Abstract
Simple SummaryThe replacement of environmental-costly resources in food and feed production is now imperative. Insects are recognized to be an effective protein source alternative to fishmeal and soy for animal husbandry. The evaluation of their nutritive properties can offer important insights to determine their potential use as feed. This study compares the pupae body composition of two different silkworm strains: a conventional polyhybrid producing white cocoons and the Nistari with golden yellow cocoons, rich in carotenoids, fed either on fresh mulberry leaves or an artificial diet. The results establish that feeding substrate composition strongly influences the fat and protein content of silkworm pupae. The feeding substrate also positively influences the pupae’ n-3/n-6 ratio while the carotenoid content is exclusively determined by the strain.The overexploitation of fishmeal and soy for the feedstuff industry has provided an opportunity to employ insects as an unconventional and more environmental friendly protein source. The evaluation of the nutritive properties of different insect species has consequently become a priority. The present study compares the pupal nutritive composition of two silkworm strains (White Cocoon Polyhybrid and Golden Yellow Cocoon Nistari) fed on two different rearing media (fresh mulberry leaves and a commercial artificial diet). Our results provide evidence that the composition of the feeding substrate strongly influences the fat and protein content of silkworm pupae. The two tested strains had higher fat and lower protein contents when fed with silkworm natural food (mulberry leaves) with respect to the commercial artificial diet. The analysis also showed that the n3/n6 ratio was affected almost exclusively by the feed substrate factor. On the contrary, the carotenoid content in pupae was specifically determined by the strain. The study identifies the interesting opportunity offered by silkworm pupae, which are usually a waste product of the silk-reeling process, to be used as alternative animal protein sources in a fully-closed circular production.
Highlights
Animal husbandry, due to the long feed chain, is highly demanding in terms of resources and is a remarkable source of greenhouse gases (GHG), accounting for almost 12% of global, 19% of anthropogenic, and 36% of agricultural emissions [1]
Considering that the nutrient quality of insects is highly dependent on the feed composition [12,24], we report on the pupal nutritive composition derived by feeding larvae on two different substrates, fresh mulberry leaves and a commercial artificial diet, to determine how the alimentary substrate affects the body composition of the insect
The two feeding substrates had similar crude fat contents, while they were statistically different in the total protein and total free sugar amount, as Florio leaves contained almost 40% less crude protein and twice as much sugar content than the artificial diet
Summary
Due to the long feed chain, is highly demanding in terms of resources and is a remarkable source of greenhouse gases (GHG), accounting for almost 12% of global, 19% of anthropogenic, and 36% of agricultural emissions [1]. Fishmeal and fish-oil are among the most exploited sources of proteins and fatty acids for feeding livestock and aquaculture [3]. 25% of these components are by-products of human fish consumption, while the remaining components come from fish purpose-caught in the open sea [4]. This causes an over-exploitation of pelagic resources due to incidental catches of juvenile forms of commercial species. Fishmeal and fish-oil are becoming scarce and expensive, and their quality is not constant because their supply depends on the fish abundance and reproduction rate, which is in turn affected by natural phenomena, such as extreme El Niño events due to climate change [5]
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