SPRING-CALVING dairy producers should be thinking about their dry-cow rations to avoid metabolic problems in early lactation and planning calving to improve fertility management later on.

There are benefits from thinking about fertility management now, says independent grazing consultant Tom Phillips. He believes many problems stem from difficult or assisted calvings or metabolic problems at calving.

“Don”t rush into assisting calvings. Too many producers assume they are doing the right thing, but often it”s not,” he advises.

Paying attention to close-to-calving diets is key to avoiding metabolic problems at or after calving, says vet Kate Burnby of Sussex-based Stock1st Vets. Herds relying on grazed grass for lactation often feed dry cows a different diet, but the rumen needs time to adjust to differences in pasture quality as well as concentrate feeding, she says.

“Sudden changes in diet from poor pasture or silage to quality grazing, with or without concentrates, puts cows at risk of metabolic problems such as ketosis,” she says.

“Herds supplementing with 4-6kg a head of concentrates after calving should start feeding 1-2kg a head 2-3 weeks before calving and also graze some quality grass.”

But because grass is low in magnesium she says it is important to supplement magnesium levels, as it is linked to calcium function and milk fever. Post-calving it is needed to prevent staggers.

Adding magnesium chloride flakes to drinking water for the first grazing round helps avoid metabolic problems in Pembrokeshire producer Nigel Evans” 200-cow herd. Pasture is then dusted with magnesium oxide to ensure adequate intakes in wetter weather during the second rotation.

“We only had two cases of milk fever last year,” he reports. The herd, which started calving on Jan 30, turned out its first group of 15-20 fresh calvers last week. “Ground conditions are reasonably good and grass growth is 3kg/ha DM a day.”

Once grass starts growing rapidly, Miss Burnby warns producers to watch out for fluctuating levels of magnesium, sodium and potassium, depending on slurry applications, sward age and climate.

She suggests producers regularly test grass to determine mineral levels. This also establishes energy, dry matter and protein content, which vary according to grass maturity.

“It”s useful to know which fields to avoid grazing with dry cows, as winter slurry or dirty water applications contain high levels of potassium. This interferes with magnesium uptake and exacerbates milk fever,” she says.

She also reminds producers to monitor cow condition fortnightly. “Dry cows won”t gain condition in the last three weeks before calving, but they can lose it. The aim is to limit condition loss in early lactation. Don”t leave it too late to do something about it.”