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Aims: To undertake a survey of the prevalence of tail deviations, trauma and shortening on a representative selection of New Zealand dairy farms, and to assess whether sampling based on milking order could be used instead of random sampling across the herd to estimate prevalence., Methods: This was a cross-sectional observational study, with 200 randomly selected farms enrolled across nine regions of New Zealand via selected veterinary practices (one/region). Veterinary clinics enrolled 20-25 farms each depending on region, with 1-2 trained technicians scoring per region. All cows (n = 92,348) present at a milking or pregnancy testing event were tail scored using a modified version of the New Zealand Veterinary Association Industry Scoring System. Palpated lesions were recorded as deviated (i.e. non-linear deformity), shortened (tail shorter than normal) or traumatic (all other lesions). The location of lesions was defined by dividing the tail into three equal zones: upper, middle and lower. A cow could have more than one lesion type and location, and/or multiple lesions of the same type, but for the prevalence calculation, only the presence or absence of a particular lesion was assessed. Prevalence of tail damage calculated using whole herd scoring was compared to random sampling across the herd and sampling from the front and back of the milking order. Bootstrap sampling with replacement was used to generate the sampling distributions across seven sample sizes ranging from 40-435 cows., Results: When scoring all cows, the median prevalence for deviation was 9.5 (min 0.9, max 40.3)%; trauma 0.9 (min 0, max 10.7)%, and shortening was 4.5 (min 1.3, max 10.8)%. Deviation and trauma prevalence varied between regions; the median prevalence of deviations ranged from 6% in the West Coast to 13% in Waikato, and the median prevalence of all tail damage from 7% in the West Coast to 29% in Southland. Sampling based on milking order was less precise than random sampling across the herd. With the latter and using 157 cows, 95% of prevalence estimates were within 5% of the whole herd estimate, but sampling based on milking order needed > 300 cows to achieve the same precision., Conclusions and Clinical Relevance: The proportion of cows identified as having damaged tails was consistent with recent reports from New Zealand and Ireland, but at 11.5%, the proportion of cows with trauma or deviation is below acceptable standards. An industry-wide programme is needed to reduce the proportion of affected cows.

Aim: To explore factors associated with the frequency of tail damage in dairy cows on 29 New Zealand farms participating in an animal welfare monitoring programme., Materials and Methods: Herd-level tail score data were collected at the cow level and then summarised at the herd level as counts for each lactation over the period 1 June 2014 to 31 May 2018. A cow's tail was considered damaged if there was evidence of any injury that deformed the anatomical structure involving either bone or soft tissue and could include loss of use. There were four categories for tail scoring. Fracture or dislocation of tail bones was considered as a deviation (score 1). When the tail had been docked above the top of the cow's udder, this was considered as docked short tail (score 2). When there was evidence of soft tissue trauma (score 3) or bone damage but no fracture (score 4), this was recorded as damaged (other). Tails were scored for each whole dairy herd. Tail scoring was performed by trained veterinarians or veterinary technicians. The primary outcome variable was counts of deviated tails (DT). Other outcome variables were docked short, damaged (other), and total tail injuries (TTI) which was a summation of all tail injuries. The potential predictor variables were area, season, farm, region, replacement rate, and herd size. A mixed-effects negative binomial or Poisson regression was fitted to the count data., Results: A total of 29 farms contributed data for tail scoring, with 54,831 cows individually scored. The unadjusted regional prevalence of TTI ranged from 3.5% (64/1,835) in Taranaki in 2014-2015 to 28.7% (1,434/4,988) in Southland/Otago in 2017-2018. The unadjusted regional herd prevalence of DT ranged from 2.1% (280/6,862) in Taranaki (2014-2015) to 13.2% (4,627/30,165) in Southland/South Otago (2017-2018). The incident rate ratio (IRR) of DT in 2015-2016 was 1.74 (95% CI = 1.20-2.53; p = 0.003) times the incident rate for the reference group (2014-2015). The IRR for TTI in 2015-2016 was 1.70 (95% CI = 1.60-1.81; p = 0.001) times the incident rate for the reference group (2014-2015)., Conclusions and Clinical Relevance: This is the first quantitative study of the frequency of tail damage within New Zealand dairy farms and whilst variable between regions, it indicates that the frequency is increasing. Opportunities exist to better understand the causes of tail injuries and to improve animal welfare.

