Although Mombasa grass is used for silage production in the tropics, little is known about the changes caused by the addition of fibrolytic enzymes in the ensiled mass. The objective of this study was to determine the effect of cellulase addition on the chemical composition, fiber digestibility, fermentation characteristics and the storage period of P. maximum (cv. Mombasa) silage. The experiment was in a completely randomized, 3 × 3 factorial design with 4 replicates (CELLUCLAST doses: 0, 3, and 6% wt/wt, g cellulase/100g cellulose; fermentation periods - 30, 60 and 120 d). Mombasa grass was cut at an approximate height of 80 cm, at 20 cm from the ground level and ensilaged in 36 PVC mini-silos of 4-L capacity. Fermentation of soluble carbohydrates released by cellulose hydrolysis promoted pH and titratable acidity adequacy, demonstrating that there was a higher VFA production and lactic acid favoring the desirable forage fermentation, reducing the DM loss and improving the nutritive value of the silage. NDF was reduced linearly and TDN increased up to 13.8% (Table 1). Cell wall degradation by cellulase during ensiling decreased NDFD by 10.53%, less than the increase in TDN, indicating that the fibrolytic enzyme addition improved the nutritive value and stability of P. maximum silages. Mass and nutrient losses (13.8% DM, 8.8% CP) observed in the longer period may indicate that the best storage time is up to 60 d. Enzyme addition was efficient to improve the fermentative and bromatological parameters. Table 1. Effect of cellulase adding and fermentation period on P. maximum silage nutritive value

Variable and fermentation period	Cellulase dose (%)1			Effect		SEM
0	3	6	Linear	Quadratic
NDF
30 d	77.3a	72.3a	72.1a	<0.01	0.1	0.80
60 d	77.7a	74.6a	65.3b
120 d	74.1a	68.7b	67.5b
TDN
30 d	52.6a	56.6a	55.7a	<0.01	0.03	0.56
60 d	52.4a	54.5a	60.8a
120 d	54.8a	58.5a	59.3a
DM, % NM	22.8	24.6	24.8	<0.01	<0.01	0.12
ADF, % DM	46.3	42.7	43.0	<0.01	<0.01	0.66
NDFD, %	36.2	32.4	35.2	0.50	0.01	1.01
pH	4.7	3.8	3.6	<0.01	<0.01	0.04
Titratable acidity, °D	5.9	12.4	13.2	<0.01	<0.01	0.28

^a,bMeans followed by the same letter, in a column, do not differ by Tukey test (P < 0.05).