The use of live insect larvae to improve sustainability and animal welfare in organic chicken production

It is known that worldwide meat consumption has drastically increased over the last decades, especially in developed countries. Indeed, recent studies show that animal-based proteins consumption increased on average from 61 g per capita per day in 1961 to 80 g per capita per day in 2011 (Sans et al.; 2015). This phenomenon is related to the rapid growth of global population, economic development of countries and urbanization (Godfray et al.; 2018). In fact, not only are countries getting richer (therefore increasing GDP and gaining access to foods that were once considered exclusive to the middle and upper class), but also meat is getting cheaper and quicker to produce (Sans et al.; 2015). Meat is now easier to produce mainly due to: 1) genetic selection of the animals: these animals are able to produce more in less time due to higher adaptability, quicker development and better feed conversion ratio (FCR) 2) selection of feed: due to the high requirements of farmed animals, nowadays feeds pre- sent high nutritional values and are especially high in proteins 3) innovative farming systems: thanks to the constant research, we can now increase the welfare of farmed animals, therefore increasing productivity (Brameld et al.; 2016). As stated before, meat consumption increased worldwide but some countries underwent strong economic transitions and are now consuming more meat than other countries. Among these, we can find Argentina, Australia, Brazil, Chile, China, New Zealand and U.S.A. The only exception to this trend is India, where most of the population prevalently consumes a vegetarian diet. This country doesn’t show any important change in meat consumption over the last decades(www.ourworldindata.org). The type of meat consumed changes across each country. On average, poultry and pork are the most consumed worldwide (www.fao.org). In 2018 FAO estimated that roughly 69 billion chickens were slaughtered for meat produc- tion. The countries with the highest poultry density are Brazil, China and U.S.A (www.fao.org). With this data overview, it is interesting to understand why poultry meat is largely consumed and why it is convenient to raise chickens for meat. It is well known that chickens underwent an important selection within the past decades. The same genetic stock can grow globally, under any type of husbandry conditions. Through the genetic selection, the chickens’ weight has dramatically increased, yet the FCR has de- creased (Brameld et al.; 2016). 2 Chickens specifically reared for meat are called broilers. These animals underwent a strong selection in order to reach market weight at a very young age as, broilers are slaughtered at 43 days of age, on average (Bianchi et al.; 2007). In 1985, broilers at 35 days of age required 3.22 kg of feed to reach a weight of 1.4 kg and had a FCR of 2.3. In 2010, broilers only required 3.66 kg of feed in order to reach a body weight of 2.44 kg at 35 days, with a FCR equal to 1.5 (Siegel et al.; 2014). In other words, modern broilers are able to produce more meat while consuming less feed. This development obviously comes with health implications since artificial selection led to several health and welfare problems. Broiler diseases may depend on their genetics and physiology. Moreover, also the farming condition can affect diseases development. Among the several diseases that affect broilers we can find: 1) Cardiovascular dysfunctions: broilers are selected to abnormally develop their breasts and thighs. The organs, on the other hand, do not grow proportionally to the targeted muscles. This incongruous ratio between energy-supplying and energy-consuming or- gans leads to various metabolic disorders, such as ascites and “sudden death syndrome” (Baghbanzadeh et al.; 2008). a) Ascites (picture 2) is characterized by myocardial hypertrophy and dilatation, abnor- mal liver function, pulmonary insufficiency, and hypoxemia (Luger et al.; 2003) b) SDS (“sudden death syndrome”) mainly affects fast-growing chickens. Suddenly the broiler, even though it appears to be healthy, flaps its wings, fallsto the side and dies. This all happens under a minute (Newberry et al.; 1987). In Europe this syndrome usually affects 3% of birds (Turner et al.; 2014). 2) Skeletal dysfunctions(picture 3): varus and valgus deformities, osteodystrophy, dyschon- droplasia and femoral head necrosis are common in broilers. These dysfunctions lead to a severe lameness in the chickens, inducing them to spend more time lying on the ground and sleeping. If the broilers spend too much time lying down, under the abnormal weight of their bodies, not only can they suffocate, but also, they will develop integument lesions (Juliani; 1998). 3) Integument lesions: these birds are often subjected to dermatitis (e.g.: hock burn, footpad lesions), hyperkeratosis and necrosis of the epidermis (picture 4). This is not only due to the poor blood circulation, but also due to the prolonged contact with the ammonia in the litter (Greene et al.; 1985). Another issue related to the production of poultry meat is its important environmental im- pact. Feeding poultry requires a huge quantity of feed and these animals annually excrete important amounts of nitrogen and phosphorus to the environment, which conditions the production sustainability of this chain (Andretta et al., 2021). Nevertheless, poultry produc- tion has been found to be relatively environmentally friendly compared to other livestock productions, such as that of cattle. (Leinonen et al., 2016). The environmental impact of poultry production can roughly be divided into feed production and transportation, housing emissions and manure emissions. One of the main critical aspects related to poultry production is the amount of feed necessary to grow these animals. These feeds are particularly high in proteins, in order to satisfy the high requirements of chickens. Poultry feeds are made of cereals and their by-products (e.g.: corn, wheat, corn gluten meal), vegetable protein meals (such as soybean meal), oils, vita- mins and minerals. The most important protein source in poultry feed is soybean, usually given as a meal. This ingredient is high in proteins, low in fibers and high in lysine and tryptophan (even if deficient in methionine). Soybean meal is relatively inexpensive com- pared to other protein sources, such as corn gluten meal. The main issue related to soybean isthat it has a strong impact on the environment, mainly due to the fact that in the past couple of decades some areas around the world (like South America and South Asia) have been converted from natural foreststo soya crops (Kastens et al.; 2017). Then this ingredient must be transported to the feed mills around the world (mainly Europe, America and Asia). The loss of ecosystem carbon storage as a consequence of such conversion was added to the carbon dioxide emissions, therefore to the global warming potential arising from this system (Leinonen et al; 2016). For what concerns the housing emissions, recent studies show an important difference in terms of emissions based on the type of housing system. Three systems were taken into consideration: standard (indoor), free range and organic. Studies show that less intensive poultry systems had higher environmental impacts compared to the more intensive ones (Leinonen et al; 2016) in such way: organic systems have higher contributions in terms of eutrophication potential and acidification potentials (due to the emissions of NH3 and N2O), but extensive poultry production can reduce the use of fossil fuels, fertilizers and has lower housing emissions (Leinonen et al.; 2016). Although organic systems show less manure in the litter, it still has an environmental impact. On average, a single broiler excretes 0,6kg of N and 0,1kg of P each year. The amount of N found in the uric acid, expresses as kg/year, is equal to 0,5 (Rotz; 2004). Usually, poultry manure is used as a fertilizer, although it must be 6 used with caution due to the high concentration of N, P and K. If used incorrectly, it could severely damage the crops and it could lead to the excessive eutrophication and acidification of the soil (Leinonen et al.; 2016). Despite what preceded, how could we possibly reduce the environmental impact of poultry meat production? Scientists all over the world are trying to find new farming strategies in order to produce high quality meat with a lower environmental impact. Genetic selections, as stated before, has improved the FCR of animals (chickens can now produce more while eating less feed, at a faster rate), but the main ingredients in feed cannot be totally substituted now. The main challenge nowadays is to find an appropriate substitute for soybean meal, which is known to be the least environmental-friendly ingredient. The purpose of the project POULTRYNSECT is to test the effects of live insect larvae on slow and medium-growing organic chickens to allow sustainable meat production and to improve animal welfare. Insect larvae are reared on organic food by-products and are used as feed ingredient and environmental enrichment for chickens.