Document Type : Research Paper
Authors
1 Department of Animal Science, Faculty of Agriculture, Urmia University, Urmia, Iran. Email: ma.mirhoseini@urmia.ac.ir
2 Corresponding Author, Department of Animal Science, Faculty of Agriculture, Varamin-Pishva Branch of Islamic Azad University, Varamin, Iran. Email: snmousavi@hotmail.com
3 Evonik Iran Co. Tehran, Iran. Email: ali.afsar@evonik.com
Abstract
Introduction: Guanidinoacetic acid (GAA), a creatine precursor, is synthesized from L-arginine and glycine. The capacity for de novo synthesis may be limiting in high-yielding farm animals, especially in those fed all-vegetable diets. As the precursor to creatine, dietary GAA can also effectively “spare” arginine from being used for GAA synthesis, so that the arginine may be used for muscle accretion and other physiological functions. It has been reported that arginine affects bone development by its involvement in the formation of collagen and connective tissue. It also has been shown that reducing the protein level in broiler diets reduces the concentration of manganese and copper in the tibia. Therefore, low-protein diets probably decrease bone density in broilers. This study was conducted to investigate the effects of GAA supplementation to low protein diets on performance, calcium and phosphorus and the strength of the tibia of broiler chickens.
Material and Methods: The 240 male broilers of Ross 308 strain were assigned to 6 dietary treatments in a 3 × 2 factorial arrangement with 4 replications and 10 birds in each replication. Dietary treatments included diets containing 80, 90 and 100% of the breeder recommended ideal protein each containing 0 and 0.06% of GAA. Feed intake, body weight gain and feed conversion ratio (FCR) were measured for the grower (11-24 days), finisher (25-42 days) and the overall period (11-42 days). On d 42, two birds from each experimental unit were killed, and the ash, calcium and phosphorus content and the strength of the tibia of the chickens were measured.
Results and Discussion: The results showed that by reducing the ideal protein to 80% of the breeder recommendation, body weight gain and feed intake was reduced significantly (P<0.05). Reduction of the dietary CP from 100 to 80%, resulted in inferior FCR during grower period. The inferior performance of broilers fed reduced protein diets is attributed to a limited availability of amino acids (AA). The supplementation of essential AA alone has failed to increase performance in reduced protein diets. The addition of GAA decreased feed intake of treatments (P<0.05) with reduced protein diet (80% of management guide recommendation). Body weight gain and FCR were not affected by dietary GAA supplementation. By reducing dietary protein to 80% of the recommendation, the strength of tibia decreased significantly (P<0.05). A low-protein diet may be associated with a hypocalciuretic effect, increased Ca retention and requirement for available P to avoid Ca:P imbalance, hormonal flux, and bone mobilization. Addition of GAA to the diet did not affect the parameters of bone strength. Tibia ash, Ca and P content were not significantly affected by dietary treatments.
Conclusion: According to the results of this experiment, reducing the dietary ideal protein to 80% of the breeder recommendation, resulted in inferior growth performance and tibia strength of broiler chickens, and dietary addition of GAA did not ameliorate those effects.
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