The effect of dietary fibre on energy utilisation and partitioning of heat production over pregnancy in sows.

A low (L) and high-fibre (H) diet were fed to six multiparous sows during gestation in a 2 x 2 repeated Latin square design. A single meal per day was given that provided 37.2 MJ digestible energy/d. The kinetics of heat production (HP) and its partitioning (fasting HP, activity HP, and thermic effect of feeding (TEF)) were determined. The TEF was partitioned between a dynamic component (TEFst) and a constant component (TEFlt). Digestibility of energy and nutrients was lower for the diet H. In spite of the lower metabolisable energy (ME) intake (33.9 v. 35.4 MJ/d for diets H and L respectively), HP was higher for diet H (30.5 v. 28.9 MJ/d) resulting in a lower energy retention. The estimated fasting HP was 270 kJ/kg body weight 0.75 per d at day 0 of gestation and increased with advancement of pregnancy. The TEFlt was not significantly different from zero for diet L, but represented 4.1% of ME intake for diet H. The TEFst was not affected by the diet but diet H delayed the postprandial peak of HP. Total TEF was higher for diet H than for diet L (11.7 v. 8.2% of ME intake). The longer duration of eating with diet H was compensated for by less physical activity between meals, so that activity HP was equivalent for both diets. The activity HP represented 20% of ME intake but was variable between sows. The ME requirements for maintenance averaged 440 kJ/kg body weight 0.75 per d. Feeding high-fibre diets increases HP, delays the postprandial peak of HP and maintains the basal HP at a higher level.