Effects Of Birth Weight On The Immune Function Of Piglets And The Nutritional Regulation Of Arginine

In swine production,the increase in litter size is usually associated with a high number of low birth weight（LBW）piglets.Compared with normal birth weight（NBW）piglets,LBW piglets have higher death rate and worse growth performance,resulting in increasing costs of feeding management.Therefore,this study was conducted to investigate the effects of LBW on the immunity and anti-oxidative capacity of piglets during neonatal,pre-weaning and post-weaning period,and diets supplemented with 1%Arginine（Arg）were assigned to determine the effects of Arg on the immunity and anti-oxidative capacity of LBW piglets,which provided new insights into the strategies of improving LBW suckling piglets’health.Experiment 1 Effect of birth weight on the immune function and anti-oxidative capacity of neonatal pigletsThe purpose of this study was to investigate the effects of LBW on organ index,serum amino acids,serum immunity and liver antioxidant function of neonatal piglets.Ten NBW（BW:1.66±0.07 kg）piglets and ten LBW（BW:0.83±0.04 kg）piglets from ten sows with similar body condition and parity were selected and sampled within 2⁴h after birth.The results showed that compared with NBW neonatal piglets,LBW neonatal piglets 1)significantly increased the kidney index（P<0.05）,and the lung index showed a tendency to increase（P=0.050）,2)significantly increased the contents of methionine,aspartic acid and glutamic acid in serum（P<0.05）,3)significantly decreased the concentrations of IgA in serum（P<0.05）,and IgM concentration showed a trend of decrease（P=0.072）,4)significantly decreased liver SOD and GPx activity（P<0.05）,and AHR activity showed a trend of decrease（P=0.76）.In summary,compared with NBW neonatal piglets,the LBW neonatal piglets exhibit higher kidneys index,higher contents of methionine,aspartic acid and glutamic acid in serum,lower immune function,lower liver AHR,SOD and GPx activity anti-oxidative capacity.Experiment 2 Effects of birth weight and weaning on the immune function,intestinal health and anti-oxidative capacity of pigletsThis study was aimed to investigate the effects of birth weight and weaning on the immune function,intestinal health and anti-oxidative capacity of piglets.The method of2×2 double factors design was adopted.Thirty NBW piglets and thirty LBW piglets from thirty sows with similar body condition and parity were selected.On day 21,twenty four NBW（BW:6.14±0.03 kg）piglets and twenty four LBW（BW:3.68±0.05 kg）piglets of average initial body weight were allocated into four groups（NBW control group and after-weaning group,LBW control group and after-weaning group）,with twelve replicates per group and one pig per replicate.Control groups were slaughtered with anesthetics on day 21 and after-weaning groups were normally raised till the third day after weaning,then slaughtered.Results were as follows:Compared with NBW piglets,LBW piglets 1)had lower body weight（P<0.05）,2)had higher concentrations of cortisol and urea nitrogen in serum（P<0.05）,while had lower concentrations of IgM and LZM in serum（P<0.05）,3)had lower mRNA expression of SOD and Nrf2 in liver（P<0.05）,4)had lower jejunum villus height,mRNA expressions of CLDN-1（P<0.05）,5)had lower mRNA expressions of b^0,+AT（P<0.05）,6)higher mRNA expression of Caspase-1（in jejunum）and IL-2（in thymus）,lower IL-2（in spleen）and IL-6（in liver and spleen）（P<0.05）,7)had higher abundance of E.coli in cecum（P<0.05）.Compared with before weaning,after-weaning NBW piglets 1)had higher body weight（P<0.05）,2)had higher concentrations of cortisol,C-reactive protein in serum（P<0.05）,while had lower complement protein 3 and lysozyme activity in serum（P<0.05）,3)had lower mRNA expression of CAT,SOD,Nrf2,NQO-1 and HO-1 in jejunum（P<0.05）,4)had lower jejunum villus height villus height/crypt depth and goblet cell numbers（P<0.05）,lower mRNA expressions of Oclauding,Caudin-1,CLDN-2（P<0.05）,5)had lower y⁺LAT1 and b^0,+AT and PEPT1in jejunum（P<0.05）,6)had higher mRNA expression of Caspase-1（in jejunum and liver）and TNF-α（in thymus）（P<0.05）,lower IL-2（in jejunum and spleen）and IL-6（in jejunum,spleen and liver）,had lower expression of TLR9,MyD88,TRIF and p65NF-?B mRNA expression（in