THE EFFECT OF ENERGY AND PROTEIN-INTAKE OF SOWS ON THEIR LONGEVITY - A REVIEW

The characterization of the effects of protein and energy intake of sows on their longevity requires long-term experiments involving large numbers of females. Results from the studies available show that sows are culled mainly for reasons involving reproductive failure, locomotion problems or poor lactation performance. Energy under-feeding during gestation is associated with lower body fat reserves at farrowing or at weaning and generally return to oestrus is delayed and conception rate is lower. On the contrary, over-feeding during gestation increases weight and condition of the sow at the end of pregnancy and this can affect the occurrence of farrowing and lactation problems and culling for poor lactation performance or locomotion problems. During lactation, it seems that there are critical levels for energy and for protein below which weaning to oestrus interval, rate of return to oestrus and pregnancy rate are affected, especially in primiparous sows. This is the main reason for early culling of sows. The mechanisms are not yet elucidated, but the metabolic status or the status of body reserves of the sows at weaning seem to be involved. It is thus necessary to apply a feeding strategy adapted to each sow, in relation to its own level of production, its behaviour and the housing conditions, in order to maintain body reserves within an optimal zone all along the reproductive life and to maximize its longevity.