Nutritional value of fresh and composted poultry manure for house fly (Diptera : Muscidae) larvae

A sand dilution assay was developed to study how composting affects the nut ritional value of stored laying hen manure for larvae of the house fly, Mus ca domestica L. Equal numbers of eggs were inoculated into graded amounts o f stock manure and incubated under standardized moisture conditions. Surviv al and mass per emerging adult diminished with progressively lower supplies of manure per larva, whether the manure was diluted into clean, white sand or placed on top of an equal volume of sand. Mass of adults per original e gg was an increasing linear function of log(2) manure supply, with extrapol ated lower supply threshold, S-L = 0.06 g per egg. It is proposed that S-L is a measure of a substrate's nutritional value-the greater the threshold, the lower its value. Dilution of the same stock manure in loam or sandy loa m reduced the manure's apparent nutritional value, and dehydration of the s tock manure to 20% water before rehydration to 70% also reduced nutritional value. Assays of bulk samples from replicated piles of laying hen manure m ixed with sunflower hulls indicated the mixture was nutritionally equivalen t to the stock manure, but that 3-4 wk of subsequent aerobic, thermophilic composting reduced it to approximate to 10% of its initial value. These res ults suggest that composting may be a useful technique for reducing the fly breeding potential of laying hen manure and other substrates that must be stored before spreading and incorporation on crop land.