MATERIALS AND METHODS

The present work was carried out in two experiments: In the first experiment, the maggot production in the different substrate was evaluated, with and without attractive substances, in the second experiment, maggots produced from ruminal content was used as a protein substitute for fish meal in cockerel.

Experiment 1: Maggot production in the different substrates and attractive substances
Study area: The study was conducted at the Teaching and Research Farm of the University of Maroua, located in Maroua (latitude: 10°35'N, longitude: 14°19'E, altitude 384 m), from March-May, 2021. The climatic characteristics of the city at the time of the study were recorded in Table 1.

Production substrates and attractive substances: To assess the effect of the type of substrate on maggot production, three substrates were used: Ruminal content, cow dung and pig manure. The fresh cow dung and ruminal content were collected at the slaughterhouse of Makabaye in the Maroua 1 subdivision, meanwhile, the pig manure was collected from a private piggery in Makabaye. Fish waste, mango puree and fresh bovine blood were used as housefly attractive.

Experimental design: The maggot production was assessed in two tests. The first testing consisted of evaluating the production of three substrates (ruminal content, cow dung and pig manure) enriched with fish waste. For the second testing, the maggot production was evaluated in ruminal content enriched with fish waste, mango puree or fresh bovine blood. For each test, the experimental design consisted of 3 treatments repeated 3 times. Each repetition consisted of 6 half cans of 20 L.

In one container, 2 kg of substrate enriched or not with 250 g of attractants were introduced. After 24 hrs of sowing, the containers were covered with non-impregnated mosquito nets. The maggots were harvested on the 5th day after sowing.

Data collection: After harvesting, fresh maggot biomass was determined. The chemical composition was estimated accordingly to the methodology described by Helrich and AOAC²¹, at the lab of nutrition and animal feed of the Faculty of Agronomy and Agricultural Sciences (The University of Dschang).

Experiment 2: Growth performance and physiological status of cockerel fed maggot meal as a protein substitute for fish meal
A total of 40 cockerels (6 weeks), weighing 151.08±35.27 g, all from a producer of layer chicks, were used. They were allowed to acclimate for a week at the farm. Chicks were kept under similar environmental and managerial conditions during the experiment (5 weeks). Feed and water were given ad libitum in adapted equipment.

Experimental design: Birds were randomly allocated to 4 treatments, each containing 10 cockerels. The 4 treatment groups were, respectively fed different diets from the beginning to the end of a 5th week experiment. Formulated diets contained maggot meal (MM) substituting fish meal (FM) at graded levels, 0, 25, 50 and 75% (Table 2). Maggots were produced at the farm and sent for analysis at the Lab of nutrition and animals feed of the Faculty of Agronomy and Agricultural Sciences (The University of Dschang). Other ingredients were purchased from the local market.

Data collection: Feed intake, weight gain and feed conversion ratios were recorded weekly. The economic evaluation was also done by determining: Cost/kg feed consumed, Feed cost/kg weight gain. Estimations were done based on the local cost of each ingredient. In the 5th week of the experiment, blood was collected from an ulnar vein of 6 birds/treatment. Blood was collected into tubes containing the anticoagulant Ethylene Diamine Tetra-acetate (EDTA) to prevent clotting. Each blood sample collected was subjected to haematological analysis of Red Blood Cell (RBC), hemoglobin, Packed Cell Volume (PCV), erythrocyte indices and platelets in the laboratory. Haematological analyses were performed using an automatic analyzer, SNFS BC30S.

Data analysis: Data collected were presented as Mean±Standard Deviation. Data were subjected to a one-way analysis of variance (ANOVA) at a significance level of p<0.05 following the general linear model procedure. When differences were significant between means, the Tukey test was used to separate means. All statistical analyses were performed using GraphPad Instat 3.1.

RESULTS

Experiment 1: Maggot production
Type of substrate and attractants in production: The fresh biomass of maggot produced in three substrates (ruminal content, pig manure or cow dung) were presented in Fig. 1. Fresh biomass of maggot was significantly lower (p<0.0001) in cow dung as compared to values of this parameter obtained in other substrates.

The fresh biomass of maggot produced in ruminal content enriched with fish waste, mature mango puree or fresh bovine blood as illustrated in Fig. 2. Maggot production in ruminal content enriched with fish waste was significantly higher (p<0.0001) than that obtained with other attractants. However, the production registered in ruminal content enriched with mature mango puree or fresh beef blood was statistically (p>0.05) comparable.

