Effect of environmental temperature on digestive tract, visceral organ size, digestibility and energy metabolism in rats fed different levels of pea fibre

A study was performed to investigate the effect of environmental termperature (18 degrees C or 28 degrees C) and increasing levels of pea fibre in the diet on digestive tract, visceral organ size, digestibility and energy metabolism in rats. Thirty-six male Wistar rats, initial liveweight (LW) 77-79 g, were allocated to six groups and housed at either 18 degrees C (three groups) or 28 degrees C (three groups). Three wheat starch, fish meal and pea fibre-based diets were prepared to contain 100, 200 and 300 g pea fibre kg(-1) (68, 110 and 157 g dietary fibre kg(-1) DM) and 160 g protein (N x 6.25) kg(-1). One group of rats at each temperature was fed one of the diets for four balance periods. Gas-exchange measurements were made and urine and faeces were quantitatively collected. Food to gain ratio was higher (P < .05) at 18 degrees C than at 28 degrees C and increased (P < .05) as the level of fibre was increased. The weight of the visceral organs from rats housed at 18 degrees C was higher (P < .05) than at 28 degrees C. The empty weight of the small intestine, caecum and colon increased (P < .05) as the level of pea fibre was increased. The digestibility of DM, protein and dietary fibre (DF) was lower (P < .05) at 18 degrees C than at 28 degrees C. As the level of pea fibre was increased, the digestibilities of nutrients and energy decreased (P < .05). However, the digestibility of DF increased (P < .05) as the level of pea fibre was increased. The partial digested energy value for pea fibre was 11.9 kJ g(-1). The metabolizable energy (ME) intake and heat production at 18 degrees C (1128 and 974 kJ (W-0.75 day)(-1) respectively) were higher (P < .05) than at 28 degrees C (831 and 674 kJ (W-0.75 day)(-1) respectively). As the level of pea fibre was increased, ME intake (W-0.75 day)(-1) and heat production (W-0.75 day)(-1) decreased (P < .05). Heat production as a percentage of ME was higher (P < .05) at 18 degrees C than at 28 degrees C: 86.6% and 81.2%, respectively. Heat production as a percentage of ME was higher (P < .05) for rats fed the 100 g pea fibre kg(-1) diet than the 200 or 300 g pea fibre kg(-1) diet. In conclusion, environmental temperature as well as DF influenced digestive tract and visceral organ size, digestion and protein and enegy metabolism.