Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item Use of hormones on New Zealand dairy farms: an analysis of the results from a survey of farmers and a survey of veterinarians(Taylor and Francis Group on behalf of the New Zealand Veterinary Association, 2025-07-09) Laven RA; Cuttance EL; Chambers GAims: To survey New Zealand dairy farmers and veterinarians on their attitude and use of reproductive hormones in treating cows identified as non-cyclers. Whilst hormones have been identified as effective tools in assisting reproduction in dairy cattle, there is widespread but anecdotal concern about their cost-effectiveness and a lack of high-quality information on the attitude and practices around hormone use on New Zealand dairy farms. Methods: Electronic links to separate farmer and veterinary survey forms were sent to all dairy clients and all veterinary employees of five, convenience-selected veterinary practices across New Zealand. Using closed, open, and Likert-style questions, the surveys covered cost-effectiveness of hormonal interventions, value judgements on their use, and impact on the public perception of dairy farming. Results: Usable surveys were returned by 424 farmers and 70 veterinarians. Response rates are not known as denominator data were not sought. Of the farmers, 253/424 (60%) reported using hormone treatments, with 153 (36%) primarily using them before mating started. However, only 163 (38%) thought treatment was cost-effective, compared to 65/70 (93%) veterinarians. Beliefs around cost-effectiveness affected use: 8/171 (5%) farmers who never used hormones believed they were cost-effective, compared to 38/94 (40%) who used hormones occasionally and 117/159 (74%) who used them routinely. Other reasons put forward by farmers for not using hormones included “breeding infertility”, “not natural”, and “not treating the cause”. Farmer and veterinary opinion also varied around the trajectory of hormone use. Amongst veterinarians, 12/70 (17%) thought use should decrease compared to 271/424 (64%) farmers, while 19/70 (27%) veterinarians thought use should increase compared to 21/424 (5%) of farmers. Conclusions: The results suggest a disconnect around hormone use between the participating veterinarians and farmers. Many farmers did not believe hormone use was cost-effective, despite strong evidence to the contrary. As other reasons for not using hormones were also cited, and as most farmers believed hormone use should decrease, it seems unlikely that further education on cost-effectiveness will change practice. Rather, it could increase the proportion who think veterinarians benefit financially more from hormone use. Clinical relevance: Veterinary focus on maximising synchronisation use and efficacy is bypassing a significant proportion of dairy farmers. There is an opportunity for veterinarians to focus on what their clients want and work with them to improve herd fertility without relying on hormones to fix management problems.Item Teat and udder morphology and pathology of New Zealand dairy ewes.(Taylor and Francis Group, 2025-02-12) Chambers G; Lawrence KE; Ridler AL; Laven RAAIMS: To describe the morphology and prevalence of teat and udder pathology of New Zealand dairy ewes. METHODS: A repeated cross-sectional study was conducted on 20 commercial New Zealand dairy sheep farms over the 2022-2023 season. Approximately 15 randomly selected ewes were examined on each farm in early, mid, and late lactation. Four udder morphology measures were scored on a 5-point scale: depth (1 = pendulous, 5 = compact udder), suspension (ratio of width at abdominal attachment to height, 1 = low, 5 = high), gland separation (1 = zero, 5 = maximum separation), and teat placement (1 = distally located, vertically oriented, 5 = laterally located, horizontally oriented teats). Teat length and width were measured, and the presence of supernumerary teats, asymmetry, visible teat/udder inflammation, and lesions were recorded. Teats and glands were palpated for consistency, gland-nodules, teat canal thickening, and patency, and teat ends scored for hyperkeratosis. Teat and gland-level pathological variables were converted to ewe-level scores. The presence of involuted, non- or minimally lactating glands was recorded. Data were analysed using descriptive statistics. RESULTS: Across the three visits, 893 observations were made on 882 unique ewes. Mean teat length and width were 27.5 (95% CI = 27.2-27.7) and 15.8 (95% CI = 15.7-15.9) mm. Udder depth, separation, suspension, and teat placement had modal scores of 4, 3, 3, and 3 respectively, and varied across visits and age groups. Asymmetrical udder prevalence was 39% (95% CI = 35.5-42%) overall and increased with age (27% for 1-year-olds, 38% for two-year-olds, 43% for mixed age ewes). Supernumerary teats were observed in 15% (95% CI = 13-17.9%) of ewes. There was between-farm variation in all udder morphology variables. Ewe-level prevalences of teat end hyperkeratosis (any degree of severity), gland/teat inflammation, lesions, palpable defects, and involuted glands were all < 6%. CONCLUSIONS: Morphological observations resembled those from overseas dairy sheep. Teat dimensions, udder depth, separation, suspension, teat placement, and presence of supernumerary teats varied between farms. Udder depth, separation, and suspension scores decreased with age, while teat placement score and the prevalence of asymmetry increased with age. Teat and udder pathology were rare. CLINICAL RELEVANCE: This is the first systematic study of teat and udder morphology and pathology in New Zealand dairy ewes. The data will be useful for farmers and industry partners, providing a comparison with their own flocks, identifying areas for improvement, and informing and contrasting with future studies.Item An observational study of farmer-reported clinical mastitis in New Zealand dairy ewes.(Taylor and Francis Group, 2024-07-01) Chambers G; Laven R; Grinberg A; Ridler A; Velathanthiri NAIMS: To describe the incidence, aetiology, treatment, and outcomes of farmer-reported clinical mastitis on New Zealand dairy sheep farms. METHODS: A prospective cohort study was conducted on 20 spring-lambing New Zealand sheep milking farms over the 2022-2023 season. Clinical mastitis was defined as a change in the appearance of milk and/or signs of inflammation in the gland. Farmers were required to report all cases of clinical mastitis and collect information on affected ewes' demographics, clinical features, treatments (where applicable), and outcomes. Milk samples from mastitic glands were submitted for microbiological culture and identification by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF). RESULTS: Partial or complete clinical mastitis data were available for 236 cases from 221 ewes on 18/20 study farms. Clinical mastitis was diagnosed in 0-6% of ewes at the farm level, with an overall incidence of 1.8 (95% CI = 1.0-3.2)% using the study data, or 2.3 (95% CI = 1.6-3.3)% using the study data and farmer estimates that included unreported cases. Cases occurred mostly in early lactation, with 59% detected during the lambing period (August-October), at a median of 7 (IQR 3, 40) days in milk. The majority of cases featured clots in the milk (59%), swelling (55%), and unevenness (71%) of the glands. Pyrexia (rectal temperature ≥ 40.0°C) was diagnosed in 25% of cases and depression (lethargy, inappetence, or inability to stand) in 26% of cases. Treatment was given to 46% of cases, with tylosin being the most commonly used treatment (50% of treated cases). The most common outcome was immediate drying off to be culled without treatment (32%), followed by still milking and recovered but with lasting problems (25%). Nearly half of all the milk samples submitted were culture negative. Streptococcus uberis (14%), non-aureus staphylococci (12%), and Staphylococcus aureus (11%) were the most common isolates, found on 12, 8 and 8 of the 16 farms with microbiological data, respectively. CONCLUSIONS: Clinical mastitis affected up to 6% of ewes at the farm level. Systemic signs were observed in one quarter of affected ewes, suggesting a role for supportive treatment. Clinical mastitis can be severe and challenging to fully resolve in New Zealand dairy sheep. CLINICAL RELEVANCE: This is the first systematic study of clinical mastitis in New Zealand dairy ewes. It provides baseline information specific to New Zealand conditions for farmers, veterinarians, and other advisors to guide the management of mastitis for the relatively new dairy sheep industry in New Zealand.