Argüelles Ramos, Mireille

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    Efecto de la suplementación de fitasa a dietas con niveles reducidos de fósforo disponible sobre el desempeño productivo, contenido fecal de minerales y contenido de ceniza del hueso de pollos para engorda
    (2005) Argüelles Ramos, Mireille; Santiago Anadón, Héctor L.; College of Agricultural Sciences; Rodríguez Carías, Abner A.; Pagán Morales, Melvin; Department of Animal Science; Domenech, Camilo Almeyda
    Phosphorus (P) is an essential mineral for growth and development of broiler chickens. The availability of P and other essential minerals in broiler diets is limited by phytic acid, resulting in an excess of mineral excretion. The addition of phytase enzyme increases the availability of P and other minerals in corn-soybean meal based diets. An experiment was conducted to determine the effects of graded levels of phytase supplementation to diets with decreased available phosphorus (AP) contents relative to NRC requirements, on performance, carcass traits, tibia ash, and mineral fecal content of broilers. Six hundred chicks were fed with one of ten dietary treatments that consisted of: a control (NRC AP), and 9 diets with a 3 x 3 factorial arrangement combining 300, 600, and 900 units of phytase per kilogram of feed (FTU/kg) and AP reductions of 0.05, 0.10, and 0.15% from NRC requirements in each of the starter (1-21 d), grower (22-35 d), and finisher (36-49 d) diets. At 21, 28, 35, 42, and 49 d of age, two birds per replicate were wing banded, placed in metabolic cages, and used for determination of mineral fecal content of P, Ca, Mg, and Zn. Feed intake (FI), bodyweight (BW), BW gain (BWG), and feed conversion (FC) were determined. At 49 d, a total of 200 birds (20 per treatment) were processed and carcass traits recorded. The right tibia of each carcass was excised and used for bone ash determination. No significant differences were observed among treatments in FI, nor in BWG up to 35 d. During the finisher phase, control birds had BWG similar to that of birds supplemented with phytase. However, birds fed diets containing 300 and 900 FTU/kg had higher BWG than those fed 600 FTU/kg. All treatments resulted in similar BW in the starter and finisher phases. However, in the growing period birds fed diets containing a 0.05% AP reduction and 300 FTU/kg were significantly heavier than those fed diets with 300 or 600 FTU/kg and a 0.15 and 0.10% AP reduction, respectively. From 22 to 35 d, broilers fed diets with reductions of 0.05 and 0.10% AP and 600 FTU/kg had significantly better FC than controls. Whereas from 36 to 49 d, birds receiving diets with a 0.10% AP reduction and 900 FTU/kg had better FC than controls. No differences among treatments were observed in the weight and percentage yield of major cuts and excised muscles. Carcass yield was significantly higher in birds fed diets with a 0.10% AP reduction and 600 FTU/kg than in those under the 0.15% AP reduction and 300 FTU/kg treatment. Tibia ash content was similar for all treatments imposed, averaging 36.2%. Fecal P concentration was significantly greater in birds fed control diets than in those fed diets with reduced AP and supplemented with phytase. However, the fecal P concentration was observed to decrease significantly in a linear fashion as dietary AP decreased regardless of phytase level. No differences in fecal content of Mg and Zn were observed among treatments. There was a significant and concomitant increase in fecal Ca concentration as the dietary AP decreased, which can be attributed to increases in the Ca:P ratio resulting from the reduction in dietary AP. There was a significant quartic response in fecal concentration of all minerals with age. The results suggest that diets formulated to contain 0.15% AP less than NRC recommendations and with addition of 300 FTU/kg significantly reduce mineral excretion without compromising bone integrity.