External balance of water and electrolytes in the horse.

The study examined the daily intake and output of water and electrolytes in five healthy Standardbred geldings. In general, the horses consumed approximately 27.6 liters of water daily and eliminated most of it through urine and feces, with urine volumes surpassing fecal output. Sodium, potassium, chloride, calcium, and magnesium eliminated through urine and feces amounted to a significant percentage of their intake; any unaccounted electrolytes were possibly excreted through sweat.

Research Methodology

• The experiment was conducted over a period of 14 days on five healthy Standardbred geldings with an average body weight of 427 kg. Average environmental conditions were also recorded, with temperature values ranging from 16 to 25 degrees Celsius and humidity percentages from 55.4 to 75.5.
• Accompanying the water supply measurements, the research tracked the intake and output of various electrolytes: sodium, potassium, chloride, calcium, and magnesium.

Key Findings

• The mean daily water intake for the group was calculated to be 27.6 liters, which relates to 64.4 ml/kg of a horse’s body weight.
• The mean urine volume was established at 9.9 liters, beyond the mean fecal water output logged at 7.2 liters.
• Notably, the electrolyte balances presented interesting findings. Sodium output through urine and feces, for instance, was 780 mmol or 79% of intake, implying that a significant portion of the consumed sodium was eliminated from the body.
• As for other electrolytes, the output of potassium, chloride, calcium, and magnesium were found to be 3163, 2521, 1824, and 1448 mmol respectively. In terms of percentage, they constituted 95, 84, 74, and 75 per cent of the intake correspondingly.
• The study suggested that the electrolytes not found in urine or feces could have been lost in sweat, though this was not directly confirmed by the research.

Comparative Analysis

• The results of this study are compared with those of a previous external balance study in horses to provide a more comprehensive understanding of the external balance of water and electrolytes in horses.
• Further research may be needed to confirm the sweat hypothesis and to determine if there are any variations based on breed, age, or physical condition of the horse.