Effect Of Probiotics On Immune And Digestive Functions Of Broilers Fed Diets With Different Nutrient Levels

The aim of this study was to evaluate the effect of probiotics on growth performance, slaughtering performance, serum parameters, antioxidant function, humoral immunity, nutrient utilization, endogenous enzyme activities and intestinal microflora of broilers fed diets with different nutrient levels. The study includes three trials and the general results are presented as follows:Trial1:This experiment was conducted to study the effects of probiotics on growth performance, serum parameters and slaughtering performance of broilers fed diets with different nutrient levels. A2×2factorial arrangement of treatments was used in the trial,320one-day-old AA broilers were randomly assigned to four dietary treatments, and each treatment had10replicates with8broilers per replicate. The treatments were as follows:(1) control with normal nutrient level(CN);(2) control with320KJ/kg less ME and0.85%less CP than CN (CL);(3) CN supplemented with0.01%probiotics(PN);(4)CL supplemented with0.01%probiotics (PL).The results showed that probiotics supplementation to diets with different nutrient levels increased21-d body weight (BW) and average daily gain (ADG) in starter phase (P<0.05), decreased feed/gain ratio (F/G) in starter phase (P<0.05), but did not affect42-d BW, ADG and F/G in finishing phase (P>0.05). Probiotics supplementation improved the content of total protein (TP) and globulin (GLB)(P<0.05), decreased total cholesterol (TC) and urea nitrogen (UN)(P<0.01), tended to improve albumin (ALB) and glucose (GLU) at21d, but did not affect serum parameters of42-d broilers. Probiotics addition to diets with different nutrient levels reduced intermuscular fat thickness and abdominal fat percentage (P<0.01), tended to reduce subcutaneous fat thickness (P=0.063), increased breast muscle percentage (P=0.055), did not affect leg muscle yield (P>0.05).Trial2:The aim of this trial was to investigate the effects of probiotics on nutrient utilization, endogenous enzyme activities and intestinal microflora of broilers fed diets with different nutrient levels.The treatments were the same as that of trial1.The results showed that probiotics added to diets with different nutritions improved utilization of crude protein (P<0.05), but those of other nutrients were not significant during11-14d. No difference was observed for utilization of all nutrients during35-38d. The activities of amylase, trypsin and lipase in the intestine did not differ among four groups at both21d and42d. However, the activity of lipase at21d in the pancreas was significantly reduced because of probiotics (P=0.003). The activities of amylase and trypsin in the21-d pancreas did not differ among all groups. Probiotics tended to reduce the activities of amylase and lipase in the42-d pancreas, but did not affect the activity of trypsin (42d).The number of E-coli in ileum was diminished (P<0.05) at both21d and42d because of probiotics supplemented to diets. Probiotics promoted the number of lactobacillus in ileum (P<0.001) at21d, but there was no effect on the number of lactobacillus in ileum (42d).Trial3:This experiment was conducted to study the effects of probiotics on immune organ indexes, antioxidant function and humoral immunity of broilers fed diets with different nutrient levels, evaluat the mechanism and immune effect of probiotics on host animals. The materials and methods used were the same as those in trial1. The result suggested that probiotics supplementation improved thymus index (P<0.01), increased spleen index and bursal index (P<0.05), but did not influence immune organ indexes. Probiotics promoted the activity of T-SOD in serum and musoca of broiler in started phase (P<0.05), decreased MDA in serum (P<0.01), also tended to reduce the content of MDA in musoca (P=0.057), enhanced T-SOD and T-AOC in serum (P<0.01) and reduced MDA both in serum and musoca (P<0.05) in finishing phase. Probiotics addition to diets with different nutrient levels increased the content of IgG in serum(21d)(P<0.05), and tended to improve IgG in musoca (21d)(P=0.077), also improved the contents of IgG and slgA in musoca (42d)(P<0.05).