Effects Of Small Peptide Chelate Irons On Growth Performance,Immunity,and Intestinal Health In Weaned Pigs

Iron is one of the essential trace elements in animal life and it plays a key role in maintaining normal growth and immune function.Weaned pigs are in the rapid growth period,and due to low body iron stores and increased iron requirements they can easily become iron deficient,which can lead to anemia,growth and development suppression,diarrhea,and even death.Therefore,it become the common strategy in pig production by injecting iron in muscle or adding adequate iron in diets to prevent iron deficiency of weaned piglets.Currently,the preparation commonly used for iron supplementation in the production are ferrous sulfate,ferrous glycine,and yeast iron but the biological titer of different iron supplementations are different.Small peptide chelate iron（SPCI）is chelated by irons and oligopeptides（mainly dipeptide and tripeptide）that have an elevated chemical stability and safety.In this study,weaned pigs were used to explore the effects of different levels of SPCI on piglet growth performance,immune function and intestinal health and to compare the effects of SPCI,ferrous sulfate（Fe SO₄）,and ferrous glycine（Fe-Gly）,in order to to provide a theoretical reference for the rational utilization of iron in production.A total of 49 Duroc×Landrace×Yorkshire pigs（with an initial body weight of 9.77±0.58 kg）were randomly allotted to seven treatment groups:T1（pigs fed with basal diet）,T2（pigs fed with basal diet containing 100 mg/kg Fe as Fe SO₄）,T3（pigs fed with basal diet containing 100 mg/kg Fe as Fe-Gly）and T4～T7（pigs fed with basal diet containing 50,75,100,and 125 mg/kg Fe as SPCI,respectively）.The trial last for 21 days and each pig was housed in a metabolic cage.On day 22,the blood samples were collected after 12 h fasting for serum biochemical analysis and the intestinal tissue samples were collected following for intestinal morphological analysis.The results show that:（1）Dietary 50～100 mg/kg SPCI addition decreased the feed-to-gain ratio（F/G）（P<0.05）and compared with T1 group,dietary 100 mg/kg Fe-Gly supplementation also decreased the F/G（P<0.05）.The addition of different levels SPCI to feed had no effect on the apparent digestibility of energy,ether extract,dry matter,etc but the digestibility of crude protein decreased by 125 mg/kg SPCI supplementation（P<0.05）.（2）Dietary 100 mg/kg SPCI addition increased the hemoglobin（HGB）and hematocrit（HCT）（P<0.05）and 75 mg/kg SPCI addition increased the standard deviation of red blood cell distribution（RDW-SD）（P<0.05）.Dietary different iron addition elevated the contents of red blood cell（RBC）and HGB（P<0.05）.Compared with T1 group,dietary 100 mg/kg Fe SO4 or Fe-Gly supplementation decreased the RBC and HGB（P<0.05）.In addition,dietary 50～100 mg/kg SPCI addition increased the serum ferritin and transferrin（P<0.05）.Compared with T1 group,dietary 100 mg/kg different iron supplementation increased the concentration of serum transferrin（P<0.05）.（3）Dietary100 mg/kg different iron supplementation increased the iron content of liver（P<0.05）.Besides,dietary 100 mg/kg SPCI supplementation the iron content in gall bladder and tibia（P<0.05）.（4）Dietary 50～125 mg/kg SPCI and 100 mg/kg Fe-Gly supplementation decreased the serum content of D-lactate and endotoxin（ET）（P<0.01）.In addition,dietary 75～100 mg/kg SPCI supplementation increased the serum concentrations of Ig M,Ig G and Ig A（P<0.01）.Dietary 100 mg/kg Fe-Gly also increased the serum concentrations of Ig M（P<0.01）.（5）Dietary Fe-Gly and SPCI added at 100 mg/kg decreased the serum concentrations of malondialdehyde（MDA）（P<0.05）.Besides,the serum glutathione peroxidase（GSH-Px）content also increased by 100 mg/kg SPCI supplementation（P<0.01）.（6）Dietary 75～100 mg/kg SPCI and 100 mg/kg Fe-Gly supplementation elevated the duodenal villus height（P<0.05）and villous height-to-crypt depth ratio（V/C）（P<0.01）and the ileal villus height and V/C（P<0.05）.The localization of tight-junction protein ZO-1 in the jejunum was also improved by SPCI or Fe-Gly adding at 100 mg/kg when compared with T2 group（P<0.01）.Dietary different iron addition did not influence the early apoptosis rate in jejunum but the early apoptosis rate in jejunum increased by 125 mg/kg SPCI addition（P<0.05）.（7）Compared with T1 group,adding 75～100 mg/kg SPCI increased the activities of duodenal lactase,duodenal sucrase,jejunal sucrase and ileal maltase（P<0.01）.In addition,adding 100 mg/kg Fe-Gly also increased the activities of ileal maltase（P<0.05）.Dietary different levels of SPCI（50～125 mg/kg）or different irons（Fe SO4,Fe-Gly and SPCI）addition decreased the concentration of MDA in ileal mucosa（P<0.05）and adding 100mg/kg Fe-Gly or 75 mg/kg SPCI increased the activity of catalase（CAT）in jejunal and ileal mucosa（P<0.05）.（8）Dietary added different iron decreased the expression level of divalent metal transporter-1（DMT1）in duodenal mucosa（P<0.01）,but the expression levels of DMT1（P<0.01）,zinc ion transpoter-1（Zn T1）（P<0.01）and peptide transport-1（Pe PT1）（P<0.05）in ileum increased by 75 mg/kg SPCI supplementation.In addition,with dietary 100 mg/kg SPCI supplementation,the expression levels of cationic amino acid transporter-1（CAT1）elevated in jejunal mucosa（P<0.05）.In conclusion,dietary added appropriate SPCI（75～100 mg/kg）or Fe-Gly（100 mg/kg）improved growth performance,immunity and increased intestinal health by elevated the intestinal morphology development,intestinal enzyme and intestinal antioxidant enzyme activity of piglets.