We recently published a paper in the Journal of Dairy Science on sample sizes and cow-selection strategies for on-farm dairy welfare assessments. (This was the topic I presented at ADSA last summer, covered in a previous blog post). You can download the full text of the paper for free through March 7, 2018 by clicking here.
Van Os, Jennifer M. C., Christoph Winckler, Julia Trieb, Soraia V. Matarazzo, Terry W. Lehenbauer, John D. Champagne, and Cassandra B. Tucker. 2018. Reliability of sampling strategies for measuring dairy cattle welfare on commercial farms. Journal of Dairy Science 101:1495-1504. doi:10.3168/jds.2017-13611.