Effects Of Dietary Supplementation Of Gallic Acid On Intestinal Morphology And Antioxidant Status In Broiler Chicks And Its Anticoccidial Effects

Plant extract phenolic compounds are widely considered as alternative natural growth promoters with a diverse range of activities,but do not result to tissue residues and resistance.Gallic acid?GA?is one of the most extensively used phenolic compounds as human food supplement for health promotion and disease prevention.The current study aimed to explore the potential growth-promoting effects and anticoccidial effects of GA in broiler chicks.Three experiments were conducted to observe the effects of dietary GA supplementation on growth performance,antioxidant status and jejunum intestinal morphology in broiler chicks under normal condition,and its anticoccidial effect after birds were chanllenged with E.tenella.The first experiment was designed to investigate the efficacy of inclusion of dietary GA at levels of 0,25,50,75,100 and 150 mg/kg on growth performance,antioxidant status and jejunum intestinal morphology of broiler chicks.In total,630 1-d-old Arbor Acres?AA?male broiler chicks were randomly allotted to 6 treatment groups for the period of 6 weeks.Each treatment contained 7 cages of 15 chicks each.The results indicate that dietary addition of GA at 75 to 100 mg/kg improved feed conversion efficiency?feed:gain?in both the grower?d 21 to 42,P=0.045?and overall?d 1 to 42,P=0.026?periods.Dietary addition of GA at a concentration?100 mg/kg was able to exhibit higher breast muscle ratio at 42 d?P=0.043?.Interestingly,dietary GA inclusion level from 50 to 100 mg/kg reduced the crypt depth?P=0.009?and increased villus height:crypt depth ratio?VCR?of the birds?P=0.006?.Moreover,dietary addition of GA linearly increased plasma total antioxidant capacity?T-AOC??P=0.039?and total superoxide dismutase activities?T-SOD??P=0.049?at 21 d of age,and decreased plasma malondialdehyde?MDA?content at 42 d of age?P=0.030?at 100mg/kg.No significant effects of dietary GA addition were observed on plasma biochemical items.The second experiment was conducted to evaluate whether dietary GA can further replicate its efficacy to prevent or treat coccidiosis in broiler chicks following oral infection with E.tenella,and growth performance,antioxidant status and immune items were observed.A total of 480 1-d-old male Arbor Acres broiler chicks were randomly assigned to 5 treatment groups as follows:Blank control?BC?=uninfected,negative control?NC?=infected,positive control?PC?=infected+100 mg/kg of monensin,and groups GA1 and GA2=infected+50 and 100 mg/kg GA,respectively.This experiment lasted for 6 weeks.All treatment groups except BC group were orally infected with 5×10⁴sporulated E.tenella oocysts at 14 d of age.In the present study,during the first week post infection?p.i.?we observed stunted growth,reduced breast muscle yield and an increased FCR in the NC group as compared to BC group.However,groups supplemented with dietary GA supplementation increased ADG?P=0.008?,muscle yield?P=0.035?,and reduced FCR?P=0.001?as compared to NC group at 7 d p.i.,and the effect was comparable to PC group treated with a standard coccidiostat i.e.,monensin.With regard to indices of pathogenicty,the results show that E.tenella provoked significant injuries to the intestinal mucosa.However,similar to PC group dietary GA supplementation showed coccidiostatic like effects as indicated by decreased fecal oocyst output per gram?P=0.001?and mild blood shedding.In the present study,dietary GA supplementation enhanced plasma antioxidant status of the broiler chicks after infection as indicated by reduced the plasma MDA?P=0.044?and enhanced T-SOD activities?P=0.048?.In addition,our study shows that dietary GA exhibits anti-inflammatory activity by reducing the plasma nitric oxide content?P=0.001?,thus protecting host tissues to minimize blood shedding.At 7 d p.i.dietary GA supplementation further increased the ileal IEL count?P=0.001?and sIgA content secreted by the cecal tonsil?P<0.001?,demonstrating that dietary GA supplementation may enhance both humoral immune response and cellular immune response to strengthen mucosal immunity for fighting against coccidiosis.The third experiment intended to assess the comparative anticoccidial efficacy of dietary GA againist dietary grape proanthocyanidins?GPCs?in broiler chicks following oral infection with E.tenella.On d 14,a total of 240 birds,randomly assigned to 4 treatment groups,were orally infected with around 10⁴ sporulated E.tenella oocysts.The treatment groups are:negative control?NC?group=infected+no treatment;positive control?PC?group=infected+100 mg/kg of monensin;GA group=infected+100 mg/kg GA and GPCs group=infected+15 mg/kg GPCs.Birds were fed a standard diet supplemented with or without dietary GA and GPCs for 6 weeks.Antioxidant markers were investigated to evaluate the relative antioxidant potential of GA and GPCs in broiler chicks after E.tenella infection.At 7 d p.i.elevated plasma MDA content was observed in the NC group compared with other groups?P<0.001?.Dietary supplementation of both GA and GPCs reduced the plasma MDA content at 7 d p.i.?P<0.001?and 28 d p.i.?P=0.015?,but the efficacy of both GA and GPCs was more apparent at 7 d p.i.in the present study.In addition,enhanced plasma T-SOD?P=0.035?activities at 7 d p.i.and 28 d p.i.?P=0.028?,and improved plasma T-AOC?P=0.003?at 7 d p.i.were observed in the GA and GPCs treated groups.But no significant effect of coccidial infection on growth performance was observed during the first week after infection.Overall,under normal production condition the suitable supplemental levels of dietary GA in broiler diets for enhanced growth performance and health are 75 to 100 mg/kg.Our studies also confirmed that dietary at GA 100 mg/kg could improve growth performance,restore the antioxidant status,and enhance the intestinal health after broiler chicks were challenged with 5×10⁴ sporulated E.tenella oocysts.In addition,our results indicated that dietary GA may be is as efficacious as monensin against E.tenella infection,and can be used as a potential therapeutic or prophylactic anticoccidial agent against avian coccidiosis.Birds were also challenged with 10⁴ sporulated E.tenella oocysts and the efficacy of both GA and GPCs was evident on the bases of antioxidant indices.However,further study is needed to investigate comparative anticoccidial effect of GA and GPCs using dosages adequate to inflict a significant challenge to broiler chicks.