In addition, duck eggs are larger and more nutritious than chicken eggs. In the Philippines ducks rank next to chickens for egg and meat production. Other popular breeds for egg production in Banlgadesh and Indonesia are Khaki Campbell and Indian Runner. Crossbreeds between wild and domestic ducks, such as the aigamo , are also popular in Japan. However, with the development of rice culture in the humid and irrigated areas of Africa, dual-purpose breeds, such as the Beijing, would be a useful introduction.
Diseases are the major limiting factor for improving productivity in scavenging systems.
Non-infectious and infectious diseases are common as a result of poor husbandry, poor quality feed and environmental changes, while vitamin and mineral deficiencies lead to malnutrition, weak legs and physical injuries. It also results in the lowering of immunity and increases susceptibility to infectious diseases. It is not uncommon for ducks to succumb to multiple infections, particularly under stressful conditions. However, the actual disease status in 'family' ducks in unknown as farmers do not generally report disease outbreaks. In additon, there is great potential for increasing the productivity of these systems by the integration of fish and the nitrogen-fixing fern Azolla .