New Zealand veterinary journal最新文献

Aims: To develop a colourimetric loop-mediated isothermal amplification (LAMP) assay for the detection of Pasteurella multocida in clinical poultry samples and compare the performance of this assay with PCR. A secondary aim was to evaluate a simple DNA extraction method that could enable LAMP-based testing in the field without the need for specialised laboratory equipment.

Methods: Primer sets for both LAMP and PCR were designed to amplify the KMT1 gene of P. multocida. DNA was extracted from 12 P. multocida isolates using a commercial extraction kit, and subjected to analysis using both LAMP and PCR. The analytical specificity of the LAMP assay was evaluated by testing it against a panel of 12 unrelated bacterial species, and the analytical sensitivity (limit of detection) was determined through testing of serial dilutions of the target DNA and compared to that of PCR. Subsequently, cloacal swabs (n = 40) from a commercial turkey flock were subjected to analysis using both LAMP and PCR assays, using a rapid DNA extraction method and a commercial extraction kit. Clinical sensitivity and specificity of the LAMP assay were calculated in comparison to PCR.

Results: A single DNA fragment of the expected size (∼ 200 base pairs), was amplified by PCR from 12 P. multocida isolates, which were also all positive by the LAMP assay. The identity of all PCR amplicons was confirmed by sequencing. Both PCR and LAMP showed similar analytical sensitivity, with a LOD of 20 pg of target DNA. As neither PCR nor LAMP assays produced positive results with 12 non-related bacterial species, the analytical specificity was assessed as 100%. However, LAMP demonstrated lower clinical specificity (94.74%) compared to PCR (100%) when 40 clinical samples were tested. None of the DNA samples extracted using the simplified DNA extraction method were amplified by either LAMP or PCR.

Conclusion: The LAMP assay developed in this study exhibits comparable performance to PCR in detecting P. multocida.

Clinical relevance: The use of a rapid and portable DNA extraction method, in conjunction with LAMP assays, could create opportunities for point-of-care testing for fowl cholera in field settings.

Aims: To describe rates of and reasons for culling and mortality of ewes between breeding and mid-lactation on New Zealand sheep farms; to investigate associations of these variables with farm demographic variables; and to describe rates of and reasons for culling of ewes at weaning.

Methods: Participants were a convenience sample of 34 farms from across New Zealand. Demographic data were initially collected for each farm via a questionnaire administered in-person to the flock owner or manager. During approximately 8 months from breeding to mid-lactation, ewe tally, culling and mortality data were collected and used to calculate various parameters related to flock performance and to investigate associations. During the main ewe-culling event at weaning, ewe-culling data were collected from 29/34 flocks participating in the study.

Results: There was considerable variation between flocks, but the between-flock mean replacement percentage was 29.2 (SD 5.0)%. Overall, a between-flock mean of 10.5 (SD 4.6)% of ewes presented for breeding were culled or dead/missing by mid-lactation and thus did not rear any lambs. Additionally, from 27 flocks that reported data on ewes' success at rearing lambs, a between-flock mean of 3.9 (SD 2.5)% of ewes that remained alive at mid-lactation failed to rear any lambs, resulting in an overall between-flock mean loss of 23.1 (SD 6.3) potential lambs per 100 ewes. Two-thirds of ewe mortalities between breeding and mid-lactation occurred during the lambing period. Model results showed flocks with higher pregnancy scanning percentages had lower rates of culling and mortality between breeding and mid-lactation. However, apart from farm contour, from breeding to mid-lactation there were no associations for culling and mortality with farm size, flock size, number of ewes per labour unit, whether ewe hoggets (7-9 months of age) were presented for breeding, or duration of the breeding period. A between-flock mean of 16.5 (SD 8.3)% of ewes present at weaning were culled, and among mixed-age ewes, the most common reasons for culling at this time were age, incisor teeth defects and udder defects.

Conclusions: To reduce unnecessary ewe culling and mortality, attention should be focused on maximising conception rates, ensuring judicious culling decisions, optimising body condition score, and identifying farm-specific causes of death over the lambing period to facilitate targeted intervention strategies.

Clinical relevance: Identifying why and when ewes exit flocks, and comparing it with the data presented here, will facilitate the development of flock-specific interventions to reduce ewe culling and mortality.

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Abbreviations: BCS: Body condition score; NI: North Island; SI: South Island.

Aims: To compare the responses of liver Cu concentrations in dairy cows between three forms of injectable Cu supplementation and a negative control group.

