In cattle units, flies are attracted to cows' eyes, teats and open wounds. In addition to the diseases they transmit, extreme discomfort caused by constant fly attack can result in reduced weight gain and lower milk yield in cattle.
Milk quality also suffers from the presence of excessive numbers of flies and production can be downgraded in the absence of adequate fly control (Lancaster, 1986).
Fly treatment has been shown to result in a significant increase in milk yield (Morgan, 1980) and in meat production (Stork, 1979).
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