Sampling strategies for assessing lameness, injuries, and body condition score on dairy farms

• Published in: Journal of dairy science 2019-09, Vol.102 (9), p.8290-8304
• Main Authors: Van Os, Jennifer M.C., Weary, Daniel M., Costa, Joao H.C., Hötzel, Maria J., von Keyserlingk, Marina A.G.
• Format: Article
• Language: English
• Subjects: animal welfare; animal-based measure; certification program; skin lesion
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2018-15134

Our objective was to evaluate how sampling strategies (i.e., how many cows to sample and which animals to include) used in 4 dairy cattle welfare assessment programs affect the classification of dairy farms relative to thresholds of acceptability for animal-based measures. We predicted that classification performance would improve when more cows were sampled and when selecting from all lactating cows versus when some pens were excluded. On 38 freestall farms, we assessed all 12,375 cows for lameness, injuries on the tarsal (hock) and carpal joints, and body condition score and calculated the farm-level prevalence for each measure. Based on approaches used in the industry, we evaluated 6 sampling strategies generated using formulas with precision (d) of 15, 10, or 5% applied to either a single high-producing pen or all lactating cows; an additional sample was included with d = 10% applied to the entire herd, selecting lactating cows in proportion to their representation in the herd. For each sampling strategy, cow records were selected randomly (in 10,000 replicates) to calculate prevalence. The strategy of assessing all cows in the high-producing pen was also compared. Farms were classified as meeting (below) or failing to meet (above) thresholds of ≤15% moderate lameness; ≤20% moderate carpal or hock injuries;