Temperature influences on the in vitro digestibility and soluble carbohydrate accumulation of tropical and temperate grasses

Abstract

Thirteen tropical or subtropical and 11 temperate grasses were grown in controlled environment under daylnight temperatures of 21/13, 27/19, and 32/24�C. Each plant was harvested 2 days after the fifth leaf on the main stem reached maximum length; other plants of Panicum maximum var. trichoglume and Lolium perenne cv. S.24 grown under the same conditions were also harvested 4, 8, 12, and 18 days after this stage of development. There was a consistent decline in the in vitro digestibility of most of the temperate grasses with increase in temperature from 21/13 to 32/24�C. This decline averaged about 5 digestibility units and was associated with a fall in the percentage of soluble carbohydrates. In contrast, temperature had little effect on the digestibility of most of the tropical grasses. However, in later harvests of Panicum the digestibility at 27/19 and 32/24� was consistently lower than at 21/13�. This was attributed to the more advanced growth stages at the higher temperatures. The temperate grasses accumulated much higher concentrations of soluble carbohydrate than the tropical grasses.