Effect of condition of sows on energy balances during 7 days before and 7 days after parturition.

Energy and nitrogen (N) balances were measured in 16 sows from day 106 until day 113 of gestation and from day 2 to day 9 after parturition. Dutch Landrace sows of at least third parity were used, eight animals in poor condition and eight in normal condition. Before parturition, energy and N gain did not depend on the sows' condition. The energy requirement of a sow of 170 kg was met by 2.3 kg of feed per day for the last 10 days of pregnancy. Efficiency of utilization of metabolizable energy for energy gain in conceptus was estimated at about 21%. After parturition, levels of feeding of 2.3 or 4.0 kg per sow per day were used. Each litter was standardized at eight piglets. Energy in sow's milk was negatively correlated with energy balance of sows. Thin sows produced less energy in their milk than normal sows. Efficiency of utilization of metabolizable energy for milk production was calculated as 55 and 70%. Milk was produced from body tissues with an efficiency of 80%. Extra feed for thin sows more adequately prevents protein loss from a sow's body than in normal sows.