The release of mineral elements from grass silages incubated in sacco in the rumens of Jersey cattle

The objective of the study was to determine the rate and extent to which calcium (Ca), copper (Cu), magnesium (Mg), potassium (K), phosphorus (P), sodium (Na) and zinc (Zn) were released from polyester bags containing grass silages incubated in the rumens of cattle. The rate of mineral disappearance from the bags was faster than the rate of dry matter disappearance. The disappearance of each mineral element from the bags was characterized by a rapid release of the mineral within 2 h of placing the bags in the rumen followed by a slower release extending up to 48 h of rumen incubation. The extent to which each mineral was rapidly released from the silages differed significantly and the minerals were ranked in the order P < Zn < Ca < Cu < K < Mg < Na. There were no differences between minerals in the rate at which they were released during the slower phase. Combination of these results with different rates of outflow of material from the rumen showed that for each of the minerals examined more than 0.65, on a proportional basis, was released from the silages; for Na the values were greater than 0.90. Indeed, all the residual Na and P remaining in the bags after 48 h rumen incubation could have resulted from bacterial