Sow factors affecting voluntary feed intake during lactation

Genetic and environmental changes during the last few decades have resulted in higher milk production and maintenance costs of lactating sows, leading to increased energy requirements, whereas the amount of body fat reserves of, in particular, young immature sows have decreased and voluntary feed intake may have decreased. As a consequence, present voluntary feed intake of sows during lactation is frequently inadequate to meet nutrient demands. This may influence subsequent reproduction. In this paper, it is argued that voluntary feed intake of lactating sows should be included in breeding programmes. To underpin this statement, it is reviewed how the sow factors body weight and body composition at farrowing, litter size during lactation, parity and genotype affect voluntary intake during lactation and possible physiological mechanisms are provided. It is concluded that, for sustainable pig production, the trends of decreasing fat reserves at farrowing and increasing energy requirements during lactation should be accompanied by a higher feed intake capacity during lactation. Genotype seems the most appropriate sow factor that can be used to realise the desired changes and selection for a higher voluntary feed intake during lactation is recommended.  2000 Elsevier Science B.V. All rights