When continuous observations just won’t do: Developing accurate and efficient sampling strategies for the laying hen

Continuous observation is the most accurate way to determine animals' actual time budget and can provide a 'gold standard' representation of resource use, behavior frequency, and duration. Continuous observation is useful for capturing behaviors that are of short duration or occur infrequently. However, collecting continuous data is labor intensive and time consuming, making multiple individual or long-term data collection difficult. Six non-cage laying hens were video recorded for 15 h and behavioral data collected every 2 s were compared with data collected using scan sampling intervals of 5, 10, 15, 30, and 60 min and subsamples of 2 second observations performed for 10 min every 30 min, 15 min every 1 h, 30 min every 1.5 h, and 15 min every 2 h. Three statistical approaches were used to provide a comprehensive analysis to examine the quality of the data obtained via different sampling methods. General linear mixed models identified how the time budget from the sampling techniques differed from continuous observation. Correlation analysis identified how strongly results from the sampling techniques were associated with those from continuous observation. Regression analysis identified how well the results from the sampling techniques were associated with those from continuous observation, changes in magnitude, and whether a sampling technique had bias. Static behaviors were well represented with scan and time sampling techniques, while dynamic behaviors were best represented with time sampling techniques. Methods for identifying an appropriate sampling strategy based upon the type of behavior of interest are outlined and results for non-caged laying hens are presented.