Background and Objective: To address the increasing pressure on the environment and feed costs in livestock, a sustainable production system with non-conventional feedstuff is an urgent priority. This study aimed to investigate the recycling potential of black soldier fly larvae (BSFL) on hatchery waste and the effect of larval biomass to serve as a protein ingredient in the diet of Brahma chicken. Materials and Methods: BSFL (4 day-old) were randomly distributed into three formulated diets D1 (66.33% of mango waste plus 33.33% of hatchery waste), D2 (66.33% of kitchen waste plus 33.33% of hatchery waste), D3 (chicken waste plus 33.33% of hatchery waste) in a completely randomized design. Larvae obtained from these substrates were further tested as protein sources in Brahma chicken feed. In a 12 week feeding trial, 54 chicks (21 days old) were randomly assigned to 3 treatments containing 0, 2.5 and 5% of black soldier fly larvae meal (BSFLM) as a replacement for fish meal. Results: Formulated diet significantly (p<0.05) affected larval biomass. The highest larval weight was recorded in D2. The Brahma chicken growth and carcass traits remained comparable across all the treatments. Incorporation of BSFLM in the diet decreased the level of red and white blood cells in Brahma chickens. The Brahma chicken intestinal microbial load was not affected by diet. As compared to the control group, the diet containing BSFLM had the lowest production cost. Conclusion: Black soldier fly larvae can be used as a source of proteins in the diet of Brahma chicken and can fully replace fishmeal with minimal effects on blood biochemistry and hematology.
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The ever-growing world population raises critical questions about our future ability to produce adequate food for all1. Earlier estimates postulate a 70% increase in global food production by 2050 to meet the additional need for food and feed2. Like other developing countries, the population growth rate in Cameroon is estimated at 2.54%3. In response to this population growth, the government of Cameroon has decided to intensify the production of short-life-cycle species like poultry and pigs4. This move by the government has led to a double increase in the production of poultry products in Cameroon in the last 20 years, representing about 55% of the livestock sector and contributing about 30% of the Gross Domestic Product (GDP). This is in line with the FAO's report entitled "The Shadow of Livestock" showing that the demand for livestock in the world will double in the next 50 years, i.e. from 229 million tons currently to 465 million tons2. However, the sector, which provides employment, nutrition and a source of livelihood to many, both in rural and urban settings is weakened by the high costs of feed, especially essential feed ingredients such as soy meal and fishmeal. Indeed, feed represents about 60-70% of the total production costs in the poultry sector. The increasing scarcity of protein ingredients is prompting the animal feed industry to explore sustainable alternatives to save the sector and above all to satisfy the entire production chain. Besides, it has been established that the growing demand for feed has potentially negative consequences on the environment in terms of greenhouse gas emissions and further implications for water, energy, land use and waste management5,6. The FAO advocates the use of insects for food and feed. Insects are a good source of energy, protein, fat, vitamins and minerals7. The breeding of insects is also more environmentally friendly, as insects produce fewer greenhouse gases and emit less ammonia than conventional livestock8. Indeed, insects have a higher feed/protein conversion ratio than cattle, pigs and poultry9. Thus, in recent years, there has been a significant increase in the number of studies and businesses associating the application of insect production with recycling and animal feed10,11. Of particular interest is Hermetia illucens commonly known as the black soldier fly (BSF). The larvae of BSF are rich in nutrients (lipids: 35% and proteins 55%) with a well-balanced essential amino acid profile12,13. BSF-based technology stands as an evergreen technology to boost food availability (animal protein and crop productivity) and contribute to a safe environment in line with the Sustainable Development Goals (SDGs) 2 (zero hunger) and 6 (clean water and sanitation)14,15. The larvae of BSF convert low-value organic waste such as coffee waste, distillery grain, vegetable waste, decaying fruit, urban organic waste, fish waste, human feces and animal manure into insect protein that can be used to feed chickens without negatively affecting their growth parameters16,17.
The production of chickens and related products generate tremendous amount of hatchery waste, which includes solid waste and wastewater. The solid hatchery waste comprises empty shells, infertile eggs, dead embryos, late hatchings and dead chickens and a viscous liquid from eggs and decaying tissue Glatz et al.17. Current disposal methods for solid hatchery waste include landfill, composting, rendering and incineration, which costs money and increases the total cost of poultry production each year17,18. The efficient management of these waste streams would require strategies that minimize costs and negative environmental impacts. Hatchery waste is rich in protein, moisture, fibre and energy17,19. Further development of these waste streams into animal feedstuffs or direct application into the soil as an organic fertiliser has great potential. However, direct soil applications could potentially pollute the environment, including groundwater17,20. Several methods of handling hatchery waste have been considered with both positive and negative implications. Recently, the use of insects such as the black soldier fly larvae in sustainable organic waste management has received growing attention globally but little is known about the use of this innovative technology in hatchery waste management. Therefore, this study aimed at investigating the potential of BSF larvae to recycle solid hatchery waste as well as use larvae reared on these waste streams in feed for chickens.
