Changes in broiler performance, duodenal histomorphometry, and caeca microbiota composition in response to wheat-barley based diets supplemented with non-antibiotic additives

The present study was conducted to investigate the effect of supplementing wheat-barley based diets with dry whey powder (DWP), chitosan (CHIT), a mixture of DWP-CHIT, and inulin (INU) on productive performance, duodenal histomorphometry and caeca microbial composition of chickens. A total of 1500 one-day-old male birds were allocated to floor pens and assigned to one of the following treatments: control diet (no additive supplementation), 60-DWP (60 g/kg of DWP), 5-CHIT (5 g/kg of CHIT), DWP-CHIT (60-DWP plus 5-CHIT), and 20-INU (20 g/kg of INU). Each treatment had 10 replicate pens, with 30 birds per pen. Measurements of productive performance were made during the starter period (day 1-21) and for the entire feeding period (day 1-42), while duodenal measurements were registered at day 21. Caeca microbiota composition was determined using Illumina amplicon sequencing at days 21 and 42. During the starter period, feeding chickens with any of the tested additives diminished their body weight (BW), average daily gain (ADG) and feed intake (FI) as compared to control diet (P < 0.05). This was also observed during the entire feeding period (P < 0.05), except for INU supplementation that showed similar values to control birds. None of treatments affected duodenal histomorphometry. Caeca microbiota composition was influenced by diet at every stage of the productive period (P = 0.001), although no clear association between microbiota and performance was detected. At day 21, no differences in microbiota composition of control, 60-DWP, 5-CHIT and 20-INU birds were found, which caeca were highly harboured by Lactobacillus gallinarum, although only control promoted greater BW, ADG, and FI. Control and 60-DWP treatments did not differ in their caeca communities at day 42, although only control increased BW, ADG, and FI. In both cases, caeca showed higher abundance of Lactobacillus gallinarum and Bacteroides vulgatus, and lower abundance of Escherichia coli/Shigella flexneri and Bacteroides fragilis. DWP-CHIT diet promoted an increase of Klebsiella pneumoniae at day 21, and of Streptococcus gallolyticus at day 42, together with a performance reduction as compared to control diet. The present findings indicate that chicken growth is reduced by supplementing wheat-barley based diets with DWP, CHIT, DWP plus CHIT, and INU, at the tested doses, as a consequence of a reduction in FI. Caeca microbiota composition and diversity varied in a diet-dependent manner during both sampled ages, although a linkage between microbiota and performance was not clear.