Serra et al., 1996. Asian-Aust. J. Anim. Sci., 9 (1): 75-81

DM disappearance and rumen solubility of calcium, phosphorus, magnesium and potassium were studied in 8 Philippine forages: para grass (Brachiaria mutica), Cynodon plectostachyus, napier grass (Pennisetum purpureum), calopo (Calopogonium mucunoides), centrosema (Centrosema pubescens), gliricidia (Gliricidia sepium), leucaena (Leucaena leucocephala) and sesbania (Sesbania grandiflora). Samples were incubated in nylon bags for 0, 3, 6, 12, 24, 48 and 72 h in rumen-cannulated sheep. The 0-h bags were washed with deionized water. For 0-h samples, 20.4, 17.2, 50.7, 52.2 and 80.1% of DM, Ca, P, Mg and K was solubilized, respectively. After 3 h incubation, DM disappearance was 10 percentage units higher than that at 0 h while mineral disappearance increased by 43, 21, 30 and 13% for Ca, P, Mg and K, respectively. After 72 h incubation, greater proportions of DM, Ca, P, Mg and K were solubilized with values of 73.8, 71.5, 85.6, 91.4 and 98.2%, respectively. Average particulate passage rate was 1.9%/h and rates of disappearance of various minerals were: 0.4 to 1.2%/h for Ca, 0.1 to 1.6%/h for P, 0.7 to 2%/h for Mg and 0.1 to 2%/h for K. Effective rumen solubilization (ERS) of macrominerals was calculated with particulate passage rate and disappearance rate of the elements were included in the equation. ERS of Ca, P, Mg and K was 50.0, 72.6, 83.9 and 94.5%, respectively. Species differences (P<0.05) in mineral solubilities were also observed. It was concluded that rumen solubility of macrominerals in selected Philippine forages was K>Mg>P>Ca.