تاثیر سطوح مختلف ریزجلبک اسپیرولینا پلاتنسیس (arthrospira platensis) بر عملکرد رشد، خصوصیات لاشه، جمعیت میکروبی روده و پاسخ ایمنی جوجه‌های گوشتی در شرایط تنش گرمایی و مقایسه آن با مکمل ویتامین e

ریزجلبک اسپیرولینا پلاتنسیس به‌عنوان یک ماده خوراکی طبیعی و عمل‌گرا، به‌دلیل اثرات پری بیوتیکی، پاداکسندگی و تقویت‌کنندگی پاسخ ایمنی، ممکن است بتواند کاهش عملکرد مرغ‌های گوشتی تحت تنش گرمایی را تخفیف دهد. این تحقیق به‌منظور ارزیابی تاثیر سطوح مختلف ریزجلبک اسپیرولینا پلاتنسیس بر عملکرد، خصوصیات لاشه، ترکیب جمعیت میکروبی روده کور و پاسخ ایمنی جوجه‌های گوشتی طراحی شد. تعداد 360 قطعه جوجه گوشتی یک‌روزه نر سویه راس 308 در قالب طرح کاملاً تصادفی به شش تیمار آزمایشی با شش تکرار 10 قطعه ای اختصاص داده شد. تیمارهای آزمایشی شامل سطوح مختلف پودر ریزجلبک اسپیرولینا پلاتنسیس: صفر (شاهد)، 25/0، 50/0، 75/0، 1 و یک تیمار حاوی 150 گرم در تن ویتامین e بود. جیره پایه بر اساس دانه ذرت- کنجاله سویا بوده و همه جیره‌ها نیز بر اساس انرژی و پروتئین یکسان فرموله و به‌مدت 42 روز در جیره‌های غذایی استفاده شدند. در دوره پایانی پرورش، استفاده از یک درصد اسپیرولینا توانست افزایش وزن جوجه‌ها و بازده مصرف خوراک جوجه‌ها را نسبت به گروه شاهد بهبود دهد (05/0>.(p بازده سینه جوجه‌ها در سطوح 5/0، 75/0 و 1 درصد، نسبت به گروه شاهد و ویتامین e بهبود یافت (01/0>p). وزن نسبی چربی محوطه بطنی در پرندگان تغذیه ‌شده با سطوح 75/0 و یک درصد اسپیرولینا، نسبت به گروه شاهد کاهش یافت (01/0>p). شمار جمعیت کل، لاکتوباسیل و اشریشیاکولی روده کور در گروه‌های مختلف تفاوت معنی‌داری با یکدیگر نداشتند (05/0

effects of spirulina platensis on growth performance, carcass traits, cecal microflora and immune response of broiler chickens under heat stress and comparing it with vitamin e

introduction: due to genetic selection, today’s strains exhibit higher metabolic activity, resulting in increased heat production and reduced heat resistance. this can negatively impact their immune system and production performance (havenstein et al. 1994).thaxton et al. (1968) showed that high ambient temperature can have a negative effect on the immune responses of broiler chickens. in recent years, in order to improve the health of chicken meat consumers, the production of broiler chickens without the use of antibiotics has been proposed, and the ban on the use of antibiotics has been issued by the european union in 1999 (youssef et al., 2016). for this reason, today there is a tendency to use alternative sources. algae and microalgae are of the natural substances whose beneficial effects have received much attention in recent years. 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 (hajati and zaghari 2019).materials and methods: a total of 360 one-day old male broiler chickens (ross 308 strain) were allocated to 6 treatments, 6 replicates and 10 birds each replicate in a completely randomized design. the experimental treatments included different levels of spirulina platensis microalgae powder: 0 (control), 0.25, 0.50, 0.75, and 1.0 percent spirulina platensis powder, and one treatment included vitamin e at the level of 150 g/ton feed. the basal diet was based on corn0soybean meal and all the diets were isocaloric and isonitrogenous and used for 42 days in diets. during the experiment, the feed consumption and weight gain of the chickens were measured weekly and the feed conversion ratio was calculated for each week and period.on 42 d of experiment, 2 birds from each replicate were randomly selected, humoral immune response was evaluated and then killed after weighing, carcass components and internal organs were weighed and their weight was calculated as a percentage of live weight. in order to evaluate the humoral immune system, the antibody titer produced against srbc was measured using the hemagglutination method. in the end of experiment, the microbial population of the cecum was counted. all the data were analyzed in the form of a completely random design by sas software and with the glm procedure, and the comparison of means was done with tukey’s test.results and discussion: results showed that the use of different levels of sp had no significant effect on the amount of feed intake during the whole period (p<0.05), but in finisher period, using %1 sp could improve body weight gain and feed efficiency of the broilers compared to control group (p<0.05). breast yield of the chickens was affected by the level of dietary spirulina, and it improved at the levels of 0.5, 0.75, and 1.0 percent sp usage compared to control and vitamin e groups (p<0.01). the relative weight of abdominal fat decreased in the birds fed with sp at the levels of 0.75 and 1.0 percent compared to control group (p<0.01). there was no difference among total count, ceca lactobacillus and e. coli in the chickens of different experimental groups (p>0.05). the response of humoral immune system was higher in all four levels of sp and also vitamin e compared to control treatment. chickens which consumed spirulina at the level of 1 percent had the highest level of antibody titer. mustafa et al. (2021) by achieving a growth performance similar to the present research, stated that the effect of sp on the intestinal microbial population, such as the increase of lactobacillus and the decrease of escherichia coli, has improved the performance of the birds under heat stress conditions. according to the reports on the effects of heat stress on digestive enzymes (sahin et al., 2002) and the efforts of previous researchers to overcome the adverse effects of heat stress on digestive enzymes by using phytogenic compounds (khosravinia et al., 2016), the researchers of the present study believe that the improvement of the mucous tissue and intestinal immune system and perhaps the increase in the secretion of digestive enzymes are the most important factors for improving the performance of birds in heat stress conditions.conclusion: under heat stress condition, using 1 percent spirulina platensis microalgae in broiler chickens’ diet could improve both humoral immune system and growth performance.