Growth of the pig: changes in body weight and body fluid compartments

Abstract

Body weight and the rate of change in total body water (TBW), extracellular water (ECW), and intracellular water (ICW) were measured in 252 anesthetized pigs during the first 12 weeks after birth. After TBW was measured with 3 H 2 O, 55 of the pigs were killed and TBW measured by desiccation. 3 H 2 O overestimated TBW by 6.5% of body weight and 4.9% of fat free wet weight, compared to desiccation (P < 0.001); mean figures for 3 H 2 O were 78.6 ± 1.02% of body weight, and for desiccation, 72.1 ± 0.45%; on a FFWW basis, 88.6 ± 0.94% for 3 H 2 O, and 83.7 ± 0.13% for desiccation. TBW decreased significantly from 85.0% of body weight at birth (1.5 kg) to 75% at 5 kg (day 28) at a rate of -3.2% body wt/kg body wt (P < 0.001 from a zero rate). After that the rate of decrease was not different from zero: -0.117% body wt/kg body wt. ECW decreased significantly from 48% at birth to 35% at day 28 at a rate of -3.802% body wt/kg body wt (P < 0.001 from a zero rate), and after day 28 the rate of decrease was not different from zero (-0.149% body wt/kg body wt) through week 12. ICW decreased, but not significantly, at a rate of -0.099% body wt/kg body wt. The changes in the rate of decrease in TBW and ECW coincided with weaning, and it was speculated that there was a direct relationship between the 2 events.