Effects Of PGRF Gene Plasmid On The Growth Of Immune-challenged Weaned Piglets

The purpose of this study was toevaluate the effect of pGRF gene plasmid on the performance and immunological function of immune-challenged Weaned Piglets for 35±2d,and also the potential mechanism of these effects were discussed.Eighteen weaned DLY pigs with age of 35±2d and initial body weight(BW) 7.86±0.59kg were not castrated and randomly assigned to three treatments according to gender and BW by single factor design.The three treatments were pGRF gene plasmid group,pGRF gene plasmid plus lipopolysaccharide(LPS) group and LPS group.Each treatment had six replicates and one piglet in each replicate.Dietary treatmenf did not have additive antibiotics.During the three weeks' experiment the piglets were allowed ad libitum to feed and water.Feed consumption,average daily gain(ADG),feed to gain ratio(F/G) and diarrhea frequency were investigated.On d 1 of the experiment,pGRF gene plasmid and pGRF gene plasmid plus LPS groups were only once injected 1.0mg pGRF gene plasmid per head and only one time,and LPS group were injected normal saline.On d 8 and 15,pGRF gene plasmid plus LPS and LPS groups were injected LPS according to 100μg per kilogram body weight,and pGRF gene plasmid group were injected normal saline.On 2 h after LPS challenge,blood samples were collected,In the peripheral blood serum,the levels of IgG were determined using immuno-turbidimetry method,and IGF-Ⅰ,IL-land IL-6 was determined by ELISA technique.The results were as follows:1.The piglets in the pGRF gene plasmid plus LPS group had a better growth performance than those in the LPS group(P＜0.05),and worse than those in the pGRF gene plasmid group(P＜0.01).The ADG of piglets in the pGRF gene plasmid,pGRF gene plasmid plus LPS and LPS groups were 394.47g/d,331.14g/d,297.94g/d respectively.The F/G of piglets in the pGRF gene plasmid plus LPS group was lower than that in the lipopolysaccharide group(P＞0.05),and higher than that in the pGRF gene plasmid group(P＜0.05).2.Compared with that in the LPS group,the diarrhea frequency in the pGRF gene plasmid plus LPS group was significantly decreased by 10.32%(P＜0.05),and higher than that in the pGRF gene plasmid group(P＜0.05).3.The serum IGF-1 level in the pGRF gene plasmid plus lipopolysaccharide group was higher(P＜0.05)or significantly higher(P＜0.01)than that in the lipopolysaccharide group,and significantly lower than that in the pGRF gene plasmid group(P＜0.01).4.The serum IgG level in the pGRF gene plasmid plus LPS group was higher than that in the LPS group(P＜0.05),and lower than that in the pGRF gene plasmid group(P＞0.05).The serum IL-1 level in the pGRF gene plasmid plus LPS group was lower(P＜0.05)or significantly lower(P＜0.01)than that in the LPS group,and higher(P＜0.05)or significantly higher(P＜0.01)than that in the pGRF gene plasmid group. The serum IL-6 level in the pGRF gene plasmid plus LPS group was significantly lower than that in the LPS group(P＜0.01),and significantly higher than that in the pGRF gene plasmid group(P＜0.01).In conclusion,Compared with those in the LPS group,in the pGRF gene plasmid plus LPS group,the levels of serum IL-1 and IL-6 were reduced,and the levels of serum IgG were increased.The statuses of immune challenge induced by LPS injection was improved.The characteristics of resisting diseases were increased.However,the characteristics of pGRF's immunoregulation may closely related to its contribution to the secretion of growth hormone,IGF-Ⅰ.