EXPERIMENTAL-ANALYSIS OF THE SEEKING BEHAVIOR OBSERVED IN RUMINANTS WHEN THEY ARE SODIUM DEFICIENT

Sodium deficiency in calves was produced by unilateral exteriorization of the parotid duct and the resultant changes in salivary Na+/K+ used to monitor sodium status. Sodium depleted calves increased their preferential intake of 0.12 M NaHCO3 but when the concentration was increased (0.24 M-0.48 M), the volume consumed was reduced. In a T-maze, normal calves were indifferent to sodium reinforcement whereas Na+ deficient calves, because of increased activity, readily obtained the reward. The development of motivation was related to rapid learning of the position of the sodium salt. Sodium depletion was also associated with excessive licking behaviour. In an operant experiment, using a variable interval or fixed ratio schedule, depleted calves rapidly learnt to push a panel for 0.48 M NaHCO3 and 0.51 M NaCl rewards. The level of operant behaviour was significantly correlated to the Na+/K+ salivary levels, blood pH and plasma Na+ concentration. These results may reflect the avidity for sodium salts shown by ruminants under natural conditions. © 1979.