Livestock and aqua-culture production offer high-quality protein sources for human consumption; nevertheless, elements of both production methods are now regarded to be unsustainable on a long-term basis.
The world's population is growing and human food preferences are changing worldwide. Therefore, enough meat production is a major issue for the future. In terms of optimization of production, enough amounts of quality feed are needed to unleash the animal's maximum genetic potential. All livestock, pets and aquaculture need high quality protein. Global per capita meat consumption is projected to rise by about 40% from 2019 to 2050. One approach to decrease farmland usage for livestock, pets and aquaculture feed is to develop alternate sources of protein synthesis. The main protein sources for livestock, pets and aquaculture nutrition, notably soybean meal, peas and fish meal, are becoming more demanding and consequently more costly, making their long-term usage unsustainable. Therefore, it is important to discover alternate sources of protein. Insects are presently regarded one of these sources, primarily owing to their high protein content, cultivation on industrial by-products and organic waste, high feed conversion, high fertility and minimal space needs in the raising process.
Challenges for conventional livestock, pets and aquaculture feeding system
The global population is currently estimated at 7.6 billion, and it is expected to reach 9 billion by 2050. Rapid population expansion puts huge stress on food producers, and that is why particular attention must be paid to sustainable food production, in particular food rich in high-quality proteins (McClements et al., 2021). It is presently difficult to raise food production to a level that satisfies the requirements of the fast increasing human and livestock population, while restricting the availability of additional agricultural land (Fróna et al., 2019). Currently, agricultural land comprises 30% of the worldwide land area, of which 70% is utilized for livestock feed production (Ramankutty et al., 2018). Intensive livestock (cattle and poultry) production is a major driver of biosphere change, contributing substantially to greenhouse gas emissions, global warming, soil degradation, air and water pollution and biodiversity loss (Smith et al., 2019). Despite the foregoing, livestock breeding and agriculture is one of the fastest-growing agricultural industries, and the demand for livestock (cattle and poultry) products is continuing to rise (Feldt et al., 2020). These dynamic processes will also enhance demand for livestock feed and alternate protein sources may assist to address these global problems.
Application of Insects in Livestock, Pets and Aquaculture Feed
Insects have been identified as having an adequate nutritional content to use in livestock (cattle, and poultry), pets and aquaculture feed (fish production, crustacean and other aquatic animals). Livestock and aquaculture production offer high-quality protein sources for human consumption; nevertheless, elements of both production methods are now regarded to be unsustainable on a long-term basis. Compound feed is provided to all livestock, pet and aquaculture species, 44% of which supports worldwide poultry production (Hawkey et al., 2021). This increase in demand for compound feed is projected to increase the burden on land-based crop production, notably for soya and rapeseed, as a result of the increase in demand. These plants are now the primary source of protein in livestock diets, which are frequently supplemented with synthetic amino acids for those with limits (De Visser et al., 2014). Whilst soybean contains high-quality digestible protein and amino acid composite, it is not considered sustainable since the needs for intensive livestock (cattle and poultry) production are becoming increased (Sánchez-Muros et al., 2014). As a result, there are growing uncertainties regarding the future of soybeans to satisfy rising protein needs (Herrero and Thornton, 2013).
Fish meal is a high-quality source of readily digestible protein. It has optimum proportions of vital amino acids and long-chain fatty acids, and it contains a significant amount of vitamins and minerals, among other characteristics. However, the increasing demand for fish meal, along with the depletion of fish populations (due to, among other things, overexploitation of fisheries throughout the globe), has resulted in a reduction in the supply of fish meal and a rise in the price of fish meal (Cashion et al., 2017).
In order to produce more livestock, more feed is inevitably needed. In 2020, more than one billion metric tonnes of feed were given to livestock. About 44% of the total livestock feed was generated for poultry, followed by about 27% for monogastric (pets and pigs), 22% for cattle and 4% for aquaculture (Bahar et al., 2020).
