PSXIII-16 Effects of different feed additives on serum hepatic enzymes, fecal pH and cecal mophometry in feedlot beef cattle.

Abstract The increased inclusion of grains in finishing diets can induce acidification of the gastrointestinal tract, which may alter intestinal integrity and liver function. This study aimed to evaluate the effect of different feed additives on serum liver enzymes levels, fecal pH, and cecal morphometry in feedlot cattle. A completely randomized design was used, with the animal as the experimental unit. A total of 48 Nellore bulls (BWi = 378.1 kg ± 8.92 kg; 20mo old) were assigned to two treatments: 1) MON - Sodium monensin 26 mg/kg DM, and 2) CRINA - a blend of essential oils 90 mg/kg DM + exogenous α-amylase 560 mg/kg DM + 25(OH) Vitamin D3 1 mg/animal/d. The finishing diet contained 10.7% sugarcane bagasse and 89.3% concentrate, including 35% ground corn and 35% reconstituted corn grain silage. Blood samples were collected on days 1, 31, and 101, and serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and γ-glutamyl transferase (GGT) were analyzed by a colorimetric assay. Fecal pH was measured on days 16, 31, 61, and 101 using an electronic pH meter. After 101 days of feeding, the animals were slaughtered, and cecal sac samples were collected and preserved in 10% formaldehyde. Histological slides were stained with hematoxylin and eosin (H&E) and evaluated by a pathologist. Data were analyzed using SAS software, with PROC MIXED used for statistical modeling. Fecal pH was analyzed as repeated measures over time, and the inflammation score was assessed using PROC FREQ. ALT and GGT levels were not affected by the additives (p >0.05) across all time points. MON showed higher AST serum levels on day 31 (103.1 vs 87.3 IU/L, p=0.03), but no differences were observed between groups at the end of the study (100.1 ± 7.7, p=0.89). Intestinal epithelial morphometry was not influenced by the additives. Crypt depth, villus circumference, goblet cell count, and enterocyte count per villus did not differ between treatments (p >0.05). The inflammation score, assessed based on the presence of inflammatory infiltrates, was similar between additives (p >0.05). Fecal pH was lower for CRINA (6.2 vs. 6.0 ± 0.05, p=0.004). Over time, a cubic pattern was observed (p=0.001), where fecal pH was highest on days 31 and 101 (pH 6.4 and 6.6), followed by day 16 (pH 6.0) and lowest on day 61 (pH 5.5), however, no additive ×time interaction was observed (p = 0.96). The lower AST level for CRINA during the initial period suggests better liver adaptation to high-concentrate diets. Despite the lower fecal pH in the CRINA group, cecal morphometry was not affected. These results suggest that CRINA could be a viable alternative to monensin, preserving gut integrity while potentially improving liver function during adaptation to high-concentrate diets.