Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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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 Heritability estimates and genetic and phenotypic correlations of skin thickness and skin temperature with key production traits in FocusPrime, Texel, Romney and Highlander sheep(Oxford University Press on behalf of the American Society of Animal Science., 2025-06-16) Graña-Baumgartner A; Dukkipati VSR; Biggs PJ; Kenyon PR; Blair HT; Pickering NK; Van der Linden DS; López-Villalobos NSkin thickness was found to be moderately heritable and genetically associated with lamb survival in a previous study on Romney sheep. The aims of this study were to estimate the heritabilities of skin thickness and skin temperature at around five and 11 months of age, and determine genetic and phenotypic correlations between them and with production traits such as fat depth, loin-eye muscle depth and width, live weights at weaning, scanning, and 12 months, and 12-month fleece weight, in FocusPrime (n=2,088), Texel (n=732), Romney (n=825) and Highlander (n=1,801) sheep breeds. Heritability estimates of skin thickness at 5-month old were moderate in FocusPrime (0.39 ± 0.12) and low in Texel and Highlander (0.11 ± 0.15 and 0.13 ± 0.09, respectively). Heritability estimates of skin thickness at 11-month old were moderate in all breeds (ranged from 0.19 ± 0.07 to 0.29 ± 0.15). Heritability estimates of skin temperature were high in FocusPrime (0.39 ± 0.11), low in Texel (0.17 ± 0.11) and Highlander (0.12 ± 0.06) and almost zero in Romney (0.04 ± 0.03). A tendency in all breeds for negative and favourable correlations was found between skin thickness and skin temperature at 11-month old sheep. Skin thickness at 11-months tended to have a positive genetic correlation with fat depth in all breeds except in Texel where the correlation tended to be negative (-0.10 ± 0.34). Genetic correlations of skin thickness at 11-month old with the weight traits were variate. There tended to be a positive correlation with weaning weight in Texel (0.14 ± 0.34) and Highlander (0.29 ± 0.22). However, there tended to be negative correlations with live weight at scanning and at 12-month of age in FocusPrime (-0.03 ± 0.18 and -0.13 ± 0.22 , respectively) and tended to be positive in Romney (0.09 ± 0.25 and 0.10 ± 0.24, respectively) and Highlander (0.26 ± 0.22 and 0.39 ± 0.21, respectively). Moreover, genetic correlations of skin thickness at 11-month of age with FW12 tended to be positive in both Romney (0.20 ± 0.22) and Highlander (0.55 ± 0.19). Further studies on the genetic correlations of skin thickness and skin temperature with lamb survival in these breeds are warranted.Item Are native shrubs a sustainable alternative to radiata pine on steep slopes? Insights using bioeconomic model for hill country farms in New Zealand(Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2025-05-07) Wangui JC; Millner JP; Kenyon PR; Pain SJ; Tozer PRLimited data on native shrubs has hindered direct comparisons with pine radiata as afforestation options for steep slopes on New Zealand hill country sheep and beef farms. This study updated a native shrub sub-model (NSM) with new research data and developed a radiata pine sub-model (RPM) for integration into a bioeconomic model using STELLA Architect. The model assessed asynchronous afforestation of 10% of effective farm area with either option, comparing impacts on feed supply, sheep dynamics, and farm economics. NSM was updated with growth curve, foliage biomass, and carbon stock data from two New Zealand sites. RPM used literature for growth curve, carbon, and log production data. Simulations included a pasture-only (base) and afforestation with either species at 10% and 20% planting rates. Native shrubs reduced feed supply by 2.5% and 4.0%, while radiata pine reduced it by 7.0% and 7.4% at 10% and 20% planting rates. Reduced feed led to smaller flocks and lower cash flow. Radiata pine generated surplus through carbon and log income, offsetting reduced sheep flock cash flow, while native shrubs did not. Carbon prices of 64.2 and137.4 NZD/NZU would be needed for viability in the best- and worst-case scenarios. Native shrubs are potential land use option on steep slopes but require policy intervention to lower establishment costs and carbon prices.Item Seasonal corneal oedema in small ruminants and camelids in New Zealand: case investigations in sheep and goats(Taylor and Francis Group on behalf of the New Zealand Veterinary Association, 2025-04-13) Hunt