Effect of urea addition on chemical composition and in vitro dry matter digestibility of Brachiaria humidicola (Rendle) Schweick hay harvest at different cutting ages

Abstract

Research to evaluate urea addition to Brachiaria humidicola hay cut at different ages, on dry matter (MS), nitrogen (N), and ash contents and digestibility in vitro of the dry matter (DIVMS), was carried out under tropical dry forest conditions in the Perija region of Venezuela. The experimental design used was completely randomized with a split plot arrangement and three repetitions. In a 1-ha area, the main plots were located on five strips corresponding to the cutting ages (30, 44, 58, 72, and 86 days), with an effective area of 102 m2 per strip. The chopped hay harvested was placed in plastic bags to which was added 0, 3, and 6% of urea diluted with 40% of water in relation to the dry weight of hay, and then stored for 28 days at ambient temperature. Samples of hay were taken for determination of chemical composition and DIVMS. The results showed an effect of urea addition (P < 0.0001) on all the variables studied, with increases in N content from 1.2 to 2.9% and in DIVMS from 65.1 to 70.8%; while MS and ash contents decreased from 93.8 to 69.6% and 6.2 to 5.7%, respectively. Cutting age also affected (P < 0.005) these variables; with increasing age from 30 to 86 days there were decreases in ash (7.4 to 5.3%), N (2.1 to 1.6%), and DIVMS (71.0 TO 64.8%), respectively. The DIVMS was also affected (P < 0.005) by the interaction cutting age x urea treatment, the highest value being 74.2% at 30 days and 3% urea.