Abstract
The objective of this experiment was to examine the effects of fly control strategies on fly abundance, fly avoidance behaviors, and animal performance in a feedlot setting. Angus bulls (n = 64; BW = 281 ± 36.2 kg) and steers (n = 36; BW = 475 ± 40.4 kg) were blocked by sex and BW and assigned to 1 of 4 experimental treatments in a randomized complete block design (7 pens/treatment; 4 bulls/pen; 3 steers/pen). Treatments included: control (CON; no fly control), abamectin, piperonyl butoxide, and zetacypermethrin insecticide tags (FT; Tri-Zap®, Y-Tex Corporation, Cody, WY), permethrin and piperonyl butoxide pour on (PO; Permectrin® CDS, Bayer Animal Health, Shawnee Mission, KS), or a garlic-powder top dress (GR) administered at 0.28 g •-1 animal •-1d. The experiment was conducted between June and September. Horn and stable fly abundance (FA) and fly avoidance behaviors (FAB; i.e. tail-flicks, stomping, head-tossing) were recorded by trained personnel. Both FA and FAB were recorded once/wk on days with similar temperatures, humidity, wind speed, and without precipitation based on Oklahoma Mesonet data (Stillwater site). There was a tendency for a treatment × time interaction for horn FA with differences in treatments occurring at wk 1, 2, 8, and 14. There was no treatment × time interaction for stable FA or FAB, however both were affected by time (P < 0.001). There were no differences in final BW (P = 0.34), overall ADG (P = 0.30), overall DMI (P = 0.53), or overall G:F (P = 0.39). There was a tendency (P ≤ 0.10) for GR to have decreased BW on d 28 and decreased ADG from d 0 to 28 compared to FT and PO. There was also a tendency (P = 0.09) for decreased DMI from d 0 to 56 for GR compared to CON and FT. Overall FA was less than expected (mean = 1 to 17 flies/animal) throughout the experiment and overall animal performance was unaffected by fly control strategy.
OFF-responses of interneurons optimize avoidance behaviors depending on stimulus strength via electrical synapses
