Fish can utilize non-protein nitrogen in manure added to pond water in appropriate amounts. In the first year, manuring had a slight negative effect on yields. During the second season, ponds fertilized with chicken manure showed a 44 per cent increase in yields of fish over a control pond, and liquid cow manure improved yields by 13 per cent. The chemical composition, and hence the nutritional value, of animal manures depends, of course, on the diet fed to the animals. Excreta of less well-fed animals may be expected to be of lower value.
Health hazards are particularly important.
The intoxication was unequivocally traced to processed poultry waste present in the feed. It is feared that the incident may have destroyed the prospects of using poultry waste as a cattle feed ingredient in Israel for quite some time. The process is aimed primarily at sewage purification and water reclamation, but the resulting algal biomass is of considerable interest as feed. This material, after harvesting, concentration, and drum drying, contains 45 to 55 per cent protein, It can replace half of the soybean meal in commercial broiler rations with no deleterious effect on growth. In vivo experiments with chicks showed that about 80 per cent of algal protein is absorbable.