Sustainable commercial maggot production (maggotry) for animal & aquafeeds in rivers state, South South Nigeria.Introduction
The costs of poultry and fish feeds have continued to increase in recent times. These high feed costs can be attributed to scarcity and high cost of feed ingredients particularly protein supplements. The cost of fish meal, the most guaranteed animal protein source has become prohibitive. Plant sources even though not balanced, are not cheap either. Good quality fish meal costs over $2.1 per kg, about thrice the cost of soyabean meal and four times the cost of groundnut cake (GNC). There is thus need for alternatives to these exorbitant protein sources. The development of non conventional protein supplements such as insect larvae in commercial quantity appears to be possible alternative. House fly larvae meal has been found to be not only rich in limiting essential amino acids, but also highly available to poultry, pig and fish, save that it is not yet available in commercial quantity. In other words, the development of insect larvae in naturally occurring decaying matter, particularly animal manure, and their use as protein sources have been widely reported only at experimental levels [1,2,3,4,5,6,7,8,9,10,11,12,13]. However, information on commercial models is lacking as all known authors and researchers are in agreement that commercial maggot production has not yet been developed and has remained the only bottle neck in the exploitation of this tested feed resource. The low cost protein emanating from this would encourage poultry, livestock and fish farmers, promote fish and poultry industry, and possibly lead to increase in animal production and consequent economic affordability of the needed animal protein. The objective of this study therefore is to develop a commercial model for sustainable maggot meal production via conversion of abattoir and other plant wastes to feed resource - a solid waste management strategy.
Materials and Methods
Daily and annual slaughter figures of two species of animals (cattle and goat) commonly slaughtered in Rivers State were monitored and determined using the Rumueme slaughter slab as a case study for 30 days. Blood potential of the slab was based on the average weight of blood yield per cow/goat from three categories (A,B,C) of each of the animal species. Official record of all registered slaughter slabs and their slaughter figures were obtained from the Rivers State Ministry of Agriculture. The actual blood yield at Rumueme Slaughter slab was used to project the Rivers State yield. Sample collection for substrate mixture (medium for larvae production) was carried out thrice per month for 12 months
Twenty-five kg of whole undiluted blood (WUB) was mixed with five kilogram of each absorbent material namely wheat brain (WB), rice dust (RD) and saw dust (SD) and exposed for biodegradation in an open sided space of 4.32[m.sup.2] demarcated into three equal parts of 1.44[m.sup.2] each. House flies laid eggs in the substrate which hatched into larvae and were harvested on the 5th day of substrate exposure. Altogether, there were three test absorbent materials (Table 1). Each of the three absorbent materials was mixed with WUB to form the substrates (representing three treatments) and were allowed to ferment for 48 hours. The odour of fresh blood and subsequently, the fermenting mixture attracted flies to enter and perch on the mixture through the opened front screen, which was closed on the 2nd day. Samples of the flies were captured and were identified by Entomologist as houseflies. HFLM per quantity of blood was determined from the most efficient treatment. Based on the projected daily and annual slaughter figures in the state, HFL potential in Rivers State was determined. Proximate analysis by  was used to determine the nutrient composition of blood and absorbent materials used in the substrate mixture. Data collected were subjected to analyses of variance procedure of  and means were separated using .
Results of blood yield (Table 2) showed that large cattle yielded significantly (P<0.5) more blood (16.16kg) than medium cattle (12.36kg) and small cattle (9.29kg), while large goats yielded significantly more blood (0.99kg) than both medium and small categories (0.61 & 0.56kg). Based on mean blood yield of 12.6kg and 0.72kg per cattle and goat respectively, the slaughter figures at Rumueme slab and projections made for the state, were 29 cattle and goats/day at Rumueme and 1,040-1,362 cattle and goats/day in Rivers State. The daily blood yield projection at Rumueme slab and Rivers State were 234.72kg and 6,744.2-6,897.5kg respectively (85,673kg and 2.461,633-2,518,000kg respectively per annum).
