Journal Articles
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Item Subclinical mastitis in New Zealand grazing dairy ewes 2: Relationships among somatic cell count, California Mastitis Test, and milk culture, and risk factors for elevated aerobic plate count(Elsevier Inc on behalf of the American Dairy Science Association, 2026-01-01) Chambers G; Lawrence K; Grinberg A; Velathanthiri N; Ridler A; Laven ROur objectives were, in grazing dairy ewes, (1) to describe SCC, California Mastitis Test (CMT) score, and ewe-level milk aerobic plate count (APC), (2) to explore the relationship between CMT and SCC, (3) to identify risk factors for elevated APC, and (4) to find the optimal SCC threshold for diagnosis of IMI. Gland-level milk samples were collected from ∼15 randomly selected ewes on each of 20 New Zealand dairy sheep farms at early, mid, and late lactation in a repeated cross-sectional study. Aerobic bacterial culture and CMT (measured on a scale of 0, trace, 1, 2, or 3) were performed at the gland level, and SCC and APC at the ewe level using composite milk samples. Milk samples were collected from 893 ewes, 870 of which had complete SCC and culture data. Geometric mean SCC was 169,039 (95% CI: 153,921–185,641) cells/mL, varying between farms and decreasing across visits. A CMT score ≥1 in one or both glands occurred in 21.2% of ewes. Mean log10 SCC increased linearly with CMT score, but the correlation between the ewe's highest gland-level CMT score and SCC was moderate (Kendall's tau = 0.47, 95% CI 0.43–0.52). Bacteria were isolated from 86 (9.9%) ewes, with the most common bacteria being NAS (7.0% of glands) and Staphylococcus aureus (0.6% of glands). A SCC threshold of ∼400,000 cells/mL had the greatest Youden's index for diagnosing IMI using a single SCC measurement. The APC was below the limit of quantification (1 × 103 cfu/mL) in 78.0% of ewes, and <100 × 103 cfu/mL in 96.9% of ewes, and varied between visits and farms. Using a mixed Bayesian ordinal regression model, elevated CMT score and SCC, positive milk culture, and subclinical mastitis, but not udder asymmetry, were confirmed as risk factors for elevated APC. These findings provide baseline milk quality data for New Zealand grazing dairy ewes, confirm that udder health should be considered when investigating elevated bulk milk APC, and can be used to help producers manage SCC, subclinical mastitis, and APC, as well as informing further research. Findings specific to New Zealand's emerging sheep dairy industry offer a benchmark for pastoral systems internationally and highlight the importance of udder health to bulk milk quality.Item Subclinical mastitis in New Zealand grazing dairy ewes 1: Prevalence and risk factors(Elsevier Inc on behalf of the American Dairy Science Association, 2026-01-01) Chambers G; Lawrence K; Grinberg A; Velathanthiri N; Ridler A; Laven ROur objectives were to describe subclinical mastitis and identify its risk factors among grazing dairy ewes in New Zealand. Gland-level milk samples were collected from ∼15 randomly selected ewes on each of 20 dairy sheep farms at early, mid, and late lactation in a repeated cross-sectional study. California Mastitis Tests (CMT; measured on a scale of 0, trace, 1, 2, or 3) and aerobic bacterial culture were performed at the gland level, and SCC at the ewe level using composite milk samples. Subclinical mastitis was defined at the ewe level as having 1 or 2 bacteriologically positive glands and SCC >500 × 103 cells/mL or a CMT score ≥1 (or both). Milk samples were collected from 893 ewes, and complete subclinical mastitis data were available for 856 ewes. Median (range) SCC was 128,000 (2,000–34,953,000) cells/mL. A CMT score ≥1 in one or both glands was found in 21.2% of ewes. Bacteria were isolated from 5.5% of glands, with the most common species being non-aureus staphylococci (4.0% of glands) and Staphylococcus aureus (0.6% of glands). The prevalence of subclinical mastitis was 6.4% (95% CI = 4.6%–8.7%) and was not strongly clustered within farms (intraclass correlation coefficient = 0.04). Ewes with moderate or severe teat end hyperkeratosis had 6.4 times higher odds of subclinical mastitis than ewes with no or mild hyperkeratosis, and ewes with asymmetric udders had 2.3 times higher odds. The odds declined across the 3 visits. The prevalence was low compared with studies of more intensively farmed ewes in the northern hemisphere, but the bacterial causes were consistent. Subclinical mastitis management should be focused at the ewe level before the farm level, given the weak clustering within farms. When addressing or preventing a subclinical mastitis challenge, producers should consider