Abstract
Rearing black soldier fly is an efficient way to dispose of organic waste by converting them into protein-rich feed to substitute animal- and plant-based sources in animal feeds. The objective of this study was to determine the optimal inclusion level of black soldier fly larvae meal (BSFLM) as a substitute for soybean meal (SBM) in broiler diets and evaluate the impact on growth and carcass characteristics. Five isonitrogenous diets (D) (20% crude protein, CP) and isocaloric (3,200 Kcal/kg) were formulated such that BSFLM substituted SBM at 0% (control, D1), 25% (D2), 50% (D3), 75% (D4), and 100% (D5) on a protein basis. A total of 270 broilers (Cobb 500) were randomly assigned to the five treatments in triplicate per diet. BSFLM displayed higher fat content (44.84 ± 0.08%). Average daily feed intake (ADFI) decreased with an increase in BSFLM in the diets (p = 0.004). However, overall weight (OW) was high (1,296.97 ± 46.19 g) on 100% substitution of SBM with BSFLM (D5). Breast fat content averaged 6.06 ± 0.97 g for D1 and 15.30 ± 0.5 g for D5. This study has demonstrated that BSFLM can partially or wholly replace conventional SBM in the diet of broiler chicken.
HIGHLIGHTS
Black soldier fly converts organic waste into protein-rich feed for animals.
Black soldier fly larvae meal diets provided better growth for broiler chicken.
Carcass characteristics significantly improved on birds fed with black soldier fly larvae meal.
INTRODUCTION
In developing countries, effective and sustainable fecal sludge management poses a sanitation challenge. The application of conventional sewer-based approaches has been limited by the high capital and maintenance requirements. Thus, onsite systems (such as pit latrines and septic tanks) have been widely adopted by 2.7 billion people globally (Strande 2014; Riungu 2021). However, safe collection, transportation, and treatment of the fecal sludge generated from onsite systems are not always guaranteed, and fecal waste is dumped in river bodies, open drains and streets, compromising public health (Lalander et al. 2013; Mberu et al. 2016).
Recent technological advances have seen the development of cost-effective technologies, such as urine-diverting dry toilets (UDDTs), pee poo bags, pour flush toilets connected to septic tanks (Strande 2014). Several effective, sustainable, and environmentally friendly management technologies have been proposed to manage the waste generated from these systems: biogas, composting, vemi-composting, black soldier fly (BSF), struvite precipitation, etc. (Strande 2014). These technologies have adopted the circular economy model which promotes the conversion of waste generated into valuable resources, i.e. nutrients available in waste are harnessed and thereafter put back in the matter cycle (Riungu 2021).
Rearing BSF (Hermetia illucens) technology is an efficient way to dispose of organic waste by converting it into protein- and fat-rich feed (Van Huis et al. 2013; Makkar et al. 2014; Wallace et al. 2017; Danieli et al. 2019). In waste management, using BSF larvae has shown a reduction in weight of between 25–55% and 66–70% of total fresh fecal wastes and domestic wastes, respectively (Diener et al. 2009; Banks et al. 2014). Also, BSF larvae effectively destroy pathogenic microbes found in human or animal fecal wastes (Banks et al. 2014). The BSF larvae can then be used to produce black soldier fly larvae meal (BSFLM). The meal can be used as an ingredient in livestock diets because of its high crude protein and lipid content. The BSFLM contains consistent essential amino acids and fatty acids when grown in diverse substrates (Rumpold & Schluter 2013; Spranghers et al. 2017; Gasco et al. 2018).
In the poultry industry, feed represents 60–70% of production costs where energy and amino acids account for more than 90% of this cost (Kiarie et al. 2013; Van Huis et al. 2013). The high cost of poultry feed is mainly due to the use of soybean meal (SBM). SBM is a plant-based source of protein and fat in poultry feed but it is scarce and expensive. In terms of nutrients, SBM is limited in sulfur amino acids (methionine and cystine) and contains trypsin inhibitor that hinders the activity of the proteolytic enzyme's trypsin and chymotrypsin in monogastric animals. This results in low protein digestibility (Liu 1997). In contrast, BSF larvae are cheap, easy to rear using domestic organic waste, and can provide high-value protein with a better amino acid profile compared with that of SBM (Tran et al. 2015). Studies have indicated that BSFLM can replace SBM in broiler diets to some extent. Onsongo et al. (2018) fed 11.0, 37.2, and 55.5% of the crude protein in the finisher feed of diets to broilers and concluded that replacement of SBM with BSFLM did not affect daily body weight gain and feed conversion ratio (FCR). Similarly, Popova et al. (2020) fed diets containing 5% full fat and partially defatted BSFLM and found that there was increased body weight gain. However, there was a significant effect on the carcass characteristics. Few studies have examined optimal inclusion levels of BSFLM when replacing SBM in broiler diets. This study, therefore, evaluated the growth performance and carcass characteristics of broiler chicks fed on diets containing BSFLM as a substitute for SBM at the finisher phase.
MATERIALS AND METHODS
Study site
The experiment was conducted at Meru University of Science and Technology, Kenya – Sanitation Research Institute.
