In vitro ouabain-sensitive respiration and protein synthesis in rumen epithelial papillae of Hereford steers fed either timothy hay or timothy hay supplemented with cracked corn once daily
1995
Kelly, J.M. | Vaage, A.S. | Milligan, L.P. | McBride, B.W.T.
Rumen epithelial papillae samples, acquired from the ventral sac of six adult Hereford steers (585 +/- 17 kg) fed either timothy hay plus soybean meal (T) or timothy hay plus cracked corn and soybean meal (TC) once daily (0900), were used in a crossover design to study the daily pattern of O2 consumption and protein synthesis. Tissue samples were acquired at 0900, 1200, 1800, and 2400 over a 10-d sampling period. Additionally, ruminal fermentation characteristics (pH, ammonia, VFA, and osmolality) were measured at 0430, 0900, 1030, 1200, 1500, 1800, 2100, and 2400. Total, ouabain-insensitive (OIO2), and cycloheximide-insensitive (CIO2) O2 consumption were greatest at 2400 (P <.01, P < .06, and P < .02, respectively). Additionally, steers fed TC had a greater CIO2 at 2400. In conjunction with a temporal effect on ruminal fermentation patterns, after an initial decline, there was an increase (P < .05) in total O2, ouabain-sensitive (OSO2), OIO2, and CIO2 consumption throughout the day. Fractional rates of protein synthesis were not different at any time point between diets. Rumen epithelial metabolism exhibits a temporal pattern in cattle fed once daily.
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