Chitosan, a derivative from chitin presented in the exoskeleton of crustaceans, has antimicrobial properties that influence nutrient utilization in ruminants. This study aimed to compare the effects of monensin (MON) and virgniamycin (VIR) with chitosan (CHI) on nutrient digestibility of Holstein steers. Eight Holstein steers (7 ± 1.5 mo age and 159 ± 6 kg BW, at the start of experiment) were enrolled in a replicated 4 × 4 Latin square experiment with 25-d periods, in which 14 d were allowed to treatment adaptation, 6 d of sampling, and 5 d of wash out. Steers were allocated in individual pens and randomly assigned to treatments (mixed into the concentrate): control; MON at 30 mg/kg diet DM (Rumensin, Elanco, Eli Lilly and Company, Indianapolis, IN); VIR at 30 mg/kg diet DM (Vmax, Phibro Animal Health, Teaneck, NJ); or CHI at 2 g/kg diet DM (Polymar Ind, Ceará, Brazil). Diet was formulated according to NRC (2001) targeting a BW gain of 700 g/d. Diet consisted of 60% of grass hay and was fed as TMR twice daily. Amounts of feed offered and orts were weighed daily to restrict refusals between 5 and 10% of feed intake. Orts samples were analyzed for DM, CP and NDF by methods of wet chemistry. Total feces collection was performed over 72 h during d 15,16 and 17 of each period and 10% aliquots were analyzed for nutrients as described earlier. Data were analyzed by PROC MIXED of SAS and differences among treatments were described through orthogonal contrasts: C1) control vs. MON+VIR+CHI, C2) control vs. CHI, and C3) MON+VIR vs. CHI. Feed additives decreased CP intake and digestibility of steers (Table 1). CHI exhibited higher CP intake, DM relative intake, and CP digestibility in comparison with MON and VIR. Chitosan promote increase of CP intake and digestibility of Holstein steers. Table 1.

Item	Diet				SEM	P-value
	CON	MON	VIRG	CHI		C1	C2	C3
Intake (kg/d)
DM	5.89	4.53	5.63	5.64	0.33	0.050	0.561	0.127
CP	0.713	0.584	0.656	0.674	0.03	0.009	0.232	0.036
NDF	2.36	1.76	2.22	2.26	0.14	0.043	0.595	0.135
Relative intake (%BW)
DM	3.24	2.49	3.05	3.13	0.10	0.082	0.642	0.030
NDF	1.29	0.97	1.21	1.25	0.04	0.098	0.685	0.096
Total apparent digestibility (%)
DM	55.8	53.9	55.2	55.5	0.01	0.545	0.751	0.754
CP	63.3	50.0	56.9	63.6	0.02	0.033	0.933	0.014
NDF	54.2	53.4	52.7	54.2	0.01	0.753	0.985	0.681