Search

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Aims: To investigate the effect of injection of trace mineral supplement (TMS) 14–28 days before calving on white blood cell count (WBCC) and function, serum antioxidant capacity (SAC) and reactive oxygen species (ROS) in pasture-fed cattle after calving. Methods: On each of two South Island, seasonally calving, pastoral dairy farms,1 month before dry-off, a random sample of 150 multiparous cows predicted to calve within 7 days of the herd's planned start of calving (PSC) were stratified on individual somatic cell count, age, breed and expected calving date. On each farm, 14–24 days before PSC, 60 selected cows were randomly assigned for TMS (Zn, Mn, Se, Cu) injection, and 60 were controls. All 240 cows were contemporaneously injected with hydroxocobalamin, and controls with Se. Blood samples were collected pre-injection and 3, 12 and 40 days after calving. Phagocytic activity, count and proportion of neutrophils, lymphocytes and monocytes, WBCC, ROS, SAC were measured. Plasma concentrations of Se, Cu and glutathione peroxidase (GPx) were monitored from a random subset of animals. Differences attributable to TMS were estimated using mixed-multivariable Bayesian analysis, expressed as mean and highest density interval (HDI). Results: Three and 40 days after calving, TMS-treated cows had 0.36 (90% HDI = 0.00–0.77) x 109 and 0.25 (90% HDI = 0.00–0.55) x 109 fewer neutrophils/L. Neutrophils comprised 6 (90% HDI = 0–11)% and 4 (90% HDI = 0–8)% less of the WBCC, and the neutrophil count was 14 (90% HDI = 0–27)% and 9 (90% HDI = 0–18)% less than controls. However, 3 days after calving, there were 7 (95% HDI = 2–12)% more cells phagocytosing and 2,900 (95% HDI = 2,600–3,200) more bacteria ingested/cell. Twelve and 40 days after calving, TMS-treated cows had 0.65 (95% HDI = 0.17–1.17) x 109 and 0.28 (95% HDI = 0.00–0.59) x 109 more lymphocytes/L. Lymphocytes comprised 10 (95% HDI = 3–18)% and 5 (95% HDI = 0–9)% more of the WBCC, and the lymphocyte count was 30 (95% HDI = 11–51)% and 9 (95% HDI = 0–9)% more than controls. There were no meaningful differences in ROS, SAC, ROS/SAC, other white blood cells, or WBCC. Plasma Cu, Se and GPx concentrations were above recommended thresholds. Conclusions: Pre-calving TMS injection was associated with differences in white blood cell population and function that may reduce the risk of disease. Abbreviations: BHOB: Beta-hydroxybutyrate; GPx: Glutathione peroxidase; HDI: Highest density interval; MESF: Molecules of equivalent soluble fluorophore; OSi: Oxidative stress index; PSC: Planned start of calving; ROPE: Region of probable equivalence; ROS: Reactive oxygen species; SAC: Serum antioxidant capacity; THI: Temperature humidity index; TMS: Trace mineral supplement; WAIC: Widely applicable information criterion; WBCC: White blood cell count. [ABSTRACT FROM AUTHOR]

To investigate the effect of parenteral vitamin B12 supplementation on the growth rate of dairy heifer calves over the summer and autumn on seven farms from the Central Plateau of New Zealand, an area historically associated with low cobalt levels in grazing pasture. This was a controlled clinical trial conducted on a convenience sample of seven farms with young female calves randomly assigned to three vitamin B12 treatment groups and followed through a grazing season. Two treatment groups received either monthly SC injections of a short-acting (SA) B12 formulation or 3-monthly injections of a long-acting (LA) B12 formulation and the third group received no treatment (NT). No additional parenteral vitamin B12 was given; however, all calves received additional cobalt (0.04–0.4 mg Co/kg liveweight) in the mineralised anthelmintic drenches given orally every month. Liveweight was recorded in December/January and at the end of the trial in May/June/July depending on farm. Pasture cobalt concentrations (mg/kg DM) were measured every month using 500-g herbage samples from 100-m transects in the area about to be grazed by the trial groups. There was evidence for a difference in growth rate between groups with mean final weight of 228 (95% CI = 212–243) kg for the LA groups, 224 (95% CI = 209–239) kg for the SA groups and 226 (95% CI = 211–241) kg for the NT groups respectively, (global p-value = 0.014). Calves given SA vitamin B12 were 3.77 (95% CI = 0.71–6.82) kg lighter than calves given LA vitamin B12 (p = 0.011). There was no evidence for a change in pasture cobalt concentrations (p = 0.32). The results of this trial raise the question as to whether the routine use of vitamin B12 supplementation in young cattle from areas traditionally thought to be cobalt deficient is necessary, and further raise the possibility that vitamin B12 supplementation by repeated injection of SA products may negatively impact growth rates. [ABSTRACT FROM AUTHOR]

