6 November 1998

Dairy farmers


Metabolic stress and its

effects on dairy cows were

key topics at the Edinburgh

conference last week.

Allan Wright reports

MANY producers are not fit to manage top yielding dairy cows, a scientist has warned after studying 10,200 animals in Britain; poor management was detected in more than half of them.

"Producers with only moderate ability to manage their cows should avoid breeding cattle with the propensity to produce very high yields because the effects of errors in management are likely to be greater in high yielding cows," Robert Ward of Liverpool University told 100 delegates at a British Society of Animal Science conference in Edinburgh last week.

"Poor management, defined as the inability to control body condition in dry cows or the proportion of protein and energy available to rumen microbes, was detected in more than half the cows tested. Progress in genetic selection for milk yield is faster than progress in the management of dairy cows."

His trial involved metabolic profiles of the 10,200 cows, mainly in the north and midlands of England, relating results to herd history.

"If farmers are to manage high-yielding cows, many aspects of management need improvement. Management of condition score is clearly poor in many herds with a very high proportion of pregnant heifers and dry cows showing too high a condition score," said Dr Ward.

He also reported that intake of macro and trace elements in heifers and dry cows was often less than optimal, with evidence of a need for more magnesium and selenium.

"The quality of grass and maize silage is very variable and a greater use of whole-crop cereal silage may be needed to give a mix of forages. Protein and energy in the rumen need to be correctly balanced throughout the day. That means the common practice of offering a high-protein or high-starch meal in the parlour to balance a low-protein or low-starch forage during the rest of the day is not adequate.

"Feed must be presented in a way to maximise intake and many farmers still do not provide adequate trough space or ensure that fresh forage is always available."

Dr Ward was worried that high yielding cows were not able to ingest enough energy from grass, particularly where they had to walk long distances in large herds. But he warned that zero grazing could lead to further problems unless housing was excellent.

He advocated feeding being tailored to encourage a flatter lactation curve and urged better milk quota management to avoid the need for cows to cope with a sudden drop in concentrate feeding at the end of the quota year.

"None of these management practices are new. But farmers will find in the future that cows selected for high milk yields will be less able to tolerate the sort of moderate management practices that are still common," said Dr Ward.

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