Novel probiotics: Their effects on growth performance, gut development, microbial community and activity of broiler chickens

摘要

Abstract A total of 294 one-day-old Cobb broiler chickens were used to investigate the effects of four Lactobacillus strains on gut microbial profile and production performance. The six dietary treatments, each with 7 replicates were: 1) basal diet (negative control), 2) one of four strains of Lactobacillus (tentatively identified as Lactobacillus johnsonii, Lactobacillus crispatus , Lactobacillus salivarius and an unidentified Lactobacillus sp.) and 3) basal diet with added zinc-bacitracin (ZnB, 50 mg/kg). Results showed that the addition of probiotic Lactobacillus spp. to the feed did not significantly improve weight gain, feed intake and feed conversion rate (FCR) of broiler chickens raised in cages during the 6-week experimental period, but tended to increase the number of total anaerobic bacteria in the ileum and caeca, and the number of lactic acid bacteria and lactobacilli in the caeca; and to significantly increase the small intestinal weight (jejunum and ileum). Furthermore, all 4 probiotics tended to reduce the number of Enterobacteria in the ileum, compared with the control treatments. The probiotics did not affect the pH and the concentrations of short chain fatty acids (SCFA) and lactic acid in both the ileum and caeca. Keywords Probiotic ; Broiler ; Performance ; Gut development prs.rt("abs_end"); 1. Introduction The use of probiotics has become a field of science, medicine and business that is growing rapidly. In agricultural science, probiotic, prebiotics, feed enzymes and organic acids, have been seen as potential alternatives to in-feed antibiotics (IFA) ( Choct, 2002 ). The addition of either pure Lactobacillus cultures or mixtures of lactobacilli and other bacteria to broiler diets has produced variable results. Kalavathy et al. (2003) found an improvement in body weight gain (BWG) and feed conversion ratio (FCR) of broilers fed a mixture of different Lactobacillus strains from 1 to 42 days of age. A consistent improvement in BWG of chickens fed a culture of Lactobacillus has also been reported ( Awad et al., 2009 ). Feeding broiler chickens up to 6 weeks of age with a diet containing a single strain of Lactobacillus acidophilus or a mixture of lactobacilli significantly improved BWG and FCR ( Jin et al., 1998a ). Cao et al. (2013) found that supplementation the broiler diets with a single strain of Lactobacillus ( Enterococcus faecium ) significantly improved the BW and BWG compared to the control. However, Ashayerizadeh et al. (2011) did not find any significant difference in the performance of chickens fed on diets containing a mixture of Lactobacillus cultures and other bacteria, compared with a non-supplemented diet. Variation in the effects of probiotics on growth performance of broiler chickens may be attributed to the differences in the strains of bacteria used as the dietary supplements. In the present study, the effects of four strains of Lactobacillus spp. on pH, the concentrations of short chain fatty acids (SCFA) and lactic acid, and growth performance of broiler chickens were investigated; the populations of total anaerobic bacteria, lactic acid bacteria, Lactobacilli , Enterobacteria and Clostridium perfringens in gut environment were detected. 2. Materials and methods 2.1. Probiotic strains A total of 235 Lactobacillus isolates were tested using an antagonistic activity assay as described by Schillinger and Lucke, 1989 and Teo and Tan, 2005 , and the four strains of Lactobacillus isolates were selected as probiotic candidates by largest inhibition zone appearance with indicator pathogenic strains of C. perfringens and Escherichia coli . These four strains of Lactobacillus were tentatively identified as Lactobacillus johnsonii, Lactobacillus crispatus , Lactobacillus salivarius and one unidentified Lactobacillus sp. All the strains were kept at ?20°C in de Man, Rogosa, Sharpe (MRS) broth (Oxoid, CM0359) with 40% glycerol. The culture medium used for growth was MRS agar (Oxoid, CM0361). The overnight culture of each Lactobacillus isolate was used as a feed additive probiotic candidate after anaerobic incubation at 39°C for 24 h. 2.2. Experimental design and bird management A total of 294 one-day-old male Cobb broiler chickens vaccinated against Marek?s disease, infectious bronchitis, and Newcastle disease were randomly assigned to 6 diets each with 7 replicates with 7 birds per replicate. Chickens were reared in multi-tiered brooder cages placed in a climate-controlled room up to 21 d, and then the birds were transferred to a metabolic cage room to 35 d. Feed and water were provided ad libitum. The room temperature was gradually decreased from 33°C on d 1 to 24°C on d 35. Eighteen hours of light was provided per day throughout the trial, excluding d 1 to 7 during which 23 h of light was provided. Each cage was equipped with a feeding and water trough placed outside and also an excreta collection tray. The commercial starter and finisher diets was formulated by Ridley AgriP