Preparation of diets
All feed ingredients (Table 1) were obtained from local reputable animal feed dealers. However, black soldier fly larvae were reared at Meru University of Science and Technology – Sanitation Research Institute using fecal matter as the feed substrate. The larvae were harvested and sundried for 14 days. The dried larvae were then ground into powder. To ensure that the processed larvae were safe for incorporation into animal feed, microbial load (Salmonella and Escherichia coli) was analyzed by culturing the BSFLM powder on nutrient agar and MacConkey agar. No growth was seen on the media after incubation at 37 °C for 24 h. This was indicative of the unique role of BSF larvae on pathogen inactivation (Lalander et al. 2013). Helminths and protozoans were analyzed using light microscopy. Physicochemical properties including human toxins as well as ecotoxins were obtained by analysing the BSFL powder sample using ultraviolet–visible spectrophotometry. The powder was then mixed with other raw materials to formulate five isonitrogenous diets (20% CP) and isocaloric (3,200 Kcal/kg metabolizable energy) such that BSFLM substituted SBM at 0% (D1) – control; 25% (D2); 50% (D3); 75% (D4); and 100% (D5) on crude protein basis (Table 1). The feed was formulated to meet the nutrient requirements for broiler finishers (National Research Council 1994).
Ingredient composition (%), calculated crude protein (%), and metabolizable energy (Kcal/kg) of diets for broiler finisher containing black soldier fly larvae meal as a replacement of soybean meal
Ingredient . | D1 (0%) . | D2 (25%) . | D3 (50%) . | D4 (75%) . | D5 (100%) . |
---|---|---|---|---|---|
Soybean meal | 20 | 15 | 10 | 5 | 0 |
Black soldier fly larvae meal | 0 | 6.25 | 12.50 | 18.75 | 25 |
Fishmeal | 5 | 5 | 5 | 5 | 5 |
Sunflower meal | 4 | 5 | 5 | 5 | 5 |
Maize germ | 14 | 16 | 15 | 14 | 15 |
Maize meal | 37 | 34 | 34 | 34 | 32 |
Wheat pollard | 17 | 16 | 16 | 16 | 15 |
Dicalcium phosphate | 1.3 | 1.3 | 1.3 | 1.3 | 1.3 |
Sodium chloride | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 |
Limestone | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 |
Methionine | 0.05 | 0.05 | 0.05 | 0.05 | 0.05 |
Lysine | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 |
Broiler premix | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 |
Mycotoxin binder | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 |
Salinomycin | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 |
Total | 100.18 | 100.43 | 100.68 | 100.93 | 100.18 |
Crude protein (%) | 19.62 | 19.58 | 20.15 | 19.37 | 20.82 |
ME (Kcal/kg) | 3,008.44 | 3,129.70 | 3,254.82 | 3,379.33 | 3,507.37 |
Ingredient . | D1 (0%) . | D2 (25%) . | D3 (50%) . | D4 (75%) . | D5 (100%) . |
---|---|---|---|---|---|
Soybean meal | 20 | 15 | 10 | 5 | 0 |
Black soldier fly larvae meal | 0 | 6.25 | 12.50 | 18.75 | 25 |
Fishmeal | 5 | 5 | 5 | 5 | 5 |
Sunflower meal | 4 | 5 | 5 | 5 | 5 |
Maize germ | 14 | 16 | 15 | 14 | 15 |
Maize meal | 37 | 34 | 34 | 34 | 32 |
Wheat pollard | 17 | 16 | 16 | 16 | 15 |
Dicalcium phosphate | 1.3 | 1.3 | 1.3 | 1.3 | 1.3 |
Sodium chloride | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 |
Limestone | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 |
Methionine | 0.05 | 0.05 | 0.05 | 0.05 | 0.05 |
Lysine | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 |
Broiler premix | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 |
Mycotoxin binder | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 |
Salinomycin | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 |
Total | 100.18 | 100.43 | 100.68 | 100.93 | 100.18 |
Crude protein (%) | 19.62 | 19.58 | 20.15 | 19.37 | 20.82 |
ME (Kcal/kg) | 3,008.44 | 3,129.70 | 3,254.82 | 3,379.33 | 3,507.37 |
Diet code: D1, 0%BSFLM +100%SBM; D2, 25% BSFLM +75% SBM; D3, 50% BSFLM +50% SBM; D4, 75% BSFLM +25% SBM; D5, 100% BSFLM +0% SBM.
BSFLM, black soldier fly larvae meal; SBM, soybean meal; ME, metabolizable energy.
Analysis of samples
The proximate analysis of ingredients and diets was carried out as described by the AOAC (1990). Dry matter was calculated by the weight difference between before and after drying the sample in the oven at 135 °C for 2 h. The crude protein was determined using the Kjeldahl method. Ash was determined by heating the samples in a muffle furnace set at 550 °C for 4 h. Ether extracts were carried out through the Soxhlet extraction method. Nitrogen-free extracts (NFEs) were estimated by subtracting the total moisture, crude protein, ether extracts, ash, and crude fiber from 100. Neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) were determined sequentially by the method of Van Soest et al. (1991).
