Partial replacement of soybean meal by slow release urea in commercial dairy herds

Abstract

Two experiments evaluated the partial replacement of soybean meal by encapsulated urea (OptigenÒII, Alltech do Brasil, Curitiba, PR, Brasil). From a Control diet, 1kg of soybean meal was replaced by an isonitrogenous mixture containing 160g of OptigenÒII + 2.5kg of corn silage in Exp.1, or 150g of OptigenÒII + 850g of finely ground corn in Exp.2. In Exp.1, 61 Holstein cows were blocked and allocated to a treatment for 21 days, and measures of the same variable at the end of the standardization period were used as covariate. In Exp.2, 97 cows were allocated to a sequence of two treatments for 21 days, in a simple reversal (crossover) design. Response to treatments was evaluated from day 17 to 21. In both experiments, the nutrient composition of the offered diet and orts, orts as a % of the offered, body weight, and body condition score of the animals did not differ across treatments. Daily milk yield was 38.4kg/d for Control and 38.9 for OptigenÒII in Exp.1 (P=0.62), and 27.0kg/d and 27.2 in Exp.2 (P=0.64), respectively. Encapsulated urea decreased milk fat content in Exp.2 (P=0.04). OptigenÒII increased milk urea nitrogen from 16.3 to 17.3mg/dL in Exp.1 (P<0.01) and the ratios of milk produced to feed consumed (P=0.08) and allantoin to creatinine in urine (P=0.03) in Exp.2. Replacing soybean meal with OptigenÒII did not induce lower performance.