jejunum）,lower TRAF6（in thymus）（P<0.05）.7)had lower abundance of E.coli in cecum（P<0.05）.Compared with before weaning,after-weaning LBW piglets 1)had lower body weight（P<0.05）,2)had higher concentration of urea nitrogen in serum（P<0.05）,while had lower complement protein 3 and lysozyme activity in serum（P<0.05）,3)had lower mRNA expression of CAT,SOD,Nrf2,NQO-1,and HO-1 in jejunum（P<0.05）,4)had lower jejunum villus height/crypt depth and goblet cell numbers（P<0.05）,lower mRNA expressions of ZO-2 and Oclaudin（P<0.05）,5)had lower mRNA expressions of y⁺LAT1,b^0,+AT and PePT1 in jejunum（P<0.05）,6)had higher mRNA expression of IFN-γin jejunum and spleen,TNF-αand Casepase-1 in jejunum and spleen and NLRP3 in spleen,lower mRNA expressions of IL-18 in jejunum and liver,IL-2,TNF-α,NLRP3 in jejunum and IFN-γin liver,lower TLR9,NOD2 and TRIF in jejunum,7)had higher abundance of E.coli in cecum（P<0.05）.In summary,compared with NBW piglets,the balance of oxidation and reduction balance in LBW piglets was damaged,the immune function was decreased,the intestinal health was impaired,and the weight was decreased.Compared with before weaning,3 d after weaning,the oxidation and reduction balance of NBW piglets was damaged,the expression of amino acid transporter was down-regulated,the expression of pro-inflammatory factor gene was increased,and intestinal structure and function were damaged.Compared with pre-weaning piglets,LBW piglets had reduced intestinal antioxidant capacity,blocked amino acid transport,increased number of harmful bacteria,destroyed intestinal structure and function,decreased expression of pro-inflammatory factor genes,and decreased body weight at 3 days after weaning.Experiment 3 Effect of LBW on the immune function and anti-oxidative capacity of suckling piglets and the nutritional regulation by arginineThe aim of this study was to investigate the effects of LBW on immune function and anti-oxidative capacity of suckling piglets and the nutritional regulation by Arg.72 NBW piglets and 16 LBW piglets from 72 sows with similar body condition and parity were selected.A total of thirty piglets（4 days old）including ten NBW and twenty LBW were selected.NBW piglets were fed with basal diet（NBW group）,and LBW piglets were fed with basal diet（LBW group）or diet supplemented with 1.0%arginine（LBW+Arg group）.The experiment lasted 21 days.The results showed that compared with NBW group,LBW group piglets 1)significantly decreased the concentration of IgG in serum（P<0.05）,and significantly decreased the mRNA expressions of TNF-α,IL-10 and TGF-β1 in spleen（P<0.05）,2)significantly decreased the mRNA expressions of TLR2,p65NF-?B,MYD88 and p38MAPK in spleen（P<0.05）,and significantly decreased the mRNA expressions of p38MAPK and MYD88 in thymus（P<0.05）,3)significantly decreased mRNA expression of ARG2 in thymus（P<0.05）,4)significantly decreased the activity of ASA and AHR,significantly increased the mRNA expressions of Nrf2 and NQO-1 in liver（P<0.05）.Compared with LBW group,LBW+Arg group piglets 1)significantly increased spleen index（P<0.05）and trended to increase thymus index（P=0.070）,2)significantly increased the concentrations of IgA and IgM in serum（P<0.05）,significantly increased IFN-γgene expression in spleen（P<0.05）,trended to increase p38MAPK gene expression in spleen（P=0.079）,3)significantly increased the activity of AHR,SOD and GPX,significantly decreased the mRNA expressions of NQO-1,IL-1βand IL-6 in liver（P<0.05）.In summary,compared with NBW suckling piglets,the LBW suckling piglets exhibit lower growth performance and concentration of serum IgG,down-regulate the mRNA expression of cytokines in spleen,decrease the mRNA expressions of immune function-related genes in spleen and thymus,and reduce ARG2 gene expression in thymus,Dietary Arg supplementation increase growth performance,serum IgA and IgM concentrations,spleen index,and IFN-γgene expression,suggesting that Arg improve the immune functions of LBW suckling piglets.In conclusion,the results of this study showed that compared with NBW piglets,LBW significantly reduced the immune function at age of 0,21（pre-weaning）and 24（post-weaning 3 d）in piglets.Dietary 1%Arg supplementation improves the immune functions and anti-oxidative capacity of LBW suckling piglets.