Growth performance trial
Evaluation of the carcass characteristics
At day 42, feed was withdrawn for 12 h but water was provided ad libitum in order to empty the digestive tracts. Fifteen birds were randomly selected from the five treatments (three birds from each diet type) and killed following the guidelines of animal welfare (Anderson 2005). Plucked and eviscerated carcasses were obtained after removing the head, neck, and feet. The spleen, liver, heart, gizzard (muscular stomach), and proventriculus (glandular stomach) weights were taken and recorded. The breast and thighs were then excised and weighed.
Data analysis
RESULTS
Proximate composition of feed ingredients
The proximate nutrient composition of feed ingredients is shown in Table 2. The main protein ingredients were as follows: BSFLM had a crude protein content of 39.40%, SBM (protein content: 47.10%), sunflower meal (protein content: 20.12%), and fishmeal (Rastrionaebola argentea) (protein content: 61.96%) (p < 0.05). Lipid content for BSFLM was highest (44.84%) (p = 0.000). Ash content was relatively low for all the ingredients except fishmeal (15.79%) but significantly different among the ingredients (p = 0.000). The crude fiber was high for wheat pollard (44.50%), sunflower meal (44.38%), and BSFLM (23.08%).
Proximate composition of feed ingredients (%) used to formulate broiler finisher diets
Ingredient . | Blacksoldier fly larvae meal . | Soybean meal . | Fishmeal . | Sunflower meal . | Maize meal . | Maize germ . | Wheat pollard . | p-value . |
---|---|---|---|---|---|---|---|---|
Proximate composition (%) | ||||||||
DM | 93.19 ± 0.02ba | 88.50 ± 0.08f | 89.58 ± 0.42ed | 94.02 ± 0.53ab | 87.40 ± 0.30g | 89.58 ± 0.03dec | 90.48 ± 0.26cd | 0.000 |
CP | 39.40 ± 1.19c | 47.10 ± 0.14b | 61.96 ± 0.65a | 20.12 ± 0.14d | 7.75 ± 0.25gf | 8.99 ± 0.14fg | 15.64 ± 0.17e | 0.000 |
EE | 44.84 ± 0.08a | 4.21 ± 0.07efg | 10.42 ± 0.08c | 14.35 ± 0.12b | 4.08 ± 0.02feg | 9.52 ± 0.07d | 4.02 ± 0.04gef | 0.000 |
Ash | 3.93 ± 0.05fde | 5.82 ± 0.12b | 15.79 ± 0.13a | 4.62 ± 0.26cde | 1.23 ± 0.10g | 4.25 ± 0.29dfce | 4.13 ± 0.20efcd | 0.000 |
CF | 23.08 ± 0.03c | 13.55 ± 0.36d | 4.11 ± 0.35g | 44.38 ± 0.49ba | 5.74 ± 0.19f | 8.15 ± 0.21e | 44.50 ± 0.20ab | 0.000 |
NFE | 18.04 ± 1.16de | 17.83 ± 0.62ed | 2.70 ± 0.07g | 10.55 ± 1.53f | 68.61 ± 0.12a | 58.67 ± 0.59b | 22.19 ± 0.05c | 0.000 |
NDF | 39.20 ± 0.69c | 34.82 ± 0.03ef | 36.01 ± 0.21d | 49.81 ± 0.33a | 47.80 ± 0.06b | 34.23 ± 0.30fe | 29.65 ± 0.38g | 0.000 |
ADF | 26.57 ± 0.17b | 4.33 ± 0.15c | 2.25 ± 0.02fge | 32.15 ± 0.18a | 1.64 ± 0.26gfe | 2.36 ± 0.09efgd | 3.01 ± 0.03de | 0.000 |
ADL | 14.79 ± 0.06a | 3.81 ± 0.06c | 0.23 ± 0.06g | 13.95 ± 0.20b | 1.06 ± 0.07fde | 1.22 ± 0.04dfe | 1.09 ± 0.12efd | 0.000 |
Ingredient . | Blacksoldier fly larvae meal . | Soybean meal . | Fishmeal . | Sunflower meal . | Maize meal . | Maize germ . | Wheat pollard . | p-value . |
---|---|---|---|---|---|---|---|---|
Proximate composition (%) | ||||||||
DM | 93.19 ± 0.02ba | 88.50 ± 0.08f | 89.58 ± 0.42ed | 94.02 ± 0.53ab | 87.40 ± 0.30g | 89.58 ± 0.03dec | 90.48 ± 0.26cd | 0.000 |
CP | 39.40 ± 1.19c | 47.10 ± 0.14b | 61.96 ± 0.65a | 20.12 ± 0.14d | 7.75 ± 0.25gf | 8.99 ± 0.14fg | 15.64 ± 0.17e | 0.000 |
EE | 44.84 ± 0.08a | 4.21 ± 0.07efg | 10.42 ± 0.08c | 14.35 ± 0.12b | 4.08 ± 0.02feg | 9.52 ± 0.07d | 4.02 ± 0.04gef | 0.000 |