To design a monitoring strategy that could be applied to regular veterinary visits to dairy farms to assess the prevalence and association between health conditions (uterine disease, hyperketonaemia and suboptimal body condition score) when diagnosed and treated at 1–7 days post-calving (DPC) and then re-examined at 28–35 DPC. This study evaluated data from 187 high-yielding dairy cows (21 primiparous, 166 multiparous) on one South Australian dairy farm on two occasions; Visit A which was 1–7 DPC and Visit B which was 28–35 DPC. On each visit, the nature of vaginal discharge, concentration of beta-hydroxybutyrate (BOH) in blood and BCS were recorded and assigned a clinical score. This was converted to a categorical outcome denoting the presence or absence of an abnormal health event, namely metritis or endometritis, hyperketonaemia (BOH concentration ≥1.2 mm/L) and suboptimal body condition score (>0.5 from optimum score). Cows with uterine disease or hyperketonaemia at either visit were treated. The prevalence of abnormal health events at each visit was determined and the association between the prevalence of disease at Visit A and Visit B (following appropriate treatment at Visit A) was measured using regression analysis. The prevalence of abnormal vaginal discharge, hyperketonaemia and suboptimal BCS at Visits A and B were 26%, 7%, 35% and 25%,16%, 33% respectively. A higher proportion of primiparous cows (Visit A: 0.86 (95% CI = 0.70–1.00); Visit B: 0.95 (95% CI = 0.86–1.00)) were found to have suboptimal BCS at both visits compared to multiparous cows (Visit A: 0.28 (95% CI = 0.20–0.35); Visit B: 0.24 (95% CI = 0.17–0.32)). A higher prevalence of hyperketonaemia at Visit B for multiparous compared to primiparous cows (19 (95% CI = 12–25)% vs. 0 (95% CI = 0–17) respectively) was identified. An increase in clinical discharge score at Visit A increased the odds of purulent vaginal discharge at Visit B (OR = 1.77 (95% CI = 1.31–2.40)). Failing to calve at target BCS was strongly associated with cows missing target BCS at Visit B (OR = 5.77 (95% CI = 2.35–13.11)) and for every unit increase in BCS at Visit A, BCS at Visit B increased by 0.40 (95% CI = 0.26–0.53). This study describes a pilot monitoring strategy for clinical parameters indicative of post-partum disease at 1–7 and 28–35 DPC. Determining the herd prevalence of these conditions will enable tracking of herd disease status over time. Abbreviations: BCS: Body condition score; BOH: Beta-hydroxybutyrate; DPC: Days post-calving; NEFA: Non-esterified fatty acids; SCHK: Subclinical hyperketonaemia [ABSTRACT FROM AUTHOR]

To assess whether adding glutamate dehydrogenase (GDH) activity measurements to measurements of gamma-glutamyl transferase (GGT) activity appreciably increases the accuracy of diagnosis of subclinical facial eczema (FE) in cattle. As part of a larger study on the impact of FE on productivity, GGT and GDH activities were measured in serum samples collected from 426 cattle from one dairy farm in the Taranaki region in April 2018. Bayesian latent class analysis was then used to estimate herd prevalence of subclinical FE as well as the specificity and sensitivity of the activity in serum of GGT or GDH alone, and of GGT and GDH activities combined, as diagnostic tests for subclinical FE. The latent class analysis estimated the true prevalence of subclinical FE in the study population as 47.5 (95% probability interval (PI) = 38.3–55.3)%. There was no evidence of any clinically relevant difference between GGT and GDH activities as predictors of subclinical FE; the difference between the areas under the receiver operating characteristic curves for the two measures was 0.005 (95% PI = –0.02 to –0.03). Using the two tests in parallel, with a threshold of 50 IU/L for GGT and 225 IU/L for GDH resulted in specificity and sensitivity of >95%, markedly increasing the accuracy of diagnosis of subclinical FE compared to using GGT or GDH alone at any threshold In this herd, combining the two tests resulted in a clinically relevant improvement in the accuracy of diagnosis of subclinical FE compared to using either test alone, which if used at the individual level will result in fewer cattle being assigned the wrong FE status. This will also apply at the herd level, with combined testing producing fewer false-positive herd test results than using one enzyme alone. This is particularly important for monitoring the efficacy of FE control measures when the expectation should be that the proportion of cattle with FE is very low. [ABSTRACT FROM AUTHOR]

