Effects of artificial diet breeding on intestinal microbial populations at the young stage of silkworm (Bombyx mori)

Abstract

The silkworm (Bombyx mori) is an economically important insect and serves as a model organism for Lepidoptera. To investigate the effects of the intestinal microbial population on the growth and development of larvae fed an artificial diet (AD) during the young stages, we analyzed the characteristics of the intestinal microbial population using 16S rRNA gene sequencing technology. Our results revealed that the intestinal flora of the AD group tended to be simple by the 3rd‐instar, which Lactobacillus accounting for 14.85% and leading to a decreased pH in the intestinal fluid. In contrast, the intestinal flora of silkworms in the mulberry leaf (ML) group showed continuous growth of diversity, with Proteobacteria accounting for 37.10%, Firmicutes accounting for 21.44%, and Actinobacteria accounting for 17.36%. Additionally, we detected the activity of intestinal digestive enzymes at different instars and found that the activity of digestive enzymes in the AD group increased by larval instar. Protease activity in the AD group was lower during the 1st‐ to 3rd‐instars compared to the ML group, while α‐amylase and lipase activities were significantly higher in the AD group during the 2nd‐ and 3rd‐instar compared to the ML group. Furthermore, our experimental results indicated that changes in the intestinal population decreased the pH and affected the activity of proteases, which might contribute to the slower growth and development of larvae in the AD group. In summary, this study provides a reference for investigating the relationship between artificial diet and intestinal flora balance.

Gut Microbiota Analysis in Silkworms (Bombyx mori) Provides Insights into Identifying Key Bacterials for Inclusion in Artificial Diet Formulations

“…Nonetheless, the commercial success and sustainability of sericulture face ongoing challenges, necessitating the optimization of rearing environments alongside the minimization of production expenses [3,4]. A significant factor in silkworm husbandry that has recently attracted considerable interest is the intricate relationship between diet, gut microbiota, and the health of the host organism [5][6][7].…”

“…The nutrient composition of mulberry leaves, particularly the balance of proteins, carbohydrates, and essential micronutrients, plays a pivotal role in the growth, development, and silk production of silkworms [4,8,9]. However, the increasing demand for silk and the need for cost-effective and efficient production methods have led to the widespread adoption of artificial diets in commercial sericulture [6,[10][11][12]. These formulated feeds, often based on a combination of soybean meal, corn powder, and various nutritional supplements, aim to provide a balanced and easily digestible nutrient profile for optimal silkworm growth [11,12].…”

“…The gut microbiota of silkworms, which encompasses a myriad of bacterial species, is of paramount importance for the digestion of nutrients, regulation of the immune system, and the general well-being of the host [6,13,16]. The dietary habits of the host substantially sway the composition and functionality of the gut microbiota, given that varying dietary inputs furnish unique substrates that promote the growth and metabolic activities of different microbes [6,16,17]. Studies have demonstrated that the transition in silkworms from a diet dominated by mulberry leaves to one consisting of artificial formulations can lead to marked changes in the gut microbiota's architecture [6,18].…”

“…The dietary habits of the host substantially sway the composition and functionality of the gut microbiota, given that varying dietary inputs furnish unique substrates that promote the growth and metabolic activities of different microbes [6,16,17]. Studies have demonstrated that the transition in silkworms from a diet dominated by mulberry leaves to one consisting of artificial formulations can lead to marked changes in the gut microbiota's architecture [6,18]. These dietary-driven alterations, involving phyla such as Proteobacteria and Firmicutes, particularly Lactobacillus, can significantly impact silkworm physiology.…”

Homeostatic Regulation of the Duox-ROS Defense System: Revelations Based on the Diversity of Gut Bacteria in Silkworms (Bombyx mori)

“…As an economically important insect, the silkworm can be fed an artificial diet at all instars, but there are associated problems such as small body size and a low larval survival rate in the AD-fed silkworm, and the mechanism of these changes not fully understood [ 25 , 26 ]. A recent study reported that at first–third instars-fed artificial feed, intestinal microbiota associated with instar growth exhibited a single trend and the intestinal pH was acidic, whilst the traditional mulberry-leaf-fed silkworm’s intestine is alkaline [ 27 , 28 ]. In this study, the gut microbial composition of the midgut of silkworms was characterized at different timepoints after being fed artificial diets (ADs), mulberry leaf at 1–4 instars (ML) and artificial feeding at 1–3 instars, followed by mulberry leaf feeding during the fourth instar (TM).…”