Effects Of Lactobacillus D₂₂ And Bursin On The Growth, Immunity Function, And Intestinal Microflora Of Broilers

The aim of present paper is to investigate the independent and synergistic effects of Lactobacillus D22 dietary supplementation and bursin (BS) immunization on gowth, immune functions, and intestinal microflora in broilers. A total of 200 one-day-old broilers (Cobb-500) of mixed sex. were randomly allocated into 4 treatments (5 replicates per treatment) as follow:Treatment LP-/BS-, the control was feed with a basal diet; Treatment LP-/BS+was feed with a basal diet and BS immunized; Treatment LP+/BS-was feed a basal diet supplemented with Lactobacillus D22 culture (0.1%w/w); Treatment LP+/BS+ was feed a basal diet supplemented with Lactobacillus D22 culture (0.1%w/w) and BS immunized. The feeding trial was conducted for 42 days. Body weight and daily diet of each pen were weighted on the morning of 21 day of age (DOA) and 42 DOA. Daily body weight gain (BWG), daily feed intake (FI), and F/G was calculated. Blood sample was obtained from the jugular vein for analysis of peripheral T lymphocyte proliferation. Serum sample was obtained by centrifuging for analysis of TP, ALB, BUN, TC, TG, IgG concentration, IL-2 and IL-6 concentration. The liver tissue was collected for analysis of antioxidant enzyme CAT activity, GSH-Px activity, SOD activity, and MDA content with serum samples. The thymus, spleen, and bursa of Fabricius were weighted for calculating immune organ index and maked tissue section for analysis of immune organ structure. Duodenum mucosa was collected for analysis of amylase activity, lipase activity, and trypsin activity. Cecal content was collected for analysis of intestinal microflora1. F/G:In the starter period (1 to 21 DOA), broilers administered Lactobacillus D22 and/or BS had significantly higher DWG and lower F/G than the control (P<0.05), but did not differ from one another (P>0.05).2. Serum biochemical status:both Lactobacillus D22 supplementation or in combination with BS immunization had significantly lower serum TG concentration at 42 DOA (P<0.05), but did not differ from one another (P>0.05).3. Antioxidant status in serum and liver:Broilers administered Lactobacillus D22 and/or BS had significantly a lower liver MDA content than the control (P<0.05), but did not differ significantly among each other (P>0.05). However, BS immunization increased CAT activities in the serum (P=0.017,0.004) and liver (P=0.013,0.042) at both 21 and 42 DOA, decreased serum MDA content (P=0.038) at 42 DOA. Lactobacillus D22 supplementation increased GSH-Px activities in the serum (P=0.005) and liver (P=0.007) at 21 DOA and liver CAT activities (P=0.003,0.017) at both 21 and 42 DOA, decreased serum MDA content (P<0.001) at 42 DOA. There were no significant effects of BS immunization and Lactobacillus D22 supplementation on the serum MDA content at 21 DOA, the liver MDA content, the GSH-Px activities in serum and liver at 42 DOA, and on the activities.of SOD in the serum and liver at both 21 and 42 DOA.4. Digestive enayme activity:Lactobacillus D22 supplementation increased lipase activity at 21 DOA(P<0.05).5. Immune organ index and composition:The TI of broilers immunized with BS alone was significantly higher than that of broilers in the control at 42 DOA (P<0.05), but did not differ between experiment treatments (P>0.05). At 21 DOA, in experiment treatments, the cortex was thicker, the lymphocytes was denser, the volume and number of thymus corpuscles was not influenced. At 42 DOA, the thymus cortex accounted for most volume of the thymus, the lymphocytes was denser, the number of thymus corpuscles was more than the control, the volume of thymus corpuscles was bigger than the control.6. Blood and serum immune capacity:Peripheral lymphocyte proliferation induced by the T cell mitogen ConA was greater in broilers supplemented with Lactobacillus D22 and/or BS immunized compared with the control (P<0.05). The highest level of peripheral lymphocyte proliferation occurred in the treatment Lactobacillus D22 administered alone (P<0.05). BS immunization increased total IgG concentrations in the serum at both 21 and 42 DOA (P=0.045,0.005). The IL-2 concentration of broilers administered BS alone or Lactobacillus D22 alone were significantly higher than that of broilers in the control at 21 DOA (P<0.05). Lactobacillus D22 supplementation increased IL-2 concentration (P=0.030) of broilers at 42 DOA, BS immunization increased IL-6 concentration of broilers at both 21 and 42 DOA (P=0.019, P=0.024).7. Intestinal microflora composition and diversity:Broilers administered Lactobacillus D22 and/or BS had a significantly lower E. coli count than the control (P<0.05), but did not significantly differ among each other (P>0.05). Lactobacillus D22 supplementation decreased total aerobes (P=0.024) and E. coli (P=0.036) counts at 21 DOA, increased total anaerobes (P=0.017) count at 21 DOA, increased Lactobacillus spp.(P=0.004,0.007) and Bifidobacterium spp. (P=0.010,0.001) counts at both 21 and 42 DOA. At 21 DOA and 42 DOA, the dendrograms of intestinal diversity were divided into two main sections corresponding to the treatments that supplemented Lactobacillus D22 in the diet, and nonsupplemented Lactobacillus D22.Broilers immunized BS alone had a significant larger number of bands (P<0.05), and the other treatments had no differences (P>0.05). BS immunization increased number of bands at 42 DOA (P=0.037).It indicated the synergy of Lactobacillus D22 dietary supplementation and BS immunization promoted the growth of broilers in the starter period, decreased serum TG concentration, and enhanced serum and liver antioxidant capacities. Lactobacillus D22 dietary supplementation combined with BS immunization had no synergistic effect on immune organ, but displayed synergistic modulation effects on cellular immunity, and BS immunization enhanced humoral immunity of broilers fed Lactobacillus D22 supplemented diet. Lactobacillus D22 supplementatin increase lipase activity, improved intestinal microflora balance and composition, BS immunization enriched intestinal microflora diversity. Overall, The synergy of Lactobacillus D22 dietary supplementation and BS immunization promoted the growth, immune functions, and intestinal microflora of broilers.