Effects of Barley- and Oat-Based Diets on Some Gut Parameters and Microbiota Composition of the Small Intestine and Ceca of Broiler Chicken

Barley and oats can be alternatives of corn and wheat in poultry nutrition and used at higher inclusion rates. Both cereals contain hulls, a structural fiber source, that can be beneficial for the gizzard function of birds. They also contain high amounts of β-glucans, of which about 60–70% is water soluble. Soluble β-glucans increase gut viscosity, impair digestion, and modify gut microbiota. The aim of this trial was to evaluate the effects of feeding oats and barley at high inclusion rates and with exogenous glucanase on some relevant gut parameters and the microbiota composition of jejunum content (JC), jejunum mucosa (JM), and cecal content (CC). A total of 360 male, Ross 308 broiler chickens were allocated randomly into three treatment groups of 5 replicate pens with 24 chickens. Beside a corn and soybean meal-based control diet (C), a barley (B)- and oat (O)-based treatment was used. In all feeding phases, barley was fed at 40, while oats at 20% inclusion rate. At day 40, 10 birds per treatment were slaughtered and gut viscosity, the cecal short chain fatty acid (SCFA) concentration, and the microbiota composition of the different gut parts determined. In spite of the glucanase enzyme addition, the barley-based diet significantly increased the viscosity of the ileal content and this was also the diversity of the bacteriota in the small intestine. On the other hand, this treatment decreased the microbial diversity in the ceca and resulted in lower SCFA contents. Barley increased the abundance of the phyla Bacteroidetes and decreased that of Firmicutes and some of them genera in the JC and CC. Oats had only a slight effect on the measured parameters. The results highlight the importance of also taking into account the soluble fiber fractions of the feedstuffs in diet formulation and to adapt the exogenous enzyme supplementation of to the actual soluble fiber contents.