Effects of two different dietary fermentable carbohydrates on activity and heat production in group-housed growing pigs

The effects of two sources of dietary fiber (DF) on behavior and heat production (HP) in group-housed growing pigs were studied. Twenty clusters of 14 barrows (50 kg) were fed one of 10 diets. Diets differed mainly in type and content of fermentable DF (fDF) and in content of digestible starch. Five diets contained solvent-extracted coconut meal (SECM) and five diets contained soybean hulls (SBH) as the main fDF source. On an as-fed basis, pigs received 3.5, 13.2, 23.0, 32.7, or 42.4 g·kg−0.75·d−1 of SECM or SBH. A total of 280 crossbred growing pigs were used, divided into clusters of 14 pigs each. Pigs were group-housed and fed at 2.5 times the assumed maintenance energy requirements. All clusters were fed similar amounts of NE, ileal-digestible protein and amino acids, vitamins, and minerals. Consequently, DMI differed among diets because NE content decreased with increasing DF content. After a 32-d preliminary period, HP was measured per cluster during a 7-d experimental period in environmentally controlled respiration chambers. Behavior of the pigs was recorded using time-lapse video recordings during two different days within the experimental period. Intake of digestible starch and fDF was different (P < 0.001) among diets, whereas intake of digestible CP was similar among diets. On average, pigs spent 153 min standing, 42 min sitting, 202 min lying on their chest, and 1,043 min lying on their flanks each day. Pigs fed SECM diets spent, on average, less time (P < 0.05) lying on their chest than pigs fed SBH diets. Total time spent on physical activity (i.e., standing plus sitting, 195 min/d) was not affected by diet. Total HP and resting HP were affected by diet and were on average lower (P < 0.01) for pigs fed SECM diets than for pigs fed SBH diets. Activity-related heat production (AHP) averaged 65 kJ·kg−0.75·d−1 and was not affected by diet. There was a linear relationship (P < 0.001) between fDF intake and HP, but there was no relationship between fDF intake and AHP. During different parts of the day, fDF intake also affected HP. The saving effect of physical activity on the NE values of fDF from SECM and SBH were 0.56 and 0.84 kJ/g of fDF intake, respectively. Neither of these saving effects was significantly different from zero. We conclude that fDF from SECM and SBH did not affect energy expended on physical activity by growing pigs, and that the NE value of fDF from SECM and SBH was not affected by changes in physical activity.