Dietary fat and reproduction in the post partum sow.

Lactating sows are not able to ingest sufficient energy to produce the large amount of milk they are presently capable of. Therefore, sows use a considerable amount of body reserves to maintain their milk production. Body weight loss is negatively associated with subsequent reproductive performance. Addition of fat to the diet is often used to increase energy intake during lactation. This review examines the effects of adding fat to the diet on subsequent reproductive performance. Fat may affect reproduction in three different ways; first, by increasing milk fat output. Higher milk fat output limits or even nullifies the effect of a higher energy intake on body weight loss in ad libitum fed sows. It has even been demonstrated that sows fed an isocaloric fat-rich diet lost more body reserves than sows fed a carbohydrate-rich diet. Second, fat-rich diets increase blood metabolite levels (non esterified fatty acids, beta-hydroxybutyrate, urea), which might negatively impact reproductive performance. Third, fat-rich diets depress secretion of insulin and IGF-1, which directly or indirectly affects LH, oestradiol and progesterone secretion and follicle development. We concluded that adding fat to the diet of lactating sows disrupts the balance between C2 and C3 compounds, which is necessary to run the Krebs cycle in an efficient way, and may negatively affect the sows' subsequent reproductive performance. Therefore, increasing energy intake during lactation might be accomplished better by adjusting other management procedures to support feed intake, such as housing temperature, water intake, and prevention of overfeeding in early lactation.