During the grazing seasons of the years 1961—63 determinations were made on the contents of monosaccharides, sucrose, fructosan, crude protein and ash in various grass species. In 1961 cocksfoot and meadow grass were investigated, in 1962 meadow fescue was included and in 1963 also timothy. Weather observations were also made during the seasons. The following results were established: At the beginning of the grazing season the contents of water-soluble carbohydrates in all the grasses were at a high level, reaching a maximum of slightly over 20 % of the dry matter. This high-sugar level lasted from one to four weeks, depending on the temperature, until the plants began to form flowering heads. At the heading stage the total amount of water-soluble carbohydrates decreased to nearly half of the previous level. During the remainder of the grazing season, or for 3—3 ½ months, the total sugar content was about 8—13 % of the dry matter, dropping sometimes, however, to as low as 6 %. At the end of the dry summer of 1963, higher contents than usual were determined. There were no great differences in the total contents of water-soluble carbohydrates between the different grass species. From the highest to the lowest sugar content, the species were: meadow fescue, meadow grass, cocksfoot. In fact timothy should be ranged as the first but this grass was not sampled from the pasture paddocks. Of the various water-soluble carbohydrates, the sucrose fraction was the largest in most of the samples. Cocksfoot contained less fructosan than the other grasses, and at the heading stage its content of monosaccharides was very high. Of the three years of the study, two were rainy and one was dry. In spite of the differing weather conditions, however, no noteworthy differences in the water-soluble carbohydrate contents were observed. The crude protein content was found to be dependent upon the growth stage. No appreciable differences were observed between cocksfoot, meadow grass and meadow fescue. Timothy, on the other hand, had a lower content of both protein and ash than the three pasture grasses. Contents of cell-wall substances were generally alike during the pasture season. Notable exceptions were evident only in the cases where the samples represented grass at an early growth stage. Meadow grass contained slightly more cell-wall constituents than cocksfoot, e. g. its xylan and crude lignin contents were somewhat higher. Furthermore, the solubility of such constituents in weak acid was slightly less for meadow grass than for cocksfoot.
Factors affecting the herbage iodine content.
