Water Efficiency of Animal Protein Production

Livestock production has been shown to be economically important and is related to increasing incomes in poor rural areas. Consumption of livestock products has important health benefits and a modest amount of animal protein in the diets of African children appears to improve mental, physical and behavioural development. However, livestock is a consumer of water, plant and crop products, placing them in direct competition with humans for these products. They compete for water supplies but fresh water resources are not evenly distributed with more than 2.3 billion people in 21 countries, and their livestock, living in water stressed basins. Thus, the competition between humans and livestock is very direct as both have similar water quality requirements for drink purposes.

There are few examples of research and assessment that attempts to understand the total water needs of livestock production and how livestock production affects water resources. Water is critical for livestock as water constitutes approximately 98% of all the molecules in the body and is the first limiting factor in livestock production. Water demand for livestock production has recently been highlighted with the development of the concept of virtual water content to describe water usage by industries within a common framework. Virtual water is the volume of water required to produce a commodity or service with livestock industries accounting for 45% of the global agricultural virtual water supplies,and this includes rainfall on grazing lands.

As part of a study to determine water fingerprints for nations in 2007, it was calculated that virtual water content ranged from 175 litres of water/kg of sugar cane to 16,656 litres of water/kg of bovine leather. In general, livestock products have higher virtual water contents than crop products. Livestock consume plant material as a feed source that requires water to grow (although in the case of grazing ruminants the crop not directly usable be people), drinking water and water during processing before producing a product. However, animal products are primarily produced for their protein content whereas crops can efficiently provide energy and in some cases, protein for the human diet. The poorer energy water efficiency of livestock is a consequent of the energy required to convert plant material to animal tissue. Livestock are also an excellent source of biologically available minerals in human diets e.g. iron for females. The water efficiency of minerals, specific fat types (omega-3) and other nutrients from livestock products has been poorly researched. Water efficiency for some livestock products is competitive with plants as protein and calcium sources in the human diet.