| A study was conducted to investigate the effects of probiotics on broilers' performance, immune responses, serum biochemical parameters. The experiment was conducted as completely random block design. A total of 3776 one-d-old male commercial Avian broilers were fed on two group (with and without flavomycin) diets supplemented with graded levels of probiotics at 0, 0.2, 0.4, 0.6%. Birds were divided randomly into 8 treatments (six replicates per treatment and 60 broilers per replicate). Every treatment had a digestive group, including 112 birds, added 0.3% Cr2O3 into diet. This experiment was conducted in two periods: starter 0-21 and finisher22-42 ,days. Light was provided 24 h a day, feed and water were provided ad libitum during the entire experimental period. Body weight gain, feed consumption and feed efficiency (feed:gain) were checked on the d 21 and the d 40. Blood samples were collected on d 14 and d 40 to determine IgG, IgA, total protein, albumin, globulin, triglycerol, total cholesterol, Ca, P and T lymphocyte proliferation ratio. On each morning of d 21 and d 42, 64 broilers of d 21 and 48 broilers of d 42 from each digestive group were used to measure spleen, bursa F, thymus, cecal tonsils and the assimilation rate of nutrients.The results showed that: the birds given diet added probiotics (1) There was no significantly effect on feed consumption, feed efficiency and weight gain of starter phase (p>0. 05), but had significantly effect on DM, OM, CP, Ca, P and part of essential amino acid (p<0. 05). The digestibility of Met, Lys, Phe, He, His at starter phase and DM, OM, CP, Ca, P at full phase were significantly improved by the group given 0.2% probiotics (p<0. 05), weight gain was significantly increased at finishing phase (p<0. 05) while feed efficiency was decreased by the group given 0.4% probiotics (p>0. 05). (2) At starter phase, probiotics can improve spleen index, bursa F index and cecal tonsils area. There was significantly effect on spleen index (p<0. 05) and bursa F index (p<0. 01) by 0.4% probiotics, and cecal tonsils area was significantly increased by 0.2% probiotics (p<0. 01). At finishing phase, there was no significant influence on immune organs (p>0. 05). (3) There was obvious effect onserum IgG and IgA content but not effect on T lymphocyte proliferation ratio. The serum IgG, IgA content was significantly improved by 0.4% probiotics (p<0. 05). (4) Probiotics can increase total protein, globulin content and G/A. The globulin content and G/A were significantly increased by 0.2% probiotics (p<0. 05). (5) There was obvious influence on the content of serum Ca > P. The content of serum P at starter phase and serum Ca at finishing phase was significantly increased by the group given 0.2% probiotics (p<0.05). (6) Probiotics can decrease the level of serum triglycerol and cholesterol, and which was significantly decreased by 0.2% probiotics (p<0. 05). (7) There was no significantly different among the groups of probiotics, flavomycin and probiotics + flavomycin (p>0. 05).Based on the above results, it was suggested that:(1) Probiotics can increase the digestibility of essential amino acid, DM, OM, CP. (2) Probiotics can improve the chicken immune response increasing spleen index, bursa F index and cecal tonsils area significantly at starter phase and the serum IgG, IgA, total protein, globulin content and G/A at finishing phase. (3)Probiotics can increase the serum Ca and P content, decrease the serum triglycerol and cholesterol level. (4) The optimal probiotics supplementation level in broiler diet is 0.2%. (5) Compared with flavomycin, probiotics can improve the chicken immune response and decrease serum triglycerol and cholesterol level more efficiently, but the effect of probiotics on gain is less than flavomycin. Probiotics and flavomycin was used at the same time can effect serum protein content and promote the assimilation of Ca. So probiotics partially substituting flavomycin is possible. |
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