Type of substrate and attractants on the chemical composition of maggot: The chemical composition of maggot produced in ruminant content, pig manure, cow dung or in ruminant content enriched with fish waste, mature mango puree or fresh bovine blood were summarized in Table 3. The highest values of dry matter, ash and fat and the lowest value of crude protein were recorded with maggot produced in ruminal content.

Maggot produced in ruminal content enriched with fish waste, mature mango puree or fresh bovine blood showed variation in crude protein content. The highest value was obtained with maggot produced in ruminal content enriched with fresh bovine blood.

Experiment 2: Growth performance and physiological response
Growth performance: Growth parameters of cockerel fed on diets containing maggot meal at the graded level were presented in Table 4. Results showed that the daily feed intake, daily energy intake, daily protein intake and the feed conversion ratio were not significantly (p>0.05) different between treatments. Although, the highest values of the daily feed intake, daily energy intake, daily protein intake and daily body weight gain were obtained with a diet containing only fish meal (R₀).

Fig. 1:

Fresh biomass of maggot produced in three different substrates Mean values with a different superscript in a row differ significantly ( p<0.05)

Fig. 2:

Fresh biomass of maggot produced in ruminal content enriched with fish waste, mature mango puree or fresh bovine blood Mean values with a different superscript in a row differ significantly (p<0.05)

The lowest value of feed conversion ratio was also registered in cockerel fed diet R₀. As compared to a diet containing only fish meal (R₀), the daily body weight gain of cockerels fed on a diet containing 75% maggot meal was significantly lower (p<0.01).

Production cost: The economic evaluation of the diets used in this study was presented in Table 4. It comes out from this table that the cost of kg feed consumed decreases with the increase of maggot meal in the diet. Inversely, feed cost per kg body weight gain increased with maggot meal quantity in diet. As compared to a diet containing only fish meal, the feed cost per kg of body weight gain, obtained in cockerels fed a 75% maggot meal diet, increased by 14.5%.

Haematological parameters: Irrespective of treatment (Table 5), Red Blood Cell count, Haemoglobin, Pack Cell Volume, platelet cell count and other haematological indexes were comparable (p>0.05).

DISCUSSION

Maggots of ordinary flies are increasingly considered in the world of animal feed. Numerous studies have thus contributed to highlighting some factors determining the production of maggots in various localities. In the present experiment, results revealed that fresh biomass was significantly lower in cow dung as compared to the quantity obtained in ruminal content of pig manure. This result could be attributed to the ability of each substrate to attract flies. Current results agreed with those of Itongwa et al.²², who reported a higher maggot production in ruminal content as compared to cow dung. Our findings showed that maggot production in ruminal content and pig manure were similar. This result is different from those obtained by Itongwa et al.²² who pointed out a significantly higher production in ruminal content as compared to pig manure. On contrary, Tendonkeng et al.⁸ reported higher biomass from pig manure. The heterogeneity between findings may be related to the fly families available in each production area or to the environmental temperature and humidity. Itongwa et al.²² revealed that the Muscidae family is more attracted by ruminal content meanwhile, the Calliphoridae family is more attracted by pig manure than by ruminal content. In our study, fish waste was added to all the substrates. Their presence could explain our results since Itongwa et al.²² showed that the Muscidae and Calliphoridae families are well attracted by fish waste. Our study identified those two fly families as predominant in our study area. During our experiment, the mean temperature was between 33-36°C and the humidity between 21 and 40%. These climate conditions were different to those of the study area reported by Tendonkeng et al.⁸ (21-33°C and >60%) or Itongwa et al.²² (15-19.5°C and 68-75%). The maggot biomass produced from ruminal content enriched with fish waste was significantly higher than those obtained from the same substrate enriched with mango puree or fresh bovine blood. These results agreed with those of Itongwa et al.²², who reported that fish waste is more attractive to Muscidae and Calliphoridae than mango peel.

The chemical composition of maggot revealed heterogeneity of value between substrates. Maggot produced from ruminal content expressed the highest value of fat (20.23% of dry matter) but the lowest content of crude protein (25.68% of dry matter) as compared to the value of the same parameters obtained from pig manure (fat: 10.08%, crude protein: 36.05%) or cow dung (fat: 9.03%, crude protein: 33.61%). These results agreed with those of Itongwa et al.²² who reported that maggots issued from ruminal content have lower crude protein and higher fat content as compared to maggots produced from pig manure or cow dung. As previously reported by Tendonkeng et al.⁸, the highest value of organic matter was obtained on maggot meal produced in pig manure.

