Plasma antidiuretic hormone (ADH) concentrations in cattle, during various water and feed regimes.

Twelve steers of three different breeds were exposed to five feed and water regimes in order to characterize changes in plasma antidiuretic hormone (ADH) concentrations. No breed differences were found in plasma ADH concentration. Plasma ADH concentration rose (4.2 to 22.0 pg/ml) during dehydration. By 3 hr hydration, plasma ADH concentrations dropped dramatically (over 50%) to 9.2 pg/ml. No changes in plasma ADH concentrations occurred during feed restriction and refeeding. Hematocrit percentages were also determined and differences are hypothesized to relate to probable differences in environmental adaptability and genetic selection for meat or milk production among the three breeds.