Effect of in ovo injection of threonine on Mucin2 gene expression and digestive enzyme activity in Japanese quail (Coturnix japonica) H. Kermanshahi a , A. Daneshmand a, *, N. Khodambashi Emami a , D. Ghofrani Tabari a , M. Doosti a , A. Javadmanesh a , S.A. Ibrahim b a Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran b Department of Family and Consumer Sciences, North Carolina A&T State University, Greensboro, NC 27411 ARTICLE INFO Article history: Received 25 November 2014 Accepted 14 March 2015 Keywords: Quail In ovo injection Threonine Gene expression Digestive enzyme A B ST R AC T A total of 540 Japanese quail eggs were assigned to 9 treatments of 4 replicates to investigate the effect of in ovo injection of threonine (THR) on mucin2 (MUC2) mRNA expression and digestive enzyme ac- tivity. Treatments were (non-injected) eggs and those in ovo injected with saline (0.05 or 0.1 ml) with or without THR (5 mg/ml) in two sites (in or under the air sac). On hatch day, 0.05 ml in ovo injected (under the air sac: TUAS) hatchlings were divided into three groups based on NRC recommendations for THR, while all 0.1 ml in ovo injected chicks were removed due to low hatchability. The remaining treat- ments received the NRC recommended diet until day 10 post-hatch. Treatments had no effect on protease and amylase activities, while TUAS increased MUC2 gene expression. In conclusion, the in ovo injection of THR increased MUC2 gene expression but had no effect on enzyme activity. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction It has been shown that there is an approximately 48–72 hr gap between hatch time and hatchlings’ access to feed and water due to different hatch times, hatchery handling and transport times to the poultry farm (Bhuiyan et al., 2011; Willemsen et al., 2010). This delay results in a lowering of development and function of the gut (Potturi et al., 2005; Yang et al., 2009), thereby reducing final body weight (Noy and Sklan, 1999), decreasing immune response to patho- gens (Dibner et al., 1998) retarding growth, and increasing mortality up to 5% (Willemsen et al., 2010). It has thus been suggested that the detrimental effects of this delay could possibly be overcome. Hatchery feeding (Kidd et al., 2007; Willemsen et al., 2010) and in ovo feeding (Uni and Ferket, 2004) are two most important clues suggested to overcome the detrimental effects of such delay. Hatch- ery feeding requires a high level of consistency in nutrients and diet formulation between hatchery management and the rearing farm, something that is practically difficult to achieve (Lilburn, 1998). Sharma and Burmester (1982) first used an in ovo method to vac- cinate chicks against Marek’s disease. In recent decades, many studies have been conducted to evaluate the effects of in ovo injection on poultry performance (Ohta and Kidd, 2001; Ohta et al., 2001). Finally, Uni and Ferket (2003) patented “In ovo Feeding” and stated that this method could beneficially affect hatchability (Uni et al., 2005), in- testinal mucosa, and body weight at hatch and at 35 days of age (Uni and Ferket, 2004). Uni et al. (2003) reported that gastrointes- tinal functionality of in ovo treated chicks was the same as that of 2 day old birds fed immediately after hatching. To investigate the effect of in ovo feeding on the performance of chickens, various nu- trients such as amino acids (Bhanja and Mandal, 2005; Bhanja et al., 2004, 2010), carbohydrates (Foye, 2005; Tako et al., 2004; Uni and Ferket, 2004), vitamins (Al-Daraji et al., 2012; Bhanja et al., 2007; Nowaczewski et al., 2012) and other nutrients (Moore, 2005; Tako et al., 2005; Zhai et al., 2008) have been administered to different poultry species. Among these nutrients, amino acids and, particu- larly, threonine (THR) have attracted more attention due to their effect on cellular (Tenenhouse and Deutsch, 1966) and humoral (Takahashi et al., 1994) immune responses, mucin structure (Gum, 1992; Lien et al., 1997), and digestive enzyme activity (Block et al., 1966; Yang et al., 1989). Kadam et al. (2008) reported that in ovo injection of THR caused better immunological responses in broil- ers, while having no effect on digestive enzyme activity. It was also demonstrated that digestive enzymes secreted by the intestinal lumen may degrade the thin mucosal layer of the intestine, enter the epithelial cell walls and cause ischemia (Godl et al., 2002). Sim- ilarly, THR can induce mucin secretion which results in an increase in the thickness of the mucosal layer and prevents enzymatic deg- radation of the intestinal mucous layer (Chang et al., 2012). These studies were done only with poultry models (Kadam et al., 2008), so consequently there is a dearth of research on in ovo admin- istration in quail. Thus, in the current study, we wanted to evaluate the * Corresponding author. Animal Science Department, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran. Tel.: +989155841134; fax: +985138796845. E-mail addresses: ali.daneshmand@stu.um.ac.ir; a.daneshmand@ymail.com (A. Daneshmand). http://dx.doi.org/10.1016/j.rvsc.2015.03.023 0034-5288/© 2015 Elsevier Ltd. All rights reserved. Research in Veterinary Science 100 (2015) 257–262 Contents lists available at ScienceDirect Research in Veterinary Science journal homepage: www.elsevier.com/locate/rvsc