Estimation of milk production in lactating sows by determination of deuterated water turnover in three piglets per litter.The milk intake in piglets from four lactating sows was measured in three 48 h periods, starting on days 3, 10 and 17 of lactation, using the deuterium oxide (D 2 O) dilution technique. The milk intake was estimated from the water turnover in the piglets corrected for the production of metabolic water. The water turnover was estimated from the water dilution space and the fractional turnover of body water, determined by the rate of D 2 O dilution. To determine the magnitude of isotopic recycling, a randomly selected piglet in each litter was not enriched with D 2 O. Milk production of the four lactating sows was also measured by the weigh -suckle-weigh (WSW) method on days 4, 11 and 18 of lactation. The average daily milk production determined by the D 2 O dilution technique (9.91 9 0.69 kg) was higher (P B 0.05) than that determined by the uncorrected WSW method (8.65 9 0.81 kg). Different procedures for selecting piglets were evaluated to obtain the best possible estimation of total milk production from three piglets in each litter. The total milk production of a sow based on three piglets in the litter was obtained from a quadratic model of the relationship between milk intake and daily gain. When the daily gain of all piglets were known the Pearson correlation between milk production determined for the whole litter (n ¼ 1) and only three median piglets was 0.98.