The prevalence of damaged tails in New Zealand dairy cattle.

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.

Validation of Brix refractometers and a hydrometer for measuring the quality of caprine colostrum.

On-farm assessment of caprine colostrum quality is important for goat farmers; the ability to quickly recognize whether colostrum is suitable to feed to kids helps achieve successful passive transfer of immunity. The study compared the use of optical and digital Brix refractometers and a hydrometer against the international gold standard radial immunodiffusion (RID), using both fresh and frozen samples. A locally available ELISA methodology was included for comparison. A total of 300 samples were collected from 2 farms (farm 1: n = 157, collected by research staff within 24 h of parturition; farm 2: n = 143, collected by the farmer within 12 h of parturition). Farm 1 provided doe age for a subset of samples (n = 86). Samples were tested fresh and then frozen for shipment and repeated testing. Specific gravity was measured using a hydrometer in a subset of samples (n = 22) from farm 2. Because no gold standard thresholds are currently available for caprine colostrum, RID-derived values of 30, 40, and 50 g/L IgG were used as potential "good quality" thresholds. Pearson (ρ) and Lin's concordance correlation coefficients (CCC) were calculated for comparison of methods. Optimum thresholds were established maximizing the Youden index and minimizing the "distance closest to the top left corner" of the receiver operator characteristic curves. Brix values were correlated with RID (optical Brix, fresh: ρ = 0.73; digital Brix, fresh: ρ = 0.71; digital Brix, frozen: ρ = 0.76) and with each other (range: ρ = 0.93 to 0.99; CCC = 0.91 to 0.99). Specific gravity measured by the hydrometer yielded a strong relationship with RID (ρ = 0.83) and with Brix values (range: ρ = 0.88 to 0.90). The ELISA method was not correlated with Brix methods (range: ρ = 0.02 to 0.09) or RID (ρ = 0.20). Depending on the colostrum IgG threshold, the hydrometer yielded high Youden indices (range: 0.78 to 0.93) and low distance closest to the top left corner criteria (0 to 0.05) at a threshold of 1.047 specific gravity. For all RID IgG thresholds, the best Brix threshold (regardless of type or whether the sample was fresh or frozen) was 18 or 19%, with the highest Youden indices (range: 0.47 to 0.61) and lowest distance to the top left corner criteria (range: 0.09 to 0.16); however, we recommend 19%, because this reduces the potential of feeding poor-quality colostrum. The ELISA method was the poorest predictor of colostrum concentration. Age was not found to affect colostrum quality; however, the sample size of this subset was small. Hydrometers are inexpensive and easy to use, whereas Brix methods use only a small amount of colostrum; we suggest that either method could be used on-farm.

A survey of antimicrobial use in dairy cows from farms in four regions of New Zealand.

AIMS: To assess the use of antimicrobials in dairy cows over three seasons in a group of dairy farms within the Southland and South Otago region, and to assess antimicrobial use in one season in a group of monitored dairy farms in four regions of New Zealand. METHODS: Sales data were collated for all antimicrobials purchased by 399, 406 and 436 dairy farms in the Southland and South Otago regions for the 2012-13, 2013-14 and 2014-15 seasons, respectively, and from 108 dairy farms in the Manawatu, Taranaki, North Canterbury, and Southland and South Otago regions of New Zealand for 2014-15. Antimicrobials were categorised by class and product type (injectable, or dry cow or lactating cow intramammary). Antimicrobial usage was calculated as the mass of active ingredient (ai) per kg biomass, or population correction unit (PCU), with biomass estimated from the number of cows and heifers in the milking herd on 1 June multiplied by 458 kg. RESULTS: Estimated annual use of antimicrobials in the Southland and South Otago herds was 8.47, 9.58 and 9.54 mg ai/PCU for the three seasons, and for herds in the four regions was 8.65 mg ai/PCU for 2014-15. Penicillins were the most commonly used antimicrobials. Between 2012 and 2015, penicillin use increased from 5.75 to 7.44 mg ai/PCU, whereas there was a decrease in use of macrolides (1.19 to 1.04 mg ai/PCU) and cephalosporins (0.82 to 0.45 mg ai/PCU). Estimated annual use in 2014-15 by herds in Manawatu, Taranaki, North Canterbury, and Southland and South Otago was 8.93, 5.28, 6.44 and 9.97 mg ai/PCU, respectively, and also varied with size of herd. In these herds, injectable products were most commonly used (4.89 mg ai/PCU), followed by dry cow intramammary (3.04 mg ai/PCU), then lactating cow intramammary treatments (0.71 mg ai/PCU). CONCLUSIONS: The use of antimicrobials in dairy cows in New Zealand appears low by international standards, but varied across years and across regions. The vast majority of antimicrobials used by class were penicillins. This is the first attempt at a national assessment of antimicrobial use by volume and type for dairy cows in New Zealand and will aid in the progression of a strategy of reduction, refinement and replacement of antimicrobial use in animals.

Demonstration of non-inferiority of a novel combination intramammary antimicrobial in the treatment of clinical mastitis.

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.