ALTERNATIVE PROTEINS ▶▶▶
To evaluate the economic value and practical application of insects in layer feeds, the chemical composition will need to be evaluated, including fatty acids and amino acids. Coeffi- cients for digestibility will also be required and can be based on a desk study and in vitro experiments. Restrictions on the use of insects in feed is subject to EU legislation and GMP+.
Due to current EU legislation only live insects can be fed to production ani- mals. However, it is not unlikely that this legisla- tion will change in the future.
ideal insect candidate should have a short reproductive cycle and be nutritious, providing high concentrations of protein and essential amino acids. To guarantee a constant supply, the ideal insect candidate should further be easy to rear un- der intensive conditions. Plants, animals or other organisms that do not occur naturally in a country can be harmful to na- ture. The ideal candidate must occur all over the world and must not pose a risk in the event of escape. The housefly meets all these criteria and would enable the cost effective production of larvae. The ideal breeding unit should be fully animal friendly. Which means flies and larvae are kept under optimum light, rest and movement conditions, and have free access to feed and wa- ter. Beds should be designed in the place where the flies are to lay their eggs as a completely calm space which is particu- larly attractive to the females. The larvae then grow in an area where the temperature, air, feed and water are fully con- trolled.
Ideally the larvae are given GMP+ certified feed. Insects are also one of the major sources of anti-microbial peptides/pro- teins (AMPs). To be able to make optimum use of the AMP, lar- vae should be fed precisely as needed. The larvae feed con- version needs to be optimum to ensure that little residue remains. The positive outcome of all this is that the larvae do not need to be separated which saves greatly on costs.
Application in poultry Poultry with access to an outdoor area pick up insects at all life stages and eat them keenly which indicates that they are evo- lutionarily adapted to eating insects as a natural part of their diet. The production of chitinase by poultry and pigs results in the partial digestion of chitin. This leads to the formation of N-acetyl-D glucosamines that contribute to immune modula- tion and reduced adherence of pathogens to cell walls. There- fore, it seems reasonable to consider the inclusion of insect proteins as a raw material in commercial feed manufacturing and to develop intensive insect farming systems for livestock.
24 ▶ POULTRY WORLD | No. 6, 2020
Nutritional value of insects Nutrients that predict animal performance are, above all, me- tabolisable energy (ME), digestible amino acids and retaina- ble minerals. In a well-balanced feed, the cost of ME will be 65-70% of the total nutrient cost, while for digestible amino acids it will be 24-26%. Of all the 22 amino acids, lysine, me- thionine/cysteine, threonine, tryptophan, valine, isoleucine and arginine are regarded to be limiting in the order as stat- ed. From the literature it appears that Amusca larvae contain less ash and more fat (Table 1). It should be noted that the fat content and fatty acid composition depends on the diet of the larvae. The protein content is similar to soybean meal. The fiber fraction in Amusca larvae is mainly chitin. Digestibility can best be evaluated with in vivo digestibility trials. Simulation of the digestive tract by incubation of stom- ach conditions (pepsin/HCl) and small intestines (buffer/pan- creas) may be effective. Therefore, it is useful to compare these with ingredients that are well described in feed tables. For poultry, the in vivo digestibility of insect-meal in terms of essential amino acids is 89-95%, depending on the amino acid, and is comparable to fish meal. Housefly pupae showed similar in vitro digestibility for organic material (OM) and pro- teins (N) compared to fish meal and poultry meal. The digesti- bility of pupae is normally lower compared to larvae. This can be explained by the fact that pupae contain more chitin which is less digestible for younger animals like broilers. Based on in vivo and in vitro trials, the digestibility coefficients of Amusca larvae are in the same order as CVB table values for meat meal and soybean meal (Table 2). For protein in lar- vae the digestibility is assumed to be higher than meat meal.
High in fat
Because of the high fat content, the ME-value of larvae is sub- stantially higher than that of fish meal, meat meal and soy- bean meal. It should be noted that the fat content and fatty acid composition depends on the diet of the larvae. The price, or market value, for ME will depend on the energy prices for feed and fuel. About 68% of the ingredient costs of feed are for metabolisable energy (ME). Assuming that the price of the ingredients for a layer feed is € 210 per tonne, the price for ME (2825 kcal/kg) in the feed will be € 142 per tonne. Extrapolat- ing this price assumption, the price for energy in larvae (4000 kcal/kg) will be € 201 per tonne. In addition, the proteins and minerals in the insects will add to their value. The amino acid profile of insects and fish meal is similar. Com- pared to soybean meal, larvae are similar in lysine, threonine
PHOTO: KOOS GROENEWOLD
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