content at the end of 3 yr, but at the end of 16 yr there were 40% and 18% declines in C in conventional tillage (CT) and no-tillage (NT) soils, respectively, at the Horseshoe Bend site. No significant changes in soil C were observed in either CT or NT soils at the end of 16 yr at Griffin. Higher clay content of Griffin soils may have contributed to this difference. Newly established NT plots on C-depleted soils on Dawson Field showed no change in C content at the end of 3 yr on both a highly eroded Pacolet sandy clay loam and a slightly eroded Cecil sandy loam. A soil under long-term NT accumulated C at a mean rate of ca. 0.6 Mg C ha⁻¹ yr⁻¹, reaching 29 Mg C ha⁻¹ after 20 yr. Steady-state levels of C in soils of the region may approach 40 Mg C ha⁻¹ (0–20 cm depth). Long-term forested and sod-based soils at Griffin showed C contents approximating this steady-state, while fertilized NT soils exceeded the estimated steady-state level.  相似文献   

Similar cefoxitin-resistance plasmids circulating in Escherichia coli from human and animal sources     

Mulvey MR  Susky E  McCracken M  Morck DW  Read RR 《Veterinary microbiology》2009,134(3-4):279-287

The aim of this study was to determine the molecular epidemiology of cefoxitin-resistance Escherichia coli identified in cattle entering feedlots and determine if there were any similarities to E. coli causing human infections in Canadian hospitals. A total of 51 E. coli were isolated from a total of 2483 cattle entering four feedlots in southern Alberta, Canada. DNA fingerprinting using pulsed-field gel electrophoresis revealed thirty-two unique patterns with two major clusters observed comprised of Cluster A (11 strains) and Cluster B (7 strains). PCR and sequence analysis revealed 38 isolates (74.5%) harboured bla(CMY-2), whereas the remainder were found to contain mutations in the promoter region of the chromosomal ampC gene, which has been previously associated with cefoxitin resistance. No resistance to nalidixic acid, ciprofloxacin, or amikacin was observed in the clinical isolates. bla(CMY-2) harbouring plasmids were transferred to E. coli DH10B. All of the plasmids carrying bla(CMY-2) contained the A/C replicon and also harboured other resistance genes. Plasmid fingerprinting using BglII revealed 17 unique patterns with all but one clustering within 70% similarity. Comparison of the plasmid fingerprints to those isolated from human clinically significant E. coli in Canada during a similar time period [Mulvey, M.R., Bryce, E., Boyd, D.A., Ofner-Agostini, M., Land, A.M., Simor, A.E, Paton, S., 2005. The Canadian Hospital Epidemiology Committee, and The Canadian Nosocomial Infection Surveillance Program, Health Canada. Molecular characterization of cefoxitin resistant Escherichia coli from Canadian hospitals. Antimicrob. Agents Chemother. 49, 358-365] revealed four strains that harboured bla(CMY-2) A/C replicon type plasmid with fingerprint similarities of greater than 90% to the ones identified in E. coli from the cattle in this study. These findings highlight the potential linkage of multidrug resistant organisms in food producing animals and human infections in Canadian hospitals. The plasmids conferred resistance to multiple antibiotics which could limit options for the treatment of infections caused by these strains.  相似文献   

Meiotic instability of common wheat strains derived from Triticum timopheevi Zhuk. crosses     

S. S. Maan  E. U. McCracken 《Euphytica》1968,17(3):445-450

Summary Meiotic instability was studied in four strains of common wheat derived from crosses involving a Triticum timopheevi derivative, C.I. 13093, and the common wheat varieties Cheyenne and Minturki. A wide range in the percentage of normal cells at six stages of meiosis, MI, AI, dyad, MII, AII, and quartet, was found. The date of sporocyte sampling influenced meiotic irregularities at six stages of meiosis. Florets from the same spikes differed in the percentage of normal cells at all the meiotic stages except MII. Plants within strains differed significantly at the MI and quartet stages only. Except at AI stage, spikes collected on the same day did not differ significantly. Apparently, environment during premeiotic phase determined the extent and the pattern of meiotic instability in spikes of these strains.Chromosome counts were taken on 213 of the highly aberrant PMC at MI. Among these, 44 different chromosome numbers ranging from 4 to 76 per cell were recorded. Cells with deviating numbers from 22 to 28 were the most frequent (30.52 percent). Chromosome numbers 12, 17, 21, 22, 24, 26 and 28 occurred in 43.9 percent of the aberrant PMC, and the number of cells with these chromosome numbers ranged from 9 to 15.The metaphase 1 chromosome pairing in deviating PMC was not related to the number of chromosomes in these PMC. Apparently, deviating PMC had a random assortment of chromosomes. In aberrant PMC and others with apparently normal chromosome numbers (but irregular meiosis) homeologous chromosomes may pair. Functional gametes from such cells may perpetuate meiotic instability that had persisted in these three advanced generation common wheat strains of hybrid origin.  相似文献   

The introduction of Hymenoscyphus fraxineus to Northern Ireland and the subsequent development of ash dieback     

Emma Baxter  Louise R. Cooke  Florentine Spaans  Irene R. Grant  Alistair R. McCracken 《Forest Pathology》2023,53(1):e12789

Ash dieback caused by Hymenoscyphus fraxineus was first recorded in Northern Ireland (NI) in November 2012. The disease was observed only on recently (<6 years) planted trees. An in-depth case study in 2015 of an ash plantation with severe symptoms indicated that many of the trees were infected at the time of planting. Apothecia were observed developing from pseudosclerotia beneath the epidermis of dead branches still attached to the tree, suggesting a possible mechanism whereby H. fraxineus could be disseminated without leaf or rachises infection. Apothecia also formed on roots, indicating that infections may also occur in the soil. Often young trees were killed by the formation of large basal lesions which did not arise from stem infections higher up. On first detecting the disease on the island of Ireland the Governments of NI and the Republic of Ireland published an “All-Ireland Chalara Control Strategy.” Part of that strategy was a ban on the importation of ash plants from regions where the disease was known to be present, to prevent the introduction of further inoculum, and the implementation of an ‘eradication and containment’ policy with the aim of preventing the establishment and spread of the disease. While these measures may have slowed disease establishment, they were ultimately unsuccessful and by 2018 ash dieback was widespread and established throughout the whole of NI in plantations and in the wider environment.  相似文献   

Hepatitis in the green tree frog (Litoria caerulea) associated with infection by a species of Myxidium     

BD HILL  PE GREEN  H A LUCKE 《Australian veterinary journal》1997,75(12):910-911

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