26 November 1999

Keep eye on cheap feed water content

By Marianne Curtis

BEEF producers looking to keep feed costs down this winter may be tempted by cheap vegetables, such as potatoes at £17/t. But bear in mind the high water content of these feeds and other associated costs before getting carried away, warn nutritionists.

"All feeds contain some water but the physical nature of feed is not a good guide to how much water it contains," explains SAC nutritionist Colin Morgan in this months Signet Beef and Sheep Notes.

"For example, potatoes contain 80% water and yet they are dry to handle, while molasses liquid contains only 25% water." Where there is uncertainty over the dry matter content of vegetable waste such as broccoli or sprouts, Dr Morgan advises having feeds analysed.

Reading-based ADAS senior livestock consultant, Elwyn Rees agrees, especially when large amounts of a particular product are being fed. "Dry matter can vary substantially in some crops such as fodder beet, depending on variety.

"When feeding large quantities of these crops, get them analysed. When sending samples for analysis it is important to make sure they dont lose water in transit, so use a sealed bag and next day delivery," advises Mr Rees.

Unless feeding ad lib, quantity of roots fed should be restricted to 30% to avoid gorging and digestive upsets. "Roots must be introduced gradually over 10-14 days to avoid digestive upsets. Too much soil on roots can also lead to poor performance." The quantity of roots included in rations varies according to type of stock, says Signet beef consultant Geoff Fish. "Steers can be fed 25kg a day of potatoes – which is nearly ad lib – with a little dry feed to speed growth.

"Heifers can sometimes be finished on just roots, but as they are low in protein, balancing with 1-1.5kg/head a day of rapemeal or malt nuts is important." For bulls, where fast growth is desirable, roots should be restricted to a maximum of 50-60% of diet dry matter, advises Mr Fish.

Roots can provide an economic alternative to cereals up to March when they start to sprout or go off. But being aware of nutritional value and haulage and labour costs is essential to make sure you dont pay over the odds for them, he warns.

"As roots are mainly an energy source, their value can be determined by comparing with barley. For example, a barley price of £75/t equates to a potato price of £17/t."

However, fast growing animals will not be able to physically consume enough roots to meet growth targets and a higher proportion of dry feed will be required, he adds. &#42

Relative value of roots compared with barley at £75/t

Vegetable £/t

Carrots 11

Fodder beet 15

Potatoes 17

Sugar beet 21

Parsnips 14