Water Efficiency of Animal Protein Production

Water Efficiency of Animal Protein Production The livestock sector is the fastest growing agricultural sector and has been predicted to continue growing at these rates for the foreseeable future. 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.

Water Efficiency of Animal Protein Production However, not all proteins have the same value in human diets and range of systems has been developed to adjust the protein for their biological value in human diets. One such system is based on feeding experiments to produce a biological value for proteins. This adjustment for protein nutritional value has been used to calculate water efficiencies in terms of protein biological value for a range of productions and countries based on water efficiency data. Although on average proteins from livestock adjusted for biological value requires more water (67,637 litres/kg) than protein from plants (25,593 litres/kg), there are some animal proteins sources that are statistically the same as those produced by plants in the terms of water efficiency. There was no plant protein source considered in this study that was significantly more water efficient than protein from eggs; only soybean protein was a more water efficient source of protein than milk, goat meat and chicken meat when protein production was compared on the basis of biological value. Sheep and pork protein, although more water efficient than beef, used significantly more virtual water than plant protein sources to produce a kilogram of protein adjusted for biological value.

Beef production has the highest demand for water of the livestock industries investigated. This is in part likely to be due to the common usage of irrigated fodder, longer turnover times and the use of higher rainfall grazing areas for beef production compared to small ruminants. The longer turnover times are a function of a longer gestation period, lower reproductive rates and longer growing time to market than other livestock species. In poverty prone regions of the world ruminants are grazed or feed mostly on crop residues, used for crop production and probably requiring much less water than those in the developed world where grain or irrigated forage are commonly as livestock feed. The water efficiencies for these countries were not included in the study above.

Overall humans only require 75 grams of protein per day with consumption beyond this amount being converted to energy. Thus, the water used to meet the first 75 gram of dietary protein can be obtained efficiently from animal products. The role of livestock proteins and other livestock nutrients for health as well as livestock utility for crop production have not been included into calculations of water productivity but should not be overlooked in any evaluation of the role of livestock in human food production.