The Effect of Chemical Buffering and Microbial Additives on Histomorphometry and Histopathology of the Small and Large Intestine of Lambs Fed High Concentrate Diets

Intestinal function in nutrient uptake depends on its morphology, and any change in villi structure, as well as changes in the differentiation and development of absorbent cells, can alter digestion and absorption capacity and thus function. Increasing the height and surface of Villus in the gastrointestinal tract of animals consuming high concentrates increases the absorption capacity and in turn, protects the animal from the accumulation of volatile fatty acids and a noticeable decrease in pH. In fact, it helps the lining of the gastrointestinal tract absorb volatile fatty acids faster and stabilize the pH. High starch in diets, followed by a decrease in pH, affects the morphology of the rumen and intestine. Any change in this morphology may predispose the intestines to dysfunction. Megasphaera elsdenii prevents a sharp decrease in ruminal pH due to lactic acid accumulation by consuming lactic acid, and in cases of subacute acidosis by converting lactic acid to propionic acid may provide an opportunity to reduce inflammation and improve energy balance in livestock. Saccharomyces cerevisiae also contributes to the growth and activity of cellulose-degrading bacteria, lactate consuming bacteria, and rumen protozoa and the concomitant use of lactate consuming bacteria with Saccharomyces cerevisiae has been confirmed. Therefore, the aim of this study was to investigate the effect of chemical and microbial buffer additives on histomorphometry and histopathology of the small intestine and large intestine during high concentrate feeding.  Twelve Arabi male sheep at 9 ± 1 months old and initial body weight of 35.95±3.55 kg were used in a completely randomized design with three treatments and four replicates, and the duration of the experiment was 35 days. The experimental treatments consisted of a 1- control diet, 2- control diet + sodium bicarbonate buffer, 3- control diet + Megasphaera elsdenii, and Saccharomyces cerevisiae (bacterial-yeast), which fed ad libitum. At the end of the experiment, the lambs were slaughtered and the small and large intestines were sampled for histomorphometry and histopathology studies. Each sample was placed separately in closed-sealed containers containing 10% formalin, and tissue changes were examined microscopically. No significant difference was observed between the experimental treatments for the tissue indices studied in the duodenum and jejunum. However, the ratio of villus height to crypt depth in the bacterium-yeast recipient treatment was numerically higher than other treatments. In ileum section, villi height, crypt depth and villi area in control treatment 653.33; 506.67; 258.42 compared to buffer treatment 430.00; 328.33; 161.40 and treatment containing bacterial-yeast 445.00; 365.00; 178.04 respectively were significantly higher (P <0.05). In the present experiment, due to the consumption of a diet with high concentrate and possibly increased production of volatile fatty acids in the rumen and their transfer to later parts of the gastrointestinal tract, increased villi height, crypt depth, and villi area in different parts Intestine was observed especially in control treatment; In fact, one of the reasons for increasing the villi height and Villus surface in acidosis, is increased the absorption capacity of volatile fatty acids and help maintain pH of the rumen, Therefore, reducing these indices in chemical buffer and bacterial-yeast treatments can be the result of the positive effects of buffer and microbial additives such as improving the pH of ruminal fluid transferred to different parts of the intestine, as a result of increased activity of cellulolytic bacteria and more acetate production, which has caused relative control of acidosis in the control treatment. Improving the Villus height to crypt depth ratio in the duodenum and jejunum in treatments receiving chemical or microbial additives can be considered as positive results of using pH-adjusting additives in the present experiment. In different parts of the small intestine, in all three treatments, inflammation of the intestinal mucosa was observed in the form of infiltration of mononuclear inflammatory cells, including lymphocytes, plasma cells with different degrees of eosinophils. In the large intestine in the control treatment, hyperemia, the infiltration of inflammatory cells of lymphocytes, plasma cells, and eosinophils in small numbers in Lamina propria and labyrinth of Lieberkohen glands as well as necrosis of the villi was observed. In general, changes in intestinal tissues are to counteract the inflammation caused by acidosis. In general, although the use of chemical buffering or microbial additives had a positive effect on the histomorphometry of the ileum, but did not have a positive effect on the histopathology of the small and large intestine. It is suggested that the present experiment be examined in the early stages of livestock growth when the microbial flora is not fully established.