The effects of the dietary replacement of soybean meal with yellow mealworm larvae (Tenebrio molitor) on the growth, nutrient digestibility and nitrogen output of fattening rabbits

Abstract

The present study aimed to obtain novel information concerning the effects of the total dietary replacement of soybean meal (SBM) with yellow mealworm (Tenebrio molitor; TM) on the coefficients of total tract apparent digestibility (CTTAD) in the diet and on the nitrogen output of fattening rabbits. Two diets were formulated that included 60 g/kg SBM (SBM diet) or 30 g/kg TM (TM diet) as the main crude protein (CP) source. The TM diet had slightly lower CP content than the SBM diet (141 vs. 150 g/kg). A total of 30 rabbits (Hyplus PS 19 x Hyplus PS 40; males) weaned at the age of 32 day were randomly allocated into 2 groups (15 rabbits per group), individually housed, and fed one of the two diets ad libitum for 47 days. Feed intake was measured daily during the entire fattening period (between 32 and 79 day of age). The total faecal and urine output were individually measured between 57 and 61 day of age. A lower daily weight gain (ADWG) between 32 and 53 day of age (by 6.9 g/day, 12 %; P = 0.034), resulting in lower live weight (LW) at the age of 53 day, and a lower feed intake (ADFI) between 32 and 79 day of age (by 13 g/day, 7 %; P = 0.047) were recorded in rabbits fed the TM diet compared to rabbits fed the SBM diet. The ADWG or feed conversion ratio concerning the entire fattening period, the final LW of rabbits, or the CTTAD of the diets were not affected by treatments. Whatever the diet, on average, losses of nitrogen in faeces represented 26 % of the nitrogen intake. Lower losses of nitrogen in urine (by 0.35 g/day, 32 %; P = 0.007) and total excretion of nitrogen (by 0.53 g/day, 23 %; P = 0.003), as well as a higher nitrogen retention coefficient (by 0.06, 11 %; P = 0.026) were detected in rabbits fed the TM diet compared to rabbits fed the SBM diet. It can be concluded that fattening rabbits effectively utilized the diet containing TM without detrimental effects on the CTTAD of the diets or on their nitrogen output.