اثر افزودن سطوح مختلف اسيدهاي آمينه ليزين و ترئونين به جيره غذايي بر عملكرد، خصوصيات لاشه و بار ميكروبي روده جوجه‌هاي گوشتي

Effect of different levels of Lysine and Threonine supplementation on performance, carcass traits and intestinal microflora of broiler chickens

زمينه مطالعاتي: اسيدهاي آمينه ليزين و ترئونين روي عوامل فيزيولوژيك و عملكرد جوجه­ هاي گوشتي تاثيرگذارند. هدف:آزمايش حاضر به منظور بررسي اثر سطوح مختلف اسيدهاي آمينه ليزين و ترئونين بر خصوصيات لاشه و بار ميكروبي روده جوجه­ هاي گوشتي انجام گرفت. روش كار: 960 قطعه جوجه گوشتي نر يك روزه از سويه راس 308 انتخاب و در يك طرح فاكتوريل با 12 تيمار و چهار تكرار و 20 قطعه جوجه در هر تكرار به صورت تصادفي تقسيم ­بندي شدند. جيره­ هاي آزمايشي شامل چهار سطح ليزين (100، 110، 120 و 130 درصد توصيه­ هايNRC) و سه سطح ترئونين (100، 110 و 120 درصد توصيه­ هايNRC) بودند. جيره­ ها در دو دوره آغازين (0 تا 21 روزگي) و رشد (21 تا 42 روزگي)، در اختيار طيور قرار گرفتند. نتايج:در دوره آغازين، سطح 120 درصد ليزين و ترئونين، سبب بهبود وزن زنده، لاشه و درصد لاشه، سينه، ران و كبد (۰/۰۵

Introduction: Broiler chicks do not require to crude protein, but broilers require accurate and balanced amino acids. Researchers are trying to formulate diets based on digestible amino acids (Ciftci and ceylan, 2004) to meet the requirements of maintenanc e and production (Mack et al., 1999). Partial replacement for intact protein (e.g. soybean meal) with crystalline, amino acids brings the dietary protein closer to ideal protein and may allow for some decrease in dietary crude protein content (Bregendahl e t al., 2002). A good number of studies showed that increasing dietary levels of lysine improved breast meat production (Mack et al., 1999). Lysine also impacts on the improvement of functional traits such as decreasing feed conversion and increasing body w eight gain (Nasr and Kheiri, 2011). Threonine is particularly involved in maintenance processes, like the renewal of intestinal mucus and the synthesis of immune proteins. It has been estimated that more than half of the dietary threonine consumed by a piglet or a human is retained at the in testinal level to fulfill these gut - maintenance functions and is primarily used in the synthesis of mucins (Corzo et al., 2007). Mucin is a main factor in the protecting the mucosal layer of intestine, which acts as a layer protecting the intestinal underl ying epithelium from infection and damage by infectious bacteria (Linden et al., 2008). This study was designed to determine the effect of added lysine and threonine on growth performance, carcass characteristics, and intestinal facultative anaerobic micro flora of male broiler chicks from hatch to 21 and 42 days post - hatch. Material and method s : A total of 960 Ross 308 one - day - old female broiler chickens were selected and randomly distributed in a factorial design with 12 treatments, four replicates and 20 chicks in each replicate . The experimental diets include 4 levels of lysine (100, 110, 120 and 130% recommendation by NRC, 1994) and 3 levels of threonine (100, 110 and 120% recommendation by NRC, 1994). The diets were fed in two phases, starter from hatch to 21 days and grower from 22 to 42 days post - hatch. Birds and feed were weighed at the start and feed changes during the experiment and feed intake and BW gain was calculated and used to calculate FCR. On days 21 and 42, two birds from each pen with a BW close to the pen average were selected and euthanized by cutting the jugular vein after 3 hours of fasting. On day 21 and 42, a sample (two birds were sampled each pan the same one used for carcass) of the ileum contents was removed and to determine the total count of intestinal facultative anaerobic microflora, the sample was transferred to the microbiology laboratory. The obtained data were analyzed as a 3×4 f actorial experiment in a completely randomized design with four replications using General Linear Models (GLM) procedure of SAS (SAS Inst. Inc., Cary, NC) . Results and d iscussion : Results showed that different levels of lysine and threonine do not show si gnificant effect on feed intake. Lysine levels, unlike threonine levels, influenced body weight gain significantly (P<0.05) and feed conversion ratio changed by different levels of lysine significantly (P<0.05) although different levels of threonine has not significant effect on feed conversion ratio . At the starter period different l e vels of lysine and threonine influenced all of the carcass traits si gnificantly except heart yield and most proper results belonged to treatment that received 120% of lysine along with 120% of threonine. At the 21 days of age, 120% of lysine and threonine addition on diets were increase the body and carcass weights and bre ast, thigh and liver yields in chicks (P<0.05). At the age of 42 days, 120% of lysine and threonine supplementation improved the body and carcass weights and carcass yields. In growth period with 120% lysine improved feed conversion ratio. In both periods of the experiment, the most proper results were related to the treatment which received 120% of lysine along with 120% of threonine. Han and Baker ( 1994 ) observed that breast meat yield increased quadratic ally in response to lysine addition . Rezaeipour et al. (2012) showed that NRC recommendations of threonine at the starter period is enough for optimal carcass performance . But in agreement with the results of this study, Kidd et al. (1997) demonstrated that lysine and threonine interacted to affect breast yields . The intestinal facultative anaerobic microflora , in 21 days of age, was significantly increased by 110% of lysine as well as 100 and 120% of threonine (P<0.05). But in 42 days of age t he level of 100% lysine created significant increase in the int estinal facultative anaerobic microflora . To our knowledge, no other researches exist focusing the consideration lysine and threonine on intestinal facultative anaerobic microflora in broiler chicks. Intestinal facultative anaerobic microflora can be affected by diet. But of course, diet is one of the most important factors that can affect the intestinal microbial population. Intestinal facultative anaerobic microflora decreased by increasing the leve ls of lysine and threonine base on NRC recommendations. Decreasing the intestinal facultative anaerobic microflora were seen by increasing duration of using high levels of lysine and threonine base on NRC recommendations at 42 days of age. In addition to t he role of threonine in the formation of mucin, lysine and threonine may be prevention the accumulation or formation of intestinal anaerobic bacteria in intestinal epithelial cells and helps to gastrointestinal health . The best levels of lysine and threoni ne to achieve the most favorable values of carcass traits at the starter and grower periods of broiler chicks are the level of 120% relative to NRC recommendations. By increasing lysine level (120%), and (120%) levels of threonine (interaction lysine and t hreonine) was related to the highest body weight gain. Conclusion : The best levels of lysine and threonine to achieve the most favorable values of carcass traits of broiler chicks are the level of 20 % above from NRC recommendations . Regarding to the result of this study it was observed improving carcass traits, growth performance and reduction of intestinal facultative anaerobic microflora due to use 120% lysine and threonine. There was probably a relation between reduction of intest inal microflora and improving carcass traits and growth performance.