Ash | 3.93 ± 0.05fde | 5.82 ± 0.12b | 15.79 ± 0.13a | 4.62 ± 0.26cde | 1.23 ± 0.10g | 4.25 ± 0.29dfce | 4.13 ± 0.20efcd | 0.000 |
CF | 23.08 ± 0.03c | 13.55 ± 0.36d | 4.11 ± 0.35g | 44.38 ± 0.49ba | 5.74 ± 0.19f | 8.15 ± 0.21e | 44.50 ± 0.20ab | 0.000 |
NFE | 18.04 ± 1.16de | 17.83 ± 0.62ed | 2.70 ± 0.07g | 10.55 ± 1.53f | 68.61 ± 0.12a | 58.67 ± 0.59b | 22.19 ± 0.05c | 0.000 |
NDF | 39.20 ± 0.69c | 34.82 ± 0.03ef | 36.01 ± 0.21d | 49.81 ± 0.33a | 47.80 ± 0.06b | 34.23 ± 0.30fe | 29.65 ± 0.38g | 0.000 |
ADF | 26.57 ± 0.17b | 4.33 ± 0.15c | 2.25 ± 0.02fge | 32.15 ± 0.18a | 1.64 ± 0.26gfe | 2.36 ± 0.09efgd | 3.01 ± 0.03de | 0.000 |
ADL | 14.79 ± 0.06a | 3.81 ± 0.06c | 0.23 ± 0.06g | 13.95 ± 0.20b | 1.06 ± 0.07fde | 1.22 ± 0.04dfe | 1.09 ± 0.12efd | 0.000 |
Values are expressed as mean ± SE (n = 3). Values in the same row with different superscript letters show differences (p < 0.05).
ADF, acid detergent fiber; DM, dry matter; CF, crude fiber; CP, crude protein; EE, ether extract; NDF, neutral detergent fiber; NFE, nitrogen-free extracts.
Proximate composition of diets
The proximate composition of the diets containing BSFLM as a replacement for SBM at 0, 25, 50, 75, and 100% on a crude protein basis is shown in Table 3. Crude protein values for the diets ranged between 18.42 and 20.45%. However, there were no significant effects between the treatments, p = 0.143. Ash content was highest (13.00%) for diet 1 and statistically different (p < 0.05) with D2, D3, D4, and D5. For crude fiber content, all the diets recorded almost similar figures (p = 0.000). Ether extracts increased with an increase in levels of BSFLM in the diets and D5 recorded the highest content (12.11%).
Proximate composition of broiler finisher diets (%) containing the blacksoldier fly larvae meal as a replacement of the soybean meal at 0, 25, 50, 75, and 100% on CP basis
Diet . | D1 (0%) . | D2 (25%) . | D3 (50%) . | D4 (75%) . | D5 (100%) . | p-value . |
---|---|---|---|---|---|---|
Proximate composition (%) | ||||||
DM | 88.92 ± 0.25decb | 88.78 ± 0.22edb | 89.31 ± 0.75cdeab | 91.00 ± 0.00ac | 90.25 ± 0.75bdec | 0.093 |
CP | 18.87 ± 0.34dabce | 20.45 ± 0.04adbc | 19.66 ± 0.66bdace | 19.63 ± 0.44cdabe | 18.42 ± 0.61edbc | 0.143 |
EE | 6.84 ± 0.17d | 6.00 ± 0.00e | 9.73 ± 0.31bc | 9.12 ± 0.15cb | 12.11 ± 0.19a | 0.000 |
Ash | 13.00 ± 1.00a | 6.75 ± 0.25dbce | 8.10 ± 0.80bdce | 8.70 ± 0.64cdbe | 7.41 ± 0.52edbc | 0.008 |
NFE | 41.67 ± 0.49dc | 47.23 ± 0.32a | 33.22 ± 0.34e | 44.05 ± 0.95bc | 43.79 ± 0.75cdb | 0.000 |
CF | 8.55 ± 0.24ced | 8.35 ± 0.31ecd | 8.61 ± 0.07b | 9.51 ± 0.03a | 8.54 ± 0.09dce | 0.000 |
NDF | 68.02 ± 0.05a | 41.89 ± 0.13bc | 41.73 ± 0.14cb | 37.86 ± 0.22ed | 37.89 ± 0.02de | 0.000 |
ADF | 31.09 ± 0.13a | 23.31 ± 0.32b | 7.27 ± 0.11de | 6.98 ± 0.10ed | 12.79 ± 0.09c | 0.000 |
ADL | 7.43 ± 0.15bc | 7.12 ± 0.11cb | 1.88 ± 0.01e | 9.16 ± 0.03a | 3.37 ± 0.16d | 0.000 |
Diet . | D1 (0%) . | D2 (25%) . | D3 (50%) . | D4 (75%) . | D5 (100%) . | p-value . |
---|---|---|---|---|---|---|
Proximate composition (%) | ||||||
DM | 88.92 ± 0.25decb | 88.78 ± 0.22edb | 89.31 ± 0.75cdeab | 91.00 ± 0.00ac | 90.25 ± 0.75bdec | 0.093 |
CP | 18.87 ± 0.34dabce | 20.45 ± 0.04adbc | 19.66 ± 0.66bdace | 19.63 ± 0.44cdabe | 18.42 ± 0.61edbc | 0.143 |
EE | 6.84 ± 0.17d | 6.00 ± 0.00e | 9.73 ± 0.31bc | 9.12 ± 0.15cb | 12.11 ± 0.19a | 0.000 |
Ash | 13.00 ± 1.00a | 6.75 ± 0.25dbce | 8.10 ± 0.80bdce | 8.70 ± 0.64cdbe | 7.41 ± 0.52edbc | 0.008 |
