Some Interesting Facts & Figures
|The following facts and statistics have been taken from this publication to highlight their significance. The Page reference for each quotation is included to provide the correct context for the quotes.||
|Box 5 (Page 42)
How Much Grain Does It Take to Produce a Pound of Meat? Conversion Rates of Human-Edible Inputs by Different Species of Food-Producing Animals
Widely varying estimates of the amount of grain required to produce a pound of meat from different species have been reported in recent years in both the popular press and in some scientific journals. Unfortunately, some of the estimates are incorrect, in some cases by a two- to four-fold margin.
Estimates (from Table 4.5) of the grain fed per unit of carcass weight of four meats produced, in developed and developing countries, are as follows:
These results from global summaries of grain fed and meat produced are consistent with the results of detailed analyses of inputs and outputs for different countries and production systems reported in Chapter 4 of this report.
A global estimate of conversion rate of human-edible feed to human food was presented by Steinfeld et al. (1997), who calculated that, worldwide, animals consumed 74 million tons of human-edible protein and produced 54 million tons of human food protein. This gives an input:output ratio of 1.4:1. As it happens, the ratio of biological value of animal protein to that of plant protein is, on average, also 1.4:1. On this basis, from the perspective of human protein nutrition, the use of animals does not decrease the amount of protein available for humans, which has been an issue of concern.
The grain:product ratios above may be contrasted with the values of 12:1 for beef and 2:1 for poultry used by Waggoner (1998), or the values of 8:1 for beef, 3:1 for pork and 2:1 for poultry presented in a recent issue of National Geographic (October 1998). Clearly, the largest differences are in conversion rates reported for beef cattle.
There are several reasons for the discrepancies. The most common is the assumption that the feed fed to animals is 100% grain. As documented in the case studies in this report, diets of all species of food-producing animals include some materials not edible by humans; for ruminants, the human-inedible portion is often 100% and always more than 50%, on a life-cycle basis. The amount of grain required to produce meat from ruminants such as beef cattle is therefore seriously overestimated by neglecting the forage and by-products that make up the largest part of their diet.
A second source of discrepancy is consideration of only a portion of the life cycle. Beef cattle in U.S. feedlots typically require five to seven pounds of feed to produce one pound of gain; 50 to 70% of the feed may be human-edible, giving a human-edible input:product ratio of 2.5 to 5:1 for this part of the production cycle. However, the animals have reached 50 to 70% of final live weight (45 to 65% of carcass weight) when they enter the feedlot, with the gain up to that time coming entirely or almost entirely from forage (see Box 2 and Table 4.16). In other words, only 35 to 55% of the meat produced by the animals is produced during the period when human-edible inputs are fed. Thus, the grain:beef ratio is between 0.9 and 2.8:1, based on final live weight of the animal, or between 1.4 and 4.4:1, based on carcass weight, consistent with the average developed country value of 2.6:1 in the table.
A third factor contributing to discrepancies in reported conversion rates is variation in choice of end point, e.g., live weight, carcass weight, boneless cuts (see Box 1).
The fact that several of the input:output ratios are greater than 1:1 does mean that feeding less grain to animals would translate to somewhat more total food for humans. It would also mean a food supply with less variety and lower nutrient density. As noted elsewhere in this report, grains fed to animals represent a buffer for human food grain supplies; whenever grain becomes scarcer and more expensive, less is fed to animals. Grains and protein supplements fed to animals also improve the conversion rates of forages and by-products to human food.
The efficiency with which animals convert human-edible inputs to human food is a factor to be considered in determining policy related to human food supply. Better policy decisions will result if the discussions on the subject are based on actual conversion rates and not on estimates from assumptions that ignore what animals actually eat.
Council for Agricultural Science and Technology (CAST)
Animal Agriculture and Global Food SupplyAnimal agriculture is an integral part of food-producing systems, with foods of animal origin representing about one-sixth of human food energy and one-third of the human food protein on a global basis. Animals convert forages, crop residues, and food and fiber processing byproducts to high quality human food; provide draught power for about half the world's crop production; and provide manure to help maintain soil fertility. Animal production makes important contributions to agricultural economies throughout the world and to food security in developing countries.
