title: Interrelationship between metabolism of tritiated water, 22sodium and dry matter intake by beef cattle consuming wheat straw and poultry litter in free choice.
abstract: 1. Metabolism of tritiated water and 22sodium was studied in six beef cows under Mediterranean summer conditions in order to find whether the turnover of these tracers can be used to evaluate pasture intake. 2. The diet of the cows included ad libitum access to two components which were given separately in different troughs: one was poultry litter and the other was wheat straw, to simulate the dry pasture. 3. Voluntary daily dry matter intake (111 g/kg0.75) was unexpectedly high considering the low digestibility of the feed. 4. The assumptions of constant ratios of water intake to water turnover and of dry matter intake to water intake were confirmed. Consequently, dry matter intake was determined accurately from water turnover measurements. 5. Sodium intake was practically equal to sodium turnover and most of the sodium secreted in feces was of endogenous origin. 6. Pasture intake can be predicted from sodium turnover once the concentration in feed and water consumed is known.
mesh_terms: D000821:Animal Feed; D000818:Animals; D001834:Body Water / Q000032:analysis; D002417:Cattle / Q000378:metabolism*; D002645:Chickens; D005260:Female; D006706:Homeostasis; D007700:Kinetics; D008954:Models, Biological; D012964:Sodium / Q000378:metabolism; D012979:Sodium Radioisotopes; D014908:Triticum; D014316:Tritium; D014867:Water
chemical_list: D012979:Sodium Radioisotopes; D014867:Water; D014316:Tritium; D012964:Sodium