1 September 2000

Nutritional stress threat

ALTHOUGH many organic units run extensive systems, organic cows may be susceptible to greater nutritional stress than conventional cows because there is no ready access to concentrates, warns John Bax, Biotal technical manager.

Speaking at the meeting, Dr Bax said: "Cows on low input diets may suffer from nutritional stress but concentrates may not be the best answer and are not always an option in organic systems. But whole-crop cereals can overcome this problem by balancing the deficiencies of grass silage and allowing high quantities of starch and sugar to be fed safely without acidosis risk."

However, whole-crop cereals must be properly rationed, he said. "It is not simply a matter of substituting one-third of your grass silage with whole-crop. They are nutritionally different and this must be taken into account."

When considering what forage crops to grow, Dr Bax advised looking at what level of performance you want from animals, considering which crops grow well on your farm and not being diverted by obscure varieties.

"With grasses, stick to mid to late perennial ryegrasses. And when growing whole-crop peas, avoid varieties which grow 7ft tall, making them difficult to harvest."

Peas should be ensiled when they are well-grown, but bi-cropping them with cereals should be avoided, he advised.

"Avoid harvesting peas at the mange tout stage because they will be low in nutrients. Wait until they are well formed, but still soft enough to squeeze between finger and thumb. Bi-cropping is tricky because both crops are unlikely to reach their optimum time for ensiling at the same time."