Effect of Exogenous Phytase on the Phosphorus and Zinc Metabolism of Fattening Bulls

Winter, Laura GND; Meyer, Ulrich GND; Hüther, Liane GND; Lebzien, Peter GND; Dänicke, Sven GND

This study investigated the effects of exogenous phytase, different dietary phosphorus (P) and zinc (Zn) levels on the P- and Zn-metabolism of fattening bulls. 48 German Holstein bulls (average initial live weight 312 ± 49 kg) were used for a feeding trial and allocated to four dietary treatments, P/Zn, P+MIN/Zn, P/Zn+PHY and P/Zn+MIN. All bulls received a diet of 80 % corn silage and 20% concentrate on a dry matter (DM) basis. The corn silage intake was for ad libitum and the concentrate intake restricted. The concentrate of P+MIN/Zn was supplemented with dicalcium phosphate. The concentrate of the P/Zn+PHY group was supplemented with an exogenous phytase (0.1 g/kg DM in the diet, 50 000 FTU/g) and the concentrate of the P/Zn+MIN group was supplemented with Zn. The P- and Zn-concentration in the diet of the P/Zn-, P+MIN/Zn-, P/Zn+PHY- and P/Zn+MIN-groups were 2.41, 2.99, 2.48 and 2.41 g P/kg DM and 33.2, 33.6, 34.0 and 38.8 mg Zn/kg DM, respectively. No differences in P- and Zn-concentration of faeces, liver, testes and performance were observed between the treatments. In the Os metacarpale, P- and phytase supplementation resulted in a slightly higher P-concentration, while the Zn addition led to the lowest value (P=0.062). Overall, it becomes clear that the microbial phytase of the rumen is sufficient enough to make the indigestible phytate-P and the hardly digestible Zn digestible for ruminants. The supplemented dietary phytase has no influence on the bioavailability of the mineral P and the trace element Zn.

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Winter, Laura / Meyer, Ulrich / Hüther, Liane / et al: Effect of Exogenous Phytase on the Phosphorus and Zinc Metabolism of Fattening Bulls. 2013.

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