Abstract
Each of two Holstein heifers, whose body weight was about 500kg, was fed by the following mixture in a stockyard at 8p.m., Oct.3, 1966 ; 200g of ladino clover (LC) seeds, 66g of sub clover (SC) seeds, 300g of Italian ryegrass (IRG) seeds, 300g of orchardgrass (0G) seeds, 300g of bahiagrass (BG) seeds, 2kg of concentrate feed, and 1.5kg of beet pulp. Next morning the heifers were moved in a small paddock where some native weeds were grown. They were kept there until 5p.m., Oct.7, being each provided with 2kg of concentrates, 20kg of fresh sorghum, and 5kg of wild grass hay per day. Number, size, and position of feces defecated by them were investigated in the paddock at 8a.m. and at 5p.m.on each day. At each time of investigation 20-30g of feces were collected to count seeds recovered in them. The seeds looking normal in shape were put to the test of their germination under room temperature. Immediately, after grazing in the paddock, feces were sampled and scattered over a Zoysia lawn with three replications. Seedlings emerged from seeds recovered in feces were counted both in the paddock and in the lawn. Recovery of seeds occurred already in feces defecated for 12-21 hrs after feeding (Table 1). This fact suggested that first recovery occurred within a half-day after feeding. Seed recovery reached maximum for 36-60 hrs after feeding, and then decreased. In practical point of view, recovery was finished on the 4th day after feeding. These results were similar to those already reported (1, 2). As to species, recovery was highest in bahiagrass, followed by Italian ryegrass and sub clover, and lowest in orchardgrass and ladino clover (Table 4). By the passage of seeds through digestive tract of dairy cows, germination percentage remarkably decreased in every species. Percentage of rotting seeds distinctly increased in sub clover, orchardgrass and Italian ryegrass, and in the other two species, substitutionally percentage of quiescent or non-germinating seeds reached up to about 80% (Table 5). These relations resulted in low percentage (below 30%) of viable seeds, which consisted of germinating and quiescent seeds, in the former three species, and high percentage (over 90%) of viable seeds in the latter two species. How many such viable seeds recovered from feces could actually grow up to seedlings? This question was not answered by the results of investigation in the paddock where fecec could not be weighed and also seedlings emerged on feces defecated for 36-45 hrs after feeding could not be counted (Table 3), but by the results of investigation in the lawn over which feces were scattered (Figs.1 and 2). On a basis of 10, 000 seeds of each species eaten, number of seedlings emerged from 1kg feces displaced on the lawn was highest in Italian ryegrass, lowest in sub clover, orchardgrass and bahiagrass, and intermediate in ladino clover (Table 6). Such relatively high seedling emergence of the two speciesmight be derived mainly from high recovery of seeds eaten in case of Italian ryegrassand from high viability of seeds recovered in case of ladino clover. Little emergence of bahiagrass was naturally caused by unsuitable low temperature for its germination. Ladino clover only showed an increase of plant number after passing through winter. This might be caused not only by delayed germination of hard seeds but by natural invasion because some ladino clover plants were observed even in the feces-free check plot. In conclusion, Italian ryegrass and ladino clover were considered most effective in dissemination by dairy cows among the five species used.