Methods: Across two dairy farms in North Canterbury, New Zealand, 80 mid-lactation dairy cows (n = 28 and 52 per farm) were randomly allocated to four treatment groups: (a) 100-mg or (b) 200-mg dose of Cu administered as Ca Cu EDTA; (c) 75-mg dose of Cu as disodium Cu EDTA combined with Se, Zn, and Mn; or (d) no treatment (negative control). Each treatment group contained 20 cows. Groups were balanced for age, plasma Cu and pre-treatment liver Cu concentration. Blood samples and liver biopsies were collected prior to treatment. Six liver biopsies were performed on the same cow over a period of 70 days and the concentration of liver Cu was measured over time and compared to pre-treatment baseline. A mixed, multivariable, linear regression model was constructed to determine the effect of treatment on the change in liver Cu concentration compared to pre-treatment concentrations, accounting for repeated measurements taken from each cow.

Results: There was a difference in the distribution of pre-treatment liver Cu concentration between farms (p = 0.008), with medians of 1,400 (IQR 1,200-1,625) and 1,050 (IQR 805-1,425) µmol/kg on Farms 1 and 2, respectively. There was an interaction between treatment group, study day, and farm, with a treatment effect confirmed only on Farm 2. In the final model, the predicted change in liver Cu concentration (compared to pre-treatment concentrations) among cows on Farm 2 that were treated with 200 mg of Ca Cu EDTA was significantly higher than that of control cows on Days 3, 14, 28 and 42, peaking on Day 14 with a difference of 325.35 (95% CI = 97.00-554.03) µmol/kg. The study found no associations between changes in liver Cu concentration and age or prior plasma Cu concentration. The intraclass correlation coefficient was 0.57 (95% CI = 0.45-0.66), indicating the proportion of variability in changes in liver Cu concentration attributable to inter-cow variation.

Conclusions and clinical relevance: This study shows there are differences in response to injectable Cu supplementation at the farm level and wide variation in liver Cu among cows from the same farm. On one farm, a 200-mg dosage of Ca Cu EDTA significantly increased liver Cu concentration for at least 42 days.

Aims: To evaluate the effects of early and late pre-partum shearing of Corriedale ewes carrying single fetuses on placental and lamb development and neonatal lamb behaviour.

Methods: At 70 days of gestation, 37 multiparous Corriedale ewes with known gestation dates were randomly allocated into three groups: S70 (n = 12) and S110 (n = 12), shorn at Day 70 and 110 of gestation, and US (n = 13), that were not shorn pre-partum. Gestation length, lambing duration, placental expulsion time, placental weight, number and weight of cotyledons, and placental efficiency (lamb weight/placental weight) were determined. At birth, body temperature, weight, morphometric measurements, ponderal index (lamb weight/lamb crown-rump length) and behaviour were recorded, with weight remeasured 72 hours later. Four male lambs per group were slaughtered immediately after parturition, and organ weight and perirenal brown fat weight and energy content recorded.

Results: Pre-partum shearing, regardless of timing, increased total dried placental weight per ewe. Pre-partum shearing at Day 70 of gestation increased the number and mean weight of the > 2 to ≤ 3-cm cotyledons, while pre-partum shearing at Day 110 of gestation increased only the weight of these cotyledons. At birth and at 72 hours, lambs from ewes shorn either at 70 days of gestation (birth: 5.5 (95% CI = 4.6-6.4) kg, p = 0.001; 72 hours: 6.4 (95% CI = 6.1-6.8) kg, p = 0.002) or at 110 days of gestation (birth: 5.4 (95% CI = 4.4-6.4) kg, p = 0.001; 72 hours: 6.5 (95% CI = 5.9-7.1) kg, p = 0.001) were heavier than lambs from unshorn ewes (birth: 4.0 (95% CI = 3.3-4.8) kg; 72 hours: 4.8 (95% CI = 3.5-6.1) kg). Lambs born to S70 and S110 ewes suckled sooner (31.5 (95% CI = 14.5-48.5) minutes, p = 0.001; and 39.3 (95% CI = 23.7-55.0) minutes, p = 0.001 respectively), than lambs born to the US group (70.3 (95% CI = 38.6-102.1) minutes). There was no evidence for an effect of pre-partum shearing on gestation length, parturition length, time of placental expulsion, placental efficiency, weight and energy of perirenal brown fat, and lamb temperature at birth.

Conclusions and clinical relevance: Shearing ewes pre-partum may lead to placental changes affecting lamb development and behaviour and associated with higher survival. The findings suggest pre-partum shearing may improve lamb survival, farm profitability and sustainability.

