Safety of Mealworm Meal in Layer Diets and their Influence on Gut Morphology

Abstract

The main objective of this study was to verify the safety of mealworm meal in the feed of laying hens from 17 to 42 weeks of age. Therefore, the feed mixtures were tested in terms of microbiological stability, fungal and mycotoxin content and selected parameters of hens’ intestinal morphology and physiology were monitored. The experiment was carried out with 30 Lohmann Brown Classic hens. Hens were divided by body mass into three equal groups with 10 replicates per treatment. The two experimental groups received feed mixtures containing 2% and 5% yellow mealworm (Tenebrio molitor L.) meal. The third group was a control group which had 0% of mealworm meal in the diet. Diets with 2% and 5% of mealworm meals did not affect the length of villi and microbiome of the caecum. The highest digesta viscosity from the ileum was found in the group with 5% mealworm, which may indicate a slower passage of the digesta through the digestive tract. Based on our results, it may be concluded that the proportion of mealworm meals does not deteriorate the quality of feeds. Mealworm meal does not negatively affect microbial stability in experimental feeds. Therefore, it can be recommended the two and (or) five percent of mealworm meal inclusion in hen’s diet.

Yellow Mealworm and Black Soldier Fly Larvae for Feed and Food Production in Europe, with Emphasis on Iceland

“…There have been few studies into the microbial content of mealworms and BSF larvae, and its effect on food safety. These studies indicate that there is a high level of bacteria on the surface and in the gut of these insects [83][84][85][86][87][88][89][90].…”

“…The current food hygiene criteria include Salmonella enterica (S. enterica), Listeria monocytogenes (L monocytogenes), Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Bacillus cereus (B. cereus) [88]. According to several studies, mealworms and BSF larvae do not act as a vector for S. enterica [73,[86][87][88][89]; however, in a study done by Raimondi et al, 2020, [84] on BSF, S. enterica was detected in some samples of prepupae. It is believed that BSF larvae possess antimicrobial capacities that make them able to reduce pathogenic bacteria such as S. enterica and E. coli [87,90].…”

“…It is believed that BSF larvae possess antimicrobial capacities that make them able to reduce pathogenic bacteria such as S. enterica and E. coli [87,90]. In most studies, L. monocytogenes and E. coli are not detected in the mealworms BSF larvae [86][87][88][89]; however, these bacteria can be detected in these species if they are reared on substrates contaminated with L. monocytogenes [91,92] and E. coli, but E. coli will be reduced in the larvae [92]. Staphylococcus aureus was detected in mealworms in a study done by Stastnik et al, 2021, [89] and coagulase-positive staphylococcus was detected in BSF prepupae in a study done by Raimondi et al, 2020 [84].…”

“…Endospores can also germinate and produce toxins when food is not cooked, cooled and stored properly [94]. Bacterial endospores highly differentiate in number between different rearing batches from the same company [83,86,87,89]; in one study, the number of endospores in mealworms varied between 1.7 log cfu/g to 5.0 log cfu/g [86]; in another study focused on mealworms, the endospores detected were between <1 log cfu/g to 3.5 log cfu/g [84]. In a study on BSF larvae reared on different substrates, the endospores varied between 3.7 log cfu/g to 7.5 log cfu/g [87].…”

“…Other pathogenic bacteria that have been detected in mealworms and BSF larvae are Clostridium spp. [83,84,87,89] and Campylobacter sp. [84,90,95] However, only low levels of Clostridium perfringens have been detected in these studies, with an average concentration under <1 log cfu/g [84,89].…”