Results of maggot production (Table 3) revealed that WB + WUB (S1) yielded the highest quantity of maggot (7.16kg). the yield was significantly better (P<0.05) than S2 (RD+WUB) and S3 (SD+WUB) that yielded 2.46kg and 0.13kg respectively. Blood yield projection and maggot yield potential in Rivers State showed that 25kg WUB has the potential to yield 7.16kg wet maggot equivalent to 3.2kg dry maggot. Therefore, state daily blood output of 6,744.2-6,897.5kg has the potential to yield 1,932-1,975.2kg wet maggot (863-883kg dry maggot). The annual maggot potential in Rivers State from blood output of 2,461,633-2,518,000kg was 705,012-721,155kg (315,089 322,304kg dry maggot).
The significant (P<O.05) difference observed in the quantity of blood yielded by meat animals of different sizes agrees with the report that blood yield is a percentage of body weight . The total projected blood yield gives an insight of the actual volume of blood that is wasted on daily basis and the pollution load that is exerted on the surface water bodies adjoining slaughter houses in Rivers State. This is consistent with the findings of [18,19,20], that blood and gut contents were discharged directly into nearby water bodies where they constitute pollution threat to aquatic life. This supports the report that facilities for waste recovery, treatment and re-use are non-existent in most Nigeria abattoir [21,20]. This practice undermines the utility of the abundant resources that abound in these "blood wastes" .
The choice of fresh animal blood and agro-by products as substrate mixtures is to remove any bias of fish/meat consumers that maggots grow in decomposing waste and animal faeces which are repugnant and distasteful [23,11]. Hence, production of maggots as in this present study is from acceptable substrate. Result showed that WB + WUB supported larval growth more efficiently and was significantly better than RD + WUB and SD + WUB. This confines from the fact that WB has better nutrient composition and availability than RD and SD [24,25,26,27]. The short metamorphic period of maggot (3 - 4 days) could have been too short a time for microbial degradation of cellulose and other fibrous components of SD and to a lesser extent RD. The high density of RD could have decreased aerobic conditions in the substrate mixture which ostensibly affected both survival of eggs and hatched larvae adversely. This view is consistent with the report that anaerobic manure was lethal or at least unsuitable for larval development . The better efficiency of WUB than DB could be attributed to reduced amount of nutrients available to the maggots. In all cases, maggot yield was found to be inversely related to the residual manure after maggot harvesting. This is consistent with the views of  who stated that as insect larvae feed on organic materials, they absorb the nutrients and reduce the waste volume significantly. It was also observed that as biodegradation of substrate by maggot progressed, the increasing size and activities of maggot appeared to be aerating the medium and reducing both moisture content and odour emission from the substrate correspondingly with the duration of biodegradation.
The blending of WB and SD was aimed at reducing the cost of WB. The result of 70:30 blend demonstrated that the combination of WB with cheaper saw dust could still support maggot production as efficiently as whole WB. Comparing the best model in this study (WB-WUB) with those reported by previous researchers, it could be seen that one kg of substrate yielded 238.7g maggot against 28.34g maggot per kg manure by  and 15.15g per kg manure by . The wide margin of over 230g maggot / kg substrate is proof of its commercial status since blood, and wheat bran and sawdust are available all year round. It could be deduced that the maggot yield is affected negatively by extreme climatic conditions (extreme dry weather and too much rain). This is consistent with the observations  that fly breeding cannot be successful at a moisture level of 30% and less and water logging prevents larval development.  Also reported that 50% of eggs laid by flies die if exposed to the sun for several hours. However, in a continuous production system these climatic factors could be managed. Substrate could be sprinkled with water in dry weather to prevent dehydration, while moisture level of the substrate could be minimized during mixing in period of heavy rainfall.
