339 - Effects of a Blend of Mannan and Glucan on Growth Performance and Immunocompetence of Newly Weaned Beef Steers

We examined the effects of dietary supplementation of a blend of mannan and glucan on the growth performance, diet digestibility, and whole-blood immune gene expression of newly weaned beef steers during a 42-d receiving period. Forty-eight newly weaned Angus crossbred steers (2 d post-weaning; 199 ± 13 kg of initial BW) were randomly assigned to 1 of 2 treatments: basal diet with no additive (CON; n = 24) or a basal diet top-dressed with 5 g of a blend of mannan and glucan (MANGLU; n = 24). Average daily gain (ADG) was calculated from weekly BW. Blood samples were collected on days 0, 14, and 42 for measurement of plasma glucose and NEFA. Expression of 84 immune-related genes was analyzed on blood samples collected on day 42. Beginning on days 37 to 42, total mixed ration, refusals, and fecal samples were collected once daily to determine apparent total tract digestibility of DM, CP, NDF, and ADF using indigestible NDF as an internal marker. Immune gene expression data was analyzed using a GeneGlobe Data Analysis Center. All other data were analyzed as a randomized complete block design using the GLIMMIX procedure of SAS. Over the 42-d feeding trial, MANGLU tended to increase final BW (P = 0.07) and ADG (P = 0.06). Compared to CON, beef steers fed supplemental MANGLU had greater DM digestibility (P = 0.03) and tended to have greater NDF digestibility (P = 0.09). No treatment effects (P > 0.10) on plasma glucose and NEFA on d 14 and 42 were detected. Compared with CON, MANGLU increased (P ≤ 0.05) the expression of five immune-related genes involved in recognition of and mounting immune defense against microbial pathogens. In conclusion, this study demonstrated that supplemental MANGLU enhances beef cattle immunocompetence and productivity during feedlot receiving period.