Aim: To describe the use of antimicrobial drugs for food animals in New Zealand, based on sales data reported to government for 2005-2018, to provide a baseline to determine the success of measures to reduce antimicrobial use for food animals and to compare usage to selected European countries., Methods: Data were sourced from official government and industry reports to update previous estimates of use (as amount sold) of antimicrobial products applied to animals in New Zealand. The data included antimicrobial sales and animal populations, weighted where appropriate by breed and age class. Antimicrobial use was estimated based on the amount of active ingredient sold, per kg of animal biomass standardised to the probable weight at time of treatment or lifetime average but not slaughter weight (population correction unit; PCU). New Zealand data for 2017 and 2018 were adjusted to account only for antimicrobials used for farm animals by discounting horticulture use, companion animal use and export., Results: Between 2014 and 2018 the estimated usage of antimicrobials in animals flattened to a 5-year rolling average of 10.40 mg/PCU. New data on use for companion animals and on exports of zinc bacitracin and tylosin, included previously in the gross New Zealand values, allow a more refined estimate of use of antimicrobials in food animals of 10.21 mg/PCU in 2018, the third lowest rate of use for countries reporting by the same methodology. The intensive industries of pigs and poultry combined use more than 500 mg/PCU whereas the extensive red meat and dairy industries use an estimated 6.25 mg/PCU. New Zealand uses proportionally more cephalosporins and macrolides, two of the critically important antimicrobial groups, when compared with European countries, but less quinolones. The most obvious difference is the extensive use of zinc bacitracin and tylosin fed to pigs and poultry in New Zealand but not in the European Union., Conclusions: Use of antimicrobials in food animals has stabilised to a rate of approximately 10.2 mg/PCU. This baseline should be used by the animal health industry to measure future success in its efforts to reduce and make more refined use of antimicrobial drugs as New Zealand works to deliver the government's Antimicrobial Resistance Action Plan. High rates of use of zinc bacitracin and some critically important macrolides represent clear targets in attempts to reduce usage.

Aim: To describe the use of antimicrobial drugs for food animals in New Zealand, based on sales data reported to government, changes over time, and in comparison with other countries and human use., Methods: Data were sourced from official government and industry reports covering 26 European countries, Australia, Canada, New Zealand and the United States of America in 2012, the last year data were available for all countries. The data included antimicrobial sales, and animal and human populations. Antimicrobial use was estimated based on the amount of active ingredient sold, per standardised biomass (population correction unit)., Results: The estimated usage of antimicrobials for food animals in New Zealand for 2012 was 9.4 mg active ingredient/kg biomass. Total sales of antimicrobials between 2005-14 increased on average by 2.5% or 1.5 tonnes per year. Over the same time total animal biomass decreased by an estimated 4.3%, with the main decrease being in sheep (25%) and beef cattle (17%), while dairy cattle increased (28%). In the countries examined, the estimated usage of antimicrobials in food producing animals in 2012 varied from 3.8 to 341 mg active ingredient/kg biomass, in Norway and Italy, respectively, with use in New Zealand being the third lowest. Usage of antimicrobials for human health in New Zealand in 2012 was estimated at 121 mg active ingredient/kg biomass, being ranked sixteenth of the countries compared. Use in humans was 12.9 times the use in animals., Conclusions: New Zealand was the third lowest user of antimicrobials in animal production and used much less than in human medicine. This is the first report of baseline data which may be used by the New Zealand animal health industry to develop, and measure success in, approaches to maximise the life of antimicrobials for animal health and welfare., Clinical Relevance: New Zealand veterinarians will soon have to make changes to adopt the World Health Organisation's global action plan to manage antimicrobial resistance. Having a benchmark of current antimicrobial use will inform priorities and allow measurement of the impact of future programmes.

