Artificial diets determine fatty acid composition in edible Ruspolia differens (Orthoptera: Tettigoniidae)
2018
Karlmax Rutaro, University of Eastern Finland, Joensuu, Finland | Geoffrey M.Malinga, University of Eastern Finland, Joensuu, Finland | Robert Opoke, Gulu University, Gulu, Uganda | Vilma J.Lehtovaara, University of Eastern Finland, Joensuu, Finland | Francis Omujal, Natural Chemotherapeutic Research Institute, Ministry of Health, Kampala, Uganda | Philip Nyeko, Makerere University, Kampala, Uganda | Heikki Roininen, University of Eastern Finland, Joensuu, Finland | Anu Valtonen, University of Eastern Finland, Joensuu, Finland
There are increasing interests in rearing edible insects in Africa, but information on how the feeds modify their fatty acids is largely lacking. In this work, the influence of artificial diets on the fatty acid contents and composition in the edible Ruspolia differens (Serville, 1838), in Uganda was assessed. R. differens was reared on the mixtures of six gradually diversified diets of two, three, four, six, eight and nine feeds. The diets were formulated from rice seed head, finger millet seed head, wheat bran, superfeed chicken egg booster, sorghum seed head, germinated finger millet, simsim cake, crushed dog biscuit pellet and shea butter. Fatty acid methyl esters were prepared using direct transesterification method, and analysed using gas chromatography. The contents of saturated, monounsaturated and polyunsaturated fatty acid differed significantly among the diets. The more diverse diets resulted in increased content of the polyunsaturated fatty acids. The n6:n3 ratio differed significantly among the diets and between the sexes, with R. differens fed on the four-feed diet having a higher n6:n3 ratio than those fed on other diets. Also, the fatty acid composition differed significantly among the diets, and diet diversification corresponded with the proportions of polyunsaturated fatty acids, especially linoleic acid. Overall, our results demonstrate that higher levels of essential fatty acids can be achieved by rearing R. differens on highly diversified diets. These findings are important in informing the design of future mass-rearing program for this edible insect.
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