H; Green D; Doohan S; Vaatstra B; Makin J; Price PCase history: A seasonal syndrome, presenting as corneal oedema and distinct from infectious keratoconjunctivitis, has been reported in sheep, goats, and camelids in New Zealand. This study details the diagnostic investigation on two properties, of multiple cases of corneal oedema in small ruminants. Outbreak 1 occurred in a mob of sheep in April/May 2023 in the Manawatū region, with 27/52 sheep affected. Outbreak 2 occurred in a group of farmed goats in February/March 2024 in the Auckland region, with 4/5 goats affected. Clinical findings: A spectrum of corneal abnormalities, including focal and diffuse corneal oedema and bullous keratopathy/corneal hydrops, were observed in both the sheep and goats. All animals had normal menace responses and pupillary light reflexes, and there was no associated blepharospasm, epiphora or ocular discharge, except in five sheep that developed secondary ulcerative keratitis. These five sheep had severe ulceration or corneal perforation necessitating euthanasia, while the other affected sheep all recovered within 5 months. The corneal oedema in all goats improved over the following 6 months, but one required a thermokeratoplasty procedure to aid resolution of the oedema and the other three goats had residual focal oedema that did not appreciably affect vision. Diagnosis: It is proposed that a primary corneal endothelial dysfunction was the cause of the oedema, but the aetiopathogenesis is not well understood. Clinical relevance: This is the first peer-reviewed description of this presentation in New Zealand. In contrast to other causes of corneal oedema in ruminants, seasonal corneal oedema is, in some cases, self-limiting with minimal impacts on production and welfare. However, secondary ulceration and corneal perforation may occur, which is painful and may lead to deep infections and permanent visual deficits. Topical antibiotic therapy does not appear to aid in the resolution of the oedema.Item Pathophysiology of Penetrating Captive Bolt Stunning in Horned and Polled Sheep and Factors Determining Incomplete Concussion.(MDPI (Basel, Switzerland), 2025-01-13) Gibson TJ; Ridler AL; Limon G; Lamb C; Williams A; Gregory NG; Bø-Granquist EGPenetrating captive bolt (PCB) is widely used for stunning and on-farm dispatch of livestock, yet its efficacy can vary, with the potential for animal welfare compromise. This study investigated the pathophysiology of PCB-induced trauma in horned and polled sheep (Ovis aries), focusing on factors contributing to incomplete concussion. Thirty-seven (n = 18 horned Scottish blackface and n = 19 polled North Country mule) mature ewes (aged 4-10 years) were shot with PCB with varying cartridge power and PCB modifications, followed by clinical assessment and post-mortem analysis using magnetic resonance imagining (MRI) and gross pathology. The results indicated that damage to the reticular activating system, bolt velocity and penetration depth are crucial for inducing irreversible unconsciousness, with depths less than 37 mm often resulting in incomplete concussion. MRI provided detailed insights into brain injuries, aligning well with gross pathological findings. This study highlights the importance of precise bolt placement and appropriate PCB configurations in ensuring humane outcomes, with MRI proving to be a valuable tool for assessing brain trauma in stunned animals. These findings enhance the understanding of effective stunning techniques and support improved welfare practices in livestock management.Item The Effects of Unfermented and Fermented Cow and Sheep Milk on the Gut Microbiota.(Frontiers Media S.A., 2019-03-06) Rettedal EA; Altermann E; Roy NC; Dalziel JE; Mayo BA variety of fermented foods have been linked to improved human health, but their impacts on the gut microbiome have not been well characterized. Dairy products are one of the most popular fermented foods and are commonly consumed worldwide. One area we currently lack data on is how the process of fermentation changes the gut microbiota upon digestion. What is even less well characterized are the possible differences between cow and other mammals' milks. Our aim was to compare the impact of unfermented skim milk and fermented skim milk products (milk/yogurt) originating from two species (cow/sheep) on the gut microbiome using a rat model. Male Sprague-Dawley rats were fed a dairy-free diet supplemented with one of four treatment dairy drinks (cow milk, cow yogurt, sheep milk, sheep yogurt) for 2 weeks. The viable starter