Case history: Over a period of 2 months in the spring and early summer of 2021, 13 cases of sudden death in cull ewes due to aortic rupture were diagnosed at a small number of New Zealand abattoirs.

Clinical findings: In 12/13 (92%) cases, a large blood clot was present in the thorax, and in one case the blood clot was seen in the tissues dorsal to the heart. There were no obvious signs of external trauma. The pluck (heart and lungs) or fixed aorta was submitted for histological examination in seven cases and in all of these, a tear in the aorta was found. Comparing the microscopic appearance of the proximal aorta in these seven cases to three clinically normal ewes from unaffected farms, the aortic wall thickness appeared thinner in the case ewes than the unaffected ewes. Subjectively, there was increased collagen in the tunica media in 3/7 and decreased elastin fibres in 5/7 case ewes compared to the control ewes. Further investigations on the index farm (where the first cases originated), found that the mean liver and serum Cu concentrations in 10 similarly aged, clinically normal ewes were within the normal reference range for New Zealand sheep. Similarly, the liver Cu concentrations of the seven case ewes were within the normal reference range.

Diagnosis: Aortic rupture due to an unknown aetiology.

Clinical relevance: Clinicians should be aware of this condition as a differential diagnosis for sudden death in older sheep and to assist the Ministry for Primary Industries in establishing the extent of this problem in New Zealand.

Aims: To describe the personal drivers, sources of information and gastro-intestinal parasite control methods used by a group of New Zealand sheep farmers identified as low users of anthelmintic (AHC), and their perception of the efficacy and impacts of this approach.

Methods: A convenience sample of 13 sheep farmers farming with a policy of reduced AHC use (no pre-determined routine treatments of ewes >19 months old and/or lambs not routinely treated at pre-determined intervals from weaning through to late autumn) were identified. Semi-structured interviews were conducted regarding their farming philosophy, motivations for reducing AHC use, perceptions of the impacts of farming with reduced AHC use, and parasite control practices. Semi-quantitative data were analysed using descriptive statistics for demographic data and categorising participants' use of AHC and non-chemical control methods. Qualitative data regarding participants' motivations, approaches and rationale were analysed by systematic analysis of the transcripts and distillation of key concepts.

Results: Participants had been operating with reduced AHC use for 3 to  ≥20 years. Key motivators for reducing AHC use were a diagnosis of anthelmintic resistance (AR) or concerns about AR developing. Parasite management information came from a wide range of sources. All respondents expressed overall positive views regarding the impacts of reduced AHC use but detailed information was not available.All identified that regular monitoring, based primarily on subjective animal and non-animal factors was important for their parasite control strategy. Most used faecal egg counts (FEC), often in an ad hoc manner. Five never treated adult ewes, two routinely treated ewes prior to lambing with short-acting AHC and the remainder occasionally treated a small number in low body condition. Four routinely treated some or all lambs at 28-30-day intervals from weaning to late autumn while the remainder based their treatment decisions for lambs on monitored information. All placed heavy emphasis on feeding sheep well, ensuring high post-grazing residuals, and cross-grazing.

Conclusions: AR was a key motivator for participants to reduce AHC use, and a range of information sources and decision-making processes were used. Key parasite management practices were monitoring, primarily using subjective assessments, emphasis on feeding stock well and cross-grazing.

Clinical relevance: The rising prevalence of AR will likely result in increasing the motivation for sheep farmers to reduce their AHC use. Veterinarians will play a key role in providing advice and assistance to facilitate changes in parasite management.

Case histories: The medical records of cats and dogs admitted to the Department of Small Animal Surgery of the Centre Hospitalier Vétérinaire Pommery (Reims, France) with a history of vehicular trauma or falls from the first floor or higher were screened for occurrences of a lower urinary tract (LUT) rupture. Signalment, reported injuries, diagnostic imaging findings, and blood test results were extracted from the medical records.

Clinical findings: A total of 585 animals were included in the study: 339 cats and 246 dogs. The overall prevalence of LUT rupture was 1.36% (8/585) and was 1.2% (3/246) in dogs and 1.4% (5/339) in cats. The most common site of rupture was the bladder (5/8 cases). All orthopaedic injuries were pelvic fractures and animals with pelvic fractures were 6.4 (95% CI: 1.67-24.41; p = 0.012) times more likely to incur urinary tract rupture than those without pelvic fractures. However, three cases had LUT rupture without associated orthopaedic injury. All affected patients had free abdominal fluid identified by abdominal focused assessment with sonography for trauma. Serum urea and creatinine concentrations were elevated in 5/8 cases of LUT rupture, and 4/8 cases were able to urinate.

