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

To assess the acclimation of pigs to heat stress, the effects of high (33 d egreesC) or thermoneutral (23 degreesC) constant temperatures on feeding be haviour and components of energy balance were studied in group-housed young pigs. Three groups of five pigs were used at each temperature. After 1 wee k of adaptation, voluntary feed intake (VFI) and heat production (HP) were recorded for thirteen consecutive days. Animals were fed ad libitum. Fastin g HP was measured on the last day. Average initial body weights (BW) were 2 1.4 and 20.9 kg at 23 and 33 degreesC respectively. Feeding behaviour was m easured individually and rate of feed intake and characteristics of feeding behaviour were calculated. The O-2 consumption, CO2 production and physica l activity of the group were used to calculate total HP (HPtot) and its com ponents, i.e. fasting HP (HPfas), HP due to physical activity (HPact) and t hermic effect of feed (TEF). The BW gain and VFI were reduced by 37 and 30 % respectively at 33 degreesC. The decrease in VFI corresponded to reduced consumption time (-34 %) and size of the meals (-32 %). Feeding behaviour w as mostly diurnal (66 % of the VFI), and the rate of feed intake (28 g/min) was not affected by temperature. Daily HPtot, HPfas and TEF, expressed per kg metabolic weight (BW0.60), were significantly decreased at 33 degreesC by 22, 18 and 35 % respectively, whereas HPact was not affected; TEF expres sed per g feed was not affected (2 kJ/g). The decrease in HPtot at 33 degre esC was caused by a reduction in TEF and HPfas (kJ/d per/kg BW0.60), which are both related to reduction in VFI.