Browsing by Author "Wells M"

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    Effect of a pre-calving injectable trace mineral supplement on white blood cell function in seasonally calving pastoral dairy cows.
    (Taylor and Francis Group, 2024-10-30) Bates AJ; Wells M; Fitzpatrick C; Laven RA
    Aims To investigate the effect of injection of trace mineral supplement (TMS) 14–28 days before calving on white blood cell count (WBCC) and function, serum antioxidant capacity (SAC) and reactive oxygen species (ROS) in pasture-fed cattle after calving. Methods On each of two South Island, seasonally calving, pastoral dairy farms,1 month before dry-off, a random sample of 150 multiparous cows predicted to calve within 7 days of the herd’s planned start of calving (PSC) were stratified on individual somatic cell count, age, breed and expected calving date. On each farm, 14–24 days before PSC, 60 selected cows were randomly assigned for TMS (Zn, Mn, Se, Cu) injection, and 60 were controls. All 240 cows were contemporaneously injected with hydroxocobalamin, and controls with Se. Blood samples were collected pre-injection and 3, 12 and 40 days after calving. Phagocytic activity, count and proportion of neutrophils, lymphocytes and monocytes, WBCC, ROS, SAC were measured. Plasma concentrations of Se, Cu and glutathione peroxidase (GPx) were monitored from a random subset of animals. Differences attributable to TMS were estimated using mixed-multivariable Bayesian analysis, expressed as mean and highest density interval (HDI). Results Three and 40 days after calving, TMS-treated cows had 0.36 (90% HDI = 0.00–0.77) x 109 and 0.25 (90% HDI = 0.00–0.55) x 109 fewer neutrophils/L. Neutrophils comprised 6 (90% HDI = 0–11)% and 4 (90% HDI = 0–8)% less of the WBCC, and the neutrophil count was 14 (90% HDI = 0–27)% and 9 (90% HDI = 0–18)% less than controls. However, 3 days after calving, there were 7 (95% HDI = 2–12)% more cells phagocytosing and 2,900 (95% HDI = 2,600–3,200) more bacteria ingested/cell. Twelve and 40 days after calving, TMS-treated cows had 0.65 (95% HDI = 0.17–1.17) x 109 and 0.28 (95% HDI = 0.00–0.59) x 109 more lymphocytes/L. Lymphocytes comprised 10 (95% HDI = 3–18)% and 5 (95% HDI = 0–9)% more of the WBCC, and the lymphocyte count was 30 (95% HDI = 11–51)% and 9 (95% HDI = 0–9)% more than controls. There were no meaningful differences in ROS, SAC, ROS/SAC, other white blood cells, or WBCC. Plasma Cu, Se and GPx concentrations were above recommended thresholds. Conclusions Pre-calving TMS injection was associated with differences in white blood cell population and function that may reduce the risk of disease. Abbreviations BHOB: Beta-hydroxybutyrate; GPx: Glutathione peroxidase; HDI: Highest density interval; MESF: Molecules of equivalent soluble fluorophore; OSi: Oxidative stress index; PSC: Planned start of calving; ROPE: Region of probable equivalence; ROS: Reactive oxygen species; SAC: Serum antioxidant capacity; THI: Temperature humidity index; TMS: Trace mineral supplement; WAIC: Widely applicable information criterion; WBCC: White blood cell count.
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    Reduction in morbidity and mortality of dairy calves from an injectable trace mineral supplement
    (BMJ Group on behalf of the British Veterinary Association, 2019-06-01) Bates A; Wells M; Laven RA; Simpson M
    The effect of a multimineral preparation on the health and growth of spring born, dairy calves was investigated on four New Zealand pastoral farms. Calves were randomly allocated injections within 24 hours of birth, 35 days and 70 days after birth. Injections contained 40 mg zinc, 10 mg manganese, 5 mg selenium, 15 mg copper and 5 mg chromium per ml (Multimin+Se+ Cu+Cr Cattle, Virbac South Africa) at 1 ml/50 kg body weight. Morbidity, mortality from natural challenge and growth rates were recorded for 140 days. There were no differences in morbidity and mortality within 48 hours of birth for treated calves compared with controls, P=0.192. Morbidity and mortality were highest at 3-35 days (7.5 per cent [95 per cent CI 5.00 to 9.99] treated calves sick and 15.6 per cent [95 per cent CI 12.48 to 18.73] controls sick, P<0.001). For this period, mortality was lower at 4.4 per cent (95 per cent CI 2.49 to 6.41) treated calves and 10.4 per cent (95 per cent CI 7.78 to 13.03) controls, P<0.001. Allowing for potential confounders, the adjusted OR of treated calves scouring between 3 and 35 days was 0.44 (95 per cent CI 0.24 to 0.82, P=0.009). Allowing for potential confounders, from 0 to 140 days a second model predicted treatment approximately halved the probability of morbidity and mortality (P<0.001). There was no difference in the daily rate of gain (0.67 kg/day [95 per cent CI 0.66 to 0.67] for treated calves).