The net contribution of livestock production to protein supply for humans

Livestock may be perceived as less efficient and in competition with crops for the human food supply because they partly consume human-edible feedstuffs to produce milk, eggs or meat. The aim of this study is to estimate the net production of protein for human consumption of ruminant, pig and poultry livestock systems in France. The total protein Conversion Ratio (pCR = kg feed protein consumed/kg protein produced by milk, eggs or meat) does not differentiate human-edible from human non-edible feedstuffs (e.g. grass, byproduct of food and biofuels industries). Thus, we used also the human-edible protein Conversion Ratio (hepCR) that needs to estimate the human-edible protein fraction (hepF) of feedstuffs used in livestock diets. First, we built a table of hepF values for feedstuffs consumed by livestock, applied to the current market and technologies used in the food industries in France (e.g. hepF of wheat grain = 66%, hepF of rapeseed meal = 0%). Then, we estimated the pCR and hepCR values for contrasted feeding systems in ruminants, pigs and poultry. As expected, the pCR values are lower than 1, between 0.05 and 0.25 for ruminant systems, about 0.4 for pigs, 0.3 for laying hens and up to 0.5 for broiler chickens. In contrast, the values of hepCR show that all livestock systems can contribute positively to the human protein supply (hepCR~or>1). Grass-based dairy cow systems can produce up to twice the amount of edible protein they consume (hepCR~2). Pig or poultry systems can respectively produce up to 1.5 (for pig) and 1.3 (for broilers) time more human edible protein that the amount they consume, depending on the proportion of corn, rapeseed/sunflower/soybean meals and other byproducts in the diet. The utilization of grass in ruminant systems and of byproducts in all livestock systems are the key factors to improve the net contribution of livestock production to human food supply, in particular if we consider that advances in food industry technology and modifications of human eating habits can reinforce the feed/food competition in the future