Deuterium oxide dilution accurately predicts water intake in sheep and goats

Abstract

The aim of this study was to test whether the deuterium oxide dilution technique accurately predicts water intake in sheep and goats. Two other issues were also studied: (i) a comparison of water intake in sheep and goats and (ii) an assessment of whether observations of drinking behaviour can accurately measure the water intake. In this study, eight dry Boer goats and eight dry German Black Head Mutton ewes were kept under controlled stable conditions. Animals had access to hay and water ad libitum. Diurnal drinking behaviour was recorded by video. Individual daily water intake was measured and estimated for 2 weeks by re-weighing water buckets and from water kinetics using the deuterium oxide dilution technique, respectively. In addition, dry matter intakes were directly measured and were significantly higher in sheep than in goats. The average daily water consumption by drinking differed significantly between the two species, with higher intakes in sheep than in goats. Total body water expressed as a percentage of body mass did not differ between species. Measurement methods of total water intake (TWI) using deuterium oxide dilution and re-weighing water buckets did not differ significantly in both species (P 5 0.926). Results obtained for measured and estimated TWI confirm that the isotope dilution technique gives reliable results for estimates of water intake in sheep and goats. The higher amount of water intake in sheep was also reflected by their drinking behaviour. Sheep spent approximately 0.3% per 24-h drinking, while Boer goats spent only 0.1%. However, measured and estimated TWIs were only moderately correlated to the daily time spent drinking. The lower water intake found in Boer goats confirms a superior water management capacity compared with Black Head Mutton sheep even under temperate conditions. Keywords: sheep, goats, water intake, isotope dilution, total body water, behaviour ImplicationsTo the best of our knowledge, this is the first study that validated the water intake in sheep and goats by using the isotope dilution technique. The results show that the applied method (isotope dilution technique) allows the estimation of water intake in sheep and goats with high accuracy. This technique has the advantage that water flux can be evaluated individually while animals are kept in herds under extensive free-range conditions. Thus, normal drinking behaviour will not be disturbed by non-representative housing conditions such as stables.

Effect of water restriction on drinking behaviour and water intake in German black-head mutton sheep and Boer goats

“…The loss of stable isotopes in faeces particularly in ruminants and the possible influences of high roughage content in the rumen on the isotope equilibration due to high faecal production have been discussed (Midwood et al, 1993). However, our results on WI, both measured (by re-weighing water buckets) and estimated (using the isotope dilution method), suggest that the isotope dilution method provides a viable method to estimate TWI in German black-head mutton sheep and Boer goats under temperate-controlled conditions, which is in accordance with previous results (Al-Ramamneh et al, 2010). The higher TBW found in Boar goats compared with sheep suggests that they may have developed different physiological responses to adapt to water shortages and heat stress, which could be a crucial factor for survival under these harsh environmental conditions.…”

“…In this context, it is of interest to note that the TBW and the ratio between estimated and measured TWI was significantly different between goats and sheep, which is in accordance with the results found earlier (Al-Ramamneh et al, 2010). The loss of stable isotopes in faeces particularly in ruminants and the possible influences of high roughage content in the rumen on the isotope equilibration due to high faecal production have been discussed (Midwood et al, 1993).…”

“…Individual samples were measured in triplicate and the averages were calculated. Total body water (TBW) and TWI were estimated from water kinetics according to established formulas described in detail elsewhere (Al-Ramamneh et al, 2010).…”

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

“…Neither TBW (%) nor TBW (kg) were affected by seasonal changes of temperature and feed quantity and quality as well as the metabolic rate indicated by changes in resting heart rate. The measured TBW values, ranging from 57.8 ± 1.8% to 71.2 ± 5.0% (mean = 64.9 ± 4%) in our ponies, were in the normal range reported for adult mammals (Hinchcliff et al, 1997;Toerien et al, 1999;Riek and Gerken, 2010;Al-Ramamneh et al, 2010, 2011. Our values are also in line with data on TBW in other equines, ranging from 55 to 67% (Julian et al, 1956;Deavers et al, 1973;Fielding et al, 2004;Radostits et al, 2005).…”

Effect of shearing on water turnover and thermobiological variables in German Blackhead mutton sheep1

“…Individual samples were measured in triplicate and the averages were calculated. Total body water (TBW) and TWI were estimated from water kinetics according to established formulas, as described in detail elsewhere (Al-Ramamneh et al, 2010). The TWI included preformed and metabolic water from food and drinking water.…”