Volume 16, Issue 4 (12-2025)
Res Anim Prod 2025, 16(4): 104-121 |
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Shahsavani F, Hosseini-Vashan S J, Farhangfar S H, Ghiasi S E. (2025). Determination of Optimal Crude Protein and Amino Acid Levels and their Effects on Growth Characteristics, Blood Biochemical Indices, Immune Response, and Intestinal Morphology of Arian Broiler Chickens. Res Anim Prod. 16(4), 104-121. doi:10.61882/rap.2025.1492
URL: http://rap.sanru.ac.ir/article-1-1492-en.html
URL: http://rap.sanru.ac.ir/article-1-1492-en.html
Forough Shahsavani1, Seyyed Javad Hosseini-Vashan *1 
, Seyyed Homayoun Farhangfar1, Seyyed Ehsan Ghiasi1
, Seyyed Homayoun Farhangfar1, Seyyed Ehsan Ghiasi1
1- Department of Animal Science, University of Birjand, Birjand, Iran
Abstract: (1268 Views)
Extended Abstract
Background: One of the major issues in the poultry industry is the continuous increase in the production of animal protein. In recent decades, the challenge of increasing the growth rate and body weight of birds at an early age has been a focus for poultry husbandry. On the other hand, the rising costs of poultry feed in recent years, especially the high price of soybean meal, the most accessible and common protein source in poultry feed, have made this challenge even more difficult. Advances in poultry diet formulation and the inefficiency of using crude protein to balance broiler diets have led to the use of more precise criteria, such as ideal amino acids or digestible amino acids in diet formulation, reducing feed costs and ensuring the necessary nutrients for poultry. Providing essential amino acids, particularly limiting amino acids, along with sufficient levels of crude protein, can enhance production efficiency and reduce environmental risks from excess nitrogen excretion. This study aimed to determine the optimal level of crude protein and the effects of various levels of amino acids (methionine, lysine, valine, and arginine) on growth characteristics, blood biochemical indices, immune response, and intestinal morphology in Arian broiler chickens.
Methods: This experiment was conducted using 540 one-day-old Arian broiler chickens in a completely randomized design with a 3×3 factorial arrangement, comprising nine treatments, five replicates, and 12 chicks per replicate. Digestible amino acid coefficients of feed ingredients were evaluated based on theNRC tables. The experimental birds were fed diets with the same metabolizable energy, three levels of crude protein (CP) (90, 95, and 100 percent), and three levels of total amino acids (TAA) (90, 95, and 110 percent), based on the recommendations of the Arian breeding guide, over 4 periods: starter (1-14 days), grower (15-24 days), finisher 1 (25-35 days), and finisher 2 (36-42 days). On day 42, two chicks were randomly selected from each replicate to collect blood samples from each, and then they were slaughtered for carcass trait measurements. Serum and plasma samples were centrifuged, transferred to sterile microtubes, stored at -20 °C, and sent to the laboratory for measuring immune response and blood biochemical indices. The concentrations of cholesterol, triglycerides, LDL, HDL, total protein, albumin, creatinine, uric acid, and activities of alanine aminotransferase and aspartate aminotransferase were determined using biochemical kits and an automatic spectrophotometer (Jason Chem 200). To examine intestinal morphology, a 1-cm section of the jejunum was cut, washed with saline, and stored in 10 percent formalin for 24 h. The formalin solution was then replaced, and the samples were sent to the laboratory for slide preparation. Statistical analysis of the data was performed using SAS software, a general linear model, and a 3*3 factorial design in a completely randomized design, with mean comparisons based on Tukey's multiple range test at a significance level of 0.05.
Results: In all four rearing periods, the interaction of recommended protein levels (100 percent) with AA levels, particularly at 100 percent amino acids, resulted in the highest body weight (P < 0.05). In the starter, finisher 1, and overall periods (0-42 days), daily body weight gain and feed intake were affected by the experimental treatments (P < 0.05). The treatment containing 100 percent CP and 110 percent AA resulted in the highest body weight gain and feed intake during the entire rearing period (0-42 days; P < 0.05). The 100 percent CP and 110 percent AA treatment led to a reduction in the feed conversion ratio in the starter period (P < 0.05). The interactions of CP and amino acids significantly affected breast, thigh, and proventriculus relative weights (P < 0.05). The experimental treatments significantly influenced albumin, total protein, and triglyceride concentrations as compared to the control (P < 0.05). Reducing CP levels and increasing amino acid levels led to an increase in the lengths of the duodenum, jejunum, ileum, and cecum (P < 0.05). The interaction of protein and amino acid levels significantly affected villus height, villus width, crypt depth, and the villus cross-sectional area (P < 0.05). The treatment containing 100 percent protein and 110 percent amino acids presented the highest European Production Efficiency Factor (EPEF) throughout the rearing period (P < 0.05).
