Abstract #W2

# W2
Are fly avoidance behaviors of dairy cows housed on pasture influenced by the use of mesh fly leggings?
R. Perttu*1, B. Heins1, H. Phillips1, M. Endres1, 1Department of Animal Science, University of Minnesota, St. Paul, MN.

The objective of this study was to evaluate the effects of mesh fly leggings (Shoofly Leggins; Stone Manufacturing & Supply, Kansas City, MO) on number of flies and fly avoidance behaviors of pastured dairy cows. The study was conducted at the University of Minnesota West Central Research and Outreach Center (Morris, MN, USA) from June to July 2017. In this replicated crossover design study, dairy cows housed on pasture (n = 80) were randomly assigned to 1 of 2 treatment groups: leggings (on all legs) and control (no leggings). Cows were exposed to their treatment for a 2-week period, then switched treatments every period for a total of 4 periods (2 replicates per treatment). Counts for face, horn, and stable flies were recorded on all cows twice daily (0930 to 1230 and 1330 to 1630), 3 times per week. A random subset of 40 focal cows was observed in 5-min intervals for frequency of foot stomps, head tosses, skin twitches, and tail swishes. Period means were used for the analysis using PROC GLIMMIX of SAS. Poisson models were built for fly count data with fixed effects of treatment, time of day, treatment and time of day interaction, period within replicate, replicate, and order of treatment, and a random effect of cow. Head toss, skin twitch, and tail swish behaviors were similar between treatment groups and time of day. Leg stomps were greater (P < 0.001) for the control group than the leggings group (mean ± SE; 2.8 and 2.1 ± 0.3 per observation, respectively), and leg stomps were greater (P < 0.001) in the afternoon than in the morning (2.8 and 2.1 ± 0.3 per observation, respectively). The number of stable flies was a predictor (P < 0.0001) of all observed behaviors and the number of horn flies was a predictor (P < 0.05) of head toss, skin twitch, and tail swish behaviors. The number of stable flies on cows was greater (P < 0.001) in the afternoon compared with the morning (20.6 ± 0.8 and 15.0 ± 0.6 per cow, respectively). The results of this study indicate that flies cause fly avoidance behaviors in cows regardless of the use of leggings. However, leggings effectively reduce leg stomps and may offer some relief to dairy cows on pasture.

Key Words: fly avoidance, behavior