Utilization of energy and protein by sows underfed during lactation

Primiparous sows fed during 4 weeks lactation on a protein-free diet or control diet (12% d.p.) at low ME daily intakes (30 MJ ME), mobilized large amounts of protein and fat to maintain milk production. Sows fed a protein-free diet reduced milk yield and percentage of protein in the milk and body. Sows fed the control diet lost more fat from the body. Nitrogen requirement for maintenance amounted to 0.37 g/kg(0.75)/d. Efficiency of utilization of digestible protein and body protein reserves for milk were 0.66 and 0.90, respectively. Energy utilization was affected by milk composition.