Reducing water use for animal production through aquaculture

Animals fed formulated diets indirectly consume large quantities of water. Globally, about 1.2 m3 of water is needed to produce 1 kg of grain used in animal feeds. Cattle in feedlots consume about 7 kg of feed concentrate to gain 1 kg in weight. For pigs this is close to 4 kg and for poultry slightly more than 2 kg of concentrate. Fish or crustaceans require less than 2 kg of grain concentrate for each kg produced, making them the most efficiently producing animals in terms of feed-associated water use. Non-feed-associated water use can also be considerable, and a comparison was made in total water use between aquatic and terrestrial animals. On-farm water use for terrestrial animals, including drinking, but excluding water for cooling animals or cleaning their sheds is only 1% of feed-associated water use. However, on-farm water use in aquaculture can be very high, attaining values of up to 45 m3 per kg produced in ponds. Intensification of aquaculture reduces on-farm water use per kg product, and only intensive aquaculture production systems are equally water-efficient as terrestrial animal farming systems. Within existing aquaculture pond systems reductions in water use can be achieved through (1) selection of feed ingredients that need little water to be produced; (2) enhancement of within-system feed production through periphyton-based technology; and (3) integration of aquaculture with agriculture. Still, these approaches will not make pond aquaculture more water-efficient than terrestrial animal production systems. That can only be attained in recirculating aquaculture systems and systems producing fish as a by-product of wastewater treatment. Currently, the most promising approach is to concentrate on further development of brackish and marine aquaculture, as such systems use small or negligible amounts of non-feed-associated fresh water