Source: SEAMEO BIOTROP's Research Grant | 2018
As Indonesia is being the third largest cocoa producer in the world, an abundant amount of cocoa pod husk (CPH) is being discarded as agricultural waste. Conventional use of CPH is by composting it or use it directly as a sheep feed. The latter did not contribute towards the increase of daily weight gain of sheep due to low nutrient content. To give higher value of CPH, black soldier fly (BSF) (Hermetia illucens) is used as a bioconversion agent to convert CPH into a biomass of protein. There is a need to study the treatments of CPH to be able to be consumed by BSF larvae which then the larvae will be consumed by sheep through mixing the larvae into rations. The objectives of this study are to get the best CPH treatment to be bioconverted by BSF larvae and to measure its proximate composition. Values from the proximate analysis will be used as a basis to formulate feed rations and then be given to sheep in various concentrations. Finally, the sheep performances were measured.
Stages of this research are select the best CPH treatment on small scale CPH bioconversion, large scale CPH bioconversion, feed formulation, and feed treatment on sheep. The CPH treatments include composted, chopped, and blended CPH as well as addition of left-over food waste on composted and chopped CPH which make the total is six treatments altogether including feeding the larvae only with leftover food waste that served as control. The best CPH treatment to be fed to BSF larvae treatment was selected based on waste reduction index, relative growth rate, efficiency of conversion of ingested food, and development time of BSF larvae during feeding period. The best CPH treatment was then subjected to proximate analysis.The best CPH treatment on small scale bioconversion is composted CPH preceded by addition of left-over food waste until the first 6 day starting from 5-day-old larvae. Therefore, the scale up process followed the best treatment on small scale with slight modification on the administration on leftover food waste and composted CPH. Instead of giving the feed separately, they were poured with three consecutive layers with 10 kg left-over food, 10 grams BSF larvae, and 50 kg composted CPH as the first, second, and third layer, respectively.
Feed formulation was done based on the data obtained from proximate analysis. The feed treatments were standard ration (control), BSF replaced 100% soybean meal, CPH residue replaced 100% coffee skin, CPH residue and BSF replaced 100% coffee skin and soybean meal, respectively, and CPH residue and BSF replaced 50% coffee skin and BSF, respectively. The treatments were fed to sheep. A total of 20 fat tail male sheep was used as the experimental unit. Sheep was divided into five groups according to experimental treatments so that each treatment is consisted of four sheep (served as replicates). Allocation of experimental rations to sheep was based on a randomized complete block design. Diet and water was provided ad libitum. Experimental period was performed for 10 weeks in which the first two weeks are adaptation period and the remaining weeks (week 3-10) are measurement period. Variables measured during in vivo feeding trial to sheep are feed and nutrient intake, rumen fermentation characteristics (pH, volatile fatty acid and ammonia concentration) and animal performance (initial bodyweight, final body weight and average daily gain).
Results showed that from six CPH treatments, BSF larvae fed with composted CPH preceded by administration of left-over food waste (LKS treatment) had the highest value of waste reduction index and second highest for relative growth rate and efficiency of conversion of ingested food. In terms of proximate analysis, BSF larvae fed with LKS treatment had higher crude protein and lower crude fat content comparedto that of control so that it may replace soybean meal and increase digestibility, respectively. Five ration treatments (R1-R5) using various concentration of BSF larvae fed with LKS treatment were allocated to be given to 20 sheep. Randomized complete block design is used in this experiment with four replicates for each treatment. Values of average daily consumption, feed conversion ratio, % dry matter, and average weight gain of R2 over a month had no significant difference with control ration. R2 is the ration where BSF replaced 100% soybean meal. Therefore, BSF larvae could be a substitute of soybean meal as a protein source in feed. However, longer observation periods (up to 3 months) are needed to make a valid statement along with the measurement of rumen fermentation characteristics.
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