teat end hyperkeratosis and udder asymmetry as simple visual screening tools but not rely on them alone to identify ewes at risk of subclinical mastitis. We present new information for New Zealand grazing dairy ewes, examine udder asymmetry as a diagnostic tool for subclinical mastitis, and show that, although prevalence was lower in New Zealand, the dominant pathogens are consistent, supporting the broader relevance of these findings to international mastitis control, albeit with adaptations for pasture-based systems.Item Common misinterpretations of statistical significance and P-values in dairy research(Elsevier B.V., 2025-11) Laven R; Yang DACareful communication of results is integral to dairy research. However, many published studies contain misinterpretation of the results of statistical analysis, which can lead to conclusions being drawn which are not consistent with the data. Many of these interpretations have arisen because of a focus on P- values rather than on the potential range of effects that are compatible with the study data. This review focuses on 3 misinterpretations: the use of levels of statistical significance to compare results between or within studies, overinterpretation of nonsignificant results, and the use of “trend” to describe results that are “close” to a significance threshold. All of these misinterpretations can be avoided by paying more attention to the range of effects that are compatible with the data. Such a focus will have many benefits—not least, making it clearer when studies have insufficient power to accurately characterize their outcomes. Focusing on compatible effects is not a panacea but will improve statistical inference and provide more thoughtful descriptions of study outcomes.Item Knowledge, Attitudes, and Practices of Smallholder Dairy Cattle Farmers in Tanzania: A Cross-Sectional Survey on Cattle Infertility(MDPI, Basel, Switzerland, 2025-10) Ngou A; Laven R; Parkinson T; Kashoma I; Donaghy DInfertility is one of the major farming constraints facing smallholder dairy cattle farming in Tanzania. Despite its impact, there is limited information on how farmers understand and manage it. The present study aimed to assess farmers’ knowledge, attitudes and practices related to dairy cattle infertility. A cross-sectional survey was conducted using a structured questionnaire involving 301 farmers across six major dairy-farming regions: Tanga, Arusha, Kilimanjaro, Mbeya, Morogoro and Njombe. Overall, 95% of respondents reported encountering infertility on their farms. Farmers were asked to identify signs of infertility from the list of 10 (8 correct and 2 distractors); the median score for correct identification was 7 (range 2–10). The most recognised sign was return to oestrus after insemination (94%). Most farmers correctly identified low milk yield and mastitis as not being signs of infertility. The main reported causes included poor nutrition/housing (93%), livestock diseases (89%), poor record keeping (85%), and poor oestrus detection (83%). Nearly all (98%) viewed infertility as a serious issue, predominantly naming repeat breeding (95%) and failure to produce a calf/year (90%). Management strategies included seeking veterinary services (94%), slaughter (69%), sell to other farmers (23%) and self-treatment (16%). Our findings highlight widespread awareness of infertility while pointing out gaps in management, which reinforces the need for improved farmer education and support services.Item An Investigation of Dairy Cattle Welfare in Commercial Iranian Farms: Results from Management Practices, Resource-Based Measures, and Farm Records(MDPI (Basel, Switzerland), 2025-10-16) Jafari-Gh A; Laven R; Khaloubagheri F; Jafari-Gh S; Mirrahimi MH; Dehghan Banadaky M; Mueller KR; Vallee E; De Rosa GThere is currently no routine systematic assessment of welfare on Iranian dairy farms and no industry-recognised welfare assessment protocols. Therefore, we aimed to design a comprehensive welfare assessment protocol and use it to assess dairy cattle welfare on Iranian dairy farms that could serve as baseline data. Out of the 54 farms on which milking time was measured, 14 had cows spending ≥4 h a day for milking. Additionally, 17/43 farms provided <6 cm of water trough length per cow, and 9/46 farms provided <47 cm of feed trough length per cow, falling short of international guidelines. Hoof trimming was considered a routine procedure with 51/56 farms trimming the hooves ≥2 times a year. The main housing problem in bedded-pack farms was lack of resting areas with 18/29 farms providing less space than the minimum requirement of 5.4 m2/cow, while in free-stall farms bedding depth was the principal