Four experiments were carried out to study the water requirements and factors that may affect the water requirements of rusa deer stags.
Experiment 1 was designed to provide some baseline data on the water consumption of Javan rusa deer (Cervus timorensis russa). During winter, eight rusa deer stags aged 4 years were given ad libitum lucerne hay and confined in individual metabolism pens for 26 days. Stags ate 2.04 kg DM/d and drank 6.4 L/d, thus the drinking water: dry matter intake (DMT) ratio was 3.3 L/kg.
In Experiment 2, 7 rusa stags were given ad libitum lucerne or oaten hay with or without barley grain supplementation for 56 days (4 periods). This experiment was conducted during winter and early spring, when the stags were exhibiting the behaviour characteristic of the rut. Rusa stags ate 1.19 and 1.17 kg DM/d of lucerne and oaten hay respectively. Rusa stags given oaten hay drank slightly more water than those given lucerne hay (5.34 and 4.47 L/d, respectively). The drinking water: DMI ratios were 3.81 L/kg for lucerne hay and 4.67 L/kg for oaten hay. Barley grain supplementation had no influence on feed or water intake of rusa stags. This study indicated that different types of feed influenced the water consumption of rusa stags, and feed neutral detergent fibre (NDF) content also affected the water consumption of Javan rusa deer.
Based on the results of Experiment 2, Experiment 3 was designed to further investigate the role of fibre on the water metabolism of Javan rusa deer stags. Experiment 3 involved 6 Javan rusa stags, 5 years old which were held in individual metabolism pens for 68 days (4 periods) during spring. These animals were given two different types of feed (chaffed oaten hay and barley straw), which supplemented with or without wheat grain, and deer were offered water ad libitum. In addition, the total body water and water turnover of rusa stags was measured using the deuterium dilution technique. It was expected that rusa deer given barley straw would drink more water due to higher fibre consumption. However, rusa stags fed oaten hay drank more water (about 1 L/d.h1) than rusa stags fed barley straw. This may be due to the higher undigested feed contained in oaten hay, which reflected in deer having lower NDF digestibility when fed oaten hay compared to barley straw. Wheat grain supplementation had no influence on water consumption of rusa deer stags when fed low quality forages. Different types of forages with or without grain supplementation did not influence total body water of stags. However, water turnover was higher for deer fed oaten hay without grain supplementation (13.4 L/d) compared to deer fed oaten hay with grain (10.3 L/d) and deer fed barley straw with barley grain (10.3 L/d).
In Experiment 4, the salinity tolerance of Javan rusa deer was investigated with seven stags, aged 4.5 years during summer. Animals were fed a medium quality chaffed lucerne hay and given five different levels of water salinity (a) control, (570 mg total dissolved solids (TDS)/L) and (b) "saline" water with TDS contents of 1000, 3500, 6000 and 8500 mg TDS/L. Feed intake, feed digestibility and nitrogen balance were not affected by increasing salt concentration in drinking water, however the drinking water intake and the water:DMI ratio increased with increasing salt concentration. During the experiment rusa deer consuming saline water showed no signs of diarrhoea, anorexia, vomiting, or weight loss. However, deer given 8,500 mg TDS/L exhibited signs of stress, expressed as orbital gland opening, head shaking, and rapid breathing. It was concluded that rusa deer stags could tolerate drinking water containing 8500 mg TDS/L on a short-term basis without harmful effect.
The results of these experiments suggest that Javan rusa deer stags' water consumption was slightly higher than that of the Timorese deer, but similar to red deer. The water consumption of Javan rusa deer stags was influenced by DMI, feed quality, particularly NDF content and digestibility, and water salinity.