Abstract:
Dry matter intake of dairy cows grazing pasture based on perennial ryegrass (Lolium perenne L.) pasture at low or high herbage allowances was estimated from pre- and post-grazing pasture masses (PMM), using n-alkanes or by calculations based on cow performance and published estimates of energy requirements (PERM). Pasture intakes were lower (14.1 vs 17.1 kg DM/day) (p<0.05) at low compared to high herbage allowance when estimated using PMM, PERM and C31/C32 alkanes. When C33/C32 alkanes were used, there was no difference in intake between the 2 allowances (18.5 vs 18.6 kg DM/day). The estimates of intake using n-alkanes were higher (p<0.05) than for PMM or PERM. Sources of error and uncertainty with each method are discussed.
