Effects of dietary fiber on mineral metabolism and caecal microbial diversity in broiler chickens (Gallus gallus L.) fed a semi-synthetic diet

Various additives used in poultry diets can change the mineral status of the body. Dietary fiber has long been considered an anti-nutritional factor due to adverse effects on feed intake and nutrient absorption. However, with increasing evidence, it has been found that dietary fiber has a positive effect on nutrient digestion, fermentation, and absorption processes in poultry. In this work, for the first time, data were obtained on the influence of dietary fibers, the microcrystalline cellulose, lactulose and chitosan on mineral metabolism and caecal microbiocenosis of broiler chickens fed a semi-synthetic diet. A decrease in the accuulation of toxic microelements in the body of a bird was demonstrated, as well as a change in the microbial community of the caecum. Experiments on the Arbor Acres cross broiler chickens (Gallus gallus L.) were carried out in the vivarium (the FSC BSA RAS). A total of 150 of week-old broiler chickens were divided into 5 groups of analogues (n = 30 each). The duration of the experiment was 35 days. The first control group C1 was fed with a semi-synthetic diet (SS). The second control group C2 received a semi-synthetic diet deficient in trace elements (DSS). For dietary fibers, test group I was fed with dietary microcrystalline cellulose (E460, 0.25 g/kg feed), test group II with dietary lactulose (1 g/kg feed), and test group III with dietary chitosan (0.5 g/kg feed). In feed and biomaterial of broilers, 25 chemical elements were assayed: Ca, Cu, Fe, Li, Mg, Mn, Ni, As, Cr, K, Na, P, Zn, I, V, Co, Se, Ti, Al, Be, Cd, Pb, Hg, Sn, Sr by atomic emission spectrometry and mass spectrometry techniques. Microbial biodiversity of the caecum was assessed on day 42. NGS sequencing was performed using a MiSeq platform (Illumina, Inc., USA). In test group I, the dietary fiber led to a statistically significant increase in the calcium (by 23,4 %. p ≤ 0.05) vs. C2. In test group III, there was a 1.5-forl decrease in the indicator (p ≤ 0.05) vs. C1 and a 26.3 % decrease (p ≤ 0.05) vs. C2. The lithium content increased 1.7 times (p ≤ 0.05) vs. C1 when chitosan was added to a semi-synthetic diet deficient in trace elements. The concentration of manganese and cobalt significantly (p ≤ 0.05) decreased in all test groups vs. C1. In group I, the amount of selenium increased 2.35 times (p ≤ 0.05) vs. C1 it decreased 1.74 times (p ≤ 0.05) vs, C2. In the same group, the iodine level increased 1.74 times and 1.5 times (p ≤ 0.05) vs. control groups. In test groups II and III, selenium decrease 4.64 times and 4.55 times (p ≤ 0.05) vs. C2. The concentration of arsenic in group II exceeded C1 1.63 times (p ≤ 0.05), and in group III, its concentration, on the contrary, decreased 1.58 times and 2.0 times (p ≤ 0.05) vs. C1 and C2. The dietary fiber scontributed to the removal of toxic elements. In test group I and group III, the concetration of strontium decreased (p ≤ 0.05) by 25.7 and 45.9 %, respectively, vs. C1. For C2, a decrease in the amount of strontium by 22.2 and 43.4 % was similarly revealed (p ≤ 0.05). In group I, the counts of Rikenellaceae increased 6.3 and 6.8 times, Lachnospiraceae 12 and 4.9 times, Ruminococcaceae 2.1 times and 3. 9 times compared to C1 and C2, respectively. In group II, the abundance of Lactobicallaceae decreased 6 times, the number of Rikenellaceae increased 6.2 times, Lachnospiraceae 9.57 times, Ruminococcaceae 3.1 times compared to C1. In group III, there was a decrease in the content of Lactobicallaceae by 13.3 and 1.55 times compared to C1 and C2. The number of Rikenellaceae increased 5.5 times, Lachnospiraceae 11.8 times, Ruminococcaceae 3.5 times compared to C1. Thus, dietary fibers added to a semi-synthetic diet led to a decrease in the content of macroelements in the body of Arbor Aikres cross broiler chickens, the elimination of toxic elements, and increased the counts of Rikenellaceae and Lachnospiraceae taxa with a simultaneous decrease in the number of Lactobacillaceae in the intestine.