Ingestion Rates and Aspects of Water, Sodium and Energy Metabolism in Caged Swamp Buffalo, Bubalus Bubalis, From Isotope Dilution and Materials Balances.

Exchanges of DM, sodium, water and energy were estimated on caged swamp buffalo of body mass (W) 297 plus or minus 13 kg. Estimates of feed ingestion estimated from rates of 22Na and 3H turnover were in close agreement with estimates from weighing. Tritium equilibrated in 6 h and 22Na in 12 h. Tritium space was 78.9 plus or minus 1.6% of body mass at 6 h and 83.9 plus or minus 1.1% at 24 h. The body pool of exchangable Na was 40.56 plus or minus 1.79 mmol/kg W at 12 h, and 44.62 plus or minus 2.12 mmol/kg W at 24 h. The daily rate of water turnover was 34.72 plus or minus 2.33 litres or 326.1 plus or minus 17.2 ml/kg W0.82, about three times that expected on the basis of body size, reflecting adaptation to a tropical swamp habitat. It was due mainly to the high rate of imbibition, 30.78 plus or minus 2.15 litres daily or 289.1 plus or minus 16.3 ml/kg W0.82 daily. Daily rates of water loss were partitioned as: faecal, 9.99 plus or minus 0.761 (94.1 plus or minus 7.0 ml/kg W0.82); urinary, 10.39 plus or minus 0.76 litres (98.2 plus or minus 7.6 ml/kg W0.82); pulmocutaneous, 14.34 plus or minus 1.37 litres (133.8 plus or minus 8.9 ml/kg W0.82). Swamp buffalo are unlikely to be able to satisfy their water requirements from food alone during the dry season in northern Australia. The daily rate of Na turnover was 6.29 plus or minus 0.41 mmol/kg W0.75. Na in the faeces was low, 8.3 plus or minus 0.9 mmol/kg dry faeces, indicating very effective alimentary absorption of Na. Apparent digestible energy intake (DE) per day for maintenance was about 651 plus or minus 41 kJ/kg W0.75. Daily rates of evaporative heat loss were high, 481 plus or minus 33 kJ/kg W0.75, exceeding the non-evaporative component of the DE, 321 plus or minus 35 kJ/kg W0.75; evaporative processes may have contributed to the high maintenance DE.