Water supply during the cold seasons might be more critical than under summer conditions.
Water is an essential nutrient necessary to support life, and adequate water supply is crucial for animal survival and productivity.
A recent study conducted by scientists in Germany was designed to determine seasonal changes in the water metabolism of horses under outdoor conditions. Total body water and total water intake of 10 adult Shetland pony mares were estimated at monthly intervals for 14 months by using the deuterium dilution technique. During the last 4 months, 5 ponies were fed restrictively to simulate natural feed shortage in winter, and 5 ponies served as controls.
The total body water in kg was closely related to body mass explaining 86% of the variation. In contrast to total body water in kg, total body water (percentage) remained relatively stable across all measurements. The total water intake showed an increase in summer and a decrease in winter. However, total water intake measured at ambient temperatures less than 0°C did not follow the same trend as total water intake at greater than 0°C. Therefore, removing total water intake values measured at ambient temperatures less than 0°C from the analysis resulted in high correlations with locomotor activity, ambient temperature, and resting heart rate.
Feed restriction had no effect on total water intake and total body water. The total body water content was unaffected by season and physical activity. The comparison of total water intake with published data on drinking water intake revealed that ponies had 1.7 to 5.1 times greater total water intakes when other sources of water such as feed and metabolic water were included. The total water intake was highly influenced by environmental conditions and metabolic rate.
Contrary to expectation, water supply during the cold seasons might be more critical than under summer conditions when water content of grass is high to allow for the compensation of limited availability of drinking water.