culture bacteria in the yogurts were depleted in this study to reduce their potential influence on gut bacterial communities. At the end of the study, cecal samples were collected and the bacterial community profiles determined via 16S rRNA high-throughput sequencing. Fermentation status drove the composition of the bacterial communities to a greater extent than their animal origin. While overall community alpha diversity did not change among treatment groups, the abundance of a number of taxa differed. The cow milk supplemented treatment group was distinct, with a higher intragroup variability and a distinctive taxonomic composition. Collinsella aerofaciens was of particularly high abundance (9%) for this group. Taxa such as Firmicutes and Lactobacillus were found in higher abundance in communities of rats fed with milk, while Proteobacteria, Bacteroidetes, and Parabacteroides were higher in yogurt fed rats. Collinsella was also found to be of higher abundance in both milk (vs. yogurt) and cows (vs. sheep). This research provides new insight into the effects of unfermented vs. fermented milk (yogurt) and animal origin on gut microbial composition in a healthy host. A number of differences in taxonomic abundance between treatment groups were observed. Most were associated with the effects of fermentation, but others the origin species, or in the case of cow milk, unique to the treatment group. Future studies focusing on understanding microbial metabolism and interactions, should help unravel what drives these differences.Item Editorial: Recent advances and perspectives on the gastrointestinal microbiota of small ruminants.(Frontiers Media S.A., 2024-09-09) Vargas-Bello-Pérez E; Altermann E; Tudisco R; Zhang Q; Puniya AK; Cherdthong A; Knut RRecent research on the gastrointestinal (GI) microbiota of small ruminants such as goats and sheep have provided fascinating insights into their microbial ecology and its impact on health and productivity. Some key advances and perspectives in this field relate to microbial diversity and composition, revealing a diverse array of microbial species inhabiting the GI tract of small ruminants. Members of these microbiomes include bacteria, fungi, protozoa, and archaea, each playing unique roles in the nutrient digestion, immune modulation, and overall gut health. It has been demonstrated that the functional capabilities of GI microbiota, include the fermentation of dietary substrates, synthesis of vitamins, and metabolite production (e.g., short-chain fatty acids). These metabolites influence host physiology, including energy metabolism and immune function.Item Amplification of Ovis aries papillomavirus type 2 DNA from an ovine cutaneous fibropapilloma.(John Wiley and Sons, Inc., 2024-04-01) Munday JS; Klobukowska HJ; Nicholson KSeven of 60 Perendale sheep within a flock developed single or multiple exophytic masses on their distal hind limbs. A mass was excised from one sheep and histological evaluation revealed epidermal and mesenchymal proliferation, papillomavirus-induced keratinocyte changes and marked keratohyalin clumping. Ovis aries papillomavirus type 2 DNA sequences were amplified using PCR.Item Pain Management in Farm Animals: Focus on Cattle, Sheep and Pigs(MDPI (Basel, Switzerland), 2021-05-21) Steagall PV; Bustamante H; Johnson CB; Turner PV; Small APain causes behavioral, autonomic, and neuroendocrine changes and is a common cause of animal welfare compromise in farm animals. Current societal and ethical concerns demand better agricultural practices and improved welfare for food animals. These guidelines focus on cattle, sheep, and pigs, and present the implications of pain in terms of animal welfare and ethical perspectives, and its challenges and misconceptions. We provide an overview of pain management including assessment and treatment applied to the most common husbandry procedures, and recommendations to improve animal welfare in these species. A cost-benefit analysis of pain mitigation is discussed for food animals as well as the use of pain scoring systems for pain assessment in these species. Several recommendations are provided related to husbandry practices that could mitigate pain and improve farm animal welfare. This includes pain assessment as one of the indicators of animal welfare, the use of artificial intelligence for automated methods and research, and the need for better/appropriate legislation, regulations, and recommendations for pain relief during routine and husbandry procedures.
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