Effect of high temperature on feeding behaviour and heat production in group-housed young pigs

Abstract

To assess the acclimation of pigs to heat stress, the effects of high (33°C) or thermoneutral (23°C) constant temperatures on feeding behaviour and components of energy balance were studied in group-housed young pigs. Three groups of five pigs were used at each temperature. After 1 week of adaptation, voluntary feed intake (VFI) and heat production (HP) were recorded for thirteen consecutive days. Animals were fed ad libitum . Fasting HP was measured on the last day. Average initial body weights (BW) were 21·4 and 20·9 kg at 23 and 33°C respectively. Feeding behaviour was measured individually and rate of feed intake and characteristics of feeding behaviour were calculated. The O 2 consumption, CO 2 production and physical activity of the group were used to calculate total HP (HP tot ) and its components, i.e. fasting HP (HP fas ), HP due to physical activity (HP act ) and thermic effect of feed (TEF). The BW gain and VFI were reduced by 37 and 30 % respectively at 33°C. The decrease in VFI corresponded to reduced consumption time (-34 %) and size of the meals (-32 %). Feeding behaviour was mostly diurnal (66 % of the VFI), and the rate of feed intake (28 g/min) was not affected by temperature. Daily HP tot , HP fas and TEF, expressed per kg metabolic weight (BW 0·60 ), were significantly decreased at 33°C by 22, 18 and 35 % respectively, whereas HP act was not affected; TEF expressed per g feed was not affected (2 kJ/g). The decrease in HP tot at 33°C was caused by a reduction in TEF and HP fas (kJ/d per/kg BW 0·60 ), which are both related to reduction in VFI.