Archive Article: 2001/10/19
USING a mill fitted to forage harvesters improves the nutritive value of urea-treated whole-crop wheat for dairy cows, but sugar supplements may be needed to obtain the full benefits.
The problem with urea-treated whole-crop is that 10-20% of starch passes through the cow as undigested whole grains, says Harper Adams University Colleges Liam Sinclair. "This results in a low energy forage and disappointing cow performance."
Forage mills fitted on forage harvesters have been developed to improve starch availability by grinding cereal grains. This was recently evaluated at the college with funding from the Milk Development Council and Maize Growers Association.
"Apparent starch digestibility was increased from 80% to 97% when using forage mills to grind grains. This equates to a 300-600g a day reduction in starch losses in dung."
The increased starch availability resulted in cows eating 2.5kg a day less forage dry matter, while maintaining the same milk yield at 30kg a day with no body condition loss. This cuts daily feed costs by 4-8p a cow, adds Dr Sinclair.
A further saving of up to 3p a day was obtained when increasing the cutting height of wheat from 18cm (7in) to 37cm (15in) to increase starch content. This is despite the 20-25% reduction in forage yield when increasing stubble length.
But feeding the short straw whole-crop reduced milk fat content by about 0.5%, due to less fibre, and increased body condition score by 0.2 units.
Forage production costs were £48/t DM for the long straw whole-crop and £55/t for the short straw. With arable aid payments, the cost falls to £34-£38/t.
"This winter, the second part of the project will look at ways to stimulate forage intake and increase milk output. We know cows can eat an extra 2.5kg DM, as shown by the cows eating unprocessed whole-crop," says Dr Sinclair.
Feeding fermentable sugars, such as molasses and lactose, has been shown to stimulate dry matter intake and this will also be investigated this winter. *