housing issue with 16/28 providing ≤10 cm of bedding. Finally, only 31/42 farms that provided farm data kept a record of more than half of the parameters that we asked for. Our findings indicate that a high proportion of farms did not provide sufficient resources or implement management practices necessary to meet welfare requirements of dairy cattle on Iranian farms.Item Comparison of a novel culture-based selection for dry cow therapy with somatic cell count-based selection: Comparing detection rates for major pathogens and subsequent udder health outcomes(Cambridge University Press on behalf of Hannah Dairy Research Foundation., 2025-09-18) Cuttance E; Nortje R; Laven R; Mason WThis study compared a culture-based protocol in which only cows identified as having intramammary infections due to major pathogens (major IMI) were treated with dry cow antibiotics (DCAT) compared with the current New Zealand somatic cell count (SCC) and mastitis-based algorithm. Healthy multiparous pregnant lactating cattle (n = 1541) were enrolled from three spring-calving New Zealand farms. A composite four-quarter milk sample was collected aseptically prior to the last milking before dry-off. Samples underwent standard culture and a culture using a novel, custom-made agar plate. Enrolled animals were classified as having a major IMI on 1) standard culture; 2) novel culture and 3) having SCC > 150,000 cells/ml at the last herd test and/or clinical mastitis (CM) in the current lactation. The sensitivity and specificity of novel culture and SCC/mastitis history for identifying cows with major IMI (compared with standard culture) were calculated. Cows were then blocked by standard culture results (major, minor or no growth) and randomly allocated to treatment based on either novel culture results (cult-SDCT) or SCC/mastitis history (alg-SDCT). Cows allocated to cult-SDCT whose novel culture result was major pathogen positive or contaminated received DCAT, while for alg-SDCT cows, all cows with either SCC > 150,000 cells/ml at the last herd test or CM in the current lactation received DCAT. The sensitivity (0.80 vs 0.67) and specificity (0.91 vs 0.81) for major IMI prediction were greater for cult-SDCT than alg-SDCT. After accounting for farm, age and dry-off SCC, alg-SDCT cows had marginal mean SCC at first herd test post-calving of 129,000 (95% CI 116-143,000) cells/ml, whereas the equivalent for cult-SDCT cows was 113,000 (95% CI 101-126,000) cells/ml. Compared to alg-SDCT, using cult-SDCT correctly identified a higher proportion of major IMI identified by standard culture and did not result in an increase in post-calving SCC.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 The Host Adaptation of Staphylococcus aureus to Farmed Ruminants in New Zealand, With Special Reference to Clonal Complex 1(John Wiley and Sons Ltd, 2025-06) Nesaraj J; Grinberg A; Laven R; Chanyi R; Altermann E; Bandi C; Biggs PJGenetic features of host adaptation of S. aureus to ruminants have been extensively studied, but the extent to which this adaptation occurs in nature remains unknown. In New Zealand, clonal complex 1 (CC1) is among the most common lineages in humans and the dominant lineage in cattle, enabling between-, and within-CC genomic comparisons of epidemiologically cohesive samples of isolates. We assessed the following genomic benchmarks of host adaptation to ruminants in 277 S. aureus from cattle, small ruminants, humans, and pets: 1, phylogenetic clustering of ruminant strains; 2, abundance of homo-specific ruminant-adaptive factors, and 3, scarcity of heterospecific factors. The genomic comparisons were complemented by comparative analyses of the metabolism of carbon sources that abound in ruminant milk. We identified features fulfilling the three benchmarks in virtually all ruminant isolates, including CC1. Data suggest the virulomes adapt to the ruminant niche sensu lato accross CCs. CC1 forms a ruminant-adapted clade that appears better equipped to utilise milk carbon sources than human CC1. Strain flow across the human–ruminant interface appears to only occur occasionally. Taken together, the results suggest a specialisation, rather than mere adaptation, clarifying why zoonotic and zoo-anthroponotic S. aureus transmission between ruminants and humans has hardly ever been reported.Item An Investigation of Dairy Cattle Welfare in Commercial Iranian Farms: Results from Animal- and Stockperson-Based Measures.