October 13, 2003
Inaccurate Belief that Pasture an Inferior Feed for Dairy Cows
Farmers should not be confused about the view that pasture is a high-quality feed, says a dairy industry scientist specialising in cattle nutrition, John Roche.
Roche, a member of Dexcel's research team, told a Taranaki field day confusion raged over the nutritional requirements of the pasture-based dairy cow in early lactation, with pasture often assumed to be a poorly balanced feed.
"Much of this uncertainty comes from nutritional wisdom from dairying systems where pasture makes up very little, if any, of the daily dry matter intake of the cow," he said.
These systems, where cows were fed total mixed rations and routinely averaged daily production of more than 3kg of milksolids, were often used to convince farmers that pasture was an inferior feed for dairy cows.
"This is not an accurate conclusion," Roche said.
Grazing dairy cows did not require any supplements (except minerals) if they had sufficient pasture.
About 80-85% of the milk yield difference between cows offered a total mixed ration and those grazing pasture was due to dry matter intake and energy expended grazing and walking.
"The other 15-20% is due to the fact that milk from pasture-based cows has a higher solid content and therefore requires more energy and a small energy cost to excrete the extra protein."
In terms of energy, pasture in winter, spring and autumn was an excellent quality feed, high in digestibility and metabolisable energy, often with the energy density of a complete mixed ration.
But at some points of the year, particularly in September, pasture was often low in dry matter content.
When this fell below 15%, it became difficult for cows to eat large enough volumes of pasture.