Effects Of Dietary Addition Of Azomite On The Growth Performance,Nutrient Utilization,Blood Biochemical Indices And Bone Development In Broiler Chickens And Its Mechanism

The substitution of feed antibiotics is one of the hot spots and challenges in broiler industry.Previous studies have shown that azomite,a rare earth mineral feed additive,has the potential to substitute antibiotics in animal feed.This study evaluated the effect and mechanism of azomite as substitute for antibiotics in broiler chicken feed and explored the feasibility of reducing the feed cost of broiler chickens by azomite application.Experiment 1 was carried out to investigate the effect of azomite(AZO)on the growth performance,nutrient availability,digestive enzymes activity,immune function,and bone mineralization of broiler chickens.A total of 240-day old male chicks Arbor Acres(AA)were randomly assigned into four dietary treatments with six replicates(n=10),which included control(without any antibiotics),control+0.25%AZO,control+0.50%AZO and control+kitasamycin(as AGPs).The experiment lasted for 42 days.The results indicate that LBW,ADG and FCR was significantly(P<0.05)improved in AZO 0.25%and0.50%than the control.Slaughter percentage,half eviscerated,eviscerated(EV),breast muscle(BM)and leg muscle(LM)were significantly(P<0.05)higher in the AZO 0.50%group than control.Availability of DM,CP,AME,Ca and P was significantly higher(P<0.05)in AZO 0.25%and 0.50%dietary treatments.Moreover,intestinal amylase and trypsin activity were improved in AZO 0.25%and 0.50%groups.Serum CREAT was significantly increased in AZO 0.50%treatment,while serum IgG was significantly improved in AZO 0.25%treatment.Tibia diameter(TD),tibia breaking strength(TBS)were numerical higher in AZO 0.25%,while Ca and P%was significantly(P<0.05)increased in azomite0.25%treatment.The results indicated that addition of azomite at the dose of 0.25%and 0.50%in the diet had beneficial effect on growth performance,availability of nutrients,digestive enzymes and bone mineralization.Experiment 2 was executed to determine the influence of azomite in low energy diet on growth performance,nutrient utilization and bone parameters for broilers chickens.A total of 180 one-day-old broiler chicks Arbor Acers(AA)were randomly assigned into three dietary treatments with six replicates and 10 birds per replicate.These treatments included(1)Control as a basal diet,(2)LME(basal diet-100kcal ME kg~-11 in starter phase and-200 kcal ME kg~-11 in finisher phase)and(3)AZO-0.25(LME+AZO-0.25%).The experiment lasted for 42 days.The results of this study showed that growth performance in terms of LBW and ADG improved significantly with AZO-0.25 supplementation(P<0.05),while FCR was lower(P<0.05)in group fed with AZO-0.25 than LME.ADFI was significantly(P<0.05)lower in CONT compared to LME and AZO-0.25 treatments.Percentage of Slaughter,half eviscerated,eviscerated carcass,breast muscle and leg muscle were higher significantly(P<0.05)in the AZO-0.25than LME.Broilers fed diet with AZO-0.25 increased(P<0.05)the availability of DM,CP,AME,P and Ca compared to LME.Serum total protein,IgG and CT levels were significantly(P<0.05)higher in AZO-0.25 than LME.Furthermore,tibia length,tibia bone strength,the content of ash,P and Ca in tibia bone increased significantly(P<0.05)in birds fed AZO-0.25 compared with LME.Overall,0.25%azomite could compensate the negative effect of low-energy diet for broiler chickens by improving the digestion and utilization of nutrients.Experiment 3 was carried out to investigate the effect of azomite(AZO)in low protein&amino acids diet on the growth performance,carcass characteristics,digestive enzymes,blood biochemical indices and bone development of broiler chickens.A total number of 180-day old male chicks Arbor Acers(AA)were randomly allocated into three treatments and each treatment was divided into six replicates(10 birds per replicate).Experimental diets included positive control(PC,having 21.5%CP for starter,and 19.0%CP for finisher,and normal levels of essential amino acids),negative control(NC,19.5%CP for starter,17.0%CP for finisher,and lower levels of essential amino acids)and AZO-0.25treatment(NC+0.25%azomite).The experiment lasted for 42 days.The results displayed that LBW,ADG,ADFI and FCR was improved in AZO-0.25 than NC significantly(P<0.05).Percentage of slaughter,half eviscerated.Eviscerated carcass,breast muscle and leg muscle were higher significantly(P<0.05)in the AZO-0.25 than NC.However,weight of immune organs and abdominal fat was not influenced by the dietary treatments.Broilers fed AZO-0.25 increased the availability of DM,CP,AME,Ca and P(P<0.05)compared to NC treatment.Moreover,trypsin activity increased(P<0.05)significantly in birds fed AZO-0.25 compared with NC.No significant effect of AZO-0.25 on serum biochemical indexes except serum creatinine and CT was significantly(P<0.05)higher in birds fed with AZO-0.25treatment.Feeding of 0.25%AZO increased significantly tibia breaking strength(TBS),the content of ash,Ca and P in tibia bone(P<0.05)than NC.Overall,azomite could compensate the adverse effect of low-CP&AA by improving growth performance,digestive enzymes activity and nutrients utilization.To sum up,the addition of 0.25%-0.5%natural rare earth mineral-azomite into the diet significantly improved the growth,nutrient utilization and bone mineralization of broiler chickens,thus achieving the effect of antibiotics growth promoter.The addition of 0.25%azomite in diets of broiler chickens can compensate for the adverse effect of reducing AME by 100kcal or reducing crude protein(amino acid)by 2 percentage.The additive effect of azomite was related to the improvement in digestive capability and nutrient deposition of broiler chickens.Therefore,it can be concluded that azomite has a great potential in antibiotic-free diets and saving feed cost for broilers.