Performance of dairy cattle fed citrus pulp or corn products as sources ofneutral detergent-soluble carbohydrates

The effects of modifying the dietary profile of neutral detergent-soluble c arbohydrates (NDSC) on milk production and rumen fermentation were determin ed. Corn silage and alfalfa hay-based diets were formulated to contain 40% calculated NDSC supplied primarily by dried citrus pulp as a source of neut ral detergent-soluble fiber (NDSF), or corn products as sources of starch. Diets were compared within cow with reversal experiments with two periods. In experiment 1, 11 multiparous Holstein cows including three ruminally can nulated animals were individually fed diets containing 23.6% citrus pulp (d iet CPD) or 25.3% corn hominy (diet HD) on a dry matter basis. In experimen t 2, 184 animals fed as two groups received diets containing 20.5% citrus p ulp (diet CPD) or 19.5% cornmeal (diet CMD). Diets CPD provided more dietar y NDSF and HD and CMD more starch. In experiment 1, cows fed HD had a great er milk protein percentage (+0.12%), and tended to yield more milk protein (0.08 kg/d) than cows fed CPD. Although ruminal H+ concentrations did not d iffer between diets, diet x time postfeeding interactions were significant. Ruminal organic acid concentrations did not differ between diets. In exper iment 2, cows fed CMD yielded more milk (3.9 kg/d), 3.5% fat- and protein-c orrected milk (2.6 kg/d), fat (0.05 kg/d), and protein (0.08 kg/d), whereas cows fed CPD produced greater concentrations of fat (+0.18%), and milk ure a nitrogen (0.76 mg/dl). Modifying the proportions of NDSC in the diet can alter milk production and composition, the pattern of ruminal fermentation, and N utilization in dairy cows.