Is insect protein a sustainable option for poultry diets?

Sustainability comprises three principal components: the environment (demand for resources and potential for environmental pollution), ethical issues (welfare of man and his animals), and economic robustness (FAO, 2012). At first glance, insect protein is a sustainable alternative to traditional protein sources such as soybean meal. Insect production requires less land, water and other resources than traditional protein sources, and they can be raised on “upcycled” material from the human food supply chain (vegetable waste), or on decomposing organic matter not typically consumed by humans. The waste stream of insect production (frass) can be a fertilizer source for crop production (DiGiacomo and Leury, 2019).

Insects provide a favourable supply of AA for broiler chickens (Veldkamp and Bosch, 2015) together with adequate energy, although levels depend on the processing method. However, the costs associated with insect protein production can be high, bringing any benefits in terms of financial robustness into doubt. Insect production remains small and is faced with problems that beset most start-ups. These include a lack of investment in research and development, the problems associated with engineering controls and scaling up and an inconsistent regulatory environment. Despite this, the industry has the potential to provide insects to production animals (DiGiacomo, 2023). This paper explores insect production and will consider its possible role in sustainable poultry production.

Although several species of insect have been used as a source of insect protein, this paper will focus on the production of Black Soldier Fly (BSF) larvae and the meal produced from them. BSF is a source of protein, fat, metabolizable energy (AME), phosphorus, and fibre, which can be used as a replacement for other protein sources, such as soybean meal (SBM) and fishmeal (Facey et al.,2023). The protein quality of BSF was comparable with fish meal and SBM (Cheng et al., 2023). It is contented BSF can be used to replace fish meal in poultry diets, but it should be remembered that very little fish meal is used in modern poultry diets because of its cost. Of interest, BSF meal produced in East Africa is exported to Europe for use by the pet food industry. For a nutritionist to utilise any ingredient, details of its energy and digestible amino acid content are required. It has been established that insect meals contain high levels of energy and digestible AA compared with ingredients commonly used in poultry diets, and although excellent values for BSF have been published (Matin et al., 2021; INRAE, 2023), the nutritionist is still faced with the variability which exists in products from different production facilities, and indeed, on which feedstock was used in their production.

Several proteins expressed by insects serve as antimicrobial peptides and may serve as an alternative to antibiotics, enhancing immunocompetence and gut health in production animals (Li et al., 2012). Insects also contain high concentrations of chitin and medium-chain fatty acids (lauric and myristic acid), which are thought to improve both gut and immune health in broiler chickens through prebiotic and antimicrobial properties, reducing the reliance on antibiotics and coccidiostats in the poultry industry (Dörper et al., 2020; Bean-Hodgins et al., 2021).

Growth performance responses to the replacement of SBM with BSF are been variable, with some research finding that when less than 30% SBM was replaced, no change or improvement in broiler performance was measured (Dabbou et al., 2018; de Souza Vilela et al., 2021) In cases where replacement exceeded 50%, reduced performance was experienced (Dabbou et al., 2018; Murawska et al., 2021). Higher relative weights of the gizzard, small intestine, pancreas, and liver were observed at higher BSF inclusion, giving rise to health concerns (Facey et al.,2023). In laying hens, the substitution of fish meal with BSF did not affect the laying rate, feed intake, or FCR, although an increase in body weight was recorded (3% BSF meal) (Patterson et al., 2021; Zhao et al., 2022).

Approximately 2.5 billion people depend on small farms globally (FAO, 2013), many living below the poverty line (WHO, 2020). These small farmers, only contribute 8% of global egg and 2% of poultry meat production (Mottet et al., 2016). Despite the many benefits of intensive production, small-scale, local production is crucial in any move towards global sustainability and poverty alleviation. Small-scale farmers often face a challenge when trying to source protein for their poultry, and the protein provided by feeding insects will address this shortfall and improve performance. In addition, they will help reduce organic waste and pollution (Khusro et al., 2012; Józefiak et al., 2015).

Several aspects of insect protein production ought to be considered. First, insect production requires some form of production facility. These can range from small-scale, subsistence systems on farms to sophisticated modern climate-controlled ones. Second, before any product of animal origin can be used in poultry diets, rendering is required before a ‘safe’ product is available to be marketed. This involves high temperature and pressure (usually 3.5 Bar for 30 minutes), and then most of the remaining moisture needs to be driven off (Koutsos, 2021). 

