15 November 1996

Cake cuts to save quota can put health at risk

By Jessica Buss

REDUCING concentrates fed to milking cows to save quota will drop yields but could compromise health and fertility, with early lactation animals most at risk.

So says John Murphy, senior researcher with Irish research organisation Teagasc, based at Moorepark, Fermoy, Co Cork.

Reducing concentrate from 7kg to 5kg/day will drop milk yield by 1.5kg; step down from 7kg to 3kg and yield drops by 4kg/day.

Total lactation yield would fall by 180 litres and 630 litres, respectively, but milk protein would also fall by 0.03 to 0.04% for each kg reduction in concentrate.

However, Dr Murphy warns that feeding less concentrate with silage below 10ME may cause excessive body weight loss, ketosis and poor fertility. "Reducing concentrates is only useful when cow body condition is good and there are generous supplies of good quality silage available," he says.

And cows fed less concentrates would eat an extra 0.45 to 0.6kgDM of silage for each 1kg drop in concentrate, he maintains.

"So when concentrates are reduced by 4kg a cow then an extra 0.6t of silage a cow will be needed in a 60-day period."

Another option to reduce milk production, but help maintain body condition, is to feed 5kg of a low protein – 12-13% – concentrate with grass silage or a 16% concentrate with maize silage. This should reduce milk yield by 2.5kg a cow a day, he says.

Dr Tony Andrews of the Royal Vet College agrees that reducing the diet protein percentage will help cows adjust to lower concentrate rations. But he is concerned she will overcome it using her own energy and protein supplies.

This increases the risk of ketosis and fatty liver, and a cow remaining in a negative energy balance at service is unlikely to conceive. Cows would adjust to low concentrate diets, but high yielders whose concentrates are cut in early lactation are unlikely to adapt before service, he warns.

One option is to offer less concentrate from the start of lactation when cows would accommodate the diet without too much trouble.

"Decide what concentrate to provide over a nine-month lactation and feed most in the first three months. This keeps cows in a positive energy balance, and you can get them in-calf and feed well for six weeks after service, before reducing concentrates."

and maintain a good vitamin and mineral balance."


REDUCING CONCENTRATE


&#8226 Yield drops by 0.75-1kg for each kg of concentrate removed.

&#8226 Reduce crude protein of concentrate to maintain energy fed.

&#8226 Adequate supplies of high quality silage needed.

&#8226 Balance vitamins and minerals.