Clinical relevance: Although LUT injury and pelvic fracture were significantly associated in this study, 3/8 cases of LUT rupture in this study had no orthopaedic injury and half retained the ability to urinate. Thus, lack of associated fractures and ability to urinate should not be used to rule out a LUT rupture. The possibility of bladder or urethral rupture should be considered in all patients with a history of severe blunt trauma.

Aims: To assess whether a whole-herd lameness score on a New Zealand dairy farm in spring could predict lameness prevalence on the same farm in summer (and vice versa) and whether a single-herd lameness score could be used to determine whether herd lameness prevalence was < 5% in both spring and summer.

Methods: Prevalence data (proportion of the herd with lameness score ≥ 2 and with score 3; 0-3 scale) from a study where 120 dairy farms across New Zealand were scored in spring and in the following summer were analysed using limits-of-agreement analysis. In addition, farms were categorised as having either acceptable welfare (lameness prevalence < 5% in both spring and summer) or not (lameness prevalence ≥ 5% in either spring or summer or both). The accuracy and specificity of a single, whole-herd lameness score at identifying herds with acceptable welfare were then calculated.

Results: The limits-of-agreement analysis suggests that 95% of the time, the prevalence of lameness in summer would be expected to be between 0.23 and 4.3 times that of the prevalence in spring. The specificity and accuracy of identifying a farm as acceptable on both occasions from a single observation were, respectively, 74% and 92% in spring, and 59% and 87% in summer.

Conclusions: A single, one-off, whole-herd lameness score does not accurately predict future lameness prevalence. Similarly, acceptable status (lameness prevalence < 5%) in one season is not sufficiently specific to be used to predict welfare status in subsequent seasons.

Clinical relevance: Whole-herd lameness scoring should be used principally as a means of detecting lame cows for treatment. A single whole-herd lameness score by an independent assessor should not be used to determine a herd's welfare status.

Aims: To investigate the effect of preservation by addition of yoghurt starter, potassium sorbate and citric acid on counts of aerobic bacteria, Lactobacillus spp., Streptococcus thermophilus and coliforms, Brix percentage, pH, protein, fat and anhydrous lactose concentrations at 0, 7 and 14 days after collection for colostrum stored at ambient temperature.

Method: Approximately 2 L of first milking colostrum was collected from 10 farms in the Waikato region. Following mixing, it was split into five 400-mL sub-samples and allocated randomly to a control (two sub-samples), or treatment with yoghurt, potassium sorbate, or citric acid preservative. Throughout the trial samples remained in the laboratory at ambient temperature with the lids slightly ajar, and were stirred daily for 15-30 seconds using a sterile spatula. Sub-samples were tested on Days 0, 7 and 14. On Days 0 and 14 aerobic bacteria (by aerobic plate count (APC)), Lactobacillus spp., coliforms and Streptococcus thermophilus counts, pH, Brix percentage, protein, fat and anhydrous lactose were measured. On Day 7 only bacterial counts were completed.The data were analysed using non-parametric clustered bootstrap sampling to estimate the effect of treatment, time, and their interaction on the outcome variables.

Results: Compared to control samples, on Day 7 the APC for potassium sorbate (1.0 (90% CI = 0.6-1.6) × 10⁸ cfu/mL) was approximately seven-fold lower than for yoghurt (7.3 (90% CI = 4.1-11) × 10⁸ cfu/mL), and approximately three-fold lower than citric acid (3.2 (90% CI = 0.2-4.3) × 10⁸ cfu/mL) remaining low to Day 14. All preservatives reduced coliform growth compared to control samples at Day 7 but growth was lower for potassium sorbate than the other preservatives. For Lactobacillus spp., at Day 7, samples with yoghurt preservative had greater counts than the other two preservatives. Potassium sorbate reduced growth of S. thermophilus compared to the other treatments, especially at Day 7, with 7-10 times fewer S. thermophilus per mL compared to the other three groups. All groups showed an obvious acidification over time, with very little variation within days and treatment groups. There was no evidence for change in fat or protein percentage over time regardless of treatment.

Conclusion and clinical relevance: Aerobic and coliform bacteria proliferate extensively in unpreserved colostrum. All preservatives decreased coliform counts compared to un-preserved colostrum, but potassium sorbate was more effective at decreasing both coliforms and aerobic bacteria than either yoghurt or citric acid.