Water and electrolyte intake and output in conditioned Thoroughbred horses transported by road.

Abstract: The objectives of this trial were to measure the water and electrolyte intake and loss, of horses during road transportation in relatively hot environmental conditions. Six mature, Thoroughbred horses in full training were used in a balanced crossover design. The horses were conditioned on a treadmill for 6 weeks before the start of the trial in order to simulate the type of horse that is transported most often over long distances in South Africa. The horses were assigned randomly to one of 2 treatment groups. On a particular day 3 horses were transported, while the other horses served as controls. One month was allowed before the crossover. Horses in the 'transport group' were transported by tarred road in a circular route over 600 km. This allowed the standardisation of measurements and use of the same instruments in both groups. Data were collected in each treatment group during transportation that lasted for 8 h (transport phase) and for 6 h after travelling (recovery phase). The following data were collected or calculated: Water and electrolyte (sodium, potassium and chloride) intake and output, changes in bodyweight and feed consumption. Although water was always available, the transport group failed to drink during transit. Based on bodyweight, the transported horses were 3% dehydrated at the end of transit. This bodyweight loss was corrected within one hour after their return due to a significantly higher water intake compared to control horses. The feed intake in the transported horses was unaffected during travelling, but was decreased for 6 h following transportation. Urinary water loss was similar in the 2 treatment groups during and following transportation. The faecal water loss decreased in the transported horses and remained lower than the control group for 6 h following transit. Total sodium and chloride intake were unaffected, while the potassium intake was decreased during transportation. Sodium and potassium loss via the faeces and urine during the transport period were similar in the 2 treatment groups, whereas potassium output in the transport group was significantly decreased during the recovery period of the study. It was concluded that transportation by road affected the water and electrolyte balance of conditioned horses for a period up to 6 h after travelling.