To investigate the relationship between Zn concentrations in serum and those in milk or faeces, and to assess the ability of the Zn concentrations in milk, serum and faeces to predict intake of ZnO in dairy cattle. Seventy cows from one commercial farm in the Waikato region of New Zealand received one of seven dose rates (0, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 g/100 kg bodyweight (BW)) of ZnO given by oral drench, every morning, for 7 consecutive days. Every afternoon, milk and blood samples were collected from all cows. Free-catch faecal samples were collected during the afternoon milking on 3 days throughout the trial. Linear mixed models were used to assess the relationship between the concentration of Zn in serum and that in milk, and in faeces, respectively, and the relationship between dose rate of ZnO and concentrations of Zn in serum, faeces and milk, respectively. Receiver operating characteristic curve analysis was used to determine the ability of the Zn concentration in serum, milk and faeces to predict that a cow had been treated with a dose of ZnO ≥2.5 g/100 kg, the industry-recommended dose rate needed to protect against facial eczema. A 1-µmol/L increase in Zn concentration in milk was associated with a 0.14 (95% CI = 0.11–0.17) µmol/L increase in Zn concentration in serum. Zn concentration in faeces was scaled by its SD; a 1 SD increase was associated with a 1.83 (95% CI = 0.54–3.12) µmol/L increase in zinc concentration in serum. Zn concentrations in serum and faeces increased with increasing dose rates of ZnO. No differences in Zn concentrations in milk were noted between animals dosed with 1.5–3.5 g ZnO/100 kg BW, inclusive. At the optimal threshold of Zn concentration in serum to predict protective ZnO intake (22 µmol/L), the sensitivity was 0.76 (95% CI = 0.69–0.82) and specificity 0.85 (95% CI = 0.80–0.89). For the concentration of Zn in faeces, the optimal threshold was 17.36 mmol/kg, with a corresponding sensitivity of 0.84 (95% CI = 0.84–0.85) and specificity of 0.85 (95% CI = 0.73–0.94). At the optimal threshold for the Zn concentration in milk (76.6 µmol/L), the sensitivity was lower than the other two sample types at 0.59 (95% CI = 0.52–0.67), but with a similar specificity of 0.84 (95% CI = 0.79–0.88). The concentration of Zn in milk shows promise as an initial screening test to identify dairy farms that do not provide adequate zinc to provide protection against FE. [ABSTRACT FROM AUTHOR]

To measure the prevalence of gross pathological damage in the livers of dairy cows at slaughter in the North Island of New Zealand in 2018 and 2019 and to determine, using Bayesian latent class analysis, the specificity and sensitivity of gross liver pathology score (GLS) as a method for detecting moderate to severe facial eczema (FE) at processing plants. Meat inspectors at four processing plants located in the Northland, Waikato, Bay of Plenty and Taranaki regions of New Zealand graded all dairy cattle livers on particular days in April and May of 2018 and 2019 using a gross liver pathology score (GLS) from 0–5 (0 = no damage, 1= fatty liver, 2 = cholangitis and early cirrhosis, 3 = cirrhosis, 4 = extensive cirrhosis, 5 = regeneration). Forty livers from each grade were selected for histopathology. Sections from the apical margin of the right and the left lobes were scored using a histology biliary score (HBS; scored from 1–16) based on the classical histological lesions of FE focussing on changes that differentiate FE from fasciolosis. Mean HBS was collapsed into scores 2–6 (no and mild damage) and score 7–12 (moderate and severe) and GLS was collapsed into grades 0–2 (no or mild damage) and grades 3–5 (moderate, severe and chronic damage). A Bayesian latent class model was developed to estimate sensitivity and specificity of HBS and GLS. The diagnostic target was moderate or severe, gross and/or histological changes in the liver consistent with FE. A total of 2,899 dairy cow livers were graded at the four plants over the two study periods. There were 700/2,899 (24.1%) livers with at least some form of gross pathology damage (GLS≥1) and 130/2,899 (4.5%) livers with moderate, severe or chronic gross pathology damage (GLS≥3). The estimates (posterior median) for the sensitivity and specificity of GLS to liver damage were 0.844 (95% credible interval (CrI) = 0.757–0.905) and 0.932 (95% CrI = 0.866–0.973) respectively. Estimates for HBS were 0.834 (95% CrI = 0.765–0.892) and 0.778 (95% CrI = 0.707–0.854), respectively. GLS is a useful means of estimating liver damage consistent with FE at slaughter. Increased use of liver scoring at slaughter could be useful for monitoring the likely impacts of FE at the country and regional levels. [ABSTRACT FROM AUTHOR]

