They said their study was conducted to evaluate the effect of small amounts of mealworm, Tenebrio molitor, and super mealworm larvae, Zophobas morio - 0.2 and 0.3% - on the growth performance, various blood parameters and immune system traits of broiler chickens.
Diet composition may modulate immune function in broiler chickens, said the Polish team, citing research by Kidd, 2004.
But there are no data in the literature on the effects of full-fat insect meals on the immune system of broiler chickens, they stressed.
They hypothesized that supplementation of broiler diets with full-fat insect meals at low dosage levels - 0.2 and 0.3% - may improve the growth performance of broiler chickens through the modulation of the immune system traits.
The team said 1,000 one-day-old female Ross 308 broiler chicks were used in two independent experiments.
In the first experiment, birds were randomly assigned into six dietary treatment groups, with 10 replicate pens per treatment and 10 birds per replicate pen. In the second trial, birds were assigned into four dietary treatment groups, with 10 replicate pens per treatment and 10 birds per replicate pen.
Starter diets were offered to all birds from 1 to 14 days of age, and grower diets were offered from 15 to 35 days of age. No exogenous enzymes were added to the diets. In the first experiment, the insect full-fat meals were added ‘on top’ of the complete diet, while in the second experiment, the insect full-fat meals were ‘calculated into’ the diets.
The experimental treatments used included the following:
Experiment 1: NC (negative control) − no additives; PC (positive control) − NC + salinomycin addition (60 mg/kg diet); TM02 − NC + 0.2% T. molitor full-fat meals; ZM02 − NC + 0.2% Z. morio full-fat meals; TM03 − NC + 0.3% T. molitor full-fat meals; and ZM03 − NC + 0.3% Z. morio full-fat meals.
Experiment 2: NC (negative control) − no additives; PC (positive control) − NC + salinomycin addition (60 mg/kg diet); TM03 − NC with 0.3% T. molitor full-fat meals; and ZM03 − NC with 0.3% Z. morio meals full-fat meals.
In both experiments, the team observed that the supplementation of insects increased body weight gain (BWG) and feed intake. They saw no negative effect on the FCR in experiment one; however, in the second trial, the supplementation of insect meal increased FCR values, they said.
“The results of the present study are in line with the experiment conducted by Biasato et al. (2017), in which the inclusion of 5 to 15% of the T. molitor meal in the diet improved the growth performance parameters.”
In both experiments, no significant effect on internal organ weights was observed.
The biochemical parameters of blood are crucial traits to assess the health status and performance of animals, including poultry (Milner et al., 2003; Lumej, 2008). Total protein (TP) and albumin concentration are useful factors to evaluate the body condition of poultry (Piotrowska et al., 2011), said the team.
Plasma proteins play a fundamental role in body homeostasis maintenance.
“In the first experiment, the TP level was not affected, while in the second experiment, the insects showed a higher value of protein level. Albumin is the most favorable source of amino acids for protein synthesis (Filipović et al., 2007). In this study, the albumin level was not affected in the first experiment; these findings were in accordance with those of Biasato et al. (2016). However, in the second experiment, the insect addition increased the albumin level.
“The changes in the TP and albumin level could be attributed to the properties of chitin contained in the insect meals (Biasato et al., 2016).”
Impact on immune response
The levels of immunoglobulins, IgM and IgY, were significantly high in the NC in comparison to the other treatments with insect inclusion and PC, they said.
“This clearly indicates that the inclusion of insect full-fat meals may have a significant impact on the immune response in broilers. The decreased levels of immunoglobulin classes IgM and IgY in the experimental groups fed full-fat insect meals could be explained by the antimicrobial effects of insect components such as AMPs and chitin,” said the researchers.
The team said that insects are not only considered for their nutritional benefits but also for their wide spectrum of activities against pathogens due to their ability to synthesize antimicrobial peptides (AMPs) (Józefiak and Engberg, 2017).
AMPs are small cationic peptides that affect the molecules of innate immunity and have shown a broad spectrum of activity against bacteria, fungi, and viruses (Boman, 1995; Imamura et al., 1999; Thacker, 2013; Józefiak and Engberg, 2017), they said.
In addition to synthesizing AMPs, insects are a rich source of chitin, whose beneficial effect in increasing the activity of the innate immune system, as well as its antibacterial effects, have been widely studied (Koide, 1998; Esteban et al., 2001; Xu et al., 2013), said the Polish scientists.
In addition, Lee et al. (2008) reported that chitin has various biological activities, including immunostimulation, they said.
Józefiak et al. (2018) found that the inhibition of possibly pathogenic bacteria and the positive modulation of microbiota in the broiler chicken GIT could be due to full-fat insect meals, potentially similar to the effects of ionophore coccidiostats, i.e., salinomycin.
“The results of the present study showed that the addition of a relatively small full-fat insect meal may decrease immunoglobulin levels, similar to salinomycin.”
The mechanisms by which insect full-fat meals function remain unknown, however, and further studies are needed to investigate them, said the Polish team.
Source: Poultry Science
Title: Tenebrio molitor and Zophobas morio full-fat meals as functional feed additives affect broiler chickens' growth performance and immune system traits
Authors: A. Benzertiha, B. Kierończyk, P. Kołodziejsk, E. Pruszyńska–Oszmałek, M. Rawski, D. Józefiak, A. Józefiak