By Shirley Macmillan

MILK PRODUCERS turning out high yielders next month should plan feed strategies now to avoid a drop in butterfats and risk triggering penalties, warn nutritionists.

They report levels as low as 3.5% in some herds which can take months to correct. A herd producing 1m litres and losing 0.2% on butterfat could be 3000 to 4000 a year worse off, reckons Shropshire-based Chris Savery of The Dairy Group. “Removing the lowest butterfat figures during the year will help the overall result.”

 He advises looking back at the past three years” milk tests following turnout. “This happens every year, so anticipate it and react quickly. Waiting for a dramatic drop in butterfats before acting is too late.”

 Fibre digesting bacteria take 10-14 days to adjust to major forage changes, says Suffolk-based independent consultant Bruce Wood-acre. “Butterfats drop because 60-80% of butterfat is made from the products of rumen fermentation.”

 Combining a gradual turnout with buffer feeding should help, but assess forage stocks now for buffer feeding. “Where maize or whole-crop will run out, cut down their use for late lactation cows to ensure supplies for 2-3 weeks” buffer feeding at grass.”

Feeding a live yeast culture over the transition between housing and grazing can give benefit as it reduces stress on the rumen, he adds.

The days of relying on grass to boost flagging milk yields are gone, says KW Agriculture”s Dave Collett. “With most herds producing a far higher lactation average, the result of turnout is often a drop in yields.

 “Cows can”t get enough dry matter intake when they have a rumen full of wet, lush grass. Over winter, intakes will have been 24-26kg DM/day. Eating 3kg less at grass means six litres of milk can be lost straight away.

“I recommend restricting 40 litre-plus cows to 5-6 hours” grazing a day and balancing the total mixed ration to complement grass nutrients.”

Also remember grass is full of rumen degradable protein. “So don”t overdo it in concentrates. Look to decrease rapemeal and increase soya or feed a protected protein.”

 But while buffer feeding can help maintain butterfats, it doesn”t compensate for the lack of diet consistency from grazed grass which upsets high yielders, points out Mr Savery.

 In addition, there is often too little time to manage buffer feeding properly. “There are other jobs to do and as a result, feed presentation is poor, the ration heats up and spoils.”

Once cows have tasted grass, it”s difficult to get them to eat sufficient long fibre, adds Dumfries-based consultant Davidson Thorburn. He suggests moving to a more fibrous summer concentrate and considering adding 25% sugar beet pulp to slow food down through the rumen.

“Offering a protected fat source to boost butterfats is expensive, but may be cost-effective for high yielders to get over the threshold and out of the penalty band,” he says.

Mr Woodacre cautions against relying on butterfat boosting products. “Some may help, but they will not solve the problem of low fibre, high protein grass. Get the rumen right first.”

 shirley.macmillan@rbi.co.uk