Effects Of Stocking Density On Growth Performance,serum Parameters And Immune Function Of Growing Pigs

With the intensive development of pig industry,the actual production will increase the stocking density in order to manage and reduce the cost.However,the stocking density is too high,which will restrict the performance of pig production and affect the health of pigs.The purpose of this study was to investigate the effects of three stocking density gradients on growth performance,serum parameters and immune function of growing pigs.Experiment I:The Effects of Stocking Density on Growth Performance,Blood parameters of Growing PigsThis study aimed to determine the effects of different stocking densities on the growth performance,LL and blood physiological and biochemical indexes on growing pigs.About288 male pigs(average body weight,44.35±0.50 kg)were randomly assigned to 3treatments(6 replications/treatments)consisting of different stocking densities within the same area(19.76 m~2)for a month.The high density,normal density,and low density groups housed 24(0.82 m~2/pig),16(1.23 m~2/pig),and 8 pigs(2.46 m~2/pig)every pen,respectively.Results were showed as follows:(1)stocking density did not affect the ADG and the ADFI or F/G of pigs(P>0.05).However,the thickness of LLs were significant decreasing with the stocking density increased.(2)The pigs in high density group had the lowest spleen weight index compared with normal and low density groups(P<0.05).(3)High stocking density increased the serum concentration of BUN,GGT,AKP,TG and IgA(P<0.05),whereas decreased the concentration of ALB,ALB/GLO,IGF-1,and IgM(P<0.05).The serum concentration of growth hormone and cortisol tended to increase,whereas that of glucose showed a decreasing tendency(0.05<P<0.1)with increasing stocking density.The results showed that the density gradients in our experiment had no obvious effect on the growth performance of the growing pigs,but could cause changes in blood parameters related to stress,immune function and energy metabolism.Experiment II:The Effects of Stocking Density on Immune Function of Growi ng PigsIgA,IgG,IgM and SIgA and cytokines IL-1?,IL 2 and IL-10 in serum are the important parameters about body's immune status,the results showed that the content of serum IgA increased significantly with stocking density increases(P<0.05),the content of IgM significantly reduced(P<0.05).High stocking density increased the serum concentration of BUN,GGT,AKP,TG and IgA(P<0.05),whereas decreased the concentration of ALB,ALB/GLO,IGF-1,and IgM(P<0.05).The gut is the largest immune organ in the body,so the experiment explored the effects of stocking density on intestinal mucosa of growing pigs.The results showed that:(1)The content of SIgA on mucosa of duodenum,jejunum or ileum increased significantly with increasing the stocking density(P<0.05).(2)Compared with ND group,the expressions of TGF-?1,TGF-?2,TLR-1 and TLR-4 mRNA on duodenum of pigs in LD and HD groups.were lower(P<0.01)than those of pigs,however,the expression of MyD88 increased(P<0.01).(3)The expression of TGF-?1,TGF-?2,TLR-1,TLR-4 and MyD88 mRNA on jejunum were down-regulated in LD and HD groups compared with ND group(P<0.01).(4)On ileum,the expressions of TGF-?1 mRNA were down-regulated,but the expressions of TLR-1 and MyD88 mRNA were up-regulated in LD and HD groups compared with ND group(P<0.01).Liver and spleen are the important immune organs,their immune functions are important to body.The result showed that:(1)The content of IL-2 in spleen or liver and IL-10 in spleen in high density group was higher than that of pigs in low or normal density group(P<0.05).(2)The expression of NF?B,TLR-1,TLR-4,MyD88 mRNA in high density group were down-regulated,however Inhibitor of I?B-?mRNA was up-regulated significantly compared with normal density group in spleen(P<0.01).(3)In liver,the expressions of NF?B and MyD88 mRNA in high density group were down-regulated,I?B,TLR-1 and TLR-4 mRNA were up-regulated compared with normal density group in spleen(P<0.01).These results showed that the stocking density affected the immune status of immune organs and intestinal mucosa of growing pigs by modulating the cytokines and gene expression of NF?B and Toll-like signaling pathway,and the serum parameters about immune status.In conclusion,the stress response was increased and immune function and health of growing pigs were affected with the increase of the stocking density.