NFE | 41.67 ± 0.49dc | 47.23 ± 0.32a | 33.22 ± 0.34e | 44.05 ± 0.95bc | 43.79 ± 0.75cdb | 0.000 |
CF | 8.55 ± 0.24ced | 8.35 ± 0.31ecd | 8.61 ± 0.07b | 9.51 ± 0.03a | 8.54 ± 0.09dce | 0.000 |
NDF | 68.02 ± 0.05a | 41.89 ± 0.13bc | 41.73 ± 0.14cb | 37.86 ± 0.22ed | 37.89 ± 0.02de | 0.000 |
ADF | 31.09 ± 0.13a | 23.31 ± 0.32b | 7.27 ± 0.11de | 6.98 ± 0.10ed | 12.79 ± 0.09c | 0.000 |
ADL | 7.43 ± 0.15bc | 7.12 ± 0.11cb | 1.88 ± 0.01e | 9.16 ± 0.03a | 3.37 ± 0.16d | 0.000 |
Values are expressed as mean ± SE (n = 3). Values in the same row with different superscript letters are statistically different (p < 0.05).
Diet code: D1, 0%BSFLM +100%SBM; D2, 25% BSFLM +75% SBM; D3, 50% BSFLM +50% SBM; D4, 75% BSFLM +25% SBM; D5, 100% BSFLM +0% SBM.
ADF, acid detergent fiber; ADL, acid detergent lignin; BSFLM, black soldier fly larvae meal; DM, dry matter; CF, crude fiber; CP, crude protein; EE, ether extract; NDF, neutral detergent fiber; NFE, nitrogen-free extracts; SBM, soybean meal.
Performance of broiler chicks fed BSFLM-based diets
The effects of the replacement of SBM with BSFLM on broiler chicks' performance is shown in Table 4. The highest FW (2,262.26 g) was recorded in diet 5, whereas diet 1 recorded the lowest (2,102.43 g). OW showed a similar trend to that observed for FW. Average daily feed intake was high in diet 1 (144.04 g) and lowest in diet 5 (134.15 g). There was no treatment effect on FW (p = 0.530) and OW (p = 0.768). However, average daily feed intake (ADFI) and FCR were significantly different (p = 0.004 and p = 0.000, respectively).
Performance of broiler chicks fed with diets containing the black soldier fly larvae meal (n = 270)
Parameter . | Dietary treatments . | . | ||||
---|---|---|---|---|---|---|
D1 (0%) . | D2 (25%) . | D3 (50%) . | D4 (75%) . | D5 (100%) . | p-value . | |
IW (g) | 487.29 ± 5.70a | 482.67 ± 5.77a | 489.67 ± 5.79a | 493.19 ± 7.36a | 488.14 ± 5.37a | 0.808 |
FW(g) | 2,102.43 ± 43.29a | 2,147.33 ± 74.40a | 2,218.29 ± 71.74a | 2,178.43 ± 84.89a | 2,262.26 ± 65.85a | 0.530 |
OW(g) | 1,216.99 ± 41.04a | 1,268.08 ± 44.36a | 1,279.83 ± 45.41a | 1,274.11 ± 45.46a | 1,296.97 ± 46.19a | 0.768 |
ADG(g) | 57.68 ± 1.61ed | 59.45 ± 2.35dec | 63.57 ± 2.26acde | 64.08 ± 0.64abcd | 65.40 ± 1.53abc | 0.053 |
ADFI(g) | 144.04 ± 0.89abc | 143.38 ± 2.07abc | 140.31 ± 1.63abcd | 136.63 ± 1.59cd | 134.15 ± 1.31ed | 0.004 |
FCR | 2.50 ± 0.06ab | 2.42 ± 0.06ba | 2.21 ± 0.05cd | 2.13 ± 0.04dce | 2.04 ± 0.03ed | 0.000 |
Parameter . | Dietary treatments . | . | ||||
---|---|---|---|---|---|---|
D1 (0%) . | D2 (25%) . | D3 (50%) . | D4 (75%) . | D5 (100%) . | p-value . | |
IW (g) | 487.29 ± 5.70a | 482.67 ± 5.77a | 489.67 ± 5.79a | 493.19 ± 7.36a | 488.14 ± 5.37a | 0.808 |
FW(g) | 2,102.43 ± 43.29a | 2,147.33 ± 74.40a | 2,218.29 ± 71.74a | 2,178.43 ± 84.89a | 2,262.26 ± 65.85a | 0.530 |
OW(g) | 1,216.99 ± 41.04a | 1,268.08 ± 44.36a | 1,279.83 ± 45.41a | 1,274.11 ± 45.46a | 1,296.97 ± 46.19a | 0.768 |
ADG(g) | 57.68 ± 1.61ed | 59.45 ± 2.35dec | 63.57 ± 2.26acde | 64.08 ± 0.64abcd | 65.40 ± 1.53abc | 0.053 |
ADFI(g) | 144.04 ± 0.89abc | 143.38 ± 2.07abc | 140.31 ± 1.63abcd | 136.63 ± 1.59cd | 134.15 ± 1.31ed | 0.004 |
FCR | 2.50 ± 0.06ab | 2.42 ± 0.06ba | 2.21 ± 0.05cd | 2.13 ± 0.04dce | 2.04 ± 0.03ed | 0.000 |
Values are expressed as mean ± SE. Values in the same row with different superscript letters are statistically different (p < 0.05).
