Seasonal changes of total body water and water intake in Shetland ponies measured by an isotope dilution technique1

Abstract

Water is an essential nutrient necessary to support life, and adequate water supply is crucial for animal survival and productivity. The present study was designed to determine seasonal changes in the water metabolism of horses under outdoor conditions. Total body water (TBW) and total water intake (TWI) of 10 adult Shetland pony mares were estimated at monthly intervals for 14 mo by using the deuterium dilution technique. During the last 4 mo, 5 ponies were fed restrictively to simulate natural feed shortage in winter, and 5 ponies served as controls. The TBW (kg) was closely related to body mass [TBW (kg) = -2.86 + 0.67 × body mass (kg); P < 0.001; n = 105] explaining 86% of the variation. In contrast to TBW (kg), TBW (%) remained relatively stable across all measurements (57.8 to 71.2%). The TWI showed an increase in summer and a decrease in winter [TWI (mL·kg(-1)·d(-1)) = 15.07 + 23.69 × month - 1.45 × month(2) (R(2) = 0.64, P < 0.01)]. However, TWI measured at ambient temperatures (Ta) < 0°C did not follow the same trend as TWI at Ta > 0°C. Therefore, removing TWI values measured at Ta < 0°C from the analysis resulted in high correlations with locomotor activity (r = 0.87), Ta (r = 0.86), and resting heart rate (r = 0.88). The multiple regression among TWI, Ta, and heart rate explained 84% of the variation in TWI [TWI (mL·kg(-1)·d(-1)) = -13.38 + 1.77 × heart rate (beats/min) + 2.11 × Ta (°C); P < 0.001]. Feed restriction had no effect on TWI and TBW. The TBW content was unaffected by season and physical activity. The established regression equation for TBW and body mass can be used to predict TBW from body mass in ponies under field conditions. The comparison of TWI 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 TWI 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.

Impact of season, age and gender on some clinical, haematological and serum parameters in Shetland ponies in east province, Saudi Arabia

“…Our results showed that all mean physiological parameters (heart rate, respiratory rate, pulse and rectal temperature) were tendentially increased in summer in comparison to winter season ( Table 1 ). The results of increased heart rate in summer in the present study is in agreement with Brinkmann et al [17] , [18] , although the differences between summer and winter heart rate values were less obvious in our study than that reported by Brinkmann et al (Mean heart rate: summer (58/beats/m), winter (35 beats/m)) [19] . In agreement with Scheibe et al [20] , increased heart rate in summer may indicate the adaptation ability of Shetland pony to hot temperatures [20] for body temperature regulation.…”

Seasonal fluctuations in body weight during growth of Thoroughbred racehorses during their athletic career

“…The range in average monthly temperature over the year at both training centres was about 23 °C, with the highest temperatures in August and the lowest in January. The horses were stabled at the ambient temperature, so the high temperatures in summer may have increased their metabolic rate and the low temperatures in winter may have reduced it, which would be consistent with the results of previous studies [ 8 , 29 , 30 ]. Although a long photoperiod induces a higher metabolic rate than a shorter photoperiod in rats and cats [ 9 , 31 ], there are no published studies, to our knowledge, on the direct relationship between photoperiod and energy expenditure by horses.…”

Nutrition of Broodmares

“…Observed intakes range from 5.1 L/100kg BW 29 to 6.9 L/100kg BW 30 in pregnant mares and from 11.9 L/100kg BW to 13.9 L/100kg BW in lactating mares 1 and are influenced by several factors, including DMI and environmental temperature. Availability of water is especially important for horses consuming dried preserved forage, such as during cold seasons and when stalled 31,32 . Water restriction during pregnancy results in decreased feed intake and loss of BW 30 .…”