Reduction of the protein and phosphorus levels in diets with phytase for broilers: performance, digestibility and excretion of nutrients / ReduÃÃo dos nÃveis de proteÃna e fÃsforo em raÃÃes com fitase para frangos de corte: Desempenho,digestibilidade e excreÃÃo de nutrientes

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Experiments were conducted in the Poultry Farming Sector at the Animal Science Department of the Federal University of Lavras, to evaluate the effect of the reduction of the levels of crude protein (CP) and available phosphorus(AP) in broilers diets with phytase on the performance, carcass traits, pollutant excretion, nutrient digestibility and energetic values of the diets. The experimental design of the performance trials was in randomized blocks in 3 x 3 + 1 factorial scheme, they being three levels of CP (15%, 17% and 19%) and three levels of AP (0.25%; 0.34% and 0.45%) over the period of 1 to 21 days (phase 1) and levels of 14%, 16% and 18% of CP and of 0.20%; 0.30% and 0.40% of AP of 22 to 42 days old (phase 2) and control diet with nutritional levels recommended by Brazilian researchers. In the diets with reduced levels of AP were added 500 FTU of phytase and Ca content was reduced by 17% for phase 1 and 20% for phase 2. In the growth trials, performance and the contents of nitrogen (N), calcium (Ca), phosphorus (P), potassium (K), copper (Cu), zinc (Zn) in the litter and carcass traits were evaluated In the metabolism trials, the values of apparent metabolizable energy corrected by nitrogen balance (EMAn) and the digestibility coefficients of dry matter (CDMS), feed intake, excretion and retention coefficient of N, P, Ca, K, Cu and Zn of the diets. For the initial phase, the worst performance results were obtained by the birds fed the diets, containing 15% of CP and 0.25% of AP. The levels of CP and AP of the diet influenced significantly (P<0.05) the contents of P, Ca, Zn, Cu and K in the litter, but they had no significant effect upon nitrogen contents. The diets with contents of CP of 155 and 17%, supplemented with synthetic amino acids, presented EMAn values superior to that of the control diet. It was found that reduced CP contents improved the DC of DM. Concerning intake, excretion and retention coefficient of P, N and Ca, it was observed that there were significant differences (P<0.05) among the diets with reduced levels of CP and AP and control diet. K intake of the broilers fed the control diet was superior to that of the diets with CP contents of 15 and 17% at the different levels of AP and diet with 19% of CP and 0.45% of AP without phytase. There was no significant difference for K retention coefficient among the diets. Less Cu intake was verified for the broilers fed diets with reduced CP and AP. Reduction in the contents of CP and supplementation of diets with phytase reduced excretion and improved Cu retention. There was a reduction in intake and excretion of Zn for the broilers fed diets with reduced CP and AP, regardless of the phytase supplementation. The retention coefficients of the diets with 0.45% of aP without phytase , in all the levels of CP, were similar (P>0.05) to the control diet, which was superior to those of the other diets. For the 22- 42 day old phase, the lower performance results were obtained by the broilers fed diet containing 14% of CP and 0.20% of AP, supplemented with synthetic aminoacids and phytase. P contents in the bedding were smaller for the birds which consumed the diets with reduced CP and AP. Ca content in the litter was smaller for the birds consuming the diets with 16% of CP in the different levels of AP than for those fed the control diet. No significant differences were found among the diets for the contents of N, Zn and Cu in the litter. There was no effect of the levels of CP and aP of the diet on carcass and cutting yield, but there was a effect of the level of CP of the diet on abdominal fat percentage. The diets with reduced levels of CP shown higher values of EMAn. Improvement in CDMS was observed for the diet with 14% of CP. The intake and excretion of P, Ca and N of the diets with reduced contents of CP supplemented or not with phytase, were smaller than those fed the control diet. The retention coefficient of P and Ca of the diet with 14% of CP and 0.20% of AP + phytase was superior to that of the control diet. N retention by the broilers fed diet with 14% of CP in all the levels of AP was higher than the retention of the control diet. There was reduction in intake and excretion of K (P<0.05) by the broilers fed diets with reduced CP and AP. The broilers fed diets with 14% of CP at the different levels of AP and the diets with 18% of CP at the levels of AP 0.30% + phytase and 0.40% without phytase shown less intake of Cu than those fed the control diet. No significant differences were observed (P>0.05) in the excretion of the control diets with reduced CP and AP and those consuming the control diet. Cu retention coefficient of the diets with 14% of CP at the three levels of AP was inferior to that of the control diet. Zn intake of the broilers fed diets with 18% of CP and 0.20% of AP + phytase and diet with 16% of CP + 0.40% of AP without phytase was equal to that of the control diet. The excretion of Zn of the broilers fed diets with 14% of CP, independent of phytase and diets with 0.30% of AP and different levels of CP, was smaller than those fed control diet. No significant difference (P<0.05) was found for zinc retention coefficient among the diets with reduced CP and AP, supplemented with aminoacids and phytase and the control diet. For the initial phase ( 1 to 21 days old ) , it was conclude that the contents of crude protein of broiler diets should be reduced to 17% and 19% and the content of available phosphorus to 0.34%, since that diets be supplemented with aminoacids and phytase. At those levels of crude protein and available phosphorus shown reduction in the environmental impact due to the reduction in the contents of P, Ca, Cu and Zn in the litter. Reduction in the levels of CP and AP to 17% and 0.34%, respectively, in diets with phytase for broilers at the initial phase (1 to 21 days old) , also improved the EMAn values and dry matter digestibility. Thus, it is possible to reduce the excretion of nitrogen, phosphorus, copper and zinc. Use of synthetic aminoacids and phytase in the diet for 22 to 42 days old broilers, enabled to reduce the levels of crude protein, available phosphorus and calcium to 14.0%; 0.30% and 0.70%, without affecting the broilers performance. Use of those levels in the diets, supplemented with synthetic aminoacids and phytase, reduced the phosphorus contents in the litter, on average, 33.92% and zinc by 14.81%. Reduction in the contents of crude protein and available phosphorus improved the values of apparent metabolizable energy, dry matter digestibility and reduced the excretion of nitrogen, phosphorus and zinc, when associated with phytase supplementation.

ASSUNTO(S)

frango de corte nutriÃÃo de monogÃstrico monogastric nutrition phytase broilers fitase zootecnia

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