Growth performance, digestibility, immune response and intestinal morphology of male broilers fed phosphorus deficient diets supplemented with microbial phytase and organic acids N. Khodambashi Emami a,n , S. Zafari Naeini b , C.A. Ruiz-Feria c a Department of Animal Science, College of Agriculture, Ferdowsi University of Mashhad, Mashhad 91779-47974, Iran b Nutrition manager in Shamim Roshd Espadan Co., Sepahan Shahr, Isfahan, Iran c Texas A&M University, Department of Poultry Science, 2472 TAMU, College Station, TX 77843, USA article info Article history: Received 9 February 2013 Received in revised form 15 August 2013 Accepted 19 August 2013 Keywords: Broilers Phytase Organic acids Digestibility Immune response abstract The poultry industry is currently facing several challenges, including the environmental impact of poultry production, bird health and immunity, and the safety of poultry products. This experiment was conducted to evaluate the effect of phytase supplementa- tion and organic acids (alone or in combination) on growth performance, nutrient digestibility, tibia ash, immunity, and gut morphology of male broiler chickens (Ross 308). The birds were allocated to 5 dietary treatments: (1) positive control diet (PC) with adequate amount of available phosphorus (4.9 and 4.4 g/kg in the starter and grower period, respectively); (2) negative control diet (NC) with a low amount of available phosphorus (3.9 and 3.4 g/kg in the starter and grower period, respectively); (3) NC plus 0.2% of a commercial organic acid (Salkil; Sal); (4) NC plus 500 phytase unit/kg diet (Phy); (5) NC plus Salkil and phytase (Sal þPhy). Each treatment had 5 pen replicates of 20 birds. The starter (0–14 d) and grower (15–28 d) maize–soybean meal based diets were fed ad libitum in mash form. The results showed that overall, birds fed the Phy þSal diet and birds fed the NC diet had the highest and lowest (P o0.001) live weight gain (50.80 g/bird/ d vs 39.68), feed intake (74.78 g/bird/d vs. 64.69) and feed conversion ratio (1.47 vs. 1.63), respectively. Broilers fed the NC diet had the lowest crude protein and ether extract digestibility (0.7751 and 0.7949, respectively), which were improved (P o0.001 and P ¼0.010, respectively) by the addition of Phy (0.8506 and 0.8645, respectively) or Phy þSal (0.8858 and 0.8561, respectively) to the NC diet. Tibia ash was improved (P o0.001) in Sal-fed broilers (374.3 g/kg) compared with NC (341.6 g/kg), but it was still lower than other treatments (PC, Phy and Phy þSal). Addition of Phy or Phy þSal to the NC diet improved villus height and villus height/crypt depth ratio in the duodenum, jejunum and ileum of broilers compared with broilers fed the PC diet. Broilers fed Phy þSal showed higher (P o0.001) IgG (2.27) in the primary and also higher (P o0.001) total Ig (7.84) and IgG (5.74) in the secondary response compared with all other treatments. In conclusion, concurrent supplementation of phytase and organic acids improve productive perfor- mance, bone mineralization, intestinal integrity, and immune response of broilers fed diets low in available phosphorous. & 2013 Elsevier B.V. All rights reserved. 1. Introduction The use of microbial phytase to reduce the need for supplementation with inorganic phosphate is common in Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/livsci Livestock Science 1871-1413/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.livsci.2013.08.014 n Corresponding author. Tel./fax: þ98 311 9517622; Mobile: þ98 9132946864. E-mail addresses: nimakhodambashiemami@yahoo.com, ni_kh276@stu-mail.um.ac.ir (N. Khodambashi Emami). Livestock Science 157 (2013) 506–513