The prevalence of lameness on New Zealand dairy farms : a comparison of farmer perception and mobility scoring : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies, Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
Several studies have compared the prevalence of lameness as perceived by farmers with the prevalence of lameness assessed using locomotion or mobility scoring. However all of these studies have been undertaken in housed cows; cows at pasture have not been studied. This study was designed to identify the difference between farmer perception of lameness and that identified by mobility scoring under New Zealand conditions in cows kept at pasture. Data were collected from 60 herds, 27 in the South Island and 33 in the North Island. All farms were visited on one occasion at the expected peak time for lameness, i.e. October/November for North Island farms and January / February for South Island farms. Data were collected via a questionnaire which included details on farm size, productivity and reproduction as well as general health. The latter included a farmer estimate of the number of lame cows which were currently on-farm. Whole herd mobility scoring, using the DairyCo 0 – 3 scale, was then used to estimate herd lameness prevalence. In the North Island, average herd size was 294 and average production was 357 kgMS/cow/year, while in the South Island the figures were 580 and 406 kgMS/cow/year, respectively. Of the 60 farms, lame cows were treated by farm staff only on 38 farms, by a combination of veterinarian and farm staff on 21 farms, and on one farm by veterinarians only. On average, farmers estimated that 2.2% of their herd was lame (range 0 to 20%), while mobility scoring identified that, on average, 8.1% of the herd was lame (mobility score =2) (range 1.2 to 36%). This means that on a herd basis, only 27.3 % (range 0 to 95%) of the cows with reduced mobility had been identified as lame by farm staff. There was no significant effect on herd size on this percentage (P=0.8), nor was there a significant differences between the two islands (South Island 28% ± SEM 4.2; North Island 23% ± 2.6). The prevalence of lameness in this study was much lower than that reported in housed cattle, but the percentage of cows with reduced mobility recognised as lame was very similar, even though in pasture-based cattle, farmers spend more time watching cows walk (to and from milking). This study shows that there is significant room for improvement in the detection of lameness on New Zealand farms, and suggests that routine mobility scoring, particularly at critical periods, could be a valuable tool for identifying lame cows.