Resumen

DRIVER, J.P. et al. Comparison of the thermostability and efficacy of a solid-substrate culture and a liquid culture phytase in broiler chickens. S. Afr. j. anim. sci. [online]. 2004, vol.34, n.4, pp.249-256. ISSN 2221-4062.

A 14-day battery trial using 336 four-day old male broilers was undertaken to compare the thermostability and efficacy of phytase produced in solid-substrate culture, a Solid Substrate Enzyme Product (SSEP), with phytase produced in liquid culture, a Liquid Enzyme Product (LEP). Five maize-soyabean meal based diets were formulated; three contained increasing levels of non-phytate phosphorus (nPP) (2.5, 3.0 and 3.5 g nPP/kg) and another two contained 2.5 g nPP/kg with 300 phytase activity (PU)/kg of either SSEP or LEP. Half of each diet was pelleted at 80 °C using a California Pelleting Mill Co. Master Model (30 hp) pelleter and conditioner. Both pelleted and mash diets were passed through a hammer mill before feeding so that a consistent particle density was achieved for all treatments. Chicks fed the diets that were first pelleted had lower weight gain, feed intake, percentage tibia and toe ash accumulation and bone breaking strength values compared to chicks fed the mash diets, although differences were not significant. Only feed efficiency was improved by pelleting the diet first. There was a significant improvement in all parameters, with the exception of feed efficiency, as the level of nPP was increased from 2.5 g/kg to 3.5 g/kg. Either variety of phytase on the unpelleted mash diet did not improve performance significantly over the unsupplemented diets with different nPP levels, although the SSEP did appear to be better than the LEP. When the same diets were pelleted, chicks that received the SSEP did not perform better than those on the 2.5 g/kg diets with no added phytase, while chicks fed the LEP performed similarly to those receiving 3.0 g/kg and 3.5 g nPP/kg. Both phytases improved percentage tibia and toe ash accumulation as well as bone breaking strength over the control (2.5 g nPP/kg) on the unpelleted mash. Pelleting completely destroyed the SSEP while the LEP was still able to show results similar to the 3.5 g nPP/kg. Treatment for tibia ash and the 3.0 g nPP/kg. Treatment for percentage toe ash and bone breaking strength. Although the SSEP was superior to the LEP on the unpelleted mash for all variables, the results of this experiment did not show any significant differences between the two phytase varieties with the exception of feed efficiency. Pelleting at 80 °C appeared to completely destroy the SSEP while a certain degree of enzyme activity was retained after pelleting the LEP.

Palabras clave : Broiler; phytase; non-phytate phosphorus; thermostability.

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