Journal Articles
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Item A comparative study between milk- and serum-based antibody detection assays for Johne's disease in New Zealand dairy cattle(Elsevier B.V., 2025-08-27) Venkatesh KM; Lopez-Villalobos N; Gupta SK; Udy GB; Laven R; Chiu S-J; Bugde P; Furuya Y; Dukkipati VSRDairy cattle are affected by Johne's disease. It is caused by Mycobacterium avium subspecies paratuberculosis (MAP). Suboptimal diagnostic tests add more to the productivity loss resulting from this disease. Agreement between and within different commercial kits is crucial in the decision-making process of disease surveillance programmes. This study compared two ELISAs, that is, Johne's disease commercial antibody detection kits (A and B), using milk and serum samples from New Zealand dairy cattle. These results were also compared with a subset of faecal PCR results. Five scenarios were considered for the comparison of ELISA tests. The point estimates of kappa coefficients (k) between the serum (0.84–0.94) assays were higher than the milk assays (0.59–0.82). The point estimates of kappa coefficients between serum and milk ELISA outcomes were higher for kit B (k = 0.79–0.86) than for kit A (k = 0.55–0.79). The point estimates of kappa coefficients between the ELISA and faecal PCR outcomes varied between 0.43 and 0.74. ELISA tests had point estimates of sensitivity ranging from 0.67 to 0.88 and specificity from 0.62 to 0.93, relative to the faecal PCR test. Results suggest that serum provides a better choice of sample type when both commercial kits A and B are used for Johne's disease surveillance of dairy cattle in New Zealand. Milk assays can be cost-effective to diagnose MAP-positive animals; kit B can be best suited for New Zealand conditions, provided the repeatability of the results is validated.Item Can we estimate herd-level prevalence of lameness in dairy cow herds kept at pasture by sampling part of the herd?(Taylor and Francis Group on behalf of the New Zealand Veterinary Association, 2025-03-26) Sapkota S; Laven RA; Müller KR; Yang DAAims: To assess whether herd-level lameness prevalence can be estimated on New Zealand dairy farms, by scoring the first, middle, or last 100 cows in the milking order. In pasture-based herds, whole herd locomotion scoring requires an assessor outside the milking parlour throughout milking. If sufficiently predictive, sampling a proportion of the herd based on milking order, could reduce the costs and time of welfare assessments. Methods: Six pasture-based, spring-calving, dairy farms in the Manawatū region of New Zealand were conveniently selected. Visits occurred at approximately 6-week intervals between October 2021 and May 2022. Cows were scored using the DairyNZ lameness score (0–3). The assessor tallied cows as they left the parlour and recorded the milking order of those with a lameness score ≥ 2. Data were analysed to determine the association between farm, visit and the proportion of lame cows in the first, middle, and last 100 cows, and the agreement between the prevalence of lame cows in those groups and from whole herd scoring. Results: Across all visits, 263 lame cows were recorded. Of these, 40.7% were in the last 100, 25.9% in the middle 100, and 14.4% in the first 100. Farm, visit and their interactions with group were all statistically significant (p < 0.001). While, overall, the last 100 cows had the highest proportion of lame cows, this pattern varied across farms and visits, Limits-of-agreement plots showed that as herd prevalence increased, agreement between the prevalence in each sample group and herd prevalence worsened. When herd prevalence exceeded 5%, only the middle 100 sampling group had a limits-of-agreement < 5%. Conclusions: Variations across farms and seasons in the proportion of lame cows in each part of the milking order lead to variations in the accuracy of predicting overall lameness from such samples. Based on limits-of-agreement, observing the middle 100 cows is likely to be the most accurate sample, but is still likely to be of limited value on New Zealand dairy farms, especially as a single, one-off measurement. Clinical relevance: On New Zealand dairy farms, locomotion scoring the middle 100 cows in the milking order as part of a welfare assessment would reduce costs and time but would not produce an accurate estimate of whole-herd lameness prevalence. However, it may be useful as a screening tool in herds routinely locomotion scoring throughout the year.Item Meta-analysis quantifying the potential of dietary additives and rumen modifiers for methane mitigation in ruminant production systems(Elsevier B.V. on behalf of KeAi Communications Co. Ltd, 2021-12) Almeida AK; Hegarty RS; Cowie AIncreasingly countries are seeking to reduce emission of greenhouse gases from the agricultural industries, and livestock production in particular, as part of their climate change management. While many reviews update progress in mitigation research, a quantitative assessment of the efficacy and performance-consequences of nutritional strategies to mitigate enteric methane (CH4) emissions from ruminants has been lacking. A meta-analysis was conducted based on 108 refereed papers from recent animal studies (2000-2020) to report effects on CH4 production, CH4 yield and CH4 emission intensity from 8 dietary interventions. The interventions (oils, microalgae, nitrate, ionophores, protozoal control, phytochemicals, essential oils and 3-nitrooxypropanol). Of these, macroalgae and 3-nitrooxypropanol showed greatest efficacy in reducing CH4 yield (g CH4/kg of dry matter intake) at the doses trialled. The confidence intervals derived for the mitigation efficacies could be applied to estimate the potential to reduce national livestock emissions