اثرات نانوذرات اکسید روی و پروبیوتیک (باسیلوس‌کوآگولانس) بر پاسخ ایمنی، برخی خصوصیات لاشه و وزن اندام‌های داخلی جوجه‌های گوشتی

Introduction: Zinc (Zn) is an essential trace element for poultry nutrition, because of its important role in various biological functions. For decades, the nutritional importance of Zn has been known, but its vital roles in immune modulation and functioning has been arisen (Bonaventura et al. 2015). The forms of Zn in the diet of poultry could be as inorganic form like Zinc oxide (ZnO) and Zinc Sulphate and as organic shapes like Zn acetate (Zhao et al. 2014). A new form of this inorganic salt is zinc oxide nanoparticles (zno nanoparticles) that have produced by nanotechnology (Song et al. 2010). Nanoparticles have larger surface area that allows higher interactions with other molecules, and the larger surface area enhances the bioavailability and the intestinal absorption of these tiny structures (Nel et al. 2009; Tsai et al.  2016). In general, little studies have indicated that the application of nano minerals in broilers production, immune responses is promising. One of the most promising spore forming lactic acid-producing species is Bacillus coagulans (B. coagulans) (Hyronimus et al.  2000). Bacillus coagulans is a safe, unique gram-positive, spore-forming, microaerophilic, lactic acid producing bacillus that does not encode enterotoxin. It possesses a protective, spore-like protein coating, which allows it to resist high temperature and to survive stomach acid and bile salts, reach the small intestine, germinate, and multiply (Hyronimus et al.  2000). It has been demonstrated that supplementation of B. coagulans in chicken feed promotes their growth performance (Hung et al. 2012). Some previous studies reported that probiotics could effectively enhance immune functions of broiler chicks. Kabir et al. (2004) found that broiler chicks fed with probiotic improved antibody titers against sheep red blood cells (SRBC). In addition, researchers have used probiotics in combination with some nanoparticles, such as nano-selenium, to improve the growth performance and immunity in broiler chicks (Saleh, 2014). In addition, another research demonstrated that probiotics decreased intestine pH, hence it increased production of short-chain fatty acids because of the modification of the gut flora with a consecutive increased mineral solubility and absorbability (Gilman and Cashman 2006; Scholz-Ahrens et al. 2007). According to the above evidences, it appears that combination of zno nanoparticles with probiotic probably causes synergism effects between them through their impact on performance. Thus, in the current study, the synergistic effects of zno nanoparticle in combination with a probiotic on the growth performance and immune responses of broilers was studied. Therefore, the aims of current study were to evaluate the effects of B. coagulans and different levels of zno nanoparticles on growth performance, carcass characteristics, and immune responses parameters.
Material and methods: This trial was conducted with 288 male Ross broiler chicks in a completely randomized design with 6 dietary treatments and 4 replicates with 12 birds per replicate. The experimental treatments were included: control diet (100 mg/kg zno), control diet plus 100 mg/kg probiotic, basal diet without zno plus 25 and 50 mg/kg zno nanoparticles with or without probiotic. The basal diet was formulized according to the dietary requirements in accordance with the Ross guidelines. In this experiment the performance parameters (body weight gain, feed intake and feed conversion ratio), humoral immune (antibody titer against sheep red blood cells), carcass parameters (relative weight of carcass, breast, thigh, spleen, liver, pancreas, bursa of Fabricius and the relative weight and length of the duodenum, ileum and cecum) and intestinal and gizzard pH were measured. On day 42 of experiment, two birds from each replicate were selected, then weighed, were slaughtered and carcass parameters were weighed using a digital scale and their relative weight to body weight were calculated. The length of the various parts of the small intestine was measured after the separation from the mesenteric with the ruler. The collected data were compared using SAS software version 9.1.
Results and discussion: Using zno nanoparticles with probiotic improved body weight gain and feed conversion ratio of broiler chicks (p < 0.05). It has been demonstrated that supplementation of B. coagulans in chicken feed promotes their growth performance (Hung et al.  2012). In other study, broiler chicks fed multi-strain probiotic diets have greater body weight gain and lower feed conversion ratio than those fed control diet (Zhang and Kim 2014). Jawad et al. (2016) were indicated that supplementation with probiotic improved body weight gain and feed conversion ratio. The possible mechanism for this improvement is that probiotic exert useful effect via retention of beneficial bacterial population in the digestive tract and improvement of feed digestion and absorption. In the present study, treatments had no significant effect on relative weight of carcass, breast, spleen, bursa of Fabricius, pancreas, and liver (P>0.05). The relative weight of liver and thighs in broiler fed with combination of zno nanoparticles and probiotic were lower and higher than control group, respectively (p < 0.05). It was reported that using probiotic (Primalac) to the diet of broilers had no effect on growth performance, carcass quality, carcass weight, carcass traits, breast, heart, abdominal fat, spleen, and bursa of Fabricius (Shirmohammad et al. 2015). In addition, treatments had no significant effect on relative weight and length of different parts of small intestine (duodenum, ileum, and cecum) and pH of gizzard and cecum of broilers (P>0.05). The antibody titer against SRBC in chickens fed with 50 mg/kg of zno nanoparticles with or without probiotic were significantly more than the control group. In other study, the variation in Zn levels affected the antibody titers against SRBC inoculation and the amounts of humoral immune response. The highest antibody titers in broiler were observed at 80 mg/kg level compared with lower levels (Sunder et al. 2008). Changes in Zn status of body influenced the T cell functions and the balance between the different T helper cell subsets (Bonaventura et al. 2015).
Conclusion: In conclusion, the results showed that the use of 50 mg/kg of zinc oxide nanoparticle with probiotic (Bacillus coagulans) caused an improvement in growth performance, some carcass characteristics, and immune responses of broiler chickens. In addition, we concluded that substitution of the mineral form (zinc oxide) with zinc oxide nanoparticle in broiler diet did not affect the broiler performance.