_1756791779 20250902054259000 Rovedar Daryoushbabazadeh@gmail.com Rovedar Farm Animal Health and Nutrition Farm Anim. Health Nutr. 2980-7905 06 28 2025 4 2 Majid Shakeri https://orcid.org/0000-0002-1857-2133 Introduction: Antibiotics have been used to promote the growth performance of broiler chickens, but significant concerns about antibiotic resistance are driving interest in finding new alternatives to support growth performance. One promising additive is probiotics, which have shown positive impacts on broiler performance. The present study aimed to investigate the effects of probiotics (Lactic acid bacteria) on growth, feed intake, feed conversion ratio, and immunity parameters such as corticosterone, compared to an antibiotic (virginiamycin) when chickens were raised in different colored environments. Materials and methods: A total of 120 one-day-old male Cobb-500 chickens, with an average weight of 45 ± 2 grams, were randomly distributed into 12 white and 12 red pens (five chickens in each pen). Three dietary treatments were assigned and each contained 4 pens from each color and totally 8 pens for each treatment. Each treatment group consisted of 40 chickens, and four replicates. The dietary treatments included a control diet, the control diet supplemented with 4 cm³ of lactic acid-based probiotic bacteria (109 CFU/kg) per kilogram of feed, and the control diet supplemented with 0.4 grams of virginiamycin per kilogram of feed. On day 42, the chickens were sampled for evaluation of performance factors, corticosterone levels, foot-pad dermatitis, and villi length of Jejunum. Results: The data showed that both probiotic and virginiamycin improved body weight and villi length compared to the control, while chickens supplemented with the probiotic in the white pens had a better growth rate compared to virginiamycin and the control. Corticosterone levels were reduced for both probiotic and virginiamycin compared to the control group, with stronger effects observed in the white pens. Chickens supplemented with either probiotic or virginiamycin demonstrated a lower incidence of foot-pad dermatitis in both pen color environments compared to the control group. Conclusion: Supplementation of chickens with probiotic (4 cm3/kg, lactic acid bacteria; 109 CFU/kg) improved body weight similarly to virginiamycin, while a white environment can reduce chickens' stress, leading to better growth performance. 06 28 2025 28 31 https://creativecommons.org/licenses/by/4.0 10.58803/fahn.v4i2.76 https://fahn.rovedar.com/index.php/FAHN/article/view/76 https://fahn.rovedar.com/index.php/FAHN/article/download/76/109 https://fahn.rovedar.com/index.php/FAHN/article/download/76/109 10.1093/ps/85.3.476 10.1093/ps/84.4.634 Ahmadi F. The Effect of different levels of Virginiamycin on performance, immune organs and blood metabolite of broiler chickens. Ann Biol Res. 2011; 2(5): 291-298. Available at: https://www.scholarsresearchlibrary.com/articles/the-effect-of-different-levels-of-virginiamycin-on-performance-immune-organs-and-blood-metabolite-of-broiler-chickens.pdf 10.1301/nr.2007.jul.316–328 10.3923/ijps.2006.593.597 10.1371/journal.pone.0043928 Ibrahim RR, Khalil F, Mostafa AS, and Emeash HH. Efficacy of probiotic in improving welfare and mitigating overcrowding stress in broilers. J Adv Vet Res. 2018; 8(4): 73-78. Available at: https://advetresearch.com/index.php/AVR/article/view/325 Mahmud A, Saima S, Rafiullah R, and Ali I. Effect of different light regimens on performance of broilers. J Anim Plant Sci. 2011; 21(1): 104-106. Available at: https://thejaps.org.pk/docs/21(1)2011/EFFECT-OF-DIFFERENT.pdf 10.1093/ps/81.6.767 10.1016/0031-9384(93)90017-A 10.5713/ajas.15.0757 10.1093/japr/16.3.304 10.3382/ps.2009-00308 10.1016/j.psj.2025.105050 10.3923/ijps.2005.396.398 10.1093/acprof:oso/9780195168761.003.0012 10.16988/iuvfd.2016.80560