Influences of sex and egg production on water turnover in chickens

Effect of dietary calcium levels near the time of sexual maturity on water intake and excreta moisture content

Three trials were conducted to investigate the effect of dietary calcium on water balance of leghorn pullets. Trial 1 involved introduction of a 4% calcium layer diet at 112, 123, 134, or 144 days of age. Introducing the layer diet early had an early but transitory effect on water intake (P less than .05) and absolute quantity of excreta moisture, although the pattern of percentage excreta moisture was not clearly defined. In a second trial, birds were moved to laying cages at 105 days, with diet change from 1 to 4% calcium occurring at 112 or 142 days. When the layer diet was offered at 112 days, percentage excreta moisture was higher from 113 to 142 days, although no difference was seen after this time. In a final experiment, introduction of a 4% calcium layer diet at either 112 or 133 days of age resulted in higher percentage excreta moisture at four measurement periods to 245 days of age, although this effect was significant only at 147 days (P less than .05). These results suggest there is a transitory effect of dietary calcium on water intake and excreta moisture content. This affect may be of concern within controlled environment buildings and with certain manure-handling systems. In commercial situations, such dietary changes are often confounded with increased dietary protein concentration, another factor known to influence water balance in pullets.

Water balance of the hen during egg formation

Laying hens consume more water on days when an egg is laid, than on non-laying days; the daily water intake is more than double--from 115 g. to 255 g. and the number of drinks taken increases proportionately. The weight of water in the egg produced is only 32 g. The requirement for this excess of water implies a considerable metabolic stress associated with egg formation. Studies have been carried out to determine why this water is consumed, and its metabolic fate. Water ingestion started to increase about 12 h. before oviposition; it rose steadily until about 2 h. before lay, then fell sharply. Urine minute volume showed similar fluctuations. At the time when the urine output fell just before lay, plasma osmolarity was higher than usual; this might be predicted from the drop in water consumption. Alterations in the water content of the oviduct were not sufficient to explain the increased fluid intake, and total body weight remained constant in spite of the consumption of the additional 140 g. water. These findings suggest that the water has a metabolic role, as it is not retained as a net fluid surplus.