Sodium chloride supplements increase the salt appetite and reduce stereotypies in confined cattle

The influence of prior exposure to high salt diets on the salt appetite and the exhibition of stereotyped behaviour patterns was investigated with individually penned calves and tethered dairy cows. In the first experiment one half of a group of 12 calves received concentrates with the sodium content increased from 4 to 9 g/kg by the addition of NaCl up to weaning at 6 weeks, the other half had no supplementary NaCl added to the concentrates. Adding the NaCl increased the food intake of the calves, the time spent ruminating and live weight. Stereotyped behaviour patterns, such as self-grooming, licking the pen or buckets and ear sucking were reduced by adding NaCl. Calves were tested for their salt preference at 6 months of age by adding varying quantities of NaCl to silage. Exposing calves to supplementary NaCl in the concentrate pre-weaning increased the preferred sodium concentration of silage from 3 to 9 g/kg dry matter (DM). In the second experiment 36 tethered dairy cows received either a restricted concentrate and forage diet with a mean dietary sodium concentration of 2 g/kg DM, or the same diet but with the sodium content increased to either 7 or 12 g/kg DM by adding NaCl to the concentrates. There was no effect of NaCl on feeding or ruminating behaviour but the total amount of stereotyped behaviour, including mouthing or rubbing the tethering chain or bars, self-grooming and nosing or pawing the ground, decreased with increasing salt in the diet. It is concluded that increasing the sodium content of the diet of young calves from 4 to 9 g/kg increased their subsequent salt appetite and that increasing the salt content of the diet of calves or cows in restricted housing conditions can reduce the amount of stereotyped oral behaviour.