ارزیابی سطوح مختلف لیزین قابل هضم و نسبت آن به اسیدهای آمینه ضروری در جوجه های گوشتی سویه آرین در دوره آغازین

Introduction: Lysine is considered the second limiting amino acid for broiler chickens, and the requirement for other amino acids relative to lysine is expressed. This experiment aimed to evaluate the levels and desirable ratios of essential amino acids to digestible lysine in broiler chickens of the Arian strain during the starter period. This study investigates the effects of different levels of lysine and various patterns of amino acids on the growth performance, carcass characteristics, feed intake, and immune parameters in broiler chickens
Material and methods: In this experiment, 540-day-old male Arian broiler chicks were allocated to 9 treatments with 5 replicates of 12 birds each. The experiment followed a completely randomized design with a factorial arrangement of 3×3 (three amino acid patterns, Arian,) Ajinomoto and Brazilian table( × three levels of digestible lysine 1.18, 1.25 and 1.32%). Observations were conducted over three periods: 0-7 days, 7-14 days, and the overall 0-14 day period.
Results and discussion: Daily weight gain during all three periods (0-7 days, 7-14 days, and total 0-14 days) was significantly affected by the level of lysine, amino acid pattern, and their interaction (p<0.05). Diets containing 1.32% lysine exhibited the highest daily weight gain. Birds receiving the Arian pattern had the highest weight gain, while those receiving the Ajinomoto pattern had the lowest (p<0.05). Daily feed intake over the entire trial period was influenced by the level of lysine and amino acid pattern (p<0.05). Birds fed diets with 1.25% and 1.32% lysine had the highest feed intake. The feed conversion ratio (FCR) during the trial period was affected by lysine level, amino acid pattern, and their interaction. Birds receiving the Arian pattern had the lowest FCR. The effects of amino acid pattern and its interaction with lysine on carcass yield were significant (p<0.05). Birds receiving the Arian pattern had a higher carcass yield compared to the Brazilian pattern. An increase in lysine level significantly increased breast weight and percentage (p<0.05). Breast weight and percentage were also influenced by the amino acid pattern, with the Arian pattern being the best. The interaction effect of lysine and amino acid pattern on breast weight and thymus weight was significant (p<0.05). Increasing lysine level increased lymphoid organ weight and percentage significantly (p<0.05). Total immunoglobulins and antibody titers against sheep red blood cells and Newcastle disease were influenced by lysine level (p<0.05), with birds receiving 1.32% lysine showing the highest response. The effect of amino acid pattern was significant only on total immunoglobulin and Newcastle disease antibody titer (p<0.05), with the Arian pattern being better than the Brazilian pattern. Based on the comprehensive results, the study investigated the impact of various experimental treatments on performance indicators in broiler chickens. Results indicated significant effects of lysine levels and amino acid patterns on live weight, feed intake, and carcass characteristics. Birds receiving diets with higher lysine content, particularly 1.49% lysine, exhibited significantly greater live weights compared to those fed with 1.18% lysine. Additionally, live weight was influenced by amino acid patterns, with birds receiving the Ariane pattern showing the highest weight gain. The interaction effects between lysine levels and amino acid patterns on live weight were also significant, emphasizing the importance of balanced amino acid profiles in diets. Daily weight gain and feed intake were significantly affected by lysine levels and amino acid patterns, with higher lysine diets and the Ariane pattern resulting in superior performance. Moreover, carcass weight and quality parameters such as breast percentage and thigh weight were influenced by lysine levels and amino acid patterns, indicating the importance of optimizing these factors for improved carcass traits. Overall, the findings underscore the significance of dietary lysine levels and amino acid patterns in optimizing broiler performance and carcass characteristics. Based on the previous sections' results, I conducted a comparative analysis. With the gradual increase in lysine levels, the rate of weight gain remained constant, while feed consumption decreased. This phenomenon suggests that the feed conversion ratio responds to higher lysine levels (Baker et al., 2002). Rostagno et al., (2007) reported the need for lysine levels above 0.95% to enhance growth rate and improve feed conversion efficiency. Abdullah et al., (2010) observed a significant improvement in feed conversion ratio with an increase in lysine levels from 0.85% to 0.90% at 25-38 days of age. Yamamoto et al. (2000) suggested that chicks prefer diets with a balanced amino acid profile, indicating that the ideal digestible lysine level in practical diets for broilers can greatly reduce the feed conversion ratio. Feed intake in poultry is influenced by factors such as energy, amino acid balance in the diet, age, environmental temperature, lighting program, physical activities, appearance and taste of feed, and water consumption. Davoodpour et al., (2012) reported that feed intake can be influenced by protein and amino acid content in the diet. Nitrogen deficiency for non-essential amino acid synthesis, unbalanced ratio of essential to non-essential amino acids, deficiency of certain essential amino acids, and differences in the utilization efficiency of synthetic amino acids compared to those present in feed for protein synthesis can affect poultry performance (Panda et al., 2011). The absorption of nutrients is influenced by the biological activity of amino acids as metabolic fuels in the body, which can affect hunger and satiety centers in the hypothalamus and feed intake (Wang et al., 2012). Abdullah et al., (2010) reported that increasing lysine levels in the diet from 1.1% to 2.1% during days 0-14 significantly improved feed intake and weight gain in Ross 308 and Hubbard broilers. Sakomura et al. (2010) reported that increasing lysine levels in broilers are beneficial as they lead to increased growth rate and reduce the days required to reach market weight. Feed intake has a direct relationship with increasing lysine levels (Norouzi et al., 2004). Imbalance in dietary amino acids can reduce feed intake (Bourre et al., 2006). Gradual increase in dietary lysine negatively affects feed intake (Nemati et al., 2008). Using birds of the same age and from multiple strains, Valerio et al., (2003) did not report any effect of lysine levels on feed consumption. Conclusion: These findings indicate that feeding Arian broiler chickens during the starter period with 1.32% digestible lysine and patterns of amino acids cataloged in the Arian strain can improve their growth performance and carcass characteristics.