Lactation demands a very high input of energy and protein for the production
of milk. It is difficult for sows to consume enough dietary energy to support
lactation and, thus, sows are forced use body tissue reserves. However,
excess catabolism of body protein for energy and amino acids is undesirable
for the productivity and longevity of sows. Protein turnover and energy
metabolism was simultaneously measured in sows on d 7 and 17 of lactation. It was found that their was a higher dietary intake of energy and protein on d 17 which reduced both whole body protein breakdown
and protein synthesis. This higher dietary energy intake on d 17 (13.4 MJ/d) was entirely accounted for by milk energy output (13.8 MJ/d). Also as energy and protein intake increased in these sows, it was
used almost exclusively for milk production. Milk energy production on d 17
was supported almost entirely by dietary energy intake. Nearly 100% of the
dietary protein intake was utilized for milk production in late lactation.