Bioconversion of Different Waste Streams of Animal and Vegetal Origin and Manure by Black Soldier Fly Larvae Hermetia illucens L. (Diptera: Stratiomyidae).

Black soldier fly larvae (BSFL) are considered a commercially viable solution for global organic waste problems. The objective of this study was to assess the feasibility of rearing BSFL on a wide range of low-value waste streams and its potential to transform them into high-quality animal feed and fertilizer. Six waste streams of different origins were selected and each tested in triplicate. Several parameters were analysed: growth performance, waste reduction index (WRI), conversion efficiency (ECI) and larval composition. Frass composition was also analysed. Larvae reared on fast food waste (FFW) had the highest ECI and WRI and the lowest values when reared on pig manure slurry mixed with silage grass (PMLSG) and slaughter waste (SW). The highest protein content was found for larvae reared on mushroom stems (MS) although this substrate had the lowest protein content. Moreover, the frass nutritional profile was proportionally related to the substrate's nutritional profile: the protein-rich substrate (SW) resulted in protein-rich frass and the low-protein substrate (MS) resulted in protein-poor frass. The same was true for the lipid content. In conclusion, this study showed that BSFL can be successfully reared on a wide range of waste streams that can affect the larval and frass chemical compositions.

Bioconversion of Digestate, Pig Manure and Vegetal Residue-Based Waste Operated by Black Soldier Fly Larvae, Hermetia illucens L. (Diptera: Stratiomyidae).

Insects can play an important role to upgrade waste streams into high-grade proteins and fats as food and feed ingredients or non-food products. The aim of this research was to assess the feasibility to use waste streams with a low value for direct application as animal feed as substrates to grow BSF larvae in terms of larval growth rate, waste reduction index, and efficiency of conversion of ingested feed. The growth of black soldier fly (BSF), Hermetia illucens larvae and conversion of biowaste was assessed in triplicate in biowaste substrates: chicken feed (CF; reference diet), pig manure solid (PMS), Betafert® solid (BTFS), swill (SW), olive pulp (OP), pig manure liquid mixed with chicken feed (PMLCF), and silage grass (SG). Per kilogram fresh substrate 2500 starter (8-days-old, second instar) larvae were incubated in 21 plastic containers (75 × 47 × 15 cm). The BSF larvae were fed according to a batch feeding system. Highest growth rate was found in larvae reared on SW (13.4 mg/d). Larval growth rate was even higher than in larvae reared on the reference substrate CF (7.2 mg/d). Growth rate in larvae reared on PMLCF (7.3 mg/d) did not differ from CF, whereas growth rate of larvae reared on PMS (3.2 mg/d) was lower than on CF. Growth rate of larvae reared on BTFS, OP and SG was very low (0.6, 0.2 and 0.7 mg/d, respectively). Waste Reduction Index (WRI) was highest on SW (11.3), followed by PMLCF (9.3), and both were higher than WRI on CF (8.5). Waste Reduction Index further decreased in descending order from PMS, SG, BTFS to OP (7.6, 4.0, 2.9 and 1.7, respectively). The Efficiency of Conversion of Ingested substrate (ECI) was highest on SW (0.31), followed in descending order by PMLCF, CF and PMS (0.25, 0.21 and 0.18, respectively). The substrates OP, BTFS and SG (0.16, 0.15 and 0.14, respectively) resulted in a lower ECI than other substrates. Highest CO2 and lowest NH3 concentrations were found above substrates with the highest larval growth performances. This study showed that BSF larvae can be reared on different biowaste substrates; the growth rate of the larvae was extremely high on SW. The effects of chemical composition and physical properties of the substrates on larval growth and gas emissions should be further considered.

Biorefinery of the green seaweed Ulva lactuca to produce animal feed, chemicals and biofuels.

The growing world population demands an increase in animal protein production. Seaweed may be a valuable source of protein for animal feed. However, a biorefinery approach aimed at cascading valorisation of both protein and non-protein seaweed constituents is required to realise an economically feasible value chain. In this study, such a biorefinery approach is presented for the green seaweed Ulva lactuca containing 225 g protein (N × 4.6) kg-1 dry matter (DM). The sugars in the biomass were solubilised by hot water treatment followed by enzymatic hydrolysis and centrifugation resulting in a sugar-rich hydrolysate (38.8 g L-1 sugars) containing glucose, rhamnose and xylose, and a protein-enriched (343 g kg-1 in DM) extracted fraction. This extracted fraction was characterised for use in animal feed, as compared to U. lactuca biomass. Based on the content of essential amino acids and the in vitro N (85 %) and organic matter (90 %) digestibility, the extracted fraction seems a promising protein source in diets for monogastric animals with improved characteristics as compared to the intact U. lactuca. The gas production test indicated a moderate rumen fermentation of U. lactuca and the extracted fraction, about similar to that of alfalfa. Reduction of the high content of minerals and trace elements may be required to allow a high inclusion level of U. lactuca products in animal diets. The hydrolysate was used successfully for the production of acetone, butanol, ethanol and 1,2-propanediol by clostridial fermentation, and the rhamnose fermentation pattern was studied.

