Abstract

The experiment was carried out to determine macromineral disappearance of tropical grass in West Sumatra during rainy and dry seasons. The forages evaluated consisted of three species of grass (Axonopus compressus, Pennisetum purpureum and Brachiaria decumbens) collected at native pasture. The mineral solubility was determined by in situ nylon bag technique through incubating the forages samples in the rumen at 0, 24 and 72 h. Results of the experiment showed that, disappearance of dry matter (DM) and minerals (solubility) significantly (p<0.05) affected by species and seasons. At 0 h incubation, the DM disappearance was approximately 16 and 25%. The highest DM disappearance was found in P. purpureum (approximately 20%) for grass. Data on macromineral showed that, P was the most soluble mineral in water followed by S, Mg and Ca, respectively in grass. Among species of grass, the highest water solubility of Ca was found in B. decumbens, P in P. purpureum, Mg in B. decumbens and S was found in B. decumbens. At 24 h incubation period, the disappearance of DM and macromineral of forages was higher than at 0 h incubation. The average increase was approximately 7.5% units for grass. The disappearance value at 72 h incubation, represents the actual solubility of minerals when forages are given to ruminants. The average DM disappearance of grass was approximately 60%, the highest value occurred in P. purpureum. Data on mineral solubility showed the average Ca disappearance of grass, 71.3%, the highest value, w, occurred in B. decumbens in West Sumatra. The average disappearance of P and Mg in grass with the highest values, were observed in P. purpureum and B. decumbens, respectively. Furthermore, the average S disappearance of grass was approximately 58%, the highest value was found in A. compressus. In general, the trend solubility of macromineral in legumes was: Ca > Mg > S > P. 

Key words: Solubility, grass species, macro minerals.