Influence of dietary fibre level on digestive and metabolic utilisation of energy in growing and finishing pigs

The aim of the experiment was to determine the effect of dietary fibre (DF) level on the digestive and metabolic utilisation of energy in pigs. Two diets were prepared: a control low DF diet ( the C diet, 100 g Total Dietary Fibre (TDF).kg(-1) DM) and a fibre-rich diet ( 200 g TDF.kg(-1) DM) which corresponded to a combination of the C diet and maize bran (the MB diet). Each diet was fed as pellets during two successive experimental periods to five, individually caged pigs at growing ( 42 kg BW) and finishing stages (76 kg BW) for the measurement of digestibility, heat production ( HP; indirect calorimetry) and its components. Energy supply was standardised between the diets (2.4 and 2.3 MJ ME.d(-1).(kg BW)(-0.60) for growing and finishing pigs, respectively). The energy digestibility was not affected by growth stage but was lower for the MB diet (83%) than for the C diet (91%). Similarly, the DE value of maize bran (11.5 MJ.kg(-1) DM), as calculated by the difference method, was similar at both stages. The fasting HP represented 56% of HP and averaged 0.724 MJ.d(-1).(kg BW)(-0.60) while the physical activity and thermic effect of feed represented on average 14 and 30% of HP, respectively. None of the components of HP was affected by the DF level. The activity HP was greater in finishing (16% of HP) than in growing pigs (12%). Energy cost of standing was constant (kJ.min(-1)) when expressed per kg BW1.25. When adjusted for similar ME intake and activity level, total HP and retained energy did not differ between the diets and between the growth stages. In conclusion, the metabolic utilisation of dietary energy was little affected by the DF level in growing and finishing pigs under the conditions of the present study.