Conclusion: Based on the experimental results, the optimal protein level for Arian broiler chickens is the recommended level (100 percent). However, reducing protein levels and increasing amino acid levels improved some growth characteristics, blood biochemical indices, and intestinal morphology. On the other hand, different protein and amino acid levels did not affect the immune response.
Background: One of the major issues in the poultry industry is the continuous increase in the production of animal protein. In recent decades, the challenge of increasing the growth rate and body weight of birds at an early age has been a focus for poultry husbandry. On the other hand, the rising costs of poultry feed in recent years, especially the high price of soybean meal, the most accessible and common protein source in poultry feed, have made this challenge even more difficult. Advances in poultry diet formulation and the inefficiency of using crude protein to balance broiler diets have led to the use of more precise criteria, such as ideal amino acids or digestible amino acids in diet formulation, reducing feed costs and ensuring the necessary nutrients for poultry. Providing essential amino acids, particularly limiting amino acids, along with sufficient levels of crude protein, can enhance production efficiency and reduce environmental risks from excess nitrogen excretion. This study aimed to determine the optimal level of crude protein and the effects of various levels of amino acids (methionine, lysine, valine, and arginine) on growth characteristics, blood biochemical indices, immune response, and intestinal morphology in Arian broiler chickens.
Methods: This experiment was conducted using 540 one-day-old Arian broiler chickens in a completely randomized design with a 3×3 factorial arrangement, comprising nine treatments, five replicates, and 12 chicks per replicate. Digestible amino acid coefficients of feed ingredients were evaluated based on theNRC tables. The experimental birds were fed diets with the same metabolizable energy, three levels of crude protein (CP) (90, 95, and 100 percent), and three levels of total amino acids (TAA) (90, 95, and 110 percent), based on the recommendations of the Arian breeding guide, over 4 periods: starter (1-14 days), grower (15-24 days), finisher 1 (25-35 days), and finisher 2 (36-42 days). On day 42, two chicks were randomly selected from each replicate to collect blood samples from each, and then they were slaughtered for carcass trait measurements. Serum and plasma samples were centrifuged, transferred to sterile microtubes, stored at -20 °C, and sent to the laboratory for measuring immune response and blood biochemical indices. The concentrations of cholesterol, triglycerides, LDL, HDL, total protein, albumin, creatinine, uric acid, and activities of alanine aminotransferase and aspartate aminotransferase were determined using biochemical kits and an automatic spectrophotometer (Jason Chem 200). To examine intestinal morphology, a 1-cm section of the jejunum was cut, washed with saline, and stored in 10 percent formalin for 24 h. The formalin solution was then replaced, and the samples were sent to the laboratory for slide preparation. Statistical analysis of the data was performed using SAS software, a general linear model, and a 3*3 factorial design in a completely randomized design, with mean comparisons based on Tukey's multiple range test at a significance level of 0.05.
Results: In all four rearing periods, the interaction of recommended protein levels (100 percent) with AA levels, particularly at 100 percent amino acids, resulted in the highest body weight (P < 0.05). In the starter, finisher 1, and overall periods (0-42 days), daily body weight gain and feed intake were affected by the experimental treatments (P < 0.05). The treatment containing 100 percent CP and 110 percent AA resulted in the highest body weight gain and feed intake during the entire rearing period (0-42 days; P < 0.05). The 100 percent CP and 110 percent AA treatment led to a reduction in the feed conversion ratio in the starter period (P < 0.05). The interactions of CP and amino acids significantly affected breast, thigh, and proventriculus relative weights (P < 0.05). The experimental treatments significantly influenced albumin, total protein, and triglyceride concentrations as compared to the control (P < 0.05). Reducing CP levels and increasing amino acid levels led to an increase in the lengths of the duodenum, jejunum, ileum, and cecum (P < 0.05). The interaction of protein and amino acid levels significantly affected villus height, villus width, crypt depth, and the villus cross-sectional area (P < 0.05). The treatment containing 100 percent protein and 110 percent amino acids presented the highest European Production Efficiency Factor (EPEF) throughout the rearing period (P < 0.05).
Conclusion: Based on the experimental results, the optimal protein level for Arian broiler chickens is the recommended level (100 percent). However, reducing protein levels and increasing amino acid levels improved some growth characteristics, blood biochemical indices, and intestinal morphology. On the other hand, different protein and amino acid levels did not affect the immune response.
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