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Simple Summary: Biting hematophagous dipterans are responsible for painful bites and blood spoliation; they induce behavioral modifications, anemia, and significant production losses in cattle. A feedlot of 100 feeder cattle would register a total loss of USD 16,000 within 5 months, which appears to be an unexpectedly huge loss caused by dipterans. Investing part of this money in fly control would probably be beneficial. In addition to blood pathogen transmission, insects of the order Diptera affect livestock through visual and contact harassment; blood-feeders are responsible for painful bites and blood despoliation, generating behavioral modifications, anemia, and production losses. Knowledge of their economic impact is a basis for cost-effective control. Here, we measured the global impact of diptera insects by comparing two batches of six feeder cattle, one in the open air and the other protected by a mosquito net. The analytical data were insect density in the open air and, for feeder cattle, tail flick counts, hematocrit values (Ht), feed intake, feed conversion ratio (FCR), and live body weight gain (LBWG). Over a period of five months, the results showed significant losses in the LBWG of cattle exposed to insects, estimated at 8.0 ± 1.5 kg/month [2.7; 13.3], with a total loss reaching 40.0 ± 5.5 kg/head. Main diurnal insects were Stomoxys spp. and Musca crassirostris. There was a strong correlation between fly density and diurnal tail flicks. Night trapping and tail flicks showed a potentially important role of mosquitoes to be further explored. The Ht levels of exposed animals were 3–4% lower than those of controls. FCRs indicated that exposed animals needed 33% more dry matter intake/kg of LBWG. An economic assessment showed that dipterans were responsible for a 10–11% loss in LBWG during the main growing period of feeder cattle (10–15 months). A feedlot of 100 calves would register a total loss of USD 16,000 within 5 months, which appears to be an unexpectedly huge loss caused by dipterans. Investing part of this money into fly control would probably be beneficial. [ABSTRACT FROM AUTHOR]

Simple Summary: Hematophagous flies are a pest for livestock due to their bites, annoyance and the diseases they transmit. Cattle exposed to biting flies exhibit defence movements such as tail flicks. The evaluation of biting fly density and annoyance by counting tail flicks of cattle has been validated in the past, but it is highly time consuming. In this study, we evaluated the use of sport pedometers attached to the tails of feeder cattle, in order to evaluate tails flick frequency in two groups of six feeder cattle: Group A was protected by a mosquito net, and Group B was in open-air. Tail flicks were also recorded visually. In addition, insect density was evaluated using three fly traps in the surrounding of Group B. A strong correlation was observed between fly density and visual records of tail flicks; a stronger correlation was found between fly density and tail pedometer records. The reports of tail flicks at night were even able to draw attention to a huge infestation by mosquitoes. Finally, in these experimental conditions, tail pedometers proved to be useful tools in evaluating density and the impact of dipterans on cattle behaviour. They will be useful tools to evaluate new biting fly control methods. Hematophagous flies are a pest for livestock; their direct impact reduces productivity, and they are vectors of parasites, bacteria and viruses. Their control using insecticides is inefficient and highly polluting. The validation of new control tools requires efficacy and cost-effectiveness evaluation. The quantification of hematophagous insects' impact in livestock is a challenging prerequisite. Tail flicks counts can reliably evaluate fly-burden; however, visual records are tedious and time-consuming. In the present study, automation of tail flick counts was made through the use of pedometers attached to the tail, in two groups of feeder cattle. Group A was kept in a pen under the protection of a mosquito net, and Group B was kept in an open-air pen. The fly density of Group B was evaluated using fly traps. The apparent density per trap ranged from 130 to 1700 in the study. The mean pedometer records per 24 h ranged from 957+/−58 bits in Group A to 11,138+/−705 bits in Group B. The night/day records observed in Group A (200/800 bits) were drastically increased in Group B (1000–4000/4000–14,000 bits) and variable along seasons. A very high correlation was observed between fly density and visual records or pedometer records (PR). Two-hour PRs proved to be a reliable predictive tool for fly density. Moreover, the pedometers revealed an unsuspected but significant nuisance of mosquitoes, which should be thoroughly investigated. [ABSTRACT FROM AUTHOR]