MATERIALS AND METHODS
Study area: The study was conducted at Obala Agricultural Institute School Farm in Bilone, located in the Center Region of Cameroon with 4°10’ North latitude and 11°31’ East longitude. At 542 m above sea level, Bilone has a mean temperature of 25°C. The general care and management of the animals followed the same guidelines as for organic farms. In this system, birds did not receive chemical medicine but were provided with a powder mixture of medicinal plants Moringa (25%), garlic (15%), thyme (25%), pepper (15%), dry aloe vera (10%), dry papaya seeds (10%). This mixture served as an antibiotic, internal deworming, hepato-protector and anticoccidial agent and was administered twice a week.
Insect colony: Black soldier fly larvae used in this study were obtained from a 5 years old domesticated colony maintained at 28°C, 60-70% RH and 12 hrs photoperiod. Male and female BSF were housed in a cage (2 m×1 m) also referred to as a love cage with the sides, top and bottom and covered with a mosquito net material. Moist hatchery substrate in plastic containers was placed inside the cage to serve as an oviposition attractant. BSF eggs were collected on pieces of cardboard with flutes along the edges and placed on the surface of the oviposition attractant21. Eggs laid were allowed to hatch and feed on chicken feed for 4 days. This allowed larvae to grow and enabled their safe and easy collection and use in the experiments.
Substrates formulation for black soldier fly larvae: Hatchery waste including a mixture of unhatched eggs, egg shells and dead chicks were obtained from Obala Agricultural Institute School Farm hatchery. Three different experimental diets were prepared by mixing the hatchery waste with mango waste, kitchen waste and chicken manure to obtain the following larval diets:
- D1 :
- D2 :
- D3 :
|66.33% of mango waste and 33.33% of hatchery waste|
|66.33% of kitchen waste and 33.33% of hatchery waste|
|66.33% of chicken manure and 33.33% of hatchery waste|
The incorporation was choice in order to maintain the same physical aspect of the substrate in each diet. The mango waste was consisted of rotten fruits without pits. Kitchen waste was consisted of boiled cassava root, cooked maize meal, vegetable and groundnut soup. Chicken waste was consisted of chicken manure from birds fed on a conventional diet (soya bean cake, maize, cotton seed cake and wheat bran). Hatchery waste was obtained after hatching ended. After formulation, each test substrate was maintained at 70-78% humidity by adding water as necessary.
Larval performance: One gram of 4 days old larvae were transferred into 150 g of diets each: D1, D2 and D3 in 3 tanks and allowed to feed. On days four and eight, 200 and 150 g of each diet, respectively were added to the respective tanks. Overall, each tank received a total of 500 g of the test diet at the end of the trial.
The larvae were harvested on day 12 and slaughtered by placing them in boiled water for 5 min. Thereafter, the slaughtered larvae were sun-dried and milled to obtain a black soldier fly larval meal for subsequent use in poultry diet formulation.
Chemical analysis of insect larval meal: Before its incorporation into the poultry diet, 50 g of the larval meal from each treatment was oven-dried for 48 h at 60°C. These samples were then transferred to the Laboratory of Animal Production and Nutrition and the Laboratory of Soil Sciences and Environmental Chemistry of the University of Dschang for proximate and mineral analysis respectively. The proximate analyses included dry matter, crude protein, crude fat, crude fibre and ash and were performed according to standard protocol provided by the Association of Official Analytical Chemists (AOAC)22, while the mineral composition [Calcium (Ca), sodium (Na), potassium (K), phosphorus (P) and magnesium (Mg)] was determined according to the protocol described by Pauwels et al.23.
Formulation of insect-based diets for laying hens: From a control ration containing fishmeal as the main source of protein, two other rations were formulated by replacing fishmeal with BSF larval meal (BSFLM) as shown in Table 1 and 2. The test diets were formulated according to the NRC24 specifications for laying hens. At each phase (starter and grower-finisher), three experimental iso protein and isoenergetic rations were formulated. Diets were prepared by replacing the fish meal content in the conventional diet (control diet) with BSFLM at 2.5 and 5% (Table 1 and 2).
Poultry management: A total of 72 Brahma chicks (36 males and 36 females) aged 28 days and weighing on average 285 g were used in this study. Birds were randomly assigned to three experimental groups (based on BSFLM incorporation rate) with four replicates of 6 birds each (24 birds per treatment). The number of animals used in this study was based on the available resources and ethical considerations (since the birds would be slaughtered at the end of the growing period). The control group received a commercial feed without BSFLM (BSFLM 0%) and the experimental groups (BSF groups) received the same commercial feed with 2.5 and 5% of black soldier fly larvae meal (BSFLM) as a replacement for fish meal. Birds were housed under identical conditions: same building, photoperiod (12 hrs of light and 12 hrs of dark), natural ventilation system and sawdust floor-bedding. The experiment lasted for 72 days. Feed was supplied ad libitum throughout the experiment.
