4 December 1998

Balancing act with high merit cows

By Emma Penny

EVEN when achieving maximum grass intake, highest yielding high genetic merit cows wont meet yield potential off grass alone, but balancing grass intake and supplements is difficult.

But work by Sinclair Mayne and postgraduate Jane Sayers, who is sponsored by Dalgety, at the Agricultural Research Institute for Northern Ireland, in association with research scientists at Pennsylvania State University.

"With good pasture management there is no need to supplement to meet the needs of a cow producing 25-30 litres. But a cow producing 40 litres will struggle to maintain yield and body condition on grazed grass alone, she needs some supplement to produce the additional litres," says Dr Mayne.

The project is being run in co-operation with Penn State researchers as American producers, who in the past have relied on confinement dairying and total mixed rations, are now looking at use of grazed grass, but continuing to use TMR to balance the ration.

"The linked research program aims to identify the ideal supplement for these high merit cows at grass and when it is best fed."

Lower grain prices mean supplements are now cheaper, making feeding concentrates with grazed grass a more attractive option, and certainly cheaper than relying on indoor feeding.

"We are attempting to bring the high genetic merit cow, grazed grass and cheaper supplements together," he says.

Identifying the right supplement involves examining the potential of the Cornell feed rationing system to identify exactly which nutrients grass supplies and which ones are missing. "By analysing pasture and predicting herbage intake we should be able to work out which nutrients are missing and what supplement needs to be fed to meet cows needs.

"A cow producing 40 litres has very strong motivation to graze, and we want to maintain that. This research hopes to find out how to supplement cows to meet their needs but maintain grazing motivation."

According to Dr Mayne, a 40-litre cow may potentially require 6-7kg of concentrate a day. "In our trials we are feeding up to 12 kg, looking at how important feed supplement levels are and how they affect grazing motivation."

A range of supplements have been fed, aiming to supply nutrients missing in grass. Pasture breaks down rapidly in the rumen, and is highly fermentable. The correct type of complementary feed also helps to balance the protein supply from well managed grass.

"We are looking at a wide range of supplement types, including starch-based supplements, and are evaluating the effect of degree of processing cereal grains on animal performance when offered with grazed grass."

The first phase of the trial has just finished, and Penn State University researchers will visit Hillsborough to help combine results from both research projects. "We are at a fundamental stage, but this first review should help identify better how to challenge high merit cows with grazed grass while meeting needs by feeding additional supplements," adds Dr Mayne.


&#8226 Challenge with grazed grass.

&#8226 Maintain production.

&#8226 Which supplements best?


&#8226 Challenge with grazed grass.

&#8226 Maintain production.

&#8226 Which supplements best?