Article Details: Received: 2020-11-04 | Accepted: 2020-11-27 | Available online: 2021-01-31 https://doi.org/10.15414/afz.2021.24.mi-prap.164-167 Probiotics and prebiotics are effective to modulate optimal conditions in gastrointestinal tract inhabited by diverse microbial population. Probiotics regulate and modulate gut microbial population thus reducing the risk of diarrhea. Positive effect on growth is confirmed. The aim of this study was to evaluate the effect of probiotic ( Lactobacillus sporogenes ) and prebiotic ( Ascophyllum nodosum ) supplements on weight gain in calves. Forty new-born Holstein calves were randomised to control and experimental group. In the experimental group, Lactobacillus sporogenes and Ascophyllum nodosum were added first to colostrum and then to milk replacer, calves in the control group were fed with colostrum and milk replacer only. The weight gains of animals were found out during the whole experiment. Evidence of animal health and diarrhea was monitored. In the end of experiment, the body weight gains in experimental calves were by 14,4% higher compared to control but without statistical significance (P>0,05). Probiotic and prebiotic treatment tended to diminish diarrhea. The health benefits of monitored treatment were noticed in experimental group. Keywords: calf, dietary supplements, nutrition, health References Blum, J. W. (2006). Nutritional physiology of neonatal calves. Journal of Animal Physiology and Animal Nutrition , 90(1-2), 1-11. DOI: https://doi.org/10.1111/j.1439-0396.2005.00614.x Cangiano, T. T. et al. (2020). Invited Review: Strategic use of microbial-based probiotics and prebiotics in dairy calf rearing. Applied Animal Science , 36(5), 630-651. DOI: https://doi.org/10.15232/aas.2020-02049 Frizzo, L. S. etbal. (2010). Lactic acid bacteria to improve growth performance in young calves fed milk replacer and spray-dried whey powder. Animal Feed Science and Technology , 157(3-4), 159-167. DOI: https://doi.org/10.1016/j.anifeedsci.2010.03.005 Gaggia, F. et al. (2010). Probiotics and prebiotics in animal feeding for safe food production. International Journal of Food Microbiology , 141(6), 15-28. DOI: https://doi.org/10.1016/j.ijfoodmicro.2010.02.031 Cho, Y. I. and Yoon, K. J. (2014). An overview of calf diarrhea - infectious etiology, diagnosis, and intervention. Journal of Veterinary Science, 15(1), 1-17. DOI: https:// doi:10.4142/jvs.2014.15.1.1 Morrell, E. L. et al. (2008). Retrospective study of bovine neonatal mortality: Cases reported from INTA Balcarce. Argentina Revista Argentina de Microbiologia , 40(3), 151-157. DOI: https://www.redalyc.org/pdf/2130/213016785003.pdf Niggemman, B. (2006). Does unconventional medicine work through conventional modes of action. Journal of Allergy and Clinical Immunology , 118(3), 569-573. DOI: https://doi.org/10.1016/j.jaci.2006.06.021 Raabis, S. et al. (2019). Effects and immune responses of probiotic treatment in ruminants. Veterinary Immunology and Immunopathology , 208, 58-66. DOI: https://doi.org/10.1016/j.vetimm.2018.12.006 Rastall, R. and Maitin V. (2002). Prebiotics and synbiotics : towards the next generation. Current Opinion in Biotechnology , 5, 490-496. DOI: https://doi.org/10.1016/S0958-1669(02)00365-8 Renaud, D. L. et al. (2019). Evaluation of a multispecies probiotic as a supportive treatment for diarrhea in dairy calves: A randomized clinical trial. Journal of Dairy Science , 102(5), 4498-4505. DOI: https://doi.org/10.3168/jds.2018-15793 Sanei, M. et al. (2012). Effects of hormone or mineral–vitamin enriched colostrum on performance and weaning age of Holstein calves. Livestock Science , 149(1-2),190-194. DOI: https://doi.org/10.1016/j.livsci.2012.07.007 Soccol, C.R., et al. (2010). 'The Potential of Probiotics: A Review'. Food Technology and Biotechnology , 48(4), 413-434. DOI: https://hrcak.srce.hr/61713 Timmerman, H. M. et al. (2005). Health and growth of veal calves fed milk replacers with or without probiotics. Journal of Dairy Science , 88(6), 2154-2165. DOI: https://doi.org/10.3168/jds.S0022-0302(05)72891-5 Uyeno, Y. et al. (2015). Effect of Probiotics/Prebiotics on Cattle Health and Productivity. Microbes Environment . 30(2), 126-32. DOI: https://doi.org/10.1264/jsme2.ME14176 Veir, J. K. et al. (2007). Effect of supplementation with Enterococcus faecium (SF68) on immune functions in cats. Veterinary Therapeutics , 8(4) , 229-238. DOI: https://europepmc.org/article/med/18183541 Vrese, M. and Schvezenmeir, J. (2008). Probiotics, Prebiotics, and Symbiotics. Advances in Biochemical Engineering / Biotechnology , 111(1), 1-66. DOI: https://doi.org/10.1007/10_2008_097 Zhang, R. et al. (2016). Effect of oral administration of probiotics on growth performance, apparent nutrient digestibility and stress-related indicators in Holstein calves. Journal of Animal Physiology and Animal Nutrition , 100(1), 33-38. DOI: https://doi.org/10.1111/jpn.12338