Transfer of pyrrolizidine alkaloids from various herbs to eggs and meat in laying hens.

To investigate the potential transfer of pyrrolizidine alkaloids (PAs), laying hens were fed for 14 days with diets containing 0.5% of dried common ragwort, common groundsel, narrow-leaved ragwort or viper's bugloss, or 0.1% of common heliotrope. This resulted in total PA levels in feed of respectively 5.5, 11.1, 53.1, 5.9 and 21.7 mg kg-1, with varying composition. PAs were transferred to eggs, in particular yolk, with steady-state levels of respectively 12, 21, 216, 2 and 36 µg kg-1. Overall transfer rates for the sum of PAs were estimated between 0.02% and 0.23%, depending on the type of PAs in the feed. In animals slaughtered shortly after the last exposure, levels in meat were slightly lower than those in eggs, levels in livers somewhat higher. When switched to clean feed, levels in eggs gradually decreased, but after 14 days were still above detection limits in the hens exposed to higher PA levels. Similar was the case for meat and especially kidneys and livers. It is concluded that the intake of PA containing herbs by laying hens may result in levels in eggs and meat that could be of concern for consumers, and as such should be avoided.

Concentrations of dimethylaniline and other metabolites in milk and tissues of dairy cows treated with lidocaine.

Lidocaine is a topical anaesthetic drug used in dairy cows for laparotomy (caesarean section, abomasal displacement). Because there are no registered drugs for this indication, it can be applied under the so-called Cascade rules (off-label use), with the restriction that the off-label withdrawal periods of 7 days for milk and 28 days for meat are taken into account. In animals, lidocaine is rapidly metabolised into various metabolites, one being 2,6-dimethylaniline (DMA) which is reported to possess carcinogenic and mutagenic properties and detected also in milk. To investigate whether the off-label withdrawal periods are long enough to exclude the presence of lidocaine and DMA, and potential other metabolites, in edible products, a study was performed with eight dairy cows treated with lidocaine by injection in the abdominal muscles. At various time points blood samples, milk and urine were collected. Four animals were slaughtered 3.5 h after treatment, the other four after 48.5 h. The injection site, meat, liver and kidney were analysed for levels of lidocaine, DMA, monoethylglycinexylidide (MEGX) and 3-OH-lidocaine. It was shown that DMA is an important metabolite in dairy cows and can be detected in both meat and milk. In addition, also MEGX, 3-OH-lidocaine and three other metabolites were identified and to some extent quantified. These metabolites were 4-OH-lidocaine, lidocaine-N-oxide and 4-hydroxy-DMA. The latter compound was the most important metabolite in urine. However, levels in milk and meat decreased rapidly after the application. Overall, it can be concluded that the off-label withdrawal times of 7 and 28 days for milk and meat, respectively, guarantee the absence of detectable levels of lidocaine and metabolites.

Actinobacillus pleuropneumoniae is impaired by the garlic volatile allyl methyl sulfide (AMS) in vitro and in-feed garlic alleviates pleuropneumonia in a pig model.

Decomposition products of ingested garlic are to a certain extent excreted via the lungs. If the supposed health-supporting capacities associated with garlic extend to these exhaled sulfurous compounds, they could have an effect on the course of pneumonia. In this study, the garlic-derived volatile allyl methyl sulfide (AMS) as a lead compound of volatile garlic metabolites was shown to exhibit an antibacterial effect against the pig pathogen Actinobacillus pleuropneumoniae serotype 9. AMS caused a delay in the appearance of the optical density-monitored growth of A. pleuropneumoniae in medium when compared to unaffected growth curves, yet without lowering the stationary phase yield at the concentration range tested. At 1.1mM, AMS impaired the in vitro growth rate of A. pleuropneumoniae serotype 9 by 8% compared to unimpeded growth. In an animal trial, a garlic-fed group of 15 pigs that received a diet with 5% garlic feed component and a control group of 15 pigs that received a diet without garlic were infected with A. pleuropneumoniae serotype 2 via an aerosol and subsequently followed for 4 days. At the day of the challenge, blood AMS in the garlic-fed group amounted to 0.32 ± 0.13 µM. A beneficial, alleviating effect of garlic on the course and severity of an A. pleuropneumoniae infection in pigs was indicated by the reduced occurrence of characteristic pleuropneumonia lesions (27% of the lungs affected in the garlic-fed group vs. 47% in the control group) and a near to significant (p=0.06) lower relative lung weight post mortem in the garlic-fed group.

