3 November 2000


GENETIC change may be gradual, but there is a vast difference between a mature cow entering the herd now compared with one in the early 1990s.

That is according to a DRC study using data from CEDAR, the University of Reading and the Institute of Grassland and Environmental Research, Hurley. Cows at both centres were third or fourth lactation and were 10-12 weeks post-calving when data was collected.

"Data from 1991 and 1998 shows that cows now need extra inputs," says DRCs Brian Lindsay.

The average cow in 1991 gave 32kg of milk a day and ate 18kg dry matter of feed. But high-yielding cows in 1998 milked three times a day, produced 48kg of milk and ate 25kg of DM. This shows an increase in feed requirement of 50%, he says.

But in addition to the increase in feed requirements that producers would expect, water requirements double, warns Mr Lindsay. In 1991, average-yielding cows needed only 50 litres of water a day; now high-yielding cows need 107 litres.

"Every four days, high-yielding cows eat and drink their own bodyweight."

Cows daily waste output has also increased substantially. In 1991, average cows produced 36kg of faeces, 25kg of urine, 575 litres of methane and 114MJ of heat energy. In 1998, high-yielding cows produced 52kg of faeces, 32kg of urine, 755 litres of methane and 166MJ of heat energy.

"Although output of methane is higher for cows in 1998, they are more environmentally friendly per litre of milk produced," says Mr Lindsay. So it is more environmentally friendly to have fewer high-yielding cows than a larger herd of average yielders.

"Producers should ask whether they are providing their cows with what they need, and whether they can cope with extra slurry output and increased size of animals."

How much mature cow size has increased is demonstrated by the higher weight of modern cows with more Holstein blood. In 1991, cows that were 30% Holstein weighed 541kg; by 1998 they were 85% Holstein, weighing 670kg.

"Genetic gain is a gradual process, but in the longer term, producers need to move ahead with feeding, cubicles and water supply." &#42

Changes in cow daily requirements and output:

1991 1998

Milk yield (kg) 32 48

Feed intake (kg DM) 18 25

Water consumed (litres) 50 107

Faeces (kg) 36 52

Urine (kg) 25 32

Methane (litres) 575 755

Heat energy (MJ) 114 166


&#8226 Meet dietary requirements.

&#8226 Check adequate water.

&#8226 Facilities for extra muck?

Modern cows eat more, drink more and produce more muck than their ancestors.

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