Irrespective of the substrate, the crude protein content (25-36%) was lower than that reported by several authors (38-61%). This would be related to the drying method used. In this experiment, maggot samples were sun-dried while in many other studies, they were oven-dried. Aniebo and Owen²³ stated that the oven-dried method increases fat content and reduces crude protein content of maggot samples. Maggot samples produced in ruminal content enriched with fresh beef blood expressed the highest crude protein content (31.09%). Tendonkeng et al.⁸ pointed out that as compared to ruminal content, blood-enriched ruminal content produced significantly higher biomass of maggot.

Under similar environmental and managerial conditions, the growth performance of healthy animals is related to the nutritional value of their feed, their feed consumption as well as their digestibility efficiency. In this study, daily feed intake slightly decreased with the increase of maggot meal in the diet. This result can be explained by an adverse effect of maggot meal on the diet. It has been reported that the texture and colour of the feed containing maggots render the feed less palatable²⁴. These findings may also be related to the variation in diets energy and protein content. It is well established that any change in poultry nutrition, especially in energy or protein content is reflected in feed intake^2,25. Poultry eats primarily to satisfy their energy needs². Following this statement, our results showed similar values of daily energy intake between treatments.

Although, feed intake and energy intake were not statistically different between treatments, daily body weight gain was significantly lower (p<0.01) in 75% maggot meal (R₇₅) as compared to 100% fish meal diet (R₀). This result can be explained at least by better utilization of the diet containing only fish meals. In fact, with 61.3% of crude protein, a fish meal could provide more essential amino acids than a maggot meal used which contains 30.65% crude protein. According to several authors, maggot meal and fish meal can both provide all the then essential amino acids needed by chickens. However, their concentration depends on several factors among which total protein content of feed^17,26,27. A diet containing 75% maggot meal as a substitute for a fish meal could have supplied less quantity of essential amino acids needed for maintenance and muscle growth. Current results on daily protein intake showed that the lowest value of this parameter was obtained with a 75% maggot meal diet. This study’s findings agreed with those of previous studies which reported that better growth performance in broiler was obtained when fish meal substitution by maggot meal was not higher than 50%^6,17. Another possible explanation for the decrease of daily body gain of cockerel fed graded maggot meal content may be a result of specific interaction between fish and maggot when combined¹⁴.

Despite that the cost of kg feed consumed decreases with the increase of maggot meal in diet, feed cost per kg of body weight gain, obtained in cockerels fed 75% maggot meal diet, increased by 14.5% as compared to a diet containing only fish meal. These findings were in agreement with the values of the feed conversion ratio obtained in this study. These results showed that a diet containing only fish meal was better converted into body weight than that containing maggot meal used in this study.

One of the most important concerns about the use of maggots in animal feeding is the living model of the house fly, being a vector of pathogens¹⁴. Haematological parameters are usually used in the diagnosis of physiological or metabolic disorders. They are also used as physiological indicators of environmental or nutritional stressors^28,29. From current results, red blood cell count, haemoglobin, pack cell volume and platelet cell count were not affected by maggot meal incorporation. The values obtained in this study were within the normal range for chicken, which indicates no harmful effects of maggot meal on the health status of the birds³⁰. The present results are in line with the findings of Duwa et al.³¹ who reported that soybean replacement in rabbits with maggot meal (5%) showed no adverse effects on haematological indices.

CONCLUSION

Ruminal content enriched with fish waste is a good substrate for maggot production during the dry season, in an environment where the main fly families identified are Muscidae and Calliphoridae. Fish meal replacement by maggot meal should not exceed 50% in cockerel. Moreover, the house fly maggot meal can be used safely in cockerel nutrition. However, in the conditions of this experiment, a diet containing only fish meal showed the best growth performance and feed cost for meat. Taking into account the determining effect of temperature and humidity on maggot production, it will be interesting to evaluate the production during the other period of the year, in the same environment.

SIGNIFICANCE STATEMENT

Housefly larvae are increasingly considered a promising alternative to animal protein in the world of animal feed. For this purpose, projects on determining the factors required for optimal production of maggots and utilization have been implemented in various localities. This study identifies the main fly families in the Maroua area and some required conditions for the good production of maggots in the dry season. The present study also contributes to determining the optimal incorporation rate of locally produced maggots as a replacement for fish meals in the starter diet of a cockerel.