Inhibition of binding of the AB5-type enterotoxins LT-I and cholera toxin to ganglioside GM1 by galactose-rich dietary components.

Cholera, travelers' diarrhea, or colibacillosis in pigs can possibly be prevented or attenuated by dietary provision of competitive inhibitors that react with the GM1-binding sites of the enterotoxins cholera toxin (CT), human Escherichia coli heat-labile enterotoxin of serogroup I (LTh-I), and porcine LT-I (LTp-I). The interfering efficiency of natural substances with binding of the toxins to the gangliosid receptor GM1 was tested using a specially adapted GM1-coated-microtiter-well enzyme-linked immunosorbent assay. The substances tested for their GM1 displacing capacity were galactose-containing or -related saccharides from bovine milk, skim milk powder, galactan from gum arabic, food stabilizers as well as ground fenugreek seed and soy bean constituents that contain galactomannans, the galactopolysaccharides agar and agarose, and larch wood and other plant materials that contain arabinogalactans. Skim milk powder, compared with the pure milk saccharides tested, interfered to a higher extent with LTh-I (65-66% inhibition at 5 mg test substance/mL) and CT binding (63-67% inhibition at 5 mg test substance/mL) when supplied before or simultaneously with the toxins in the GM1-enzyme-linked immunosorbent assay. Ground fenugreek seed counteracted GM1 binding of 5 ng LTh-I/mL as well as 5 ng and 1 microg LTp-I/mL (43-65% inhibition at 5 mg test substance/mL), and 4 ng CT/mL (61-92% inhibition at 5 mg test substance/mL) very efficiently when supplied before the toxin-GM1 complex had formed. With 50 mg/mL fenugreek seed, inhibition percentages of even 92-99% were reached for LTh-I and CT binding. Efforts to resolve already bound toxin from GM1 with the test substances were less effective than preincubations and concurrent incubations.

The occurrence and prevention of ethanol fermentation in high-dry-matter grass silage.

Ethanol is a common, usually minor fermentation product in ensiled forages, the major product being lactic acid. Occasionally, high levels of ethanol are found in silages. The aim of this study was to determine the incidence of high-dry-matter (DM) grass silages containing ethanol as the main fermentation product (ethanol silages), to describe the fermentation process in such silages and to determine the effect of grass maceration prior to wilting and addition of a bacterial inoculant containing Lactobacillus plantarum and Enterococcus faecium strains on fermentation. Twenty-one laboratory silages produced between 1993 and 1995, 21 farm silages produced between 1980 and 1989 and 36 farm silages produced in 1995 (all produced without additive) were examined for pH and chemical composition. Dry matter (DM) loss during ensilage was determined for the laboratory silages only. Four laboratory silages were identified as ethanol silages. Mean concentrations of ethanol, lactic acid and acetic acid were 48.1, 15.5 and 6.0 g kg-1 DM respectively. In the silages that contained lactic acid as the main fermentation product (lactic acid silages) these values were 7.7, 45.5 and 15.1 g kg-1 DM. Mean DM loss and pH were 62.8 g kg-1 DM and 5.32 respectively for ethanol silages and 24.4 g kg-1 DM and 4.69 for lactic acid silages. There was no difference between ethanol silages and lactic acid silages in the mean concentration of ammonia-N (94 g kg-1 total N), and butyric acid was not detected (<0.2 g kg-1 DM), indicating that both types of silages were well preserved. Analysis of the composition of the grass at ensiling showed a positive correlation between the concentration of soluble carbohydrates and the development into ethanol silage. Analysis of the farm silages indicated that 29% of the silages produced between 1980 and 1989 and 14% of those produced in 1995 were ethanol silages. Maceration prior to wilting and addition of silage inoculant improved lactic acid fermentation and prevented high ethanol levels. The micro-organisms responsible for ethanol fermentation as well as the implications of feeding ethanol silages to livestock remain to be resolved. © 2000 Society of Chemical Industry.