International Journal of Poultry Science 7 (11): 1095-1099, 2008 ISSN 1682-8356 © Asian Network for Scientific Information, 2008 1095 The Use of Some Feed Additives as Growth Promoter in Broilers Nutrition Ali Khosravi, Fathollah Boldaji, Behrouz Dastar and Saeed Hasani Department of Animal Science, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran Abstract: This study was undertaken to investigate the effects of some feed additives on the performance and blood parameters of broilers. In a completely randomized design, 320 1-d-old chicks were divided into four replicate groups. A control diet was prepared, based on NRC recommendations. For preparing other diets, control diet supplemented with propionic acid, protexin and nettle extract at the levels of 2, 0.1 and 1 g/kg of diet, respectively. Diet contained propionic acid resulted in significant increase in BWG during the starter and from 0-42 periods. The birds fed control diet had more FI and PI during the finisher period than those fed propionic acid. When diet supplemented with propionic acid and protexin, a significant improvement in FCR and PER was observed among this diets and other diets. Propionic acid also significantly increased HDL and decreased LDL compared to other feed additives. In conclusion, based on the results of this experiment, propionic acid and protexin can be used as a suitable alternative to antibiotic growth promoters whereas nettle extract can not. Key words: Broilers, performance, blood parameters, growth promoters INTRODUCTION Prior to birth, the Gastrointestinal tract (GI) of birds is free of any strains of microbial populations (Mead and Adams, 1975; Kelly and King, 2001) and bacteria from the diet, water, excreta and the environment begin to colonize in the GI almost shortly (Dibner and Richards, 2005). The GI of young birds is far more susceptible to pathogenic bacteria compared to other birds (Koopman et al., 1984) therefore, balance of this population using feed additive can play a key role for immune system development and increase birds’ performance (Patterson and Burkholder, 2003). In order to balance this population by damaging the pathogenic bacteria, antibiotic feed additives have been used since 50 years ago. Because many of these antibiotics are useful for treating bacterial infections in humans, use of these in animal husbandry can led to a worldwide increase in antibiotic resistance strains of bacteria and hereby damaging the balance of humans’ microflora. Therefore, nowadays the use of these feed additives in birds’ diet is removing in many countries. Removal of antibiotics from the food cycle of animals can cause increase acute pathogenesis (e.g., Escherichia coli, Campylobacter and Salmonella) in GI. These pathogens can produce many chronic gut disorders (e.g., gastritis, peptic ulcer, irritable bowel syndrome, bowel cancer, ulcerative colitis, Crohn's disease, pseudomembranous colitis) and finally lead to serious damage to animal husbandry. Therefore, animal researchers and animal feed manufacturers are looking for a suitable alternative to antibiotics in order to prevent these damages and to improve breeding performance. Thus, alternatives to antibiotics are of great interest to the animal industry. Reviewing of scientific reports indicates positive effects of organic acids, probiotics and plant extracts in poultry diets (Vogt et al., 1981; Runho et al., 1997; Jin et al., 1998). Several studies indicated that acidifiers could, as antibiotics, improve poultry performance by reducing colonization of pathogenic microorganisms, increase digestibility of 1) proteins and mineral and reduce toxic components of bacteria (Kishi, 1999; Chaveerach et al., 2004). The modes of action of probiotics in the chickens, it is not completely known, but it seems that the mode of action of those is mainly due to low redox potential, reductions in the population of Escherichia coli competition for adhesion receptors in the intestine and reduction of toxin release (Montes and Pugh, 1993; Martins et al., 2005). Plant extracts have recently been used in poultry diets as feed additive. Several studies indicated that these feed additives could be used in poultry diets as an antifungal, antibacterial, antioxidant and or antimutagenic compounds (Osawa et al., 1995; Nielsen et al., 1999; Wuthi-udomler et al., 2000; Hernandez et al., 2004). It seems that plant extracts are other suitable alternatives to antibiotic growth promoters. However, due to inconsistent results about the effects of organic acids, probotics and plant extracts on poultry performance therefore, a decisive assessment about the use of these feed additives as suitable alternative to antibiotics; needs more research to be done. Therefore, this study was conducted to evaluate the effects of dietary propionic acid, protexin and nettle extract as growth promoter on the performance and on some blood parameters of broiler chicks.