Abstract #M11

# M11
Feeding a low-starch fresh cow diet may increase NDF digestibility.
Caroline E. Knoblock*1, Weina Shi1, Ilkyu Yoon2, Masahito Oba1, 1Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada, 2Diamond V, Cedar Rapids, IA.

The objective of this study was to determine the total-tract nutrient digestibility of Holstein dairy cows (n = 38) supplemented with or without a Saccharomyces cerevisiae fermentation product (SCFP, NutriTek, Diamond V, Cedar Rapids, IA) during the periparturient period. All animals were fed a common basal close-up diet containing 13% starch, and fed high- or low-starch diets (HS vs. LS; 27 and 21%, respectively) immediately after calving. Animals were assigned to 1 of 4 treatments (CON+HS, CON+LS, SCFP+HS, SCFP+LS) in a randomized block design. Apparent total-tract nutrient digestibility was determined at wk 1 and 3 after calving using indigestible neutral detergent fiber (NDF), determined after 288 h in situ digestion, as an internal marker. There was no treatment effect of SCFP supplementation on the total-tract nutrient digestibility. Although dry matter or organic matter digestibility was not affected by dietary starch content, cows fed the LS diets increased NDF digestibility compared with those fed the HS diets on wk 1 (40.7 vs. 35.3%; P = 0.01), and multiparous cows on the LS treatments tended to increase NDF digestibility on wk 3 (40.6 vs. 35.8%; P = 0.08). For wk 1, there were no correlations (P > 0.05) between NDF digestibility and dry matter intake or any rumen fermentation variables measured in the current study, including mean pH, minimum pH, the duration under pH 5.8, and volatile fatty acid profile. However, NDF digestibility for wk 3 was positively correlated with dry matter intake (r = 0.40; P = 0.01) and molar proportion of acetate in rumen fluid (r = 0.49; P = 0.04). Feeding the low starch diets increased total-tract starch digestibility of multiparous cows on wk 1 (98.7 vs. 97.8%; P = 0.01) and wk 3 (98.7 vs. 97.7%; P < 0.01), but decreased starch digestibility of primiparous cows on wk 1 (98.6 vs. 99.1%; P = 0.04) and wk 3 (98.7 vs. 99.3%; P = 0.04). These data suggest that feeding fresh cows a low-starch diet may increase total-tract NDF digestibility, but that its effects on total-tract starch digestibility are not consistent.

Key Words: Saccharomyces cerevisiae fermentation product, NDF digestibility, rumen pH