Diet code: D1, 0%BSFLM + 100%SBM; D2, 25% BSFLM +75% SBM; D3, 50% BSFLM +50% SBM; D4, 75% BSFLM +25% SBM; D5, 100% BSFLM + 0% SBM.
ADFI, average daily feed intake; ADG, average daily gain; BSFLM, black soldier fly larvae meal; FCR, feed conversion ratio; FW, final weight; IW, initial weight; OW, overall weight; SBM, soybean meal.
Carcass and organ characteristics of broiler chicks fed diets containing BSFLM
The results of carcass and organ characteristics are shown in Table 5. Diet 2 recorded the highest dressed weight (2,580.33 g) and diet 5 the lowest (1,928.00 g), p = 0.949. There were no significant effects on wings and breast meat (p = 0.323 and p = 0.488, respectively) between the treatments. Breast fat weight was highest (15.30 g) in diet 5 and lowest (6.06 g) in diet 1. Diet 4 had a higher heart weight (15.99 g) and spleen (3.83 g). Weights of internal organs (kidney and spleen) were statistically similar (p = 0.340 and p = 0.307, respectively).
Carcass and organ characteristics of broiler chicks fed with diets containing the black soldier fly larvae meal
Body parts . | Dietary treatments . | |||||
---|---|---|---|---|---|---|
D1 (0%) . | D2 (25%) . | D3 (50%) . | D4 (75%) . | D5 (100%) . | p-value . | |
Dressed weight (g) | 1,941.00 ± 132.04dbce | 2,580.33 ± 160.15abc | 2,357.67 ± 61.99bdace | 2,231.66 ± 115.56cdabe | 1,928.00 ± 190.14edbc | 0.033 |
Thighs (g) | 566.67 ± 29.24ecd | 600.67 ± 38.59cebd | 687.67 ± 19.24bca | 723.00 ± 26.03ab | 577.00 ± 42.53dec | 0.021 |
Wings (g) | 204.33 ± 16.27a | 232.67 ± 14.24a | 237.33 ± 5.55a | 222.33 ± 6.33a | 206.00 ± 17.62a | 0.323 |
Breast meat (g) | 695.00 ± 41.29a | 743.67 ± 82.83a | 833.33 ± 31.47a | 744.33 ± 58.32a | 661.00 ± 99.57a | 0.488 |
Breast fat (g) | 6.06 ± 0.97ed | 12.61 ± 1.74debca | 14.89 ± 4.48bdca | 14.41 ± 2.81cdba | 15.30 ± 0.57adbc | 0.134 |
Internal organs weight (g) | ||||||
Liver | 42.09 ± 3.81edbc | 47.00 ± 4.76dbce | 58.18 ± 3.79abc | 49.86 ± 3.65abcde | 49.38 ± 4.30cbeda | 0.163 |
Heart | 12.23 ± 1.34dcbe | 13.35 ± 1.39cdbea | 13.62 ± 0.88bdcae | 15.99 ± 0.75acbe | 11.44 ± 0.43eabcd | 0.081 |
Kidney | 14.87 ± 1.60a | 17.01 ± 2.27a | 18.25 ± 1.19a | 14.93 ± 0.99a | 13.82 ± 1.60a | 0.340 |
Spleen | 2.43 ± 0.66a | 2.42 ± 0.17a | 3.44 ± 0.57a | 3.83 ± 0.77a | 3.20 ± 0.11a | 0.307 |
Gizzard and proventriculus | 75.92 ± 1.70edb | 83.07 ± 4.82deb | 105.51 ± 6.75a | 91.63 ± 8.87ced | 94.93 ± 5.00bed | 0.044 |
Body parts . | Dietary treatments . | |||||
---|---|---|---|---|---|---|
D1 (0%) . | D2 (25%) . | D3 (50%) . | D4 (75%) . | D5 (100%) . | p-value . | |
Dressed weight (g) | 1,941.00 ± 132.04dbce | 2,580.33 ± 160.15abc | 2,357.67 ± 61.99bdace | 2,231.66 ± 115.56cdabe | 1,928.00 ± 190.14edbc | 0.033 |
Thighs (g) | 566.67 ± 29.24ecd | 600.67 ± 38.59cebd | 687.67 ± 19.24bca | 723.00 ± 26.03ab | 577.00 ± 42.53dec | 0.021 |
Wings (g) | 204.33 ± 16.27a | 232.67 ± 14.24a | 237.33 ± 5.55a | 222.33 ± 6.33a | 206.00 ± 17.62a | 0.323 |
Breast meat (g) | 695.00 ± 41.29a | 743.67 ± 82.83a | 833.33 ± 31.47a | 744.33 ± 58.32a | 661.00 ± 99.57a | 0.488 |
