Microbiological safety assessment of silkworm farms: a case study.

Silkworms have been farmed for their silk since ancient times. After silk reeling, their chrysalides are consumed as food in several Asian countries. Despite the long rearing tradition of this insect, few studies have investigated the silkworm's microbiological safety all along the life cycle, focusing on detecting silkworm pathogens or on the safety of the dried chrysalis for food consumption. However, the in-farm rearing process, which takes around forty days, may affect the microbial load of the silkworm and of the rearing environment, as well as the quality of fresh cocoon and other performance parameters. No data is available on how microbial contamination changes during the rearing period and between different farmers. Furthermore, in light of the possible use of the chrysalis as food, it is crucial to understand how its microbial load varies according to the water content. To address these specific questions, we conducted an investigation involving the analysis of specific microbial indicators commonly used in the food chain. We collected environmental and silkworm samples from several farms. The examination covered the entire life cycle of silkworms, beginning with the first instar larvae and concluding with the scrutiny of both freshly harvested and dried pupae. Silkworm farms in Northeast Italy proved to be an appropriate model system for carrying out the experimentation. Additionally, an evaluation of rearing performance was conducted, with a focus on the quality of fresh cocoons and the survival rate of the insects.

Feeding silkworm (Bombyx mori L.) oil to growing rabbits improves the fatty acid composition of meat, liver and perirenal fat.

Silkworm oil was used in a rabbit diet to evaluate its benefit on the fatty acid (FA) profile of different carcass portions. Two experimental diets were prepared: a control diet (commercial diet with 13 g/kg sunflower oil) and a silkworm oil diet (SWO) (commercial diet with 13 g/kg silkworm oil). Rabbits received the experimental diets the last three weeks before slaughter, which occurred at 10 weeks of age. At slaughter, hind leg meat, liver, and perirenal fat were sampled for FA profile analysis. The SWO diet significantly increased the n-3 FA of all three sampling sites and halved the n-6/n-3 ratio of hind leg meat and perirenal fat. Furthermore, the liver of SWO rabbits was also richer in C22:6 n-3 compared to that of control rabbits. In conclusion, this study demonstrated that the total dietary replacement of sunflower oil with silkworm oil in fattening rabbits positively changed the FA profile of the considered carcass tissues.

Effect of a dietary inclusion of full-fat or defatted silkworm pupa meal on the nutrient digestibility and faecal microbiome of fattening quails.

Silkworm (Bombyx mori L.) pupae are a by-product derived from silk production, which is often treated as waste and thus discarded: this can cause serious environmental problems and a loss of nutrients. Silkworm pupae are a rich source of protein and lipids, and the resulting protein meal can provide promising outcomes as livestock feed, notably for monogastric species. However, one possible issue that needs to be considered is the possible implication of the 1-Deoxynojirimycin (1-DNJ), a bio-compound of the silkworm that impairs glucose absorption, in poultry nutrition. Therefore, the present study evaluated the effect of the dietary inclusion of full-fat or defatted silkworm pupa meal (SWM) on the apparent digestibility of nutrients, feed choice and faecal microbiome in meat-producing quails. For the digestibility trial, a total of thirty-three 27-day-old Japanese quails (Coturnix coturnix japonica) were individually housed in digestibility cages and received three experimental diets: a control diet (control, commercial feed for fattening quails), and two other diets containing the 12.5% of either a full-fat SWM (SWM-FULL) or a defatted SWM (SWM-DEF). Subsequently, twenty-seven 33-day-old quails were simultaneously provided with Control, SWM-FULL and SWM-DEF diets for a 10-day feed choice trial. The results of the digestibility trial showed that the DM intake and excreta production were higher in both SWM groups than in the Control one (P < 0.001). The apparent digestibility of DM, organic matter, CP, ether extract, starch and energy was lower in both SWM groups than in the control group (P < 0.001), suggesting the possible implication of chitin and 1-DNJ. The feed choice test showed that quails preferred the Control diet (P < 0.001). From the microbiome analysis of the excreta, families such as Streptococcaceae (P < 0.05), Rikenellaceae and Eubacteriaceae (P < 0.01) and taxa at species level such as Lactobacillus delbrueckii (P < 0.05), Aneurinibacillus thermoaerophilus and Bacillus thermoamylovorans (P < 0.01) scored higher in SWM-FULL quails than in SWM-DEF and Control treatments. The present study demonstrated that a successful dietary inclusion of SWM for fattening quails needs to overcome the digestive criticalities caused by the of presence specific bio-compounds, namely chitin and 1-DNJ.

Modulation of leucine absorption in the larval midgut of Bombyx mori (Lepidoptera, Bombycidae).

In the larval midgut of Bombyx mori a K(+)-dependent transporter for leucine and amino acids with a hydrophobic side chain is responsible for the absorption of most essential amino acids. We investigated if a modulation of its activity occurred as a result of starvation or after hormonal treatments. We measured amino acid uptake in brush border membrane vesicles (BBMV) purified from the anterior-middle (AM) and posterior (P) regions of the midgut in fifth instar larvae. Silkworms were either starved or topically treated with low dosages of fenoxycarb, a molecule often used as a juvenile hormone mimic. The maximal uptake value of K(+)-driven leucine transport was increased in BBMV of AM- and P-midgut regions of starved larvae. The initial uptake rates of serine and glutamine, two amino acids transported by the same cotransporter as leucine, were also increased. Leucine kinetics proved that V(max) was the kinetic parameter modified by starvation in both midgut regions. Topical applications of fenoxycarb at a dose of 2.5 fg/larva immediately after the fourth ecdysis, induced an increase of leucine initial uptake rates and of intravesicular accumulation of leucine in both AM- and P-BBMV. Kinetic analysis of leucine uptake indicated again that V(max) was increased in BBMV from both midgut regions in treated larvae.