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Author: search.filters.author.Dowling ASubject: search.filters.subject.Dairy herds

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    The milk production impacts of liver fluke (Fasciola hepatica) infection in dairy cows on the West Coast of the South Island, New Zealand
    (Elsevier B V, 2025-05) Dowling A; Lawrence KE; Howe L; Scott I; Pomroy W
    The impact of fasciolosis has been estimated on many occasions and can vary from mild to severe effects on animal productivity. The aim of the current study was to utilise observations on seroconversion of dairy cattle to Fasciola hepatica over the course of a lactation and compare their milk production with other cattle who remained serologically negative throughout the same lactation. Four spring-calving dairy herds on the West Coast of the South Island of New Zealand were selected based on prior knowledge of endemic liver fluke infection. Over the four herds, a total of 485 cows were blood sampled twice during one lactation, in early November (spring) and early March (autumn). The F. hepatica antibody titre of F. hepatica antibody was quantified using a commercial ELISA test (IDEXX Fasciolosis Verification, IDEXX Europe BV, Hoofdorp, The Netherlands). Milk production was estimated by a series of 3–4 herd tests over the lactation where each cow is individually measured during the morning and evening milking on the same day with samples analysed for milk yield, milk fat (MF), protein (MP), lactose (ML) and total milk solids (MS). Energy corrected milk (ECM) was then calculated using the formula: ECM (kg/d) = 12.55 × MF (kg/d) + 7.39 × MP (kg/d) + 0.2595 × milk yield (kg/d). At the spring sampling, 52 % of cows had antibodies detected which increased to 63 % in autumn. For the sampled cows, those that were in the negative IDEXX test category in autumn and spring were categorised as ‘uninfected’ while those which were negative in spring and seroconverted to the strong positive category in autumn were categorised as ‘infected’. Those in the intermediate categories were ignored. A total of 235 cows were categorised as ‘uninfected’ at the spring testing, being in the negative IDEXX diagnostic category. Of those 235, at the autumn testing, 152 remained in the negative diagnostic category and 50 were in the strong positive IDEXX diagnostic category and were categorised as ‘infected’. A model was fitted which described the lactation curve of each milk component (MF, ML, MP, ECM), a variable describing the infection status of the cow was then tested in the model. The only significant change detected was mean Milk Fat (MF) % being 0.24 MF% points (95 % CI 0.04–0.44 %) lower for ‘infected’ compared to ‘uninfected’ cows. Using a value of6.044/kg MF New Zealand dollars (NZD) this represents an economic loss of NZD 60.2 per ‘infected’ cow in a West Coast herd. Although small, such an effect will still have an appreciable impact on the economic return to a dairy farmer.
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    The seroprevalence and spatial distribution of liver fluke infection in a sample of West Coast and Canterbury dairy herds
    (Elsevier B.V., 2025-01-17) Dowling A; Lawrence KE; Howe L; Scott I; Pomroy W
    The West Coast region of the South Island of New Zealand is recognised as having a high prevalence of liver fluke infection, however, few studies have tested this assumption. This study aimed to estimate the seroprevalence and spatial distribution of liver fluke infection in most West Coast and some Canterbury dairy herds using bulk milk ELISA. Herds were bulk milk sampled on three occasions, twice, a week apart in March 2017 (n = 430 and n = 99) and once in October 2017 (n = 412). The concentration of liver fluke antibodies was estimated using the IDEXX Fasciolosis Verification ELISA (IDEXX Europe BV, Hoofdorp, The Netherlands) on these bulk milk samples. Herds were categorised according to the test instructions, with “medium” (≥20 % cows infected) or “strong” (≥50 % cows infected) results designated as production limiting. All herds were also sent a short questionnaire about awareness of liver fluke and treatment in their herds. The agreement between the IDEXX results for 99 herds sampled twice in March 2017, and between the IDEXX results for March and October for all herds was assessed with a Kappa test. There was a substantial agreement between the two March tests, kappa = 0.7 (95 % CI 0.58–0.82) and moderate agreement between the March and October samples kappa = 0.41 (95 % CI 0.34–0.48). The results of the questionnaire were linked to the IDEXX results, and the distribution of herds categorised by their IDEXX result plotted. At the March and October samplings 0/35 (0 %) and 0/27 (0 %) Canterbury herds, 248/395 (63 %) and 193/385 (50 %) of West Coast herds had a production limiting seroprevalence of liver fluke infection. Mapping showed that West Coast herds with a production limiting infection were clustered in coastal areas, whereas those without, were clustered in inland valleys. The odds of a coastal West Coast dairy herd having a production limiting seroprevalence of liver fluke were 10.7 (95 % CI, 6.6–17.3) times that of an inland herd in March and 8.6 (95 % CI, 5.4–13.8) times in October. There was no effect on IDEXX ELISA SP% (p = 0.92) of herds which were treated for liver fluke at dry off soon after the March test compared to their SP% in the following October test, soon after calving. The results show that liver fluke infection is a potentially serious problem for West Coast dairy herds especially for those on coastal river plains prone to flooding.