Growth performance, conversion and survival rates of Tenebrio molitor (Coleoptera: Tenebrionidae) reared on various livestock diets

The yellow mealworm Tenebrio molitor (Coleoptera: Tenebrionidae) started recently to be used as a feed and food to replace traditional products. The optimization of mass rearing conditions and the choice of appropriate diets are the most important factors governing the production of these insects and secondary products. The aim of this study was to study the performance of T. molitor on six affordable animal feed diets (two different dairy cow feeds, calf starter feed, chick starter and grower feeds and wheat bran) in addition to a control diet based on wheat bran and starter feed for Chick (60:40 ratio). Larvae showed the highest mass gain and growth rate when fed on wheat bran only. The control and the wheat bran diets were the most consumed by T. molitor larvae, while the other feeds were less appreciated. Conversion and survival rates did not vary significantly between the diets. The results should be taken into consideration for large scale mass-rearing of T. molitor.  Keywords: Animal feeds; growth rate; mass rearing; weight gain; yellow mealworm

The mealworm

Agricultural activities generate important amount of crop residues that need to be managed in appropriate way usingecofriendly and cost effective tools. The mealworm Tenebrio molitor (Coleoptera: Tenebrionidae) is a potential candidate to valorize crop residues thatcan produce atthe same time an alternative feed based on insect larvae. Four crop residues (citrus, tomato, pepper and potato) mixedwith wheat bran (ratio 50:50) were evaluated as diets for mass rearing of T. molitor under controlled environmental conditions (T= 28 ± 1°C; RH=70 ± 5 % and total darkness). Five zootechnical parameters (weight gain, growth rate, mortality rate, weight of consumed feed and conversion rate) were adopted to evaluate thegrowth and life developmental traits of larvae during 45 days. The effect of crop residues used as diet had a significant impact on bothweight gain and growth rate. Importantly, crop residues used alone has a negative effect on all zootechnical parameters evaluated. Indeed, the amendment of wheat bran has a significant positive impact on these parameters. Citrus and tomato were the most toxic diets showing a mortality rate of 92 and 98 %, respectively. The most efficient diets werethe mixture of citrus residues andwheat branfollowed by the mixture of potato residues and wheat bran and the mixture ofpepper residues and wheat bran. Fed substrate had no impact on conversion rate