Abstract

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The effect of addition of crude and ammonium sulphate ((NH^SQi) precipitation of P-D-mannanase produced by Penicillium italicum on in vitro dry matter digestibility (IVDMD) and in vitro protein digestibility (IVPD) of rice bran meal intended for animal feed formulation was studied. Firstly, the crude enzyme (non-precipitated), and (NH-1)SO4 precipitated enzyme were incorporated in the series of enzymes activities. Secondly, the effect of p-D-mannanase preparation and incubation time was evaluated on IVDMD and IVPD. Crude enzyme produced in basal medium supplemented with rice bran meal as the carbon source was assayed by dinitrosalicylic acid method and precipitated from culture supernatant with 70% ammonium sulphate concentration. Measurement of IVDMD and IVPD were carried out using pepsin pancreatine assay. Results from statistical analysis showed significant interaction between the kind of enzyme preparations and activities on IVPD and IVDMD. In vitro protein digestibility (IVPD) of rice bran meal prepared with different enzyme preparations increased significantly (P<0.05) with increase in enzyme concentration. In vitro protein digestibility (IVPD) of rice bran meal prepared with ammonium sulphate increased all through the experiments with increase in enzyme concentration (0.1-0.5 mL), while decrease in protein digestibility was observed in rice bran meal prepared with crude mannanase beyond 0.4 mL enzyme supplementation. To study the effect of incubation time on digestibility of rice bran meal, 400 ul and 500 pi were used for crude and ammonium sulphate enzyme preparations respectively. IVPD of any enzyme additions (crude and ammonium sulphate enzyme preparations) at every incubation time was significantly above the non-enzyme treatment. Treatment with crude enzyme at 6 h incubation showed the highest IVPD, while ammonium sulphate precipitated enzyme at 8 h showed the highest IVPD. Incorporation of crude and ammonium sulphate precipitated enzyme improved the percentage IVDMD of rice bran meal all through the fermentation time. Incorporation of p~ D-mannanase might enhance the digestibility of ration containing high mannan, and ezyme precipitation with ammonium sulphate could be applied.

Keywords: Penicillium italicum; in vitro dry matter digestibility; in vitro protein digestibility; rice bran meal; p-D-Mannanase