It was observed that housefly population in a netted system depleted about the 3rd month in a continuous production system. The depletion of housefly population could be due to expiration of their life span [33,34]. It implies that the continued production and harvesting of larvae which are never allowed to pupate or metamorphose into adult flies has the tendency of bringing a housefly population to extinction. To ensure continuity of the process, intermittent batches of larvae population could be allowed to undergo complete metamorphosis to bring back a new and vibrant generation of houseflies into the system.
It is concluded that the mixture of WUB + WB is the best substrate for maggot production or a combination of WB + SD in a ratio of 70:30 mixed with WUB for further reduction in production cost. Where blood is not available in large quantity, 50% dilution with water will suffice.
We appreciate the following persons who assisted in the course of this study, Chinoso Onyeguili Jonathan Chigbu, Mr. Peter Ajuogu & Mrs Aniebo Grace Chineme, Mr. Friday Owuno and Dr. Okoli I.C and the butchers union of Rumueme slaughter slab for their assistance and understanding.
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A.O. Aniebo *, S.N. Wekhe *, E.S. Erondu *** O.J Owen *, E.N Ngodigha **** and N.O. Isirimah **
* Department of Animal Science, ** Department of Soil and Environmental Science, Rivers State University of Science and Technology, PMB 5080 Port Harcourt, Nigeria email@example.com
*** Department of Animal Science and Fisheries, University of Port Harcourt. Nigeria.
**** Department of Animal Science and Fisheries, Niger Delta University, Wilberforce IslandBayelsa State. Nigeria.
Table 1: Characteristics of Substrate Mixtures Substrate Characteristics Treatment Absorbent material WUB S1 5kg Wheat bran 25kg S2 5kg Rice dust 25kg S3 5kg Saw dust 25kg Table 2: Blood Yield Projection Based on Data from Rumueme Slaughter Slab (Kg) Parameters Cattle Blood yield/animal from category A 9.29 [+ or -] 0.72 (c) Blood yield/animal from Category B 12.36 [+ or -] 0.87 (b) Blood yield / animal from category C 16.16 [+ or -] 1.28 (a) Av. Blood yield / 12.6 animal Av. Daily slaughter 18 figure at Rumueme Av. Daily blood yield at Rumueme 226.8 Projected daily slaughter figures in 498 Rivers State Projected annual blood yield at 82,782 Rumueme Projected daily blood yield in Rivers 6,274 State Projected annual 2,290,300 blood yield in Rivers State Parameters Goats Total Blood yield/animal from category A 0.56 [+ or -] 0.10 (b) 9.85 Blood yield/animal from Category B 0.61 [+ or -] 0.11 (b) 12.97 Blood yield / animal from category C 0.99 [+ or -] 0.23 (a) 17.15 Av. Blood yield / 0.72 13.32 animal Av. Daily slaughter 11 figure at Rumueme 29 Av. Daily blood yield at Rumueme 7.92 234.72 Projected daily slaughter figures in 652-864 1040-1362 Rivers State Projected annual blood yield at 2,891 85,673 Rumueme Projected daily 469.44- blood yield in Rivers 622.5 6,744-6,897 State Projected annual 171,400- 2,461,633- blood yield in Rivers 227200 2,518,000 State a,b,c, means within the same column with different superscripts are significant (P<0.05). Table 3: Blood Yield Projection and House Fly Larvae Potentials in Rivers State. (kg) Parameters Blood Fresh maggot Dry potential maggot potential Yield from WB+WUB 7.16+0.82 (a) 3.2 Yield from RD+WUB 2.46+0.5 (b) 1.1 Yield from SD+WUB 0.13+0.05 (c) 0.06 Quantity of HFL per blood Using WB+WUB 25 7.16 Daily blood yield 6,744-6,898 1,932-1975 863-883 and corresponding HFL potential in Rivers State Annual blood yield 2,461,633 705,012-721,155 315,089- and corresponding -2,518,000 322,304 HFL potential in Rivers State A, b, c, means within the same column with different superscripts are significant (P<0.05)