Water intake and fluid regulation in the horseNyman, Sara
The aim ofthis thesis was to study factors affecting water intake and fluid regulation in the horse, both at rest and in connection with exercise. Exercising horses sometimes show little inclination to drink despite extensive fluid losses and free access to drinking water. The results from this thesis confirm that a lack of an osmotic thirst stimulus (i.e. increase in plasma sodium concentration) reduces the post-exercise voluntary water intake in the horse. The water supply method had a great influence on the daily water intake. The daily intake was about 40% higher when horses were drinking from buckets than from an automatic water bowl (float valve, 3 L/min). In a two-choice preference test all horses showed a strong preference for buckets compared to an automatic bowl (pressure valve, 8 L/min). Different strategies for voluntary rehydration during endurance exercise were tested in a field trial. It was found that horses offered a saline solution to drink (9g NaCl/L) had the highest fluid intake and regained 84% of their body weight losses (<3h post-exercise) compared to 46% in the horses drinking only water. To give concentrated salt paste (NaCl) did not increase water intake and since there were signs of an altered fluid distribution between body compartments, this strategy cannot be recommended. This thesis shows that it takes several days to fully regain fluid balance after an exercise-induced fluid loss (10-15 kg). When horses were supplemented with 10 L of saline solution, fluid balance was regained already on the exercise day. Plasma aldosterone increased during the recovery phase in all horses with fluid losses above 10 kg which were not supplemented with NaCl in connection with exercise. The exerciseinduced changes in plasma concentrations of atrial natriuretic peptide and argininevasopressin were influenced by hydration status which suggest that both hormones are involved in blood flow control during exercise.
Keywordsaldosterone; arginine-vasopressin; atrial natriuretic peptide; dehydration; electrolytes; exercise; faeces; fluid balance; fluid regulation; horse; hyperhydration; plasma osmolality; plasma sodium; sweat; thirst; urine; water intake,water source
Published inActa Universitatis Agriculturae Sueciae. Veterinaria
2001, number: 98
Publisher: Swedish University of Agricultural Sciences
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