Quitosana em dietas de novilhos holandeses: consumo, digestibilidade e metabótilos plasmáticos

Abstract

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 chitosan (CHI) with monensin (MON) and virgniamycin (VIR) on nutrient intake and digestibility of Holstein steers. Eight Holstein steers, non-castrated, (7±1.5 months age and 146±78,7 kg BW, at the start of experiment) were enrolled in a replicated 4×4 Latin square experiment with 16-d periods, in which 12 d were allowed to treatment adaptation, 4 d of sampling, and 5 d of wash out. Steers were allocated in individual pens and randomly assigned to treatments (mixed into the concentrate): CO - control; MON - 30 mg/kg diet DM (Rumensin, Elanco, Eli Lilly and Company, Indianapolis, IN); VIR - 30 mg/kg diet DM (Vmax, Phibro Animal Health, Teaneck, NJ); or CHI - 1,77 g/kg diet DM (Polymar Ind, Ceará, Brazil). Diet was formulated according to NRC (2001). The forage: concentrate ratio was 40: 60 which diet consisted of grass hay (Cynodon spp) and concentrate consisted of corn, soybean and minerals. Animals were fed 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 determination of DM, CP and NDF by methods of wet chemistry. Total feces collection was performed over 48 h during the 14° and 15° days of each period and 10% aliquots were analyzed for nutrients as described earlier. Blood sampling were done in the 16o day of each period. Data were analyzed by PROC MIXED of SAS (2009) at 5% significance. Diets with additives promoted lower DM kg/day intake (P<0,05) in constrast to CON, without any additives. Steers fed CHI exhibited higher CP intake, DM relative intake, and CP digestibility (P<0,05) in comparison with MON and VIR. Chitosan promote increase of CP intake and digestibility of Holstein steers (P<0,05). QUI had an effect on plasma metabolites, CHI increased glucose levels (mg / dL), similarly to MON and VIR. The total protein values (mg / dL) were higher (P <0.05) than the MO and VIR. Chitosan decreased total cholesterol (mg / dL) in relation to other treatments (P> 0.05). Additives reduced plasma triglycerides (mg / dL). The treatments had no influence on albumin, urea and blood urea nitrogen. The results were positive regarding the use of chitosan as an organic additive, and some results were similar and even superior to MON and VIR. Based on that, chitosan is a potential substitute to these antimicrobial additives.