Breast fat (g) | 6.06 ± 0.97ed | 12.61 ± 1.74debca | 14.89 ± 4.48bdca | 14.41 ± 2.81cdba | 15.30 ± 0.57adbc | 0.134 |
Internal organs weight (g) | ||||||
Liver | 42.09 ± 3.81edbc | 47.00 ± 4.76dbce | 58.18 ± 3.79abc | 49.86 ± 3.65abcde | 49.38 ± 4.30cbeda | 0.163 |
Heart | 12.23 ± 1.34dcbe | 13.35 ± 1.39cdbea | 13.62 ± 0.88bdcae | 15.99 ± 0.75acbe | 11.44 ± 0.43eabcd | 0.081 |
Kidney | 14.87 ± 1.60a | 17.01 ± 2.27a | 18.25 ± 1.19a | 14.93 ± 0.99a | 13.82 ± 1.60a | 0.340 |
Spleen | 2.43 ± 0.66a | 2.42 ± 0.17a | 3.44 ± 0.57a | 3.83 ± 0.77a | 3.20 ± 0.11a | 0.307 |
Gizzard and proventriculus | 75.92 ± 1.70edb | 83.07 ± 4.82deb | 105.51 ± 6.75a | 91.63 ± 8.87ced | 94.93 ± 5.00bed | 0.044 |
Values are expressed as mean ± SE (n = 3). Values in the same row with different superscript letters show differences (p < 0.05).
Diet code: D1, 0%BSFLM + 100%SBM; D2, 25% BSFLM + 75% SBM; D3, 50% BSFLM + 50% SBM; D4, 75% BSFLM + 25% SBM; D5, 100% BSFLM + 0% SBM.
BSFLM, black soldier fly larvae meal; SBM, soybean meal.
DISCUSSION
Proximate composition of ingredients and diets
Proximate analysis is used in the initial evaluation of feeds and feedstuffs to provide information on their major nutrients. In the present study (Table 2), the proximate composition of fishmeal (Rastrionaebola argentea), SBM, sunflower meal, and maize meal was close to the values obtained by Maina et al. (2007); Kirimi et al. (2021); and Shumo et al. (2019). The disparity observed in nutrient composition could be due to the place of origin, production, processing methods, and adulteration by unscrupulous traders (Anjum et al. 2012; Kirimi et al. 2021; Munguti et al. 2021). In order to minimize variation, the ingredients were purchased from the same animal feed dealer and similar batches were selected. However, this can little address the issue of ingredient adulteration because unscrupulous dealers can add extraneous materials at any point within the animal feed value chain. The analyzed crude protein content for BSFLM was 39.40%, a figure lower than 47 and 43.90% reported by Sumbule et al. (2021) and Onsongo et al. (2018), respectively, but higher than 36.90% obtained by De Marco et al. (2015). Similarly, ether extract content in BSFLM was higher (44.84%) than 32.50 and 34.30% reported by Shumo et al. (2019) and Vilela et al. (2021). BSF larvae apparently store large quantities of fat as an energy source to carry through pupation. This may be responsible for the high-fat content in the meal (Oluokun 2000). The variation in crude protein and ether extract may be due to the substrate where the larvae are reared (Makkar et al. 2014). A study by Shumo et al. (2019) on BSF reared on different substrates (chicken manure, kitchen waste, and spent grain) had a crude protein of 41.10, 33.01, and 41.30% and fat content of 30.10, 34.30, and 31.02%, respectively. Thus, the quality and quantity of substrate play a substantial role in determining the body composition of the larvae. Substrates with quality protein and carbohydrates lead to enhanced development of BSF larvae, with high protein and fat content (Holeh et al. 2022).
