Passive aeration co-composting using four mixtures of chicken manure and swine manure at 1:0, 1:1, 3:7 and 0:1 with sawdust and rice husk was carried out to study the effects of co-composting on the physicochemical properties of the organic materials. The experiment, which lasted 66 days, was carried out in bins equipped with inverted T aeration pipes. The results showed that nutrient losses decreased as the proportion of chicken manure in the mixtures decreased for saw dust and rice husk treatments. This indicates better nutrientst conservation during composting in swine than chicken manure. Manure mixtures with rice husk had higher pile temperatures (> 55^oC), total carbon and total nitrogen losses, while manure mixtures with saw dust had higher total phosphorus loss and carbon to nitrogen ratio. Composts with rice husk demonstrated the ability to reach maturity faster by the rate of drop of the carbon to nitrogen ratio.