DEVELOPMENTAL-CHANGES IN GLUCOSE AND BUTYRATE METABOLISM BY ISOLATED SHEEP RUMINAL CELLS

The ontogeny of glucose and butyrate metabolism in developing sheep ruminal epithelium was determined using an isolated ruminal cell system. Ruminal cells were isolated from 21 lambs at seven ages before weaning. Rumen weight increased in proportion to increases in body weight, except between 28 and 42 d, when rumen weight increased threefold, whereas body weight increased only 33%. Glucose oxidation rates [expressed as nmol/(1 x 10(6) ruminal cells.120 min)] by ruminal cells were low at birth (14.2 +/- 5.08), increased sharply by 14 d (71.38 +/- 16.71), and remained elevated until 42 d. Following 42 d, glucose oxidation declined to rates lower than those observed at birth (6.11 +/- 0.83). Butyrate oxidation to CO2 increased from birth (20.03 +/- 3.41) to a peak at 4 d (134.0 +/- 31.71) and decreased throughout the remainder of the preweaning period (56 d; 36.32 +/- 7.48). Butyrate inhibited glucose oxidation by ruminal cells isolated at 14, 28 and 42 d. Similarly, glucose inhibited butyrate oxidation by ruminal cells isolated from 4 d to 28 d following birth. Beta-Hydroxybutyrate production [nmol/(1 x 10(6) ruminal cells.120 min)] from butyrate by ruminal cells was undetectable at birth, but measurable by 4 d (3.28 +/- 2.15). Rates of beta-hydroxybutyrate production remained unchanged through 42 d; however, by 56 d, production had increased 10-fold (36.71 +/- 0.67). The metabolic adaptations of the ruminal epithelium are intimately associated with the physical development of the tissue, and major shifts in the fate of glucose and butyrate carbon occur prior to weaning.