First report of the apparent metabolisable energy value of black soldier fly larvae fat used in broiler chicken diets

• For the first time, the Hermetia illucens fat metabolisable energy was evaluated. • The insect fat apparent metabolisable energy was calculated for broiler chickens. • The insect fat metabolisable energy varied depending on bird age. • This study indicates that insect fat energy density is similar to soybean oil. • Regression models have been proposed for metabolisable energy calculation. In the available literature, there are limited data about the energetic value of insect-derived products. In particular, insect fat cannot be used in practical broiler nutrition due to the lack of precise apparent metabolisable energy ( AME ) value. Therefore, the present study aimed to investigate the AME and apparent metabolisable energy corrected to zero nitrogen balance ( AME N ) levels of Hermetia illucens larvae fat for broiler chickens of various ages. A total of 400 1-day-old male Ross 308 chicks were randomly allotted to four dietary groups (10 replicate pens per treatment; 10 birds per pen). The following treatments were applied: HI0 – basal diet without dietary fat inclusion, HI03 – basal diet enriched with 30 g/kg H. illucens larvae fat, HI06 – basal diet enriched with 60 g/kg H. illucens larvae fat, and HI09 – basal diet enriched with 90 g/kg H. illucens larvae fat. Broilers had ad libitum access to mash form feed and water. Excreta samples were collected on d 14, d 28, and d 35. To determine the AME and AME N values of H. illucens larvae fat, the simple linear regression method was used. The results show that the AME and AME N values of H. illucens larvae fat for broiler chickens are 9 049 kcal/kg (37.86 MJ/kg) and 9 019 kcal/kg (37.74 MJ/kg), respectively. Additionally, because the birds’ age significantly ( P < 0.001) affected the AME and AME N levels, the implementation of H. illucens larvae fat to broiler diets should be considered in each nutritional period using the recommended regression model AME = 2 559.758 + 62.989 × fat inclusion (%) + 7.405 × day of age and AME N = 2 543.2663 + 62.8649 × fat inclusion (%) + 7.3777 × day of age. The present data emphasised that the H. illucens larvae fat metabolisable energy is similar to that of soybean oil.