Late harvest boosts dairy cow feed intake
HARVESTING maize at a later stage of maturity does not improve the efficiency of energy use by cows for milk production despite the higher starch and lower fibre content of resulting silage.
That is the view of CEDAR researcher Sarah Harrison. Addressing the MGA/BGS meeting, she said research at Reading concluded the optimum dry matter of maize at harvesting for dairy cow performance is between 28% and 33%. "Increasing dry matter from 23% to 33% at harvesting boosts milk yield by 3.6 litres/cow."
Even feeding maize harvested at 23% dry matter increases milk yield compared with feeding a diet based on grass silage alone. "This proves benefits are still gained when growing maize in more challenging areas, such as Scotland."
But Dr Harrison asked whether the higher milk yield linked with feeding more mature maize is due to cows eating more feed or more efficient energy use by cows. This was recently investigated by measuring all inputs and outputs, including methane and heat.
"Milk yield responses were due to higher feed intakes as there were no differences in energy partitioning towards milk production," she explained.
However, a discrepancy was found between predicted values of metabolisable energy content by lab methods and value measured in cows. For maize cut at 23% dry matter, ME was underestimated by 2.2MJ/kg DM using the lab method. *
The optimum dry matter of maize at harvesting for dary cow performance is between 28% to 33%, says Sarah Harrison.