SU MMARYThe proportions of alkanes in plant cuticular waxes are influenced by sampling date, site and grazing pressure. Alkanes in organs of major wild forage grasses in Japan were evaluated to estimate the intake and diet composition of grazing animals. Samples of four grasses from a fixed site in native grassland and three grass species from different sites were collected from June to November, to test the temporal and spatial effects on alkane concentrations. Most alkane concentrations in Miscanthus sinensis Anderss, Pleioblastus chino (Franch. Et Savat.) Makino, Sasa nipponica and Zoysia japonica increased from June to July, and then decreased to mid November. Alkane concentrations in the Z. japonica sward used to test the effects of grazing pressure decreased from May to September. Although the sampling dates affected the alkane concentrations, the species effects accounted for 70-93 % of the observed variation. Grazing pressure affected only the C 29 (n-Nonacosane) alkane concentrations in dead aboveground materials of Z. japonica, but altered the ratios of C 29 :C 31 (n-Hentriacontane) in both dead and live Z. japonica. There were positive correlations between C 27 (n-Heptacosane), C 29 and C 35 (n-Pentatriacontane) alkane concentrations in live leaves of M. sinensis and of C 31 in live leaves of P. chino with growing season temperature and radiation. The concentrations of C 25 , C 27 and C 29 in dead leaves of M. sinensis and of C 33 (n-Tritriacontane) and C 35 in live Z. japonica were significantly correlated only with radiation. Alkane concentrations differed between the sampling sites, and considerable differences were observed between samples from Iwate and Kumamoto. Both live leaf and dead leaf samples from M. sinensis contained substantial amounts of C 27 , C 29 , C 31 , C 33 and C 35 , and showed that alkane concentrations in stems were much lower during the whole growing season. Although concentrations of C 29 were highest in Sasa nipponica (Makino) makino et Shibata, concentrations of C 31 or C 33 were highest in the other three grass species. Grazing pressures had little effect on alkane patterns, in which alkanes with odd-numbered carbon chains were predominant and most alkanes were of chain length C 25 (n-Pentacosane) to C 35 (n-Pentatriacontane).

Radioactive cesium (Cs) concentration of vegetation and soil was monitored in grasslands in seven farms located at a distance ranging from 90 to 180 km from the Fukushima nuclear power plant during seven months following the reactor meltdown in March 2011. The monitored sites included six sown meadows used to produce hay or silage, three sown pastures and one native pasture used for cattle grazing. The radioactive Cs concentrations of the soil ranged from 264–1593 Bq kg−1 dry matter (DM). The radioactive Cs concentrations in vegetation (aboveground parts of dominant grasses) were high with values ranging from 639–19 823 Bq kg−1 DM for the meadows, 949–7161 Bq kg−1 DM for the sown pastures and 5088–358 549 Bq kg−1 DM for the native pasture. Although the radioactive Cs concentrations tended to decrease over time in most grasslands, there was no clear decreasing trend for grassland soils low in exchangeable potassium concentration and clay content. The transfer of radioactive Cs from soil to herbage tended to be lower in soils with higher exchangeable potassium concentration and clay content. Detailed measurements in one meadow showed highest radioactive Cs concentration in surface litter, followed by standing dead and live plant material. Approximately, 71, 21 and 7% of radioactive Cs in the meadows were present in the soil, litter and standing dead material, respectively. Further regular monitoring of radioactive Cs concentration in grasslands in the affected areas surrounding the nuclear power plant is required to amend the existing guidelines regarding livestock feeding.

The appropriate nutritional management of grazing dairy cows requires an accurate estimation of the content of total digestible nutrients (TDN) in fresh herbage from grazing pastures. The present study aimed to confirm the accuracy of existing estimations of TDN developed for fresh meadow fescue for perennial ryegrass (PR)-white clover mixed herbage, and to develop a new TDN estimation for PR-WC mixed herbage. The herbage was harvested from a PR-WC mixed pasture from April through October. A total of 16 Suffolk wethers were used for this study to evaluate the digestibility of the herbage. The TDN content of the herbage ranged from 68.9% to 77.7% dry matter (DM). The TDN estimated using the existing lignin-based model were similar to the actual TDN, whereas the existing organic b fraction (Ob)-based models underestimated the actual TDN. This may have been caused by high Ob digestibility due to high Ob content and the same level of lignin content in the herbage, as compared with those of meadow fescue. There were significant negative correlations between TDN content and acid detergent fiber (P < 0.01), lignin (P < 0.001), and Ob (P < 0.001) contents. These results demonstrated that the TDN content of PR-WC mixed herbage could be estimated accurately using the following estimations: TDN (% DM) =-4.33 lignin-0.39 cellulose + 94.64 (R 2 = 0.83, P < 0.001) or TDN (% DM) =-0.57 Ob + 93.39 (R 2 = 0.87, P < 0.001).

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