Exploitation of bedding in dairy outdoor calf hutches by immature house and stable flies (Diptera: Muscidae).

Abstract

Examination of bedding in outdoor calf hutches (614 samples from 16 hutches on six dairy farms, 4 each during the summers of 1983 and 1984) revealed a consistent but variable abundance of house fly, Musca domestica L., and stable fly, Stomoxys calcitrans (L.), maggots. House fly density averaged 72.9 and 50.8 maggots per 1-liter sample during respective summers and was generally greater than stable fly density, which averaged 12.5 and 42.7 maggots per liter. Both house and stable fly density differed significantly between farms and, in a variable pattern, between external and internal areas of hutches. Numbers of both house and stable flies also differed significantly among sites within hutches, with house flies being generally most abundant in bedding under feed containers and in center-internal sites. Stable flies were most abundant in bedding near water containers and in center-external and center-internal sites. House and stable fly densities increased rapidly during weeks 1–3 after the introduction of a newborn calf, and thereafter remained variably constant, with maximum values occurring during weeks 4–7. Lowest overall house and stable fly densities ($\bar x$ = 12.3, 11.6, 0.1, and 0.1 for 1983 and 1984) occurred in hutches set on a slope and bedded lightly with coarse sawdust. Highest overall house and stable fly densities ($\bar x$ = 143.7, 125.8, 21.3, and 94.6) occurred in hutches bedded with straw and set on level ground. The estimated 25,000–40,000 house and stable fly maggots that develop in an outdoor calf hutch during a summer represent an outcome of dairy management that warrants corrective action.