Can farm weeds improve the growth and microbiological quality of crickets (Gryllus bimaculatus)?

Abstract

Farming of edible insects has been proposed as a means to reduce current practices of harvesting from the wild. While farming could relieve the pressure on wild populations, as well as on their natural habitats, and generate a continuous supply of edible insects to the consumers, the high cost of commercial chicken feeds is still a challenge to many farmers. The aim of this study was to investigate whether the partial replacement of commercial chicken feed with the farm weed, wandering Jew (Commelina sinensis), would have an impact on weight gain and microbial quality of farmed field crickets (Gryllus bimaculatus). Therefore, we have experimentally compared two types of feed: (1) starter commercial chicken feed only (SO); and (2) starter commercial chicken feed supplemented with fresh wandering Jew weeds (S+W). After a feeding period of thirty days, the final body weight differed significantly (P=0.026) between crickets fed with SO and with S+W, which averaged at 1.11 and 1.39 g, respectively. Generally, high counts of total aerobic, Enterobacteriaceae, lactic acid bacteria, bacterial endospores, yeasts and moulds were observed in both experimental groups. However, bacterial endospore counts of S+W fed crickets (2.7 log cfu/g) were significantly lower (P=0.021) than these of the SO fed ones (3.9 log cfu/g). Metagenetic analyses indicated that Proteobacteria, Firmicutes and Tenericutes were the most abundant phyla, while members of the family Coxiellacea, and the genera Lactobacillus, and Spiroplasma were the most abundant operational taxonomic units (OTUs). Concerning the food safety, a few OTUs could be associated with potential food pathogens, such as Clostridiaceae, Staphylococcus and Enterobacteriaceae. In summary, the inclusion of fresh wandering Jew weeds in commercial starter chicken feed produced crickets with increased body weight and improved microbial quality.

A Literature Review of the Use of Weeds and Agricultural and Food Industry By-Products to Feed Farmed Crickets (Insecta; Orthoptera; Gryllidae)

“…Higher survival rates were documented for A. domesticus reared on diets supplemented with alternative feeds when compared to a control (Sorjonen et al, 2019;Harsányi et al, 2020;Quek et al, 2020). Higher weight gain was recorded in supplemented diets compared to control diets for G. bimaculatus (Ng'ang'a et al, 2020) and A. domesticus (Quek et al, 2020). Ng 'ang'a et al (2020) found that bacterial endospore counts were lower for G. bimaculatus that had been fed chicken feed supplemented with the local weed Commelina sinensis than on a pure chicken feed diet.…”

“…ADF, acid detergent fiber; C, carbohydrate; CF, crude fiber; CP, crude protein; DM, dry matter; NDF, neutral detergent fiber. 2016), microbial counts and relative abundance (Ng'ang'a et al, 2020), maturity period (Oloo et al, 2020), nitrogen efficiency, phosphorus content, total fatty acids (Oonincx et al, 2015), developmental rate, glycoalkaloid concentrations, fatty acid content and composition (Sorjonen et al, 2019), daily DM intake, and periodic FCR (Vaga et al, 2019).…”

“…Sex has also been shown to have a significant effect on a number of growth and survival parameters, with female adult fresh weight higher than male (Kulma et al, 2019;Ng'ang'a et al, 2020). Male A. domesticus have also been shown to have higher crude protein, and lower lipid content than females.…”

“…Nutritional variation by developmental stage has also been shown to significantly impact growth and survival parameters. A number of studies have shown that there is no observed difference in weight gain across experimental and control diets within the first 1-5 weeks of development, after which there is a sharp decline in weight gain observed for less nutritious alternative feeds (Patton, 1967;Ng'ang'a et al, 2020;Oloo et al, 2020;Vaga et al, 2020). Delaying the onset of lower-nutrient experimental diet regimes until 1-2 weeks after hatching ensures that the groups have equal metabolic capacity during later stages of significant growth (Lundy and Parrella, 2015;Dobermann et al, 2019).…”

“…For example, the onset of experimental diets varies from <1 day old to 57 days old (Supplementary Table 1). This makes comparing performances in response to diet across studies difficult, as a variation in nutritional quality throughout the life cycle has been shown to cause differences in growth and survival across the entire lifetime (Patton, 1967;Ng'ang'a et al, 2020;Oloo et al, 2020;Vaga et al, 2020).…”