Animals also consume one-third of the global cereal grain supply. In a world with human population forecast to reach 7.7 billion by the year 2020, a fixed or possibly shrinking quantity of arable land, and an estimated 800 million undernourished people, quantifying the net contribution of animal production to quantity and quality of the food supply is important.
Current global food supply is sufficient to provide everyone with an adequate diet. The inequitable distribution of food, which leads to hunger in some areas, is caused by inequities in income distribution, a complex issue not likely to be addressed effectively by changes in any one component of agricultural production systems.
Consumption of meat, milk, and eggs varies widely among countries, reflecting differences in food production resources, production systems, income, and cultural factors. Per capita consumption of these foods is much higher in developed countries but the current rapid increase in many developing countries is projected to continue. Total meat consumption in developing countries is projected to more than double by the year 2020, while, in developed countries, it is projected to increase no more and, in some cases, less than population growth. Because most of the world's population is in developing countries, which are experiencing the most rapid growth rates, global demand for meat is projected to increase more than 60 % of current consumption by 2020.At low levels of intake of meat, milk, and eggs, an increase in consumption of these foods is known to be nutritionally beneficial, particularly for young children. These benefits result from the higher content and nutritional availability of essential amino acids and several micronutrients, including minerals and vitamins. Thus, if achieved, projected increases in per capita intake of meat and other animal products in developing countries should improve people's nutritional status. In developed countries, on the other hand, intakes of food from animals are higher than justified by nutritional grounds alone. Opinions differ as to whether a decrease in intake of these foods would benefit the health of the general population. In all countries, the palatability and dietary diversity contributed by meat, milk, and eggs are undoubtedly important factors, in addition to nutritional content, in determining intake levels.
Conversion rates of the energy and protein in feeds consumed by animals to human food energy and protein vary, depending on species, production system, feed type, and product. Poultry and pork production are most efficient on the basis of total food produced from total feed intake but, on average, ruminants (cattle, sheep, goats) return more human food per unit of human-edible feed consumed because most of their feed is obtained from materials that cannot be consumed directly by humans. This fact has been overlooked in some assessments of the role of animals in food production.
On a global basis, less than three kilograms (kg) of grain are required to produce a kg of meat from any of the species and less than one kg of grain per kg of milk. Less grain is fed to livestock in developing than in developed countries. It has been estimated that, on a global basis, animals produce a kg of human food protein for each 1.4 kg of human-edible protein consumed. The biological value of protein in foods from animals is about 1.4 times that of foods from plants. Thus, diverting grains from animal production to direct human consumption would, in the long term, result in little increase in total food protein and would decrease average dietary quality and diversity. Also, feed grains can be and are diverted to direct human use during periods of temporary food grain shortage. An additional consideration is that maize, the principal feed grain, yields much more per hectare than wheat, the number one food grain.Recently, conversion rates of grains to meat, milk, and eggs have improved significantly in both developed and developing countries. Applying known technologies to a larger proportion of the world's animal populations offers the potential for substantial additional improvements in efficiency and, with continued investment in research, new technologies undoubtedly will contribute to additional increases. This suggests that grain requirement per unit of animal food product should decrease. However, the largest increases in demand are forecast for poultry, pork, and aquaculture products, which are foods from species requiring relatively high human-edible content diets. The net effect on grain demand is, therefore, difficult to predict but it is estimated that an annual rate of growth in cereal production between 1.1 and 1.4%, i.e., a lower rate than in recent decades, should meet needs for both food grains and the feed grains required to meet the projected per capita demand for meat, milk, and eggs.
Livestock have both positive and negative environmental effects. Improved management of livestock grazing, better management and use of manure, and increased care in design and siting intensive production operations will be necessary to maximize beneficial effects and minimize detrimental effects of livestock. Government policies related to land use and economic development are important.
Meeting projected demand for foods of both plant and animal origin in 2020, while sustaining the productive capacity of the land, will be challenging but feasible. Animal agriculture will continue to be an important part of food-producing systems. Investment in agricultural production research and development and implementation of policies that encourage production, while protecting the environment, will be essential to achieving the goal of an adequate global food supply.
Bruce T. Bowman, Archivist
Last Updated: Thursday, July 26, 2018 01:30:16 PM