Influence of temperature on the digestibility of the tropical legume Macroptilium atropurpureum

The effect of temperature on the nutritive value of Macroptilium atropurpureum cv. Siratro and line 10–105 was determined in a controlled environment at day/night temperatures of 24/18, 30/24 and 36/30°C, and a 13‐h daylength. Estimated dry matter digestibility, cell wall and lignin concentrations of leaf, stem and stubble were measured in two 5‐week regrowth cuts. Siratro and line 10–105 were similar in digestibility and responded similarly to temperature with whole tops, stem and stubble decreasing by an average of 0.0023, 0.0026 and 0.0056 units of digestibility for each 1°C rise in growth temperature. These changes reflect the increase in cell wall and lignin concentrations with higher temperature. The digestibility of young, just‐expanded leaves was increased by increased growth temperature. This effect may be explained by the faster rate of leaf expansion at high temperature which reduced cell wall and lignin concentrations at this stage of leaf development. However, for the bulk leaf fraction digestibility was unaffected by temperature. Leafiness declined at high temperatures.