ENERGY-METABOLISM IN PREGNANT SOWS AND NEWBORN PIGS

Measurements of heat production(HP; indirect calorimetry) and its part ition between maintenance, physical activity, thermoregulation, and th ermic effect of feed or energy gain were carried out in sows maintaine d in different situations: primiparous of multiparous; pregnant or non pregnant; thermoneutral or cold conditions; varied feeding levels; and varied body weights (BW). Metabolizable energy requirements for maint enance average 420 kJ/kg BW.75 at thermoneutrality and moderate physic al activity. This value is not significantly affected by parity, pregn ancy, and stage of pregnancy. Physical activity is a major factor caus ing differences in energy balance between sows because activity is var iable and its energy cost (27 kJ.kg BW-75.100 min(-1) standing) is fou r to five times higher than in other species. Lower critical temperatu re (LCT) is approximately 20 degrees C in pregnant and individually ho used sows, and daily HP is increased by approximately 15 kJ/kg BW(.75) for each degree Celsius decrease of ambient temperature below LCT. Ef ficiencies of utilization of ME for meeting energy requirements for ma intenance, maternal gain, and uterine gain are 77, 75, and 50%, respec tively. Equations for predicting energy deposition in the uterus and m ammary gland are proposed. In addition to activity and thermoregulatio n, energy requirements of pregnant sows depend on body reserves of ene rgy. Studies with newborn pigs indicate that they are quite sensitive to ambient temperature (i.e., +25 J.kg BW-.75.min(-1) for each degree Celsius decrease of temperature), and their LCT is 32 to 34 degrees C. The energy demand of pigs for thermoregulation just after birth relie s mainly on carbohydrates from glycogen reserves or colostrum. Surviva l of newborn pigs is highly dependent on the supply of colostrum.