Water accounts for as much as 80% of body weight at birth and declines to approximately 50% in a finished market pig. Water requirements are primarily associated with body weight and feed intake. Suckling piglets drink around 1.5 oz of water per day on the first days after birth and gradually increase consumption to around 1.5 cups daily by weaning at 28 days (Fraser et al., 1988; Nagai et al., 1994). Water intake during the nursing period may prevent dehydration and promote survival of piglets with low milk intake (Fraser et al., 1988). After weaning, water requirements are highly variable. In general, water requirements are commonly based on water to feed ratios, with normal ratios of 2:1 to 3:1 for nursery and grow-finish pigs, declining as pigs grow (Shaw et al., 2006).
In gestation, restricted-fed sows consume most of the water between meals and there is no relation between water and feed intake. Water requirements for gestating sows range from 3 to 6 gallons of water per day (Brumm, 2010). In lactation, sows have the greatest water requirement attributed to meeting the demands of milk production. Also, water consumption is important to encourage feed consumption in lactation. Water requirements for lactating sows range from 5 to 10 gallons per day (Kruse et al., 2011).