Food security concerns have highlighted a need to find more sustainable sources of protein for use in animal feeds. Insects are increasingly being recognised as a potential substitute for conventional sources. Many insect species are highly nutritious and their production has less environmental impact compared with traditional sources of animal protein.
The researchers, led by Harinder Makkar of the Food and Agriculture Organisation (FAO), conducted a review of existing research on the five major inspect species that are emerging as potential animal feed products: black soldier fly, mealworm, locusts, grasshoppers and crickets, housefly maggots and silkworms.
High flyers
Black soldier fly larvae emerged as the most promising source, capable of replacing soymeal in poultry and pig diets.
“However, more in-depth studies are required to optimise its levels of inclusion, and at its high levels of inclusion to also optimize the levels of deficient amino acid supplementation,” wrote the researchers.
In laying hens, maggots could replace up to 50% of fishmeal without any adverse effects, suggested the researchers. For broilers, up to 10% soymeal or fishmeal could be replaced with maggots or mealworm, when supplemented with methionine.
Grasshoppers emerged as an interesting protein source for broilers, as they result in a number of meat quality parameters, such as higher antioxidant potential, longer shelf life, increased protein and decreased cholesterol content.
Silkworm could be a promising feed resource for cattle, owing to its low rumen degradability, reported the researchers. They said that in fattening diets of Jersey calves, defatted silkworm meal could replace 33% of groundnut cake without affecting performance, and that experiments in growing and finishing pigs how shown that defatted silkworm meal could replace 100% of soymeal or fishmeal.
Peak protein content
The researchers reported that the crude protein contents of these alternate sources were high, varying from 42-63%, which is comparable with soymeal. After defatting, the crude protein content in insect meals is expected to be higher than that of soymeal.
“Some insect meals, for example, black soldier fly larvae, housefly maggot meal, mealworm, silkworm, contain as much as 36% oil, which can be isolated and used for the preparation of biodiesel, and the rest of the defatted meal could find a place as a protein-rich resource in the feed industry,” wrote the researchers.
They said that defatted insect meals would be an ideal choice for ruminants as the presence of high levels of lipids in the meals can decrease fibre digestion in the rumen.
Enough amino acids?
The researchers concluded that “overall levels of essential amino acids in insect meals are good; most essential amino acid levels in silkworm pupae meal and black soldier fly larvae being higher than in soymeal or the FAO reference protein.”
They suggested that a 50:50 mixture of black soldier fly larvae and housefly maggot meals would provide a balanced amino acid composition for use in livestock feed as soymeal replacers.
Levels of arginine - an essential amino acid for laying hens – in all insect meals were found to be lower than in soymeal, suggesting that diets of hens fed insect meal would have to be supplemented with arginine.
Calcium supplementation necessary
Calcium is important for poultry, pigs and milk producing cattle. Whilst black solder larvae are rich in calcium (7.56%), calcium levels for other insect meals were found to be very low, meaning that calcium supplementation would be required if they were used in animal feed.
Large scale production
In order for insect meals to be a significant part of the animal diets produced by the feed industry, the researchers said there was a need for cost effective, mass insect rearing facilities, a regulatory framework and sanitation procedures for safe use of bio-wastes and managing diseases, heavy metals and pesticides.
They also called for more studies evaluating insect meals as livestock feed, life cycle studies to measure the environmental impact of using insects as animal feed and data on the feed conversion efficiency of various insects, to make informed decisions.
Source: Animal Feed Science and Technology
DOI: http://dx.doi.org/10.1016/j.anifeedsci.2014.07.008
Published online 27 July 2014
“State-of-the-art on use of insects as animal feed”
Authors: Harinder P.S. Makkar, Gilles Tran, Valérie Heuzé and Philippe Ankers