| The purpose of this experiment was to study the effects of low protein diet supplemented with different chain length fatty acids on growth performance,immune ability,antioxidant ability,intestinal health and microflora of weaned piglets.A total of 120 healthy weaned piglets(Landrace × Large White × Duroc)weighing7.93 ± 0.7 kg,were selected and divided into 5 treatment groups according to a completely randomized design in this experiment.Each group had 6 replicates and each replicate had4 weaned piglets,each duplicate housed in the same pen.The 5 experimental groups were fed 20% CP diet(Contriol group,CON group),16.5% CP diet(Low protein diet group,LP group),16.5% CP diet with 0.2% sodium butyrate group(LP + SB group),16.5% CP diet with 0.2% medium chain triglyceride group(LP + MCT group),16.5% CP diet with0.2% n-3 polyunsaturated fatty acid group(LP + PUFA group).The trial period was 31 days,the pre-trial period was 3 days,and the pilot period was 28 days.Fasting weighing was performed on the first and 29 th days of the trial period.Before feeding on the 28 th day of the pilot period,6 piglets were randomly selected from each group for anterior vena cava blood collection,and 1 piglet each replicate.On the 29 th day,6 piglets were randomly selected from each group and slaughtered for the samples of jejunum,colonic mucosa and colonic chyme,and 1 piglet each replicate.The results showed that:(1)Growth performance.The final weight and average daily gain of CON group were significantly higher than those of LP group,LP + SB group,LP+ MCT group and LP + PUFA group(P < 0.05);The feed/ gain of CON group were significantly lower than those of LP group,LP + SB group,LP + MCT group and LP +PUFA group(P < 0.05);The average daily feed intake of LP group,LP + MCT group and LP + PUFA group were significantly lower than that of CON group(P < 0.05),but there was no significant difference between LP + SB group and CON group in average daily feed intake(P > 0.05);The diarrhea rate and diarrhea index of LP group,LP + SB group,LP + MCT group and LP + PUFA group significantly decreased compared with CON group(P < 0.1).(2)Immunoglobulin.There was no significant difference in plasma immunoglobulin Ig A,Ig G and Ig M among the five groups(P > 0.05).(3)Cytokines.IL-6 in LP group,LP + SB group,LP + MCT group and LP + PUFA group were tend to lower than that in CON group(P = 0.07);IL-8 in LP + SB group,LP + MCT group and LP +PUFA group were significantly lower than that in LP group(P < 0.05);IL-10 in LP +PUFA group was tend to higher than that in CON group(P = 0.13),and IFN-γ in LP +MCT group and LP + PUFA group were tend to lower than that in the CON group(P =0.09).(4)Antioxidant function.There was no significant difference in the activities of TAOC,T-SOD,TNOs and i NOS among the five groups(P > 0.05);The activity of CAT in LP + MCT group was tend to higher than that in LP group(P = 0.10);The activity of GSH Px in LP + SB group,LP + MCT group and LP + PUFA group were significantly higher than that in CON group and LP group(P < 0.01).(5)Intestinal development.There was no significant difference in jejunal villus height and villus height/ recess depth ratio(V/C)among the five groups(P > 0.05);The recess depth in LP + SB group,LP + MCT group and LP + PUFA group were significantly higher than that in CON group(P < 0.05);The jejunal lymphocytes in LP + MCT group was significantly more than that in LP group(P < 0.05);The height of colonic villi in LP group,LP + SB group,LP + MCT group and LP + PUFA group were significantly lower than that in CON group(P < 0.05);There was no significant difference in colonic recess depth and V/C among the five groups(P >0.05).The colonic lymphocytes in LP + PUFA group was tend to more than that in CON group(P = 0.61).(6)Expression of related m RNA.The relative expression of ZO-1m RNA in LP group was significantly higher than that in the other four groups(P < 0.05);The relative expression of occludin m RNA in LP group was significantly higher than that in CON group,LP + SB group and LP + PUFA group(P < 0.05);The relative expression of claudin-1 m RNA in CON group and LP group were significantly higher than that in LP + SB group,LP + MCT group and LP + PUFA group(P < 0.05);The relative expression of TLR4 m RNA in LP + SB group,LP + MCT group and LP + PUFA group decreased significantly compared with CON group and LP group(P < 0.05);The relative expression of IKKa m RNA in LP + SB group and LP + PUFA group were significantly lower than that in CON group and LP group(P < 0.05),and the relative expression of IKKa m RNA in LP + MCT group was significantly lower than that in CON group(P <0.05);There was no significant difference in the relative expression of NF-κB and Keap1 m RNA among the five groups(P > 0.05);The relative expression of Nrf2 m RNA in LP+ MCT group and LP + PUFA group were significantly higher than that in LP group(P <0.05).(7)Expression of related proteins.There were no significant differences in the expression of TLR4 protein,NF-κB protein and MYD88 protein in colonic mucosa among the five groups(P > 0.05).(8)Colonic microflora.There was no significant difference in ACE,Chao1,Shannon and Simpson indexes of colonic chyme microorganism among the five groups(P > 0.05);Firmicutes and Bacteroidetes were the dominant bacteria in piglet colon.The relative abundance of Bacteroidetes in LP group and LP + PUFA group showed a decreasing trend compared with CON group(P = 0.12);The relative abundance of Erysipelotrichaceae in LP group was significantly higher than that in the other four groups(P < 0.05);The relative abundance of RuminococcaceaeUCG-014 in LP group was tend to higher than that in CON group,LP+MCT group and LP+PUFA group(P = 0.09);The relative abundance of [Eubacterium]-coprostanoligenes＿group in LP+MCT group was tend to higher than that in CON group(P = 0.08).In conclusion,the addition of fatty acids with different chain lengths to low-protein diets cannot eliminate the negative impact of the reduction of dietary protein level by 3.5percentage points on the growth performance of 28 day weaned piglets,but it can reduce the diarrhea rate and plasma inflammatory factor level of piglets,and improve plasma antioxidant function,intestinal immune function and colonic microbial diversity of piglets. |
