Movement of nutrient and non-nutrient elements in the liquid phase in sheep rumen.

Changes in the concentrations of B, Ca, Fe, K, Mg, Mn, Na, P, S, Sr and Zn in the liquid phase in sheep rumen were determined to obtain information on their rate of disappearance from the soluble pool after feeding. Sheep were fed alfalfa (Medicago sativa) hay hourly. The concentration of infused Cr(III)-EDTA into the rumen (over a period of 4 d) was used to establish steady-state conditions, after which feeding was stopped and the rapidly changing elemental concentrations in 30,000 x g ruminal supernatant fluid were determined by plasma emission spectrometry. The concentrations of all elements, apart from Fe, Na and P, decreased in a first-order manner over 5 h after feeding. For one sheep, these concentrations (microM) were: B, 199 to 126; Cr, 184 to 111; Ca, 4,150 to 1,130; K, 51,000 to 28,800; Mn, 11 to 4.2; Mg, 4,190 to 1,810 and Zn, 14 to 7.8. For S, first-order decay was observed over only the 0- to 2-h period (2230 microM to 865 microM). Phosphorus increased from 10.4 to 13.1 mM over the 5-h period, whereas Na remained constant (85 mM); this was attributed to saliva input. Mean half-lives for B (8.8 h), K (7.5 h) and Zn (5.3 h) were similar to those of Cr (6.3 +/- .3 h), the water flow marker. Mean half-lives of Ca (2.6 h), Mg (4.0 h), Mn (3.3 h), Sr (3.3 h) and S (1.8 h) were shorter (P less than .01) than that of the Cr marker.(ABSTRACT TRUNCATED AT 250 WORDS)