Growth of the pig: patterns of changes in electrolytes, water, and protein.

In 246 pigs studied from day of birth through week 12, mean plasma concentration of Na was 144.2; K, 3.89; and Cl, 103 mEq/1. Fifty-five pigs were analyzed for total body water (TBW), Na, K, Cl, protein, and fat. TBW was 83% fat-free wet weight (FFWW) at birth and declined, but not significantly, over the 12 weeks. Water content of tissues differed from each other as well as in the rates at which their water content changed. Concentration of electrolytes Na, K, Cl (mEg/100 g FFWW) decreased significantly in whole pig, viscera, brain, and skin; while Na increased and K and Cl decreased significantly in skeletal muscle. Of the tissues, skeletal muscle contributed 32% (fat-free tissue weight as per cent of total FFWW) at birth and 44% at week 12; and viscera, 15% at birth and 21% at week 12. The contribution of skeleton decreased over the same period from 22 to 15%, skin from 14 to 6%, and brain from 2 to 0.5%. The contribution of total water by the various organs changes in the same direction as the contribution to total FFWW. Na, K, Cl, and protein as a per cent of total in skin also show the same directional change. In skeletal muscle there was a decrease in conribution to total Na and Cl, but an increase to total K and protein. In the skeleton, except for protein, there is an increase in contribution of total Na, K, and Cl. There was a correlation of 0.99 and 0.94 between the sum of total Na and K in milliequivalents and TBW in millimeters for the whole pig and skeletal muscle respectively.