Effect of silkworm (Bombyx mori) dietary inclusion on chickens’ growth performance and carcass traits

The present experiment tested the effect of a partial replacement of soybean meal with a defatted silkworm (Bombyx mori) chrysalis meal (SWM-DEF) in the diets for growing chickens, on their live performance and slaughter traits. To this aim, a total of ninety ROSS 308 broiler chickens were randomly divided into three dietary groups consisting of 5 replicated pens/diet. The first group received a control diet (commercial poultry feed; C) throughout the growing period of 42 days, the second group received a diet including 4% SWM-DEF during the starter phase (1-10 days) (SWM1) and the C diet up to slaughter, and the third group was fed with the C diet in the starter phase and the 4% SWM-DEF diet up to slaughter (SWM2). Diets were isonitrogen and isoenergy and birds had free access to feed and water throughout the study. During the experiment, live weight (LW) and feed intake (FI) were recorded to calculate body weight gain (BWG) and feed conversion ratio (FCR). At 42 days of age, 15 chickens/treatment were slaughtered at a commercial abattoir, carcasses were weighed, and yield calculated. Afterwards, breast and legs were excised, weighed and yields computed. Data were analysed by using the one-way ANOVA with diet as fixed effect. Results highlighted that the dietary treatment did not affect neither the LW, nor the BWG of chickens. Differently, FI was lower in SWM2 compared to the other groups (P<0.05), but only in the starter phase. In the grower and finisher phases and considering the whole cycle, FI was not affected by the diet. Despite BWG and FI were similar in treatment groups, SWM1 and SWM2 chickens displayed the lowest, thus better, FCR (P<0.05) considering the 42 days growing period. At slaughter, chicken of the three dietary groups showed comparable carcass, breast, and leg weights and yields. Overall, the present experiment indicated that SWM-DEF can be considered a promising alternative feed ingredient to replace soybean meal in chicken rations. The 4% inclusion level seems a good choice to ensure optimum chicken growth, even improving efficiency, and satisfactory carcass traits. Also, different administration periods did not provide appreciable different outcomes, thus SWM-DEF can be provided in different growth phases, according to cost-benefit ratio. Further research should focus on the nutritional characteristics of the meat, a key factor for consumer’s health.