Beware heat stress to cows.

DAIRY farmers are being warned to keep an eye on their cows' food intake during the current humid weather and be aware of the effects of heat stress on their production, health and fertility.

When the temperature rises above 25C, the UK dairy herd feed intake falls by an estimated 8%-12%, according to nutrition experts.

KW nutritionist Dr Richard Wynn said: "All dairy producers should be watching out for heat stress symptoms at the moment, with increased respiration rate (panting), higher water intakes and prolonged standing in shade all obvious signs. And because digesting forage creates more heat than concentrates, cows will cut back grazing intakes first, so appetites in the parlour won't necessarily be reduced.

"The net result is an increase in acidosis, reductions in milk yield, lowering milk fat content and leading to problems with fertility, laminitis - in a month or two - and mastitis."

He recommends farmers cut forage fibre to the safe minimum and replace it with nutrient-dense feeds high in digestible fibre, such as sugar beet feed and wheatfeed, to maintain rumen health in hot weather. "Use yeasts and buffers to help counter the rise in rumen acidity, provide shade where possible - shade can increase milk production by 10-19% - and ensure plentiful, easy access to drinking water, the cooler the better," he said.

"Maximise intakes during cooler periods of the day, offering 60-70% of the feed between 8pm-8am.

"It might mean buffer feeding indoors during the day, and grazing at night, but the effect on intakes and milk output will be well worth the extra effort during any hot, humid periods this summer."

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WARNING Hot weather can harm dairy cows' health and milk production, so it can be worth feeding them indoors during the day and letting them graze at night, say nutrition advisers.