Browsing by Author "Weston JF"

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An Assessment of the Epidemiology and Herd-Level Impact of the Fractured Humerus Epidemic in New Zealand Dairy Cattle, 2007-2015: Results from Four Studies
(MDPI (Basel, Switzerland), 2024-02-05) Hunnam JC; Lawrence K; Rashid ZBA; Hitchcock B; McDougall S; Wehrle-Martinez A; Weston JF; Miranda Castañón MI
A multi-method approach integrating data from four independent sources was used to describe some key features of the epidemiology and estimate the herd and within-herd incidence of fractured humeri in New Zealand dairy cattle for the period 2007-2015. The first dataset was from a national case series where cases of humeral fractures in dairy cattle were identified by veterinarians across New Zealand between the 2007/2008 and 2011/2012 lactation seasons. The second dataset was from a pet food company based in the Waikato region, which collated the number of casualty first- and second-lactation cows found to have a fractured humerus post-slaughter in the 2014/2015 lactation season, and the third dataset was a case series conducted by veterinarians employed in a Waikato veterinary business, also from the 2014/2015 lactation season. For the final dataset, 505 randomly selected New Zealand dairy farmers completed a phone survey on the incidence of non-responsive, non-weight-bearing forelimb lameness in first- and second-lactation cows in the 2014/2015 lactation season. Using the telephone survey results, the within-herd and herd-level incidence of cases for first- and second-lactation dairy animals was calculated. The national case series reported 149 cases of humeral fractures in 22 dairy herds; the pet food case series identified 61 cases from 41 farms; and the practice-based case series found 14 cases from 10 farms. Humeral fractures exclusively affected first- and second-lactation dairy cows and had a peak incidence between calving and early mating. The national telephone survey found that non-weight-bearing forelimb lameness requiring euthanasia of first- or second-lactation cows occurred in 11.7% of herds, with a mean within-herd incidence of 2.6% for first lactation cows and 2.8% for second-lactation cows for affected herds. These combined datasets demonstrate that humeral fractures in young, lactating dairy cattle are more common than previously suspected and that they occur nationally and over multiple years on some farms. Further work on this condition is urgently required in New Zealand to establish cost-effective management practices that will reduce unnecessary animal suffering and waste.
The association between fluoride concentrations and spontaneous humeral fracture in first-lactation dairy cows: results from two New Zealand studies
(Taylor and Francis Group, 2024-11-17) Wehrle-Martinez A; Dittmer KE; Back PJ; Rogers CW; Weston JF; Jeyakumar P; Pereira RV; Poppenga R; Taylor HS; Lawrence KE
AIM: To assess whether the fluoride concentration in the humeri of first-lactation, 2-year-old dairy cows with a spontaneous humeral fracture is significantly different from that of first-lactation, 2-year-old dairy cows without a humeral fracture. METHODS: Two studies were conducted, the first with nine bone samples from 2-year-old, first-calving dairy cows with a humeral fracture (all from the Waikato region) age-matched with seven control bone samples from the Waikato, Bay of Plenty and Manawatū-Whanganui regions. The second study used 26 bone samples from 2-year-old, first-lactation dairy cows with a humeral fracture (from the Otago, Canterbury, Southland, West Coast, Waikato and Manawatū-Whanganui regions) age-matched with 14 control bone samples (all from the Manawatū-Whanganui region or unknown). Control bone samples were from first-lactation, 2-year-old dairy cows that did not have humeral fractures. Bone fluoride concentration was quantified for all samples. RESULTS: The median fluoride concentration of humeri from first-lactation, 2-year-old dairy cows with a humeral fracture was significantly higher than humeri from unaffected control cows in both studies. In Study 1, the median bone fluoride concentration was 599 (IQR 562.7-763.5) mg/kg from case cows and 296.6 (IQR: 191.2-391.7) mg/kg from control cows (p < 0.001), and in Study 2 the median bone fluoride concentration from case and control cows was 415 (IQR: 312.5-515) mg/kg and 290 (IQR: 262.5-410) mg/kg (p = 0.04) respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Although there are limitations to this study due to the unbalanced regional distribution of cases and controls, the results indicate that sub-clinical fluoride toxicosis may be linked to spontaneous humeral fractures in first-lactation dairy cows in New Zealand. Further research is required to determine if bone fluoride concentrations play a role in the pathogenesis of these fractures.
Use of adjusted cut-off values for Neospora caninum antibody ELISA in calves after colostrum intake: on-farm evaluation as part of a neosporosis eradication programme
(Taylor and Francis Group on behalf of the New Zealand Veterinary Association, 2025-06-04) van Velsen CM; Laven LJ; Laven RA; Weston JF
Aims: To assess the effectiveness of testing young calves using an ELISA for antibodies to Neospora caninum with adjusted cut-off values to account for the presence of maternal antibodies, as an aid in decision-making during calf-rearing, with the purpose of eradicating neosporosis from endemically infected dairy herds. Methods: Replacement heifer calves on two dairy farms with endemic neosporosis were blood sampled at approximately 1–4 weeks of age. Sera were tested with an ELISA for antibodies to N. caninum, with the thresholds increased (based on unpublished data) to account for colostrum intake. The sample/positive (S/P) cut-off value for seronegative animals was increased from the manufacturer’s recommendation of S/P < 30 to < 70; the S/P value for seropositive was increased from ≥ 40 to ≥ 100; and S/P values 70–100 were considered inconclusive. Calves with inconclusive results were retested using standard thresholds at approximately 4 months of age (after colostral antibodies had waned). Seropositive calves were removed from the replacement herd. This protocol was first implemented in 2016. From 2018 onwards, parentage testing was carried out, and the calves’ results were extrapolated to their dams. Dams of seropositive calves were bred predominantly to beef semen. The proportion of seronegative calves in each cohort from 2016 to 2023 was calculated, and the reproductive performance of seronegative replacement calves (% producing a calf at approximately 24 months of age) was analysed. Results: The proportion of seropositive replacement calves peaked in 2017 (19.5%) and by 2023 had reduced to 1.2%. The odds of a heifer being seronegative in 2023 compared to 2016 were 14.0 (95% CI = 4.12–87.56) times higher. Compared to 2014/2015 when replacement heifers’ serostatus was unknown, after 2016 (the first year when replacement heifer serostatus was established) at least 12.9% more heifers produced a calf at approximately 24 months of age; compared to 2014 the odds were at least 2.88 (95% CI = 1.75–4.88) times higher. Conclusions and clinical relevance: Combining early testing of replacement heifers with the identification and breeding management of dams of seropositive replacement heifers reduced the proportion of seropositive heifer calves in subsequent years and improved the reproductive performance of heifer cohorts. Further research is required to establish optimal ELISA cut-off values, but this strategy is likely to be a useful tool to reduce the N. caninum seroprevalence in endemically infected dairy herds.