Antimicrobial Effects of Black Soldier Fly and Yellow Mealworm Fats and Their Impact on Gut Microbiota of Growing Rabbits

Abstract

This study aimed to evaluate the in vitro antimicrobial activities of two types of insect fats extracted from black soldier fly larvae (HI, Hermetia illucens L.) and yellow mealworm larvae (TM, Tenebrio molitor L.) and their effects as dietary replacement of soybean oil (S) on cecal fermentation pattern, and fecal and cecal microbiota in rabbits. A total of 120 weaned rabbits were randomly allotted to three dietary treatments (40 rabbits/group) —a control diet (C diet) containing 1.5% of S and two experimental diets (HI diet (HID) and TM diet (TMD)), where S was totally substituted by HI or TM fats during the whole trial that lasted 41 days. Regarding the in vitro antimicrobial activities, HI and TM fats did not show any effects on Salmonella growth. Yersinia enterocolitica showed significantly lower growth when challenged with HI fats than the controls. The insect fat supplementation in rabbit diets increased the contents of the cecal volatile fatty acids when compared to the control group. A metataxonomic approach was adopted to investigate the shift in the microbial composition as a function of the dietary insect fat supplementation. The microbiota did not show a clear separation as a function of the inclusion, even if a specific microbial signature was observed. Indeed, HI and TM fat supplementation enriched the presence of Akkermansia that was found to be correlated with NH3-N concentration. An increase in Ruminococcus, which can improve the immune response of the host, was also observed. This study confirms the potential of HI and TM fats as antibacterial feed ingredients with a positive influence on the rabbit cecal microbiota, thus supporting the possibility of including HI and TM fats in rabbit diets.

Effect of host breeds on gut microbiome and serum metabolome in meat rabbits

“…The relative abundance of Subdoligranulum and Ruminococcus_2 has also been found to differ in different broiler chicken lines from the same poultry farm [25]. Additionally, Ruminococcus species have been reported to improve the immune response in rabbits [26].…”

Evaluation of the Production Performance and the Meat Quality of Chickens Reared in Organic System. As Affected by the Inclusion of Calliphora sp. in the Diet

“…In fact, in this first phase, the weight of the chicken increases the initial weight up to four times. This fact determines its subsequent growth [ 5 , 10 ]. That is why the contribution of nutrients of high biological and nutritional quality, such as insects, are key to the correct productive development of the chickens.…”

Beyond the protein concept: health aspects of using edible insects on animals

“…The dietary ingestion of HI and TM fats in substitution of 50 and 100% of soybean oil in the diets of growing rabbits did not influence the gut morphometry or alter the liver functions (Gasco et al, 2019b), although a positive effect on microbiota has been suggested (Dabbou et al, 2020). Indeed, an increase in the relative abundance of Bacteroides, Clostridium, Akkermansia and Ruminococcus has been observed.…”

“…Akkermansia has been indicated as being able to degrade the mucin in the intestine, with a consequent production of SCFAs and consequent positive effects on gut health. Ruminococcus are also butyrate producing bacteria that contribute to the positive effect on the caecal microbiota of rabbits (Dabbou et al, 2020).…”

“…The authors did not report any effect against Gram-negative bacteria. The in vitro antibacterial activity of insects fats extracted from both HI and TM larvae were also investigated in rabbit against common Gram-positive and Gram-negative bacterial pathogenic strains (Salmonella tiphymurium, Salmonella enteritidis, Yersinia enterocolitica, Pasteurella multocida and Listeria monocytogenes) (Dabbou et al, 2020). These bacteria are foodborne pathogens posing public health concern (De Cesare et al 2017;Kylie et al 2017;Massacci et al 2018;Rodriguez-Calleja et al 2006).…”