Effects Of Functionaladditives Replacing Antibiotics In Standard Diet Or Low Protein Diet On Production Performance,Nutrient Digestibility,and Fecal Microbiota In Growing-finishing Pigs

The purpose of this study was to investigate the effects of functional additives replacing antibiotics in standard diet or low protein diet on growth performance,nutrient digestibility and fecal microorganisms in growing-finishing pigs.Experiment 1 was conducted to study the effects of replacing antibiotics with functional additives in standard diets on growth performance,nutrient digestibility and fecal microbial quantity in growing pigs.A total of 96 ’ Large White × Landrace ’ binary growing pigs weighing about 45 kg were selected and divided into 6 treatments according to the litter source and body weight by random block method.Each treatment had4 replicates,4 pigs per replicate with half male and half female.The experiment lasted for 35 days.The control group was fed the standard diet,and the experimental groups were supplemented with 75 mg/kg chlortetracycline,1000 mg/kg α-GML,100 mg/kg oregano oil,100mg/kg compound plant essential oil and 0.2% fermented Andrographis paniculata in the standard diet respectively.The results showed that there was no significant difference in growth performance between the experimental groups and the control group(P>0.05).The addition of chlortetracycline significantly increased the digestibility of calcium and phosphorus(P<0.05).The oregano oil significantly increased the digestibility of dry matter,calcium,phosphorus and crude fat(P<0.01).The compound plant essential oil significantly decreased the digestibility of crude protein(P<0.01),and fermented andrographis paniculata significantly increased the digestibility of calcium and phosphorus(P<0.01).The addition of fermented andrographis significantly reduced the number of Escherichia coli and Salmonella in feces(P<0.05),and oregano oil significantly reduced the number of Salmonella(P<0.05).Experiment 2 was conducted to study the effects of functional additives replacing antibiotics in low protein diets on growing-finishing pigs.Experiment 2-1,effects of replacing antibiotics using nutrition strategy of low nitrogen diet added small peptide on growth performance,nutrient digestibility and fecal microbial abundance in growing pigs.In this experiment,48 healthy ’ Yorkshire × Landrace ’ binary growing pigs with a body weight of about 14 kg were selected,half male and half female.According to the litter source and body weight,they were divided into 4treatments by random block method.Each treatment had 3 replicates and each replicate had 4 pigs.The experimental period lasted 29 days.Four treatments were 18.5% cp standard diet + 100 mg/kg chlortetracycline,16.5% cp low protein diet,low protein diet + 100 mg / kg chlortetracycline,low protein diet + 0.25% small peptide respectively.The results showed that compared with the control group,the low protein + small peptide group significantly reduced the diarrhea index(P<0.05).Compared with the control group,the low protein group significantly reduced the dry matter digestibility(P<0.05),and significantly reduced the crude protein digestibility(P<0.01).The low protein + small peptide group significantly increased the dry matter digestibility(P<0.01)and significantly increased the phosphorus digestibility(P<0.05).Compared with the low protein group,the low protein + chlortetracycline group significantly increased the digestibility of dry matter(P<0.05),the low protein + small peptide group significantly increased the digestibility of dry matter and crude protein(P<0.01),and significantly increased the digestibility of phosphorus(P<0.05).There was no significant difference in the Alpha diversity index of each treatment(P>0.05).Compared with the control group,the abundance of Bacteroidota in the low protein + chlortetracycline group was significantly increased(P<0.05).Experiment 2-2,effects of replacing antibiotics with functional additives in low protein diets on growth performance,nutrient digestibility and fecal microbial abundance in finishing pigs.A total of 112 healthy ’ Large White × Landrace ’ binary fattening barrows with about 80 kg body weight were selected in the experiment.According to the litter source and body weight,they were randomly divided into 7 treatments with 4 replicates per treatment and 4pigs per replicate.Seven treatments were 13.5% CP standard diet(control group),standard diet + 75 mg/kg chlortetracycline,10.5% CP low protein diet,low protein diet + 75 mg/kg chlortetracycline,low protein diet + 100mg/kg oregano oil,low protein diet + 0.16% small peptide,low protein diet+ 0.16% small peptide + 0.2% fermented andrographis paniculata respectively.The results showed that the average daily gain of the standard diet + chlortetracycline group was significantly higher than that of the low protein group,the low protein + chlortetracycline group,the low protein +oregano oil group and the low protein + small peptide group(P<0.05).The feed to gain ratio of the low protein + chlortetracycline group was significantly higher than that of the control group and the standard diet +chlortetracycline group(P<0.05).The nutrient digestibilities of low protein treatment was decreased significantly due to decrease 3 percentage points of dietary protein level.Compared with the low protein group,the addition of chlortetracycline,oregano oil,small peptide,small peptide + fermented andrographis can improve the digestibility of nutrients in the low protein diet.The Shannon index of low protein + oregano oil group,low protein +small peptide group and low protein + small peptide + fermented andrographis paniculata group was significantly higher than that of control group(P<0.05).Compared with the control group,the abundance of Bacteroidota in the low protein group,the low protein + chlortetracycline group,the low protein + oregano oil group,and the low protein + small peptide + fermented andrographis paniculata group were significantly increased(P<0.05).The abundance of Bacteroidota in the low protein +small peptide group was significantly increased(P<0.01).Compared with the standard diet + chlortetracycline group,the abundance of Bacteroidota in the low protein + small peptide group was significantly increased(P<0.05),and the abundance of Firmicutes was significantly decreased(P<0.05).In summary of Experiment 1 and Experiment 2,in the standard diet,oregano oil,fermented andrographis paniculata and α-GML can replace chlortetracycline.Fermented andrographis paniculata and oregano oil can improve the nutrient digestibility of growing pigs and inhibit the number of harmful bacteria.In the low-protein diet,the growth performance of growing pigs was not affected by the low-nitrogen small peptide nutrition strategy,which could reduce the diarrhea index,improve the nutrient digestibility,and did not affect the richness and diversity of the microbial community.In low-protein diets,reducing dietary protein levels by 3percentage points in fattening pigs had adverse effects on growth performance and nutrient digestibility.The addition of small peptide,oregano oil,small peptide + fermented andrographis paniculata in low protein diet could improve the digestibility of nutrients and the diversity of microbial community in feces.Low protein diet group can increase the abundance of Bacteroidota.Small peptide,oregano oil,small peptide +fermented andrographis paniculata can replace antibiotics.