Abstract
Grass lines with high magnesium concentration have been developing to minimize hazards of grass tetany in ruminant. To know the effect of higher Mg concentration for digestibility, two high-Mg lines Italian ryegrass 'Magnet' and Tall fescue 'HiMag' were compared with three commercial cultivars of each species. Enzymic hydrolysis method was applied to partition dry matter into three cellular constituents. These lines were evaluated at four harvests, where for Italian ryegrass in 2003 and for tall fescue in 2003 and 2004. Both of 'Magnet' Italian ryegrass and 'HiMag Tall fescue were higher in cell content, high-digestible cell wall composition, and TDN and lower in low-digestible cell wall composition at all four harvests. There was no difference in ash content of both high-and low-digestible fractions. Several highly positive correlations were obtained between Mg concentration and high digestible cellular fractions including TDN. Many negative correlations were obtained with low-digestible cell wall composition. These results indicate that selection to higher Mg concentration is not linked with lower digestibility.