Poultry are mostly fed grains, although they are also given soyabean meal and fishmeal as protein sources. Monogastric (pets and pigs) are also omnivores fed with grain, soyabean and fish meal and oilseed, root crops and legumes. Cattle are herbivores, and they eat grass, grain, and soyabean in small quantities. Fish raised in aquaculture are mainly carnivorous, such as salmon and trout, and are frequently given fishmeal in pellet form, as well as soybean, grains, and legumes as less expensive sources of protein and nutrients (Van Zanten et al., 2019; Gaillard et al., 2020; Li et al., 2021).
The fact that fishmeal and soyabean meal are essential components of livestock (cattle and poultry), pets and aquaculture feed across the board becomes clear as a result. The processing of wild fish (collected in the ocean) to produce fishmeal and fish oil (as well as 5 million metric tonnes of fish trimmings) accounts for about 16 to 17 million metric tonnes of wild fish processed each year (Hawkey et al., 2021). Most fishmeal and fish oil are used in aquaculture to raise fish for human consumption, with the bulk of it going to feed fish (Gasco et al., 2020). Fish meal costs have risen owing to strong demand, and as a result of increasing fish output in aquaculture, farmers have begun to depend more on protein-rich plant-based feed.
It is important to note that 80% of the world's soybean output is utilised for livestock, and aquaculture feed. The disadvantage of soybean production is significant environmental stress, particularly severe land use change (huge deforestation), reduced soil fertility, damaged biodiversity and the consumption of large quantities of water (Onsongo et al., 2018). The use of an alternative to soybean in livestock and aquaculture feed has the potential to decrease the negative effect of soyabean production on the environment.
In the distant future, insects may provide an alternate source of protein. Both live insects and insect protein categorized as processed animal protein have the potential to be utilized in livestock (cattle and poultry), pets and aquaculture feeding. The overall protein content of insect meal may range from 40–60% depending on the species. It is also worth noting that the digestibility of amino acids in insect protein is very high, ranging between 91% and 95%. Compared to grains and legumes, insect larvae are a great source of energy. Additionally, edible insects have lipids with a favorable fatty acid composition, which makes them a good source of fat for livestock and aquaculture (Siemianowska et al., 2013).
Main Insects Species used for Livestock, Pets and Aquaculture Feed
There are several species of insects that can be raised for livestock (cattle and poultry), pets and aquaculture feed, including the black soldier fly (Hermetia illucens), the domestic fly (Musca domestica), mealworm (Tenebrio molitor), Superworm (Zophobas morio), Buffalo worm (Alphitobius diaperinus), House/Domestic cricket (Acheta domesticus), the Tropical domestic cricket (Gryllodes sigillatus), Jamaican field cricket (Gryllus assimilis), Dessert locust (Schidtocerca gregaria), Silkworm (Bombyx mori) and Greater wax moth (Galleria mellonella). Flies and beetles generally are given as larvae, while crickets are supplied as adults. This is generally a nuisance, since there is significant fluctuation in the dietary content between the larval and adult phases. Currently, breeding procedures are developed and managed to generate more uniform lots in terms of their fat content (maximum variability, with dry matter between 5 and 50%) and protein (which can exceed 50-60%). It is necessary to standardize the substrates on which insects are raised in order to produce insect-based feed products that are uniform in composition and high in high-quality protein, vitamins, and minerals.
Nutritional Value of Insects used in Livestock, Pets and Aquaculture Feed
The use of insects as livestock (cattle and poultry), pets and aquaculture feed has mostly been based on their potential function as nutrient concentrators, which is linked with their capacity to develop on low-quality substrate to produce high-quality protein and a variety of other important nutrient (amino acids. fatty acids, chitin, and melanin). Insects' nutritional value varies depending on the species, their diet and stage of development. In general, they are an excellent energy source, high quality protein and a variety of vitamins and minerals (Williams et al., 2016). Table summarizes the nutritional composition of the 11 insect species most commonly considered as livestock (cattle and poultry), pets and aquaculture feeding sources, with energy content similar to other protein-rich sources, such as soybean and fish meal.
Table: Nutrient composition (%) and energy content (MJ/kg) of Potential Insects Species used in Animal, Poultry and Aquaculture feed.