Effects Of Dietary Protein Sources On Growth Performance And Immune Function Of Early Weaned Piglets

This experiment was conducted to study the effects of dietary protein sources ongrowth performance,gut morphology, serum hormone secretion, immunoglobulins concentration and alexinic secreti on early weaned piglets. A total of 320 DLY weaning piglet (22±1 days old,7.00±0.19 kg) were randomly allocated into 4 groups,5 replicates each group and 16 piglets each replicate.Piglets were inoculated with swine fever attenuated vaccine on 2 d before weaning, different dietary protein were fed immediately after weaning for 10 d, Protein sources were spray-dried plasma protein,soybean protein concentrate,whey protein concentrate and spray-dried whole eggmeal. diets were changed to the same diet during the 11～32 d post weaning. Feed intake,daily gain,feed/gain,diarrhea rate and diarrhea index were recorded.Four piglets were slaughtered per group on 10 d after weaning to collect the small intestine,spleen. detect intestinal morphology, and the spleen tissue mRNA expression of the toll-like receptor 3,toll-like receptor 7 and toll-like receptor 9 by RT-PCR.Serum samples were collected on 2 d before weaning,1 d,5 d,10 d,32 d after weaning.serum immune globulin (IgG,IgA,IgM) secretion by RIA.Serum hormone (IGF-Ⅰ,cortisol) and cytokine (IL-1β,IFN-γ,IL-10) secretion by ELISA.The results were as follows:1. ADG of piglets fed SDP was increased respectively by 6.44%,5.47% and 5.71% compared with SPC(P<0.05), WPC and SDE. Feed/Gain in SDP group was decreased respectively by 16.67%,14.11% compared with SPC(P<0.01) and SDE(P<0.05). Intestinal villus height in piglets fed SDP was greater than SPC(P<0.05).Cortisol concentration was lower in SDP at 5 and 10 d postweaning (P<0.05) compared with SPC,serum cortisol concentration was lower in SDP and WPC at5d postweaning (P<0.05), and was lower in SDE than SPC at 10 d post-weaning(P<0.05),while IGF-I was not affected(P>0.05). Diarrhea index was not affectedat10 d postweaning (P>0.05). At remaining 22d,compared with the other three gro-ups,ADG and Feed/Gain tended to increase,wheras diarrhea rations in SPC-fed piglets trended to decrease.2. Stomach index of SDP-fed piglets was significantly higher than SPC-fed piglets (P<0.05),There were no significant difference for liver, kidney and pancreas index among groups(P>0.05).The spleen index of SPC-fed piglets was higher than SDP(17.22%),WPC (13.33%) and SDE(8.21%)-fed piglets (P>0.05).Serum IgG, IgA,C3 concentration in SDP-fed piglets were increased respectively by 17.50%, 9.31%,4.41%(P<0.05)compared with SPC-fed piglets at 10 d post weaning, while SDE-fed piglets had higher IgA at 5and 10 d postweaning (P<0.05),and higher C3at 10 days postweaning (P<0.05).3. SDP and WPC-fed piglets had significantly higher IFN-γthan SDE-fed pigletsat 5 d post weaning(P<0.05), SPC group IL-10 significantly higher than the SDP,WPC (P<0.05) and SDE (P<0.01);SDP-fed piglets IFN-γwas higher than WPC(P<0.01) at 10 d post weaning, significantly higher than SPC (P<0.05);SPC-fed piglets IL-10 group was significantly higher than the SDE (P<0.01)and WPC-fed piglets (P<0.05) at 32 d post weaning.4. The TLR3,TLR7,TLR9 mRNA expression in spleen were not significantly different at post-10d among groups;TLR3 mRNA expression of SDP-fed piglets trend to increase.Compared with WPC,SDP-fed piglets had higher,TLR9mRNA expression was increased 61.11% (P=0.084).5. The classical swine fever antibody titers of SDP-fed piglets was significantly higher than SPC-fed piglets (P<0.05) at 5d post weaning.SDP, WPC and SDE-fed piglets were higher than SPC-fed piglets 13.33%(P=0.097),6.23%,3.33% at post-10 d, SDP-fed piglets has 100% protection of classical swine fever during thewhole trial period.These results demonstrated that:1. SDP-fed piglets had higher growth performance than SPC,WPC and SDE-fed piglets at 10 d postweaning,while SPC group is an ideal protein sour-ce during the whole trial period.2. SDP-fed piglets had higher growth performance than SPC,WPC and SDE-fed piglets at 10 d postweaning,mechanisms responsible for that might be that SDP could improve intestinal morphology, reduced serum cortisol conce-ntrations,improve serum IgG,IgA,C3 levels, and thus alleviate stress and enh-ance humoral immunity.3. SDP-fed piglets can enhance the immune effect of the vaccine and the promotion of classical swine fever antibody production, mechanisms responsi-ble for that might be that SDP-fed piglets can Activate the complement system,increase serum IFN-y level,up spleen TLR3,TLR9mRNA expression.