Intake of nutrients from pasture by pigs.

The domestic pig evolved from the omnivorous wild boar and has retained many natural foraging behaviour patterns. Although most modem commercial pigs are housed and fed concentrate diets, interest in the potential nutrient contribution from pasture has increased due to growth in outdoor and organic pig production systems. The energy requirements of outdoor pigs are increased by approximately 15% under Northern European conditions as a result of greater climatic energy demand and locomotory activity. The nutritional contribution made by pasture will depend on the availability, nutrient composition, grazing intake and digestive utilisation of herbage. Information on these topics is currently very sparse. Herbage availability is often low due to farm rotational policy or destructive foraging by the pigs. Herbage composition shows large varietal and seasonal differences, but the high fibre content reduces the efficiency of energy utilisation and may impair utilisation of other nutrients. Intake of grazed herbage varies widely between individuals, but is typically approximately 2.0 kg DM/d for dry sows fed restricted concentrate, and approximately 0.1 kg DM/d for growing pigs offered ad libitum concentrate. This intake can contribute 50% of the maintenance energy requirement and a high proportion of the amino acid, mineral and trace element requirements of dry sows, but < 5% of requirements of growing pigs. Whilst the potential to increase nutrient intakes from grazing exists, this process requires better understanding of herbage intake and digestion, and development of better systems for paddock management.