Effects of tannic acid extract on performance and intestinal health of broiler chickens following coccidiosis vaccination and/or a mixed-species Eimeria challenge.

Two experiments were conducted to investigate the effects of tannic acid extract (TAE) formulations on the performance and intestinal health of male Cobb × Cobb 500 broilers exposed to coccidiosis. In the first experiment, 320 broiler chicks were randomly assigned to 5 treatments with 8 replicates. Treatments included non-medicated, uninfected (NC); non-medicated, infected (PC); salinomycin (SAL, 66 mg/kg); tannic acid (TA, 0.5 g/kg) and TAE (TAE, 0.5 g/kg). On d 14, all groups (except NC) were orally inoculated with Eimeria acervulina, E. maxima and E. tenella oocysts. Intestinal lesion scores, fecal oocyst counts (OPG) and performance were evaluated on d 20. The PC had greater lesions and higher FCR than infected, supplemented groups. Only TAE reduced OPG compared to PC (P < 0.05). In the second experiment, 3,000 broiler chicks were vaccinated on day of hatch with live coccidial oocysts, then randomly assigned to 5 treatments with 15 replicates. Treatments included non-medicated (CNT); salinomycin (SAL, 66 mg/kg); robenidine (ROB, 33 mg/kg); TAE (0.5 g/kg) and TAE with Bacillus coagulans (TAE+BC, 0.5 g/kg). On d 29, a subset of pens (n = 20) were challenged with a mixed Eimeria spp. oral inoculum; performance, lesions and OPG were evaluated on d 35. An immune challenge was created in half the pens by issuing broilers feed without supplementation materials during the challenge. For the non-challenged pens (n = 55), performance was measured up to d 49. Performance of non-challenged, vaccinated-CNT birds was improved with all treatments at d 21 and d 49. Among the challenged birds, withdrawal of SAL or ROB resulted in FCR similar to the challenged CNT group (P > 0.05), whereas withdrawal of TAE or TAE+BC maintained improved FCR compared to challenged-CNT birds (P < 0.05). These findings indicate supplementation of TAE and TAE+BC with coccidiosis vaccination can be considered as a potential alternative strategy to address coccidiosis in broiler chickens.

Contributions of valine-292 in the nicotinamide binding site of liver alcohol dehydrogenase and dynamics to catalysis.

The participation of Val-292 in catalysis by alcohol dehydrogenase and the involvement of dynamics were investigated. Val-292 interacts with the nicotinamide ring of the bound coenzyme and may facilitate hydride transfer. The substitution of Val-292 with Ser (V292S) increases the dissociation constants for the coenzymes (NAD(+) by 50-fold, NADH by 75-fold) and the turnover numbers by 3-7-fold. The V292S enzyme crystallized in the presence of NAD(+) and 2,3,4,5,6-pentafluorobenzyl alcohol has an open conformation similar to the structure of the wild-type apo-enzyme, rather than the closed conformation observed for ternary complexes with wild-type enzyme. The V292S substitution perturbs the conformational equilibrium of the enzyme and decreases the kinetic complexity, which permits study of the hydride transfer step with steady-state kinetics. Eyring plots show that the DeltaH for the oxidation (V(1)) of the protio and deuterio benzyl alcohols is 13 kcal/mol and that the kinetic isotope effect of 4.1 is essentially temperature-independent. Eyring plots for the catalytic efficiency for reduction of benzaldehyde (V(2)/K(p)) with NADH or NADD are distinctly convex, being temperature-dependent from 5 to 25 degrees C and temperature-independent from 25 to 50 degrees C; the kinetic isotope effect of 3.2 for V(2)/K(p) is essentially independent of the temperature. The temperature dependencies and isotope effects for V(1) and V(2)/K(p) are not adequately explained by semiclassical transition state theory and are better explained by hydride transfer occurring through vibrationally assisted tunneling.