Published online by Cambridge University Press: 27 March 2009
Sheep were exercised on a treadmill to study the effect of increased energy demand on roughage intake and ruminal characteristics.
The experiment consisted of a pre-exercise period during which exercise sheep walked for 30 min/day at 2 km/h against a gradient of 0° followed by a full exercise period during which they walked a total of 9 km/day at 3 km/h against a 10°gradient during six daily sessions of 30 min each. Control sheep received no exercise but were treated similarly to exercise sheep in all other respects.
The mean values obtained during the pre-exercise period for the exercise and control groups and during the full exercise period for the exercise and control groups respectively were 1347, 1125; 1177 and 1114 g/day for organic matter (OM) intake; 956, 921; 803 and 848 g for rumen OM contents; 11·8, 13·6; 12·2 and 12·3 h for rumen retention time of water; 17·5, 20·2; 16·8 and 17·6 h for rumen retention time of fermentable OM; 27·3, 28·2; 26·4 and 26·7 h for rumen retention time of unfermentable OM and 46·9, 48·1, 44·4 and 45·9 kg for empty body weight. Only the decline in OM intake from pre-exercise to full exercise period differed significantly between exercise and control groups.
It is concluded from these results that an increase in the difference between energy demand and supply per se is not responsible for the apparent increase in the upper limit to OM accumulation in the rumen and concomitant increase in roughage intake observed during other situations of increased energy output such as lactation and severe cold.