The crude protein content of BSFLM (39.40%) was close to 38% for full-fat SBM (produced by heat treatment of whole soybeans) (Kirimi et al. 2021). This is a clear indication that BSF larvae are a good source of protein and fat and can be used as an ingredient in animal feeds (Sauvant et al. 2004; De Marco et al. 2015). The crude protein content of the experimental diets ranged from 18.42 to 20.45%. This was within the recommended range for broiler finisher feed (NRC 1994). The observed variation in crude protein content for the diets may be attributed to varying the ingredients in order to balance crude protein and other nutrients (Kirimi et al. 2021). Failure to analyze the ingredients crude protein prior to formulation might also have led to the variation. To minimize this, it is recommended to use actual analyzed figures when formulating feed. Successive substitution of SBM with BSFLM increased ether extract in the diets. This can be attributed to the high-fat content (44.84%) in BSFLM, the major protein ingredient substituting SBM in the diets. However, the range of fat content in the diets (6.84 and 12.11%) was above the recommended broiler ration (NRC 1994). Therefore, de-oiling BSFLM before inclusion in the broiler diets is necessary not only to reduce the fat content but also to increase the level of crude protein. This can be achieved by applying a tincture press to sliced larvae which facilitates leakage of intracellular fat (Kroeckel et al. 2012). The crude fiber content of BSFLM was 23.08%. Besides protein, BSFLM also contains higher levels of chitin which increase the fiber content of the diets. The high crude fiber content in BSFLM was not reflected in the diets. This was probably due to the high crude fiber (13.55%) in SBM hence the small range in variation. The crude fiber content in the diets was higher than recommended (2–5%) in broiler chick ration (NRC 1994). High levels of crude fiber in the diet decrease energy density thereby increasing feed intake (Elfaki & Abdelatti 2015; Bekele et al. 2020).
Growth performance and carcass characteristics
In relation to the broiler chicks’ growth performance (Table 4), BSFLM-based diets provided better performance than those fed diets containing conventional SBM (D1). Black soldier flies larvae meal being an insect-based ingredient is rich in key nutrients such as a crude protein with a high biological value, fat, and minerals (Makkar et al. 2014). There was a noticeable decrease in the average daily feed intake of birds with successive increases in BSFLM (25, 50, 75, and 100%) in the diets. This may be attributed to high-fat content as a result of increased levels of BSFLM with high fat (44.84%). This was translated to the diet, consequently increasing dietary energy density and thereby decreasing feed intake. However, despite a decrease in ADFI with increased levels of BSFLM in the diets, there was an increase in ADG among the birds. This was due to an adequate supply of nutrients to the birds provided by the various diet types (Sumbule et al. 2021). Poor growth performance in the control diet (SBM-based, 0% BSFLM) despite similar crude protein levels across the diets implies there was an adequate supply of nutrients to the birds. The nutrients were probably deficient in SBM which was the major protein ingredient being substituted by BSFLM. SBM is deficient in methionine and cystine (Kirimi et al. 2020) and contains proteinase inhibitors which reduce the availability of amino acids. However, there was the addition of limiting amino acids (methionine and lysine) across the treatments. This source of nutrients may have provided an extra supply of limiting essential amino acids, though it could not compensate for the deficient nutrients in the SBM-based diet (D1) that led to low growth performance. The quality of feed, therefore, is a function of the ingredients used and how well it meets the nutrient requirements of the birds.
In this study, an increase in organ weight with increasing levels of BSFLM, in the diets was observed (Table 5). The increase in gizzard and proventriculus may be due to the bulkiness of the diets containing BSFLM, hence the bigger volume of the gizzard (Oluokun 2000). The results are consistent with Fathalla et al. (2015) and Esonu et al. (2006) who reported an increase in gizzard and heart weight. This is attributed to an increased amount of work performed by these organs as a result of increased fiber digestion leading to organ hypertrophy (Molist et al. 2009). For the liver and kidney, the increase in weight was probably due to increased metabolism of high energy in BSFLM-based diets (Table 1) (Oluokun 2000). In relation to the breast's fat deposits, there was an increase in fat with increased substitution of SBM with BSFLM such that broiler birds fed a diet with 100% BSFLM (D5) had more breast fat. This may have been due to increased dietary energy intake in excess of body requirements (Ghaffari et al. 2007; Fouad & El-Senousey 2014). In this case, as the birds increased in body weight, the excess energy was deposited as breast fat. Excess fat has an effect on the carcass quality. It is worth noting that the dressed weight for the birds on D5 (Table 5) was lower than other diets despite recording the highest final body weight (Table 4). The discrepancy observed might be due to the fact that birds for slaughter were randomly picked and possibly those with lower body weight were selected; hence, low-dressed weight. However, the low-dressed carcass weight of birds despite being of the same strain might be due to metabolic differences and variation within the strain (Sumbule et al. 2021; Vilela et al. 2021).
CONCLUSION
The results of the present study showed that broiler chicken fed on BSFLM-based diets at all levels performed better in terms of growth and carcass characteristics than 100% SBM. Hence, BSFLM can totally replace SBM in broiler diets without negatively affecting the growth performance and carcass characteristics. However, more research is needed on the optimal inclusion levels. The focus should be more on de-oiling BSFLM in order to reduce the fat content and boost protein levels. The economics of using BSFLM should also be investigated and the possibility of production on a large scale to meet the market demand.
FUNDING
This work was part of the project ‘Towards Circular Economy-Based Sanitation Provision: An entry point to Cleaner, Healthier Cities’ funded through GCRF Block Grant funding 2020/2021.
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.
CONFLICT OF INTEREST
The authors declare there is no conflict.