Effects Of Glycine Complexed Trace Minerals On Growth,Immunity,Antioxidant Capacity,Minerals Deposition And Excretion In Piglets And Bioavailability Evaluation

Now,the phenomenon of adding excessive inorganic trace minerals in pig husbandry is very common.The high discharge of fecaluria trace minerals in intensive farming has attracted much attention with the increasing emphasis on environmental protection.Numerous studies indicate that organic trace minerals have higher bioavailability than inorganic,not only promote the deposition process of minerals in animal tissues but also reduce the emission of metal elements.However,the research on the replacement of inorganic trace minerals by organic trace minerals was generally aimed at one or two minerals,rare research was studied focusing on the substitution of organic trace mineral complex for inorganic trace minerals.Hence,this study was designed to investigate the effects of inorganic trace minerals partially replaced by glycine complexed minerals on growth performance,antioxidant capacity and immunity in piglets,and to evaluate the effect on tissue minerals deposition and heavy metal emission.A total of 160 "Duroc×Landrace×Large White" weaned piglets(35d)with similar weight were selected and randomly divided into 5 groups with 4 replicates,8 piglets per repeat.Five groups of test piglets were fed with the following diets:(T1)basal diet+100%inorganic trace minerals(ITMs)as the control group(Cu,Fe,Zn and Mn from sulfates);(T2)basal diet+50%ITMs+50%glycine complexed minerals(GCMs);(T3)basal diet+50%GCMs;(T4)basal diet+50%proteolytic complexed minerals(PCMs);(T5)basal diet+70%GCMs.The feeding period lasted 28 d and was divided into 2 stages(0 to 14 d and 15 to 28 d),feces were collected at each stage to determine the apparent digestibility of trace minerals.Upon finishing the feeding trial,6 pigs per treatment were randomly selected for slaughter and sampling,and the relevant indicators were calculated and analyzed.The results are as follows:(1)During the second,and the overall feeding phases,the average daily weight gain(ADG)of T1,T2,and T3 was significantly higher than that of T4(P<0.05).The feed/gain(F/G)of T1,T2,T3,and T5 in the second period was significantly lower than that of T4(P<0.05),and the F/G of T1 and T2 was significantly lower than that of treatment 3 and 5(P<0.05).During the whole period,there was no significant difference in the F/G of T1,T2,T3,and T5,but they were significantly lower than that of T4(P<0.05).(2)The apparent digestibility of trace minerals in piglets increases as the level of dietary trace elements decreases.In the second period,the apparent digestibility of Zn and Fe in the low-dose trace mineral treatments(T3,T4,and T5)was significantly higher than that in the inorganic group(P<0.05);the apparent digestibility of Zn and Fe in the 50%and 70%GCMs was significantly higher than that in the 100%ITMs(P<0.05)throughout the whole period.(3)The serum ferritin concentration of the low-dose trace minerals group in piglets decreased significantly(P<0.05),The activities of Cu/Zn SOD and GSH-Px in liver were significantly increased(P<0.05),but serum MDA concentration,SOD and GSH-Px activities did not change significantly.(4)The level of serum immunoglobulin,complement and immune factors in piglet were not affect by the concentration of trace minerals in diets.50%PCMs significantly increased the secretion of sIgA in the ileal mucosa.The expression levels of ZnTl and Fpnl mRNA in 50%PCMs group and ZnT1 mRNA in 70%GCMs group increased significantly.The mRNA expression levels of Ctrl and DMT1 increased with the decrease of trace minerals in the diet,but there was no significant difference between the treatments.(5)The intestinal villi height of duodenum in the 70%GCMs treatment was significantly higher than other groups(P<0.05),and the jejunal crypt depth in the 50%PCMs and 70%GCMs treatment was significantly higher than that in the T1 and T2(P<0.05).There was no significant difference in the villi height/crypt depth between duodenum and j ejunum.In the results of intestinal section and SEM,the intestinal villi of GCMs groups(T3、T5)was more intact,and the microvilli were arranged more densely.(6)The amount of trace minerals deposited in various tissues was positively correlated with supplemental level of trace minerals in the diet.Tissue minerals retention in groups of 100%supplemental minerals(Group 1,2)is generally higher(P<0.05)than that in the 70%or 50%supplemental OTM groups(Group3,4,5).It was observed that minerals retention exhibited organ or tissue specificity due to supplemental different mineral sources.Serum Cu of group 2 were 8.47%(P<0.05)higher than that from group 1.Liver Cu,Zn,Fe and Mn of group 2 were 9.76%,12.68%,12.71%and 10.58%(P<0.05)higher than that from group 1.In pancreas,Cu content in group 2 was increased by 9.21%(P<0.05)than that in group 1.In kidney,the retention of Zn and Fe was increased by 9.11%,6.67%(P<0.05)than that in group 1.In heart,the concentration of Cu and Mn in group 2 were 13.91%and 17.39%(P<0.05)higher respectively than that in group 1.In muscle,the concentration of Mn in group 2 was 61.54%(P<0.05)higher than that in group 1.In general,comparing tissue minerals retention between the treatments with same level of mineral supplementation,pigs fed with GCMs exhibited higher tissue minerals retention than those fed with ITM or PCMs,however the statistical differences are not all in consistent.The concentration of Fe,Zn,Mn,and Cu in feces and urine of pigs fed low level of organic trace minerals is significantly lower than that from 100%ITM group and 50%ITMs with 50%GCMs group.In urine,the concentration of Cu,Zn,Fe in group 2 was significantly lower than that in group 1(P<0.05).Except fecal Mn,mineral concentrations in feces from group 2 exhibited numerical lower than those from group 1,however there was no statistical differences.The above results suggest that the use of low-dose glycine chelated trace minerals can reduce trace minerals emissions without affecting the growth performance and health of piglets.From the perspective of feasibility,50%GCMs is more recommended than others.