Abstract
Seasonal variations of estrogenic activity of orchard grass, tall fescue, timothy and Italian ryegrass were investigated. Three kinds of grasses except Italian ryegrass were harvested four times. Italian ryegrass was harvested five times. Estrogenic activity of each sample was estimated by uterine weight responses of ovariectomized immature mice. The results obtained are as follows: 1. A slight estrogenic activity was shown in orchardgrass, being almost constant throughout the seasons. The activity of narrow-leaf clone was higher than that of wideleaf clone, suggesting a possibility of varietal difference of the activity. 2. The estrogenic activity of tall fescue and timothy were high in the 1st cutting, and slightly decreased in the 2nd cutting. In the 3rd and 4th cutting, the activity was low. Estimated activity per 100gm dry matter of the 1st, 2nd, 3rd and 4th cuttings of tall fescue were equivalent to 0.61μg, 0.52μg, 0.15μg and 0.16μg of DES (diethylstilbestrol) and those of timothy were 0.58μg, 0.40μg, 0.15μg and 0.12μg of DES, respectively. 3. The estrogenic activity of Italian ryegrass was quite low in the 1st cutting, but it increased remarkably in the 2nd cutting and decreased in the 3rd, 4th and 5th cuttings. The 1st cutting of Italian ryegrass at different stages, of maturity had a few activity. The activity of the second year crop remained under a half of the first year crop.