Commercial BSF production is high-intensity animal production, a methodology familiar to poultry producers. Climate control entails well-insulated growing rooms, which determine the quantity and quality of insect meal. Several parameters must be controlled, including food stock (substrate) and room temperature, humidity, ammonia and CO2 levels. The process requires energy-efficient technologies and sophisticated climate control computers (www.insectengineers.com, 2023). An idea of the production scale is given by (Farrugia, 2022). A minimum viable level for onsite production would be approximately 2,000 tons of wet larvae a year (7 tons a day), representing about 2 tons on a dry matter basis. The use of non-conventional substrates is being explored for mass production of insects. These include food waste streams, agricultural by-products or manure from livestock farms. This application of the circular economy reduces the environmental footprint and economic costs associated with insect production. However, edible insects can also be associated with several food safety hazards, including biological agents (bacterial, viral, fungal) and chemical contaminants (pesticides, toxic metals, pharmaceuticals). Farming insects under controlled hygienic conditions and implementing sanitary processing techniques reduces some hazards, but any production system should include mechanisms to prevent, detect, identify and mitigate such food safety concerns (FAO, 2021).

The nutrient content and the performance aspects of reared insects depend on the substrate used. Spranghers et al., (2017) offered BSF larvae three different vegetable waste substrates and chicken feed (17.5% CP) as a control. They found that the protein level and AA profile were constant regardless of the substrate fed, but that the fatty acid profile and mineral content differed. Despite the finding that they could effectively rear fly larvae on waste streams, the difference between feeding vegetable waste and chicken feed is insightful. The larvae fed chicken feed required 12.3 days to pupate, achieving a mass of 220 mg (17.9 mg/day), whereas larvae fed restaurant waste required 19 to pupate and weighed 154 mg (8.1 mg/day). In this authors opinion it should be questioned whether it is financially sustainable to throttle the output of an expensive animal production facility by using cheap inputs? Is it sensible to risk contamination in any waste stream when ‘clean’ feed could be used instead?

Measuring sustainability is complex because the entire value chain must be considered. This would include aspects such as the source of the substrate, any impact on the built environment, energy costs and the cost of logistics (Pelletier, 2015). In the case of feeding BSF, assessment is complicated by the multitude of different systems used, both to produce the insects and in terms of the poultry that will ultimately consume them. Where locally available waste streams are used on farm, and live insects fed on the same farm using insects as poultry feed is sustainable (van Huis & Oonincx, 2017; Veldkamp & van Niekerk, 2018).

The higher the bioconversion efficiencies, defined as the proportion of nutrients provided in the substrate that are incorporated into the insect biomass, the better the sustainability performance of a system will be. The efficiencies of nutrient conversion and gaseous emissions during BSF production were measured to quantify bioconversion efficiency (Parodi et al., 2020). Bioconversion efficiencies ranged from 14% (potassium) to 38% (nitrogen). Direct GHG emissions associated with BSF rearing were 16.8 ± 8.6 g CO2eq per kg of dry larvae, without considering the energy used in its production. By comparison, a value of 0.580 g CO2eq is given for locally produced SBM (INRAE, 2023).

The use of insect protein in the poultry industry is in its preliminary stages. Insects can convert waste streams, unfit for human consumption, into a nutrient and energy source for animal feeding, although the risk of contamination with rogue chemicals may be high. Insect protein is useful in subsistence poultry production, where it often forms the only dietary protein source. High-intensity, commercial insect production requires sophisticated facilities. Few proper assessments of the sustainability of commercial insect production have been published, however, the existent data would indicate that the carbon footprint of insect protein is likely higher than alternative ingredients. It has been shown that feeding insects a balanced feed, more than doubles their growth rate, so using low-density waste streams in high-intensity production systems may be questionable. Relative to the requirements of the poultry industry, the output of insect products is small. Perhaps the true sustainability of insect protein should be viewed in two dimensions. Small-scale production and the feeding of live insects to chickens that are probably deprived of protein is most undoubtedly sustainable, but large-scale commercial production is unlikely to be so.