Previous feeding level influences plateau heat production following a 24 h fast in growing pigs

Abstract

Factorial approaches to estimate energy requirements of growing pigs require estimation of maintenance energy requirements. Heat production (HP) during fasting (FHP) may provide an estimate of maintenance energy requirements. Six barrows were used to determine effects of feedinglevel on components of HP, including extrapolated plateau HP following a 24h fast (FHPp). Based on a cross-over design, each pig was exposed to three feeding levels (1·55, 2·05 and 2·54MJ metabolisable energy/kg body weight (BW)0·60 per d) between 30 and 90kg BW. Following a 14d adaptation period, HP wasestimated using indirect calorimetry on pigs housed individually. Dynamics of HP were recordedin pigs for 5d during the fed state and during a subsequent 24h fast. Metabolisable energy intake was partitioned between thermal effect of feeding (HPf), activity HP (HPa), FHPp and energy retention. Feeding level influenced (P<0·05) total HP during the fed state, HPf and activity-free FHPp (609, 644 and 729 (se 31) kJ/kg BW0·60 per d for low, medium and high ME intakes, respectively). The value of FHPp when expressed per kg BW0·60 did not differ (P=0·34) between the three subsequent experimental periods. Feeding level did not (P=0·75) influence HPa. Regression of total HP during the fed state to zero metabolisable energy intake yielded a value of 489 (se 69) kJ/kg BW0·60 per d, which is a lower estimate ofmaintenanceenergy requirement than FHPp. Duration of adaptation of pigs to changes in feeding level and calculation methods should be considered when measuring or estimating FHPp, maintenance energy requirements and diet net energy content.