| چکیده انگلیسی مقاله |
Introduction: Spirulina platensis (SP) is a filamentous blue-green microalgae (cyanobacteria) generally regarded as prebiotic and source of high quality protein, minerals, essential fatty acids, essential amino acids, pigments and phenolic acids. Many studies have shown that Spirulina has antioxidant, immunomodulatory, anti-inflammatory, antiviral, and antimicrobial activity in various experimental animals. Several studies have demonstrated the growth-promoting effects of spirulina platensis on broiler chickens. Jamil et al., (2015) showed that feeding 0.2, 0.4, or 0.8 percent spirulina increased weight gain and linearly decreased feed conversion ratio (FCR) of broiler chickens. Similar results were reported by Shanmugapriya et al., (2015). They reported that feeding 1% of spirulina platensis to broiler chicks caused to improve growth performance. As well as growth performances, treatment with S. platensis was reported to increase the carcass percentage and ready-to-cook yields of broiler chicks in the studies of Raju et al. (2004), Kaoud (2012) and Holman & Malau-Aduli (2013). The cecum plays an important role in preventing colonization of pathogens and detoxifying harmful substances (Jorgensen et al., 1996), therefore may play an important role in improving nutrients absorption and better performance. A previous study in broiler chickens also concluded that intestinal microbial-including cecum is highly associated with the production performance of broiler chickens (Jeong and Kim, 2014). Park et al., (2018) indicated that broiler chickens fed a Spirulina supplemented diet led to higher cecal Lactobacillus concentration, but had no effect on the number of coliform bacteria. Some other studies suggest that microalgae have potential antibacterial, antiviral, and antifungal activities. de Mule et al., (1996) observed that methanolic and aqueous extracts of Spirulina inhibited the growth of Candida albicans whereas Lactococcus lactis was promoted by the extract, with growth increasing from 7.5 to 14.7%.Materials and Methods: Three hundred one-day- old male Ross 308 broiler chicks were assigned to 5 dietary treatments with 6 replicates and 10 birds each in a completely randomized design. Dried Spirulina Platensis (SP) powder provided from Pars Jolbak Co. in Shiraz, Iran and after chemical analysis was used in diets. All experimental diets were corn soybean based and formulated to reach ROSS 308 broiler chicken requirements. Dietary treatments were 0 (control), 0.25, 0.5,0.75 and 1 % Spirulina Platensis (SP). All diets were isocaloric and isonitrogenous and were fed to birds during 6 weeks. The average daily feed intake (FI) and weight gain (WG) were measured for each group and feed conversion ratio was calculated. Daily mortality was weighed, recorded and used to correct the feed conversion ratio. Daily FI was determined from the difference between supplied and residual feed in each pen and was adjusted for mortality. At the end of the experiment, two birds per each replicate (similar to cage average weight) were selected. The birds were killed by cervical dislocation. Breast, thigh, pancreas, abdominal fat and liver were removed, weighed and expressed as a percentage of live weight at 42 d of age. At the end of experiment, cecal samples collected from each bird. One gram of cecal sample from viable counts of bacteria in the cecal samples were conducted by plating serial 10-fold dilutions onto Lactobacilli MRS agar plates and MacConkey agar plates to isolate Lactobacillus spp. and coliform bacteria, respectively. The lactobacilli agar plates were then incubated for 24-72 h at 37◦C under anaerobic conditions. After the incubation periods, colonies of the respective bacteria were counted and expressed as the logarithm of colony-forming units per gram (log10 CFU/g). All data analyzed by ANOVA using the GLM procedure described by the SAS Institute (2009). Tukey test was used to determine the significant differences between the treatment means.Results and discussion: The results showed that feed intake of birds was not influenced by SP supplementation during the whole period, but weight gain of birds fed diets containing 1 % SP, was increased (P< 0.05) and feed conversion ratio was decreased significantly (P< 0.05) as compared as control birds. Similar to our results, Park et al., (2018) showed that up to 1% SP in broiler diets, did not affect the feed consumption of broiler chickens. They showed that increasing dietary SP from 0 to 1 %, caused to increase in weight gain during total period. Shanmugapriya et al., (2015) reported that feeding 1% of spirulina platensis to broiler chicks caused to improve growth performance.The mechanism of action of Spirulina has not been clearly established, but previous studies have reported that dietary supplementation of Spirulina has positive effects on growth performance in poultry. Carcass yield and breast relative weight in chickens fed more than 0.5 % SP were significantly increased (P< 0.05), but abdominal fat, liver and thigh relative weight were not affected. Similar to our results, increase in carcass percentage and ready-to-cook yields of broiler chicks were reported in the studies of Raju et al. (2004), Kaoud (2012) and Holman & Malau-Aduli (2013). In present study, the chickens fed more than 0.5% SP had lower cecal E.Coli concentration and nonsignificant increase in Lactobacillus concentration. Similarly, Park et al., (2018) indicated that broiler chickens fed a Spirulina supplemented diet led to higher cecal Lactobacillus concentration. Regard to previous study which concluded that intestinal microbial-including cecum is highly associated with the production performance of broiler chickens (Jeong and Kim, 2014), therefore in our study, the better performance of chickens fed higher than 0.5% SP may be associated with decrease in cecal E.Coli Concentration.Conclusion It is concluded that dietary supplementation of broiler diets with 1% Spirulina platensis, could improve the growth performance, carcass yield and cecal microbial population of broiler chickens at 42 day of age.Keywords: Prebiotic, Feed Conversion ratio, Carcass yield, Escherichia coli, Algae |