Aim: To test the non-inferiority of a novel combination intramammary product containing penicillin and cloxacillin to a reference intramammary product containing oxytetracycline, oleandomycin, neomycin and prednisolone with regard to bacteriological cure and clinical cure., Methods: Clinical cases of mastitis were sourced from 30 spring-calving dairy farms in the Southland region of New Zealand. Affected quarters were infused three times at 24 hourly intervals with either the novel combination product containing 1 g penicillin and 200 mg cloxacillin, or a reference product containing 200 mg oxytetracycline, 100 mg oleandomycin, 100 mg neomycin and 5 mg prednisolone. Cows were enrolled when a farmer detected a case of clinical mastitis. Milk samples were collected for microbiological culture immediately before treatment (Day 0) and on Days 9, 16 and 23. Bacteriological cure was compared for 187 and 178 quarters treated with the reference and novel product, respectively, and clinical cure was compared for 235 and 223 quarters, respectively. Non-inferiority was assessed by calculating the difference in cure rates between the two products and constructing a 95% CI around the difference, using the variance inflation factor to account for herd level clustering. The non-inferiority margin was 20% for both bacteriological and clinical cure. Generalising estimating equation models were used to determine predictor variables., Results: The bacteriological cure percentage, adjusted to account for herd-level clustering, was 8.5 (95% CI=-1.7-21.8)% higher for quarters treated with the novel than the reference product. The adjusted clinical cure percentage was 0.3 (95% CI=-11.2-12.0)% higher for clinical quarters treated with the novel than the reference product. Bacterial species was the only covariate for bacteriological cure (p=0.003), and quarter score at enrolment (indicating udder inflammation) was the only covariate for clinical cure (p=0.032) in the multivariable models., Conclusion: The novel combination product was demonstrated to be non-inferior to the reference product with regards to both bacteriological cure and clinical cure., Clinical Relevance: Clinicians treating mastitis now have access to this novel combination intramammary product, and demonstration of its non-inferiority compared to the existing reference product will provide options for treatment approaches. The novel product contains fewer antimicrobials; which are of a narrower spectrum of activity.

Aims: The main aim of this study was to describe the prevalence of primary subclinical ketosis (SCK) in mainly pasture-grazed dairy cows in three dairy-farming regions of New Zealand 7-12, and 35-40 days post-calving. A second aim was to investigate herd- and cow-level factors associated with the prevalence of SCK., Methods: A cross-sectional longitudinal prevalence survey was undertaken in 1,620 dairy cows from 57 herds. A random sample of cows without disease in the prior 30 days were enrolled at one farm visit within 5 days of calving, and blood samples were collected 7 and 28 days later (7-12 and 35-40 days post-calving) for measurement of beta-hydroxy butyrate (BHBA) concentrations using an electronic cow-side meter. SCK was defined as blood BHBA concentration ≥1.4 mmol/L., Results: Mean cow-level prevalence of SCK varied with interval post-calving (16.8 and 3.2% at 7-12 days and 35-40 days post-calving, respectively) and age (13.0 and 13.1% of 2-year olds and ≥8-year olds, respectively, compared to 7.2% of 3-4-year-old cows). Mean herd-level prevalence of SCK was 14.3 (min 0, max 60.0)% and 2.6 (min 0, max 24.4)% at 7-12 days and 35-40 days post-calving, respectively, and was greater in Southland (13.3%) than Waikato and Canterbury herds (6.9 and 4.7%, respectively)., Conclusions: This is the first population-based report of the prevalence of SCK in New Zealand dairy herds and demonstrates that age and interval post-calving are important risk factors determining prevalence; and that there is wide variation in prevalence between herds., Clinical Relevance: Subclinical ketosis may be unrecognised but common in many New Zealand dairy cows in the first 2 weeks of lactation.

