Effects of feeding chitosan on nutrient digestibility in beef heifers

Abstract Text: The objective of this study was to determine whether adding the biopolymer chitosan, would increase efficiency of beef heifers by improving apparent total tract nutrient digestibility of a low quality diet. Twenty-four crossbred heifers (318 ± 35 kg) were used in a randomized block design replicated in two experimental periods. Heifers were stratified by weight and randomly assigned to 12 pens (2 heifers/pen), and pens were randomly assigned to one of six treatments in a 2×3 factorial arrangement. Factors included diet [a high concentrate (85% concentrate; HC), and a low concentrate (36% concentrate; LC)], and chitosan inclusion level (0.0, 0.5 and 1.0% of dietary DM).  Heifers were housed in the University of Florida-Feed Efficiency Facility in Marianna, FL, where diets were offered ad libitum and individual intake was recorded by a GrowSafe system. Feed and fecal samples were collected for four consecutive days to determine apparent total tract digestibility of DM, OM, CP, NDF, and ADF using indigestible NDF (iNDF) as an internal digestibility marker. Feed samples were collected once a day and fecal samples were collected by rectal grab twice daily (0700 h and 1500 h). Feed and fecal samples were pooled within pen and heifer, respectively. Concentrations of iNDF in feed and feces were determined by in vitro incubations conducted using a 4:1 buffer to ruminal fluid ratio for 288 h. Data were analyzed using MIXED procedure of SAS with heifer as the experimental unit, including the fixed effects of diet and chitosan inclusion level, and the random effect of period. Orthogonal polynomial contrasts were conducted to determine linear and quadratic effects of chitosan inclusion level on nutrient digestibility. There was a diet × chitosan interaction for digestibility of DM (P = 0.05) and OM (P = 0.04). Inclusion of chitosan in LC at up to 1% diet DM linearly increased (P < 0.05) digestibility of DM and OM as compared to control (40.3 vs. 33.2%, and 41.1 vs. 34.5% for DM and OM digestibility, respectively). No differences (P> 0.10) were found for digestibility of CP, NDF, or ADF. In conclusion, adding 1% chitosan to low concentrate diets increased apparent total tract digestibility of DM and OM by 21 and 19%, respectively.

Keywords: Beef, Chitosan, Digestibility