Dietary supplementation with silkworm pupae prevents growth retardation in broilers under heat stress conditions

Global warming poses a major challenge to livestock production, particularly in broiler chickens. They are highly sensitive to heat stress due to their elevated metabolic activity associated with rapid growth and high productivity. Pupae of the silkworm (Bombyx mori) are known for their immunostimulatory properties. In this study, we investigated the effects on broiler performance of dietary supplementation with defatted silkworm pupae (DSP) under elevated ambient temperatures (neutral, days 0-21; increased temperature, days 21-43). DSP was included in the feed at concentrations of 0.01 % and 0.1 %. Growth performance and mortality were assessed, alongside hepatic transcriptomic analysis using RT-qPCR and RNA sequencing to explore underlying molecular mechanisms. The results showed that broilers fed 0.1 % DSP exhibited an approximately 250 g increase in body weight at 42 days post-hatching, accompanied by increased feed intake (p < 0.05). Mortality due to hyperthermia occurred in five broilers in the control group, one in the 0.01 % DSP group, and none in the 0.1 % DSP group. RT-qPCR analysis revealed significantly higher hepatic expression of heat shock proteins (HSPs) in the treatment groups (p < 0.05), suggesting improved cellular protection and protein refolding capacity under heat stress. Additionally, pro-inflammatory cytokine expression was downregulated in DSP-fed broilers, while anti-inflammatory cytokine levels were upregulated (p < 0.05). RNA sequencing further indicated normalization of hepatic function and induced immune function in the 0.1 % DSP group. These findings suggest that dietary DSP activates the HSP axis by modulating immune responses, contributing to thermotolerance and improved performance in broilers under heat stress.