Work package 34.2.2 Larval preservation
on the preservation of black soldier fly ( Hermetia illuscens L.) larvae were conducted at the HBLFA Raumberg-Gumpenstein from 2018 to 2019. The killed, non-defatted larvae contained 27% dry matter, 50% crude protein, and 27% crude fat in dry matter. Due to the high protein and fat content, as well as the minimal sugar content (1%), the larvae were very difficult to ensile. Ensiling the black soldier fly larvae without additional, readily fermentable substrate or silage additives was characterized by insufficient pH reduction, undesirable fermentation with butyric acid formation, severe protein degradation (leading to the formation of ammonia and biogenic amines), loss of fermentation liquid, and a strong spoilage odor. The addition of lactic acid bacteria, molasses, tannins, and various combinations of these silage additives did not improve fermentation quality, or only to a minimal extent. Chemical preservatives such as formic acid and, in particular, sodium nitrite, were more effective. The greatest fermentation success was achieved by adding an absorbent, readily fermentable substrate in the form of barley meal. A barley meal addition of 20% or more resulted in sufficient pH reduction through lactic acid fermentation and complete binding of the silage effluent. The combination of 20% barley meal with sodium nitrite or lactic acid bacteria (Silasil Extra) ensured successful fermentation while simultaneously preventing spoilage odors. The ensiling of larvae with the addition of 40% barley meal yielded excellent fermentation results and impeccable feed hygiene, even without additional silage additives. However, the content of some biogenic amines (putrescine, cadaverine, and tyramine) increased significantly during ensiling, even with a barley meal content of 40%. Ensiling reduced the amino acid content by 21% compared to fresh larvae, with lysine being particularly affected. Gentle larval drying at 50–55 °C resulted in less loss of nutritional value compared to ensiling; however, drying also reduced the total amino acid content by 10% compared to fresh larvae. Given the lower amino acid content of preserved larvae, defatting the larvae before preservation would be advisable, as this could significantly increase the amino acid content. The ensiled larvae were stable after opening; they showed no aerobic spoilage after 9 days in open air at room temperature.
Variants of larval silage, Source: Resch R.
Work package 34.2.3 Broiler fattening and emission measurement
The substitution of certain proportions of soy protein with larvae meal was investigated in broiler production at the HBLFA Raumberg-Gumpenstein in three fattening cycles from 2019 to 2020, each involving 420 broilers. The experimental feed was compared to a control feed, and success was measured using biological fattening parameters (daily weight gain, final weight) as well as emissions (ammonia). The first attempt, to replace 75% of the soy protein, failed due to negative effects of the larvae meal on animal health, reduced fattening performance, and increased NH3 emissions . The high proportion of 75% insect protein in the feed rations was physiologically unacceptable for Ross breed broiler chickens. The reduced proportion of larvae meal in the experimental feed, from 35–40% (replacing soy) in the subsequent two trials, led to a significant improvement in animal health. The number of losses in the experimental groups decreased to the level of the control groups, the animals' excrement showed a reduced watery consistency, and the animals' plumage was comparable to that of birds fed conventionally. However, compared to the control group, the mean daily weight gain was reduced by 6 g and the mean slaughter weight by 226 g per animal. The higher emissions (mean NH3 concentration in the exhaust air, mean NH3 emissions per animal place per year, mean odor concentration) with larvae meal feeding indicate inadequate protein digestion. Presumably, a further reduction in larvae protein to 10–20% could also lead to a similarity between the experimental and control groups in this respect.
Broiler trial control group, Source: Kropsch, M.
Final report
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