Black soldier fly larval growth performance and waste reduction: Larvae were weighed at 4 day intervals till the end (day 12) using a 0.01 g sensitivity balance of the Aroma brand to compare larval growth performance among diets. At the end of the larval phase, mortality was recorded. Residual waste was collected in each container and weighed using the same scale. The recycling parameters of BSFL evaluated include: waste reduction index, waste reduction rate and larval bioconversion rate11, which were calculated as follows:
Growth, carcass and hematological characteristics of Brahma chickens: Body weight, body weight gain and feed intake of chickens were recorded weekly for each replicate. At the end of the 72 days, six birds per treatment were randomly selected and slaughtered (after 12 hrs of feed deprivation), weighed and eviscerated. Feed conversion ratio (FCR) was defined as the ratio of the amount of feed ingested throughout the rearing period to the body weight gained during that period. Dressing-out percentages were computed as the ratio between warm carcasses and live weights at slaughter. The length of the intestine was measured from the duodenal loop to the cloaca using a tape measure. The density of the intestine was calculated using the following equation:
During the slaughter process, 04 mL of blood was collected in two test tubes, one with EDTA and one without EDTA. Blood was transferred to the laboratory for hematological analysis. The hematological parameters mainly the white blood cell, red blood cell, platelet and hematocrit were analyzed using an automatic hemocytometer, Genius, model K-T 6180. Blood containing anticoagulant was centrifuged at 3000 rpm for 15 min, then the serum was collected and stored in a freezer at -20°C until analysis of aspartate aminotransferase, alanine aminotransferase, total protein, globulin, urea, triglycerides, creatinine and cholesterol as describe by Abdel-Fattah et al.25.
Caecal microbiota: Faeces from each animal slaughtered during carcass evaluation were collected in sterile plastic tubes and directly submitted for microbiological analysis. The bacterial colonies sought were salmonella, enterobacteria, Escherichia coli and lactobacillus. The determination of the number of colonies involved a dilution with distilled water of 1 g of faeces in 9 mL, then 1 mL of the mixture was diluted 6 times consecutively in the tubes also containing 9 mL of distilled water to reduce the concentration of bacteria and to facilitate enumeration. From tubes 2, 4 and 6, 1 mL of the mixture was transferred into culture media previously heated to 60°C in a tight bath or an autoclave and cooled to 50°C. After the mixture had solidified, each jar was stored anaerobically (lactobacillus) or aerobically (salmonella, enterobacteria and E. coli ) in an incubator at 37°C. The colony count was performed twice: the first count was 24 hrs after incubation and the second was 48 hrs after incubation. The number of colonies were determined using the jar which had the lowest number of spots, then this number was multiplied by the power indicated by the number of the jar (102, 104 or 106).
Profitability: The cost per kilogram of feed was estimated from the price of ingredients on the local market at the time of the study. The cost of feed consumption was obtained by multiplying the average consumption of the animals by the price of the corresponding kg of feed. The cost per kilogram of feed multiplied by consumption index was used to calculate feed cost per kilogram of live weight of chickens26.
Data analysis: Data on feed intake, body weight, carcass characteristics, development of digestive organs, cost of production and blood biochemical parameters were subjected to one-way Analysis of Variance (ANOVA). When there was a significant difference between the treatments, the means were separated using Duncan's test at the 5% significance level. Statistical Package for Social Sciences (SPSS 21.0) was used for these analysis.
Recycling parameters of hatchery waste: Apart from the final live weight which was significantly (p<0.05) affected by diet, all other BSFL growth parameters were not affected by diet (Table 3). However, the association of hatchery waste and poultry feces (D2) recorded the highest biomass production.
The results of the reduction efficiency and the bioconversion rate are presented in Table 4. Except for feed intake and the reduction rate which were significantly affected by the type of diet, all other characteristics were comparable between the different substrates.
Consequently, feed intake recorded in D2 was significantly higher (p>0.05) than that of D1 and D3. This lowest waste reduction rate was recorded in D2 diet. On the other hand, the bioconversion rates and the reduction efficiency presented comparable results (p>0.05) in all groups.
Growth performance of brahma chickens: The inclusion of BSFLM in feed did not impair (nor did it improve) the growth performance of Brahma chickens as none of their growth performance was significantly affected (p>0.05) (Table 5). However, with treatment BSFLM5, which contained the highest level of larvae meal (5%) in the diet, heavier birds were recorded.