Nitrogen and energy metabolism of sows during several reproductive cycles in relation to nitrogen intake

By feeding the same diet during pregnancy and lactation sows are fed above the nitrogen requirement during pregnancy due to the relatively high nitrogen requirement during lactation. For feeding closer to the requirements at least two diets are needed: one diet with a low nitrogen content during pregnancy and an other diet with a higher nitrogen level during lactation. The consequences of such a feeding strategy were investigated. A lower nitrogen supply during pregnancy had no effect on the development of the products of conception, but the development of the maternal protein mass was reduced during the first reproductive cycle. In the second and third parity a compensatory effect was observed. The nitrogen excretion decreased with about 35 % during pregnancy. Sow with a higher lysine supply during lactation mobilized a less nitrogen and more fat during lactation. The nitrogen excretion per sow per year can be reduced with about 25 %. However, the efficiency of the utilization of dietary nitrogen into retained nitrogen remained at a relatively low level.For an further improvement of the efficiency of the utilization of dietary nitrogen into retained nitrogen a multiphase feeding strategy in combination with a restricted development of the live weight of sows is proposed.