Aim: To estimate, ex vivo, the torque required to cause vertebral dislocation of cattle tails. Methods: Five tails from dairy cows, severed at the junction between the sacrum and the first caudal vertebra, were sourced from a slaughterhouse. Within 2 hours of slaughter, the severed end of each tail was clamped in a vice and a steel collar was placed halfway along the tail. A torque wrench was attached to the steel collar, which was then rotated to produce an audible and palpable vertebral dislocation, and the torque at the time of the break was recorded. Results: The maximum torque required to break a tail was 20 Nm, the minimum was 9.8 Nm, and the uncertainty was 4.9 Nm. Conclusion: The torque required to break a cow's tail is unlikely to be applied accidentally if cattle are handled following recommended best practice. Thus if cattle on a farm can be shown to have broken tails due to manipulation by farm staff, cattle handling is not meeting the recommended best practice of the New Zealand Dairy Cattle Code of Welfare. [ABSTRACT FROM AUTHOR]

In New Zealand, the recommended intake of Se for dairy cattle (0.03 mg/kg dry matter (DM)) is lower than in the United Kingdom and Australia (0.1 and 0.04 mg/kg DM, respectively), and much lower than in the United States of America (0.3 mg/kg DM). Advisors in New Zealand often suggest that New Zealand intake recommendations are far too low and that recommendations from the United States of America should be used. This has created confusion as farmers are given very different advice depending on which recommendations their advisor uses. In this review, we assess whether the published evidence supports the existing dietary requirements and associated Se status thresholds, or if change is required. We focus particularly on the evidence-base in cattle fed a primarily pasture-based diet, as it is critical that dietary recommendations are derived from data created using cows fed similar diets. Accordingly, we also consider whether the increased use of fodder crops, especially during the dry period, is likely to have altered the Se requirements of dairy cows in New Zealand. We report that the science behind the dietary requirements for Se is robust, being supported by factorial models validated using New Zealand data, and on-farm experimental studies. Published nutritional data suggest that the increased use of fodder crops is unlikely to have altered the dietary balance of pro- and antioxidant factors in New Zealand dairy cows in a way that would meaningfully affect Se requirements. However, the lack of specific data on the vitamin E and fatty acid content of the crops being fed in New Zealand means that more information is needed to confirm this conclusion. In general, the existing New Zealand recommendations for Se-status thresholds are supported, although studies are still lacking to properly characterise the upper threshold of the marginal range. Nevertheless many studies in New Zealand, of herds with marginal or low adequate Se status (using New Zealand recommendations), have failed to show an effect of Se supplementation on milk production, intramammary infection or reproductive performance, so it is highly unlikely that the upper threshold of the range is much higher than the current recommendation. Proponents of the hypothesis that Se intakes in New Zealand dairy cattle should be increased by at least 10 times the current recommendations are therefore not using the evidence base correctly. [ABSTRACT FROM AUTHOR]

Aims: To assess the inter-observer agreement for detecting bovine digital dermatitis (BDD) lesions in digital colour photographs of the hind feet of cows, which had been taken while the animals were standing to be milked, between two trained observers. Methods: Thirty-six photographs were selected from a total of 184 photographs held by the first author (R1), who had classified them as negative (n=11) or positive (n=25) for BDD. They were delivered to a technician (R2) who had previously visually inspected cattle for BDD lesions, and who then recorded the photographs as being either BDD-positive or BDD-negative. The percentage agreement between R1 and R2, and two other inter-observer agreement statistics, Cohen's κ and Gwet's first-order chance correction agreement coefficient (AC1), were calculated. The cumulative membership probabilities of Cohen's κ and Gwet's AC1 were then calculated for different benchmark ranges of κ. Results: The percentage agreement between R1 and R2 was 33/36 (92%), Cohen's κ was 0.80 (95% CI=0.57-1.0) and Gwet's AC1 was 0.86 (95% CI=0.69-1.0). Based on the cumulative membership probabilities for Gwet's AC1, there was 75% probability that the two observers had almost perfect agreement (κ≥0.81). For both Cohen's κ and Gwet's AC1, there was >95% probability that the two observers had at least substantial agreement (κ≥0.61). Conclusions: The two trained observers had at least substantial agreement in identifying from a digital photograph as to whether BDD lesions were present or absent. Therefore results from the two could be used interchangeably. Clinical Relevance: Visual assessment for BDD lesions in the milking parlour can be subjective. However a high agreement between these two trained BDD inspectors means BDD prevalence reported from different regions in New Zealand by these two can be directly compared. [ABSTRACT FROM AUTHOR]