Regulatory effect of tannins on ruminal digestion, colon microbiota, blood biochemistry and non-specific resistance in sheep (Ovis aries)

Recently, one of the important problems in animal husbandry remains the conflict between high productivity and physiological capabilities of the body. Therefore, an important role is given to the use of natural bioactive substances with certain functional properties, in particular tannins, in animal nutrition. Here, for the first time, we revealed the regulatory effect of the developed energy-protein granulated product (EPP) supplemented with an extract of Dahurian larch (Larix dahurica Turez) bark as a source of tannins on rumen digestion, microbial landscape of the gastrointestinal tract and metabolic processes in sheep. Our goal was to study tannins of Dahurian larch bark as a functional product, a regulator of enzymatic processes, microbiocenosis in the rumen and large intestine and their indirect effect on pathogenetic resistance and metabolic indices in sheep. The studies were conducted on six fistulated Romanov sheep (Ovis aries) using the group-period method (the physiological yard of the Ernst Federal Research Center for Animal Husbandry, 2022). The duration of each observation period was 21 days with 14-day equalizing breaks between them. The sheep were fed a diet consisting of 1.5 kg of cereal-forb hay, 0.2 kg of OK-80 sheep feed (OOO YuV Zorya, Russia) and mineralized salt lick. During test periods, the sheep were additionally given 155 g of EPP consisting of substandard products of the confectionery industry and by-products of grain processing with feed calcium phosphate and salt. The EPP was supplemented with Dahurian larch bark ( Larix dahurica (5 g, ExtraKor, AO Ametis, Russia) aqueous extract containing condensable tannins proanthocyanidins (65 %), dihydroquercetin (16 %), and phenolic acids (14 % hydroxybenzoic acid). At the end of each period, 1 and 3 h after feeding, rumen contents were sampled to measure pH (an Aquilon 420 pH meter, AO Aquilon, Russia). The total amount of volatile fatty acids (VFA) was determined by steam distillation, the ammonia nitrogen concentration by the Conway microdiffusion method, and amylolytic activity photometrically. The biomass of protozoa and bacteria in the rumen contents was measured by differential centrifugation. Microbiological analysis of the large intestine contents was carried out by 10-fold serial dilution method using growth and diagnostic media for deep (1.0 ml) and surface (0.2 ml) cultures to count the number of colony-forming units (CFU/g). To assess animal metabolic status, blood were sampled from the jugular vein at the end of the period. The dietary EPP and tannins had a positive effect on the rumen digestion and the digestibility of dietary nutrients, on metabolism, clinical parameters, and the pathogenetic resistance of sheep. In the experimental period, compared to the control, the ruminal pH decreased from 6.56 to 6.25, VFA concentration increased by 42.7 % (p 10 CFU/g. As a result, the digestibility of dietary nutrients increased, e.g., organic matter, crude protein, crude fat, crude fiber by 0.79, 4.38, 2.32, 2.47 abs.%, respectively. During the test period, albumin content increased by 8.3 % globulins decreased by 5.1%, urea increased by 8.9 %, creatinine by 48.5 %, triglycerides by 171.4 %, cholesterol by 7.1 %, and glucose level decrease by 3.8 %, bilirubin by 32.0 %, and alkaline phosphatase by 30.1 %. In mineral metabolism, the phosphorus-calcium ratio normalized (p function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }