Evaluation of Coated Urea Products as Supplemental Nitrogen Alternatives to Soybean Meal in Dairy Cow Diets

Coated slow-release urea (SRU) may provide an alternative source of supplemental nitrogen in dairy cattle diets, but its ruminal release behavior can vary among formulations. This study compared three palm-oil-coated SRU products with different nominal release specifications using nonlactating, nonpregnant, rumen-cannulated Chinese Holstein cows. Three cows were used in an in situ experiment to characterize dry matter (DM) and urea disappearance from 0.5 to 12 h, and four cows were assigned to a 4 × 4 Latin square feeding trial. The control treatment consisted of a basal diet plus 500 g/d supplemental soybean meal (SBM), whereas the SRU treatments received the same basal diet plus 100 g/d SRU I, SRU II, or SRU III as approximately isonitrogenous supplemental nitrogen alternatives. SRU I consistently showed slower early DM and urea disappearance than SRU II and SRU III, whereas differences between SRU II and SRU III were less consistent across incubation times. Dietary treatment did not significantly affect DM, crude protein, or neutral detergent fiber intake, apparent total-tract digestibility, ruminal pH, total or individual volatile fatty acid concentrations, or hematological variables. Ruminal ammonia nitrogen differed among treatments (p = 0.04), with SRU III having a higher concentration than the control and SRU I and SRU II showing intermediate values. These results demonstrate formulation-dependent in situ disappearance patterns among coated SRU products and suggest that they can serve as alternative supplemental nitrogen sources under the conditions tested.