through the implementation of these dietary interventions.Item A scoping review on the epidemiology and public significance of Brucella abortus in Chinese dairy cattle and humans(Elsevier B.V., 2024-01-31) Wang Y; Vallée E; Heuer C; Wang Y; Guo A; Zhang Z; Compton CBrucellosis, caused by Brucella spp., is a re-emerging One Health disease with increased prevalence and incidence in Chinese dairy cattle and humans, severely affecting animal productivity and public health. In dairy cattle, B. abortus is the primary causative agent although infections with other Brucella species occur occasionally. However, the epidemiological and comparative importance of B. abortus in dairy cattle and humans remains inadequately understood throughout China due to the heterogeneity in locations, quality, and study methods. This scoping review aims to describe the changing status of B. abortus infection in dairy cattle and humans, investigate the circulating Brucella species and biovars, and identify factors driving the disease transmission by retrieving publicly accessible literature from four databases. After passing the prespecified inclusion criteria, 60 original articles were included in the final synthesis. Although the reported animal-level and farm-level prevalence of brucellosis in dairy cattle was lower compared to other endemic countries (e.g. Iran and India), it has been reported to increase over the last decade. The incidence of brucellosis in humans displayed seasonal increases. The Rose Bengal Test and Serum Agglutination Test, interpreted in series, were the most used serological test to diagnose Brucella spp. in dairy cattle and humans. B. abortus biovar 3 was the predominant species (81.9%) and biovar (70.3%) in dairy cattle, and B. melitensis biovar 3 was identified as the most commonly detected strain in human brucellosis cases. These strains were mainly clustered in Inner Mongolia and Shannxi Province (75.7%), limiting the generalizability of the results to other provinces. Live cattle movement or trade was identified as the key factor driving brucellosis transmission, but its transmission pattern remains unknown within the Chinese dairy sector. These knowledge gaps require a more effective One Health approach to be bridged. A coordinated and evidence-based research program is essential to inform regional or national control strategies that are both feasible and economical in the Chinese context.Item Measuring hoof horn haemorrhage in heifers: A history.(Elsevier B.V., 2024-06-27) Laven R; Laven LUnderstanding the aetiology and pathogenesis of claw-horn disease (CHD) is essential for developing prevention/treatment programmes. Haemorrhages in the hoof horn (i.e. white line/sole haemorrhages) are an important part of the pathogenesis of CHD, being precursors to and predictors of lesions such as white-line disease and sole ulcer. Understanding haemorrhage development can provide useful information about the aetiology and pathogenesis of CHD. The development of hoof horn haemorrhages is best studied in cattle without previous claw-horn damage, as previous history of damage can markedly alter the hoof's response to stressors. Since the early 1990s, many prospective studies of the risk factors associated with CHD have been undertaken in late pregnant and early lactation heifers, which have a low risk of having had CHD but which are exposed to the same risk factors as lactating cows. Those studies have used a range of methods to assess hoof horn haemorrhages, with the principal focus, particularly initially (but also more recently), being on measuring lesion severity. However, as the science developed it became clear that measuring lesion extent was also important and that combining severity and extent in a single measure was the best approach to assess hoof horn haemorrhages. Studies of hoof horn haemorrhage in heifers have significantly increased our understanding of CHD, demonstrating the importance of housing and the relative lack of importance of post-calving nutrition. Most importantly, they have shown the importance of parturition as a risk factor for CHD, and how parturition interacts with other risk factors to accentuate their effect. The use of such studies has decreased in recent years, despite recent research showing that we still have much to learn from prospective studies of hoof horn haemorrhages in heifers.Item First report of the within-farm prevalence of bovine digital dermatitis in Chinese Holstein dairy cows in Jiangsu, China: A Bayesian modelling approach(Elsevier Ltd, 2024-06) Ma X; Laven RA; Jiang P; Yang DADigital dermatitis is one of the most important causes of lameness in dairy cattle, particularly in housed, intensively-managed cattle. The number of modern intensive dairy farms in China has increased markedly in recent years; however, we lack research on digital dermatitis in Chinese dairy cattle. This preliminary study aimed to estimate the prevalence of digital dermatitis on three conveniently selected farms in Jiangsu, China. The washed hind feet of all lactating cows on all three farms were examined during milking with the aid of a mobile phone light source. True prevalence was then estimated from the apparent prevalence using a Bayesian superpopulation approach to account for the imperfect nature of identifying digital dermatitis in cows during milking. Despite none of the farms having thought it necessary to implement routine digital dermatitis monitoring or control, the disease was found on all three sampled farms. All lesions observed were either chronic M4 or M4.1 type-lesions, with no M2 lesions (i.e. acute ulcerated lesions) observed. The estimated true prevalences on the farms were 7.3% (95% credible interval [CrI]: 5.4%-9.6%), 8.3% (95%CrI: 6.3%-10.8%), and 29.8% (95%CrI: 22.9%-37.2%).