Abstract: A study was conducted on the effect of an increasing natural infestation of stable flies (Stomoxys calcitrans) and its relation with the behaviour of dairy cows under semi-arid conditions. Twenty-one milking Holstein cows raised in pens in a semi-intensive system were used. The number of stable flies was determined every other day over 62 days by counting the number of flies present on the front legs of the cows every 30 min from 11: 00-14: 00 h. The number of cows lying and standing was also recorded at this time. The following behaviours of the cows were counted during nine 5 min episodes every 15 min during the same observation periods: head movements, ear flicks, skin twitches, stamp/kicks and tail movements. The maximum number of flies observed per cow per day was 55. The number of cows standing or showing fly dislodging behaviours was at maximum frequency when there were between 25 and 30 flies per cow, respectively. Up to this number of flies there was a linear relation between the number of flies and the number of cows lying and the number of tail movements. When the fly count rose from 0-15, standing cows increased from 0-62%, respectively. Tail movement was the most frequent behaviour observed in response to fly increment, with a maximum of 150 tail movements per hour of observation, followed in frequency by ear flicks, skin twitches, head shaking and stamp/kicks, with a correlation of rs = 0.91 (p< 0.05) among these five dislodging behaviours. It is concluded that: S. calcitrans induces restless in dairy cows and even though tail twitching may become maximized at certain fly population, it is the most frequent behaviour observed in response to fly population increment.
M.I. Vitela , C. Cruz-Vazquez , J.J. Solano and A. Orihuela , 2007. A Note on the Associations Between the Prevalence of Stable Flies (Stomoxys calcitrans) and the Behaviour of Dairy Cows under Semi-Arid Conditions . Journal of Animal and Veterinary Advances, 6: 1284-1290.