(MDPI (Basel, Switzerland), 2025-01-27) Jafari-Gh A; Laven R; Khaloubagheri F; Mirrahimi MH; Jafari-Gh S; Banadaky MD; Mueller KR; Vallee E; Salari FDairy cow welfare can impact both the economic performance of an individual farm and the public perception of the sector, thus influencing the sustainability of the dairy farming industry. Intensive dairy farming in Iran started in the 1940s, but there is limited data available regarding dairy cattle welfare in the country. Therefore, the aim of this study was to design and use a comprehensive bespoke welfare assessment protocol in intensive Iranian dairy farms to provide baseline data for Iran and other countries with similar farming systems. The protocol consists of animal-based, stockperson-based, and resource-based measures. The first part of the welfare assessment protocol (being presented in this paper) was developed from the existing literature and contained 11 animal-based and 2 stockmanship measures. The protocol was applied in 62 intensive dairy cattle farms in five arid and semi-arid provinces of Iran. Welfare Quality sample size suggestions were used to reach the minimum sample size for all animal-based measures except for the locomotion score, where either the whole milking herd was scored or all cows in the early lactation (<150 days in milk) group. Results show that there was a good focus on nutrition management on the farms. Lameness prevalence and the incidence of hock lesions were too high, although within the range seen in many housed cows outside Iran. In addition, 13.5% of cows had damaged ears. The prevalence of dirty legs was high (≥80% of cows), and the hygiene score was unrelated to the farming system. Finally, the extremely high median prevalence of tail damage (60%) indicates a significant welfare issue that needs to be addressed with urgency.Item Etiology and epidemiology of digital dermatitis in Australian dairy herds.(Elsevier B.V., 2024-02-06) McPherson A; Tranter B; Phipps A; Laven R; House J; Zadoks RN; Rowe SABSTRACT Bovine digital dermatitis (BDD) is an important cause of lameness in dairy cows worldwide. However, there is very little known about this disease in Australian herds, which are predominantly managed on pasture. The primary objectives of this cross-sectional study were to describe the presence and prevalence of BDD in Australian dairy herds and to characterize the microbiota of healthy skin and M4 lesions of BDD-affected, pasture-managed cows. Cows from 71 dairy herds were examined at milking time to identify the presence of BDD lesions. True prevalence was estimated using Bayesian methods with informative priors for sensitivity and specificity. Biopsy samples (n = 60) were collected from cows with and without BDD-lesions in 7 pasture-based herds. The microbiota in the superficial and deep strata of each tissue biopsy were characterized via sequencing of the V3-V4 region of the bacterial ribosomal RNA gene. Lesions were detected in 1,817 (11.5%) of 15,813 cows, and in 68 of 71 (95.8%) herds. The median herd-level apparent and true prevalences of BDD were 8.5 and 18.1%, respectively, but this varied considerably between farms. On farms with BDD, M4 lesions accounted for 70 to 100% of all lesions (interquartile range = 95.1 to 100%, median = 100%). M2 lesions (i.e., large ulcerative lesions) were observed at low prevalence (<2.2%) in the few herds (7/71, 9.9%) where they were found. There was a statistically significant difference in the composition of the microbiota between healthy skin and M4 lesions but not between superficial and deep tissue layers. Several gut- and effluent-associated bacterial taxa, including Lentimicrobium and Porphyromonas, which have previously been associated with BDD, were abundant in BDD lesions but not in control biopsies. Our study supports the idea that such taxa are involved in, though possibly not essential to, lesion development and persistence in pasture-managed cows in Australia. Our results also suggest that Dichelobacter may contribute to the disease process. We conclude that BDD is likely to occur in most Australian dairy farms, but that further studies are needed to identify its impact on cow welfare and productivity. Further investigation of the etiology of BDD in Australian dairy herds is also necessary to inform prevention and control strategies. INTERPRETIVE SUMMARY: We visited 71 farms in Australia to estimate the prevalence of bovine digital dermatitis (an infectious skin disease that causes lameness in cows). Most farms (68 / 71) were identified to be endemic for the disease, but that the painful lesion types (score = M2) were uncommon. Microbiome analysis was conducted on 60 biopsy sample of cows with and without BDD lesions. We found that cows with BDD had higher abundances of gut- and effluent-associated bacterial taxa, including Lentimicrobium and Porphyromonas. We conclude that BDD is present on most Australian dairy farms.