Changes in Nutritive Values of Grazing Grass at Annual Ryegrass-Brachiariagrass Rotation Pasture in South-West Japan.

In south-west Japan, reproductive cattle grazing is an important industry. Nevertheless, grazing of fattening cattle is very rare. Fattening in barns using imported grain is common. Fattening on pasture must be considered to mitigate the use of imported grain and to use abandoned farmland.

We conducted fattening of Japanese Black and Japanese Brown steers using rotational grazing on winter Italian ryegrass and summer Brachiariagrass pasture in the south-west Japan. We investigated the grass intake by grazing steers and the nutritive values available from rotation paddocks for three years. This report describes nutritive values of grass intake by grazing steers.

The total digestible nutrients(TDN) values of Italian ryegrass generally increased from autumn (around 65%dry matter(DM)) through January (over 75%DM). They then declined until summer (around 60%DM). Furthermore, results show very low values (below 50%DM) when Italian ryegrass showed heading in spring. The TDN values of Brachiariagrass were lower than 60.5%DM. Seasonal change are not clear. The crude protein(CP) values in both grasses showed unseasonal wide range changes and the values were very low (below 10%DM) in spring with Italian ryegrass heading. Differences in nutritive values between adjacent periods depend on paddock differences. We didn’t adjust the fertilizer rate among paddocks with different grass growth rates. Therefore, high CP values (over 20%DM) in both grasses resulted from excessive nitrogen fertilizer application.

These results suggest that the TDN in Italian ryegrass pasture can be estimated from seasonal changes under a no-heading condition. The TDN in Brachiariagrass cannot be estimated, nor can the CP for either grass. To reduce differences in nutritive values, especially CP between paddocks, it is necessary to clarify the optimum fertilizer rate dependence on growth in the respective paddocks.