Aims: To test equivalence between two different cephalonium dry-cow therapy (DCT) products with regard to the incidence of bacteriological cure of existing infections of quarters, the incidence of new intramammary infections (IMI) from 2-5 days postpartum and the incidence of clinical mastitis from drying-off to 21 days postpartum., Methods: All cows (n=1,570) on four commercial dairy farms in Southland were eligible for inclusion. Power analysis using a variance inflation factor indicated a required minimum of 2,101 quarters per treatment group. Cows were blocked by herd, parity, previous history of mastitis and most recent somatic cell count (SCC), and then randomly allocated to either of two cephalonium treatments at the cow level, viz the treatment group (new formulation cephalonium) or the positive control group (existing reference formulation cephalonium). All quarters within a cow were assigned the same treatment. Samples collected from all quarters with a SCC ≥500,000 cells/mL at drying-off, and those with a positive culture postpartum were cultured, as well as samples from all quarters collected between 2-5 days postpartum. All cases of mastitis were recorded and sampled for culture. The risk of quarter-level incidence of bacteriological cure, IMI and clinical mastitis was modelled using a GLM and generalised estimating equation (GEE), including the effects of treatment group, age,farm, udder-health status at drying-off and length of dry period., Results: For 829 infected quarters, the estimated incidence of bacteriological cure for all pathogens was 78.0 (95% CI=64.3-91.6)% for the treatment group and 75.7 (95% CI=61.6-89.8)% for the positive control group (p=0.71). Incidence of cure varied with the farm (p=0.001), type of pathogen pre-treatment (p=0.009) and log(10)SCC at drying-off (p<0.001). For 4,530 quarters, the estimated incidence of new IMI, with any pathogen, for treatment and positive control groups was 16.1 (95% CI=13.1-19.7)% and 16.0 (95% CI=13.0-19.5)% respectively (p=0.91). Incidence of IMI varied with farm (p<0.001), pathogen and SCC status before treatment (p<0.001), and length of the dry period (in days) (p<0.001). For 5,136 quarters, the estimated incidence of clinical mastitis was 1.0 (95% CI=0.5-1.7)% in the treatment group and 1.1 (95% CI=0.6-2.0)% in the positive control group (p=0.64)., Conclusions: Use of the two different cephalonium products at drying-off in four dairy herds in Southland resulted in equivalence with respect to incidence of bacteriological cure of existing infections, incidence of new IMI postpartum, and incidence of clinical mastitis in early lactation.

Aim: To compare the proportions of clinical and bacteriological cure of glands of dairy cows diagnosed with clinical mastitis, following treatment with one of three different intramammary antibiotic preparations., Methods: Cows from dairy cow herds (n=28) across New Zealand which were diagnosed with clinical mastitis in one or more glands at any stage of lactation were randomly assigned at the cow level within sequentially presented groups of three animals to be treated with one of three intramammary antibiotics. The treatments were 1 g procaine penicillin, 0.25 g cefuroxime, and a combination of 1 g procaine penicillin and 0.5 g dihydrostreptomycin (DHS). All treatments were infused on three occasions at 12-hourly intervals. Duplicate milk samples were collected for bacteriology before initial treatment, and 21-42 days later. Logistic regression or generalised linear mixed models were used to analyse the proportion of cows or quarters retreated for mastitis within 30 days of initial treatment ('clinical treatment failure'), and the proportion of glands from which bacteria were isolated initially but from which the same bacterial species was not re-isolated ('bacteriological cure')., Results: The annual herd average cumulative incidence rate of clinical mastitis was 12.7 cases/100 cows. The incidence rate was higher in young (2-year-old) and old (> or = 9-year-old) cows relative to 3- and 4-year-old cows, and was higher in Friesian than Jersey or crossbred cows. Streptococcus uberis was the pathogen most commonly isolated, and its relative prevalence declined with time postpartum. Cows treated with cefuroxime were more likely (p<0.01) to be re-treated for clinical mastitis in the 30 days after initial treatment than cows treated with procaine penicillin or procaine penicillin and DHS. Bacteriological cure occurred in 74% of treated glands and there was no difference in the proportion of cures among the treatments (p=0.4). The proportion of cures was lower when treatment occurred 28-72 days after calving (p<0.01) and if a major pathogen was isolated (p<0.001)., Conclusions and Clinical Relevance: There was no benefit in terms of clinical or bacteriological cure rate in treating clinical mastitis cases with the combination of procaine penicillin and DHS compared to treatment with procaine penicillin alone. The proportion of clinical mastitis cases re-treated differed among herds, and more cows treated with cefuroxime were retreated within 30 days of initial treatment. However, the bacteriological cure proportion was the same among the treatments. Cure proportions were lower in cows from which major mastitis pathogens were isolated and when treatment commenced 28-72 days after calving.