Beet for finishing lambs, not ewes

Fodder beet is high-energy feed that can be grown for relatively low cost if the yields are good, Kerry Dwyer writes.

In Crops and Forage9 Minutes

Fodder beet became very popular in the late 1990s and early 2000s as a winter feed option. That popularity has probably peaked with close to 70,000 hectares being grown annually.

A small area of the crop had been grown in New Zealand before this expansion, driven by the availability of superior varieties and better herbicides for weed control.

Fodder beet has the advantage of higher yield potential than brassicas, a crop of more than 40 tonnes drymatter (DM)/ha being reported this year in Mid-Canterbury. It is high energy feed; and can be grown at a lower cost per kg DM than some crops.

Lessons have been learned in growing and utilising fodder beet, through trial and error in our conditions.

Diet transition

Fodder beet is typically higher in carbohydrate than other fodder crops, but is lower in protein and fibre than most. As a consequence, ruminants need to be transitioned on to the crop to avoid acidosis which will impair the animal or kill it. That transition should also be managed when the stock come off the crop back to a pasture diet.

Transitioning the diet will take 14–21 days to have the least impact on animals’ health and growth. Therefore it makes sense to have stock on beet for a long enough period to make that transition time worthwhile, e.g. allowing 28 days transition along with 100 days full diet is more relevant than say 28 days transition and 28 days full diet.

For that reason, wintering pregnant ewes on beet has not been that common.

If the ewes are to be put on the crop after mating and to be taken off well before lambing, the available time for beet feeding is cut to under 90 days total; that allows maybe 60 days full feeding of fodder beet in their diet.

Compare that to finishing cattle that can be put on to the crop in April and finished in October. That time frame can allow about 150 days of full beet diet.

For dairy cows to get the full benefit of wintering on beet they should be fed some during the end of their milking period and early spring, to allow that transition time.

Because of the risk of acidosis, all stock should be transitioned on to fodder beet. When conditioned the stock will eat to capacity with no complications, with some residual continually remaining on the paddock.

Alternatively farmers will allocate a tight ration each day, leaving no residual and avoiding health issues. That normally goes with underfeeding. I have been watching two neighbours winter dairy cows on beet with tight rationing; the cows lost condition and they had crop remaining in spring; but no acidosis issues.

Fodder beet composition

Fodder beet bulbs are high in sugars while low in protein and fibre. The leaves are high in protein but make a low proportion of the winter crop. Feeding a new break every day gives some leaf protein in the grazing diet, which goes some way to supplying sufficient dietary protein.

Pregnant ewes will be fed insufficient protein for their requirements, especially in late pregnancy, and if carrying multiples. Along with the diet transition time this is a major limitation for using beet for ewes. Protein can be supplied via hay or silage to the stock on beet, with the proviso there is enough supplied, and with enough feeding area if placed in feeders.

Cattle and lambs can achieve very good growth on beet. Put that with a long growing possible grazing period and the crop is a winner. At a full diet, growing cattle might eat 10kg DM/hd/day and achieve more than 1kg/day liveweight gain which is superior to other winter growth possibilities.

I have some dairy farmer clients who put condition on their cows wintering on beet and see a lot who use the crop as a maintenance diet. The latter may gain the benefit of low cost a kg DM, but wastes the potential benefit from better-conditioned cows at calving.

Environmental considerations

In NZ we typically feed fodder beet and winter brassica crops on the area they have grown, in situ. That has some environmental effects that have been subject to management by farmers and regulatory organisations.

A fodder beet crop might well have double the stocking rate of a brassica crop, because of its higher yield. It also might well have less residual after grazing because of better utilisation of the leaf and bulb than say a stalky kale crop. Put that with a big rainfall and you have a challenge.

Because fodder beet has the risk of acidosis, taking stock off the crop for a period, for example to limit pugging, can have risks when re-entering the crop. Harvesting beet to store and feed elsewhere may be an option, requiring planning and machinery.

Fodder beet can yield higher than brassica, due to a longer growing period and different photosynthetic potential. It also can hold quality longer than most brassica crops. The cost per kg DM can be lower than a winter brassica crop given a sufficient yield.

The benefit of fodder beet is its ability to put weight gain on stock, especially growing stock, over a longer time period. That fits with cattle and deer better than sheep. Using beet for maintaining stock does not achieve the full potential of the crop, so think about diet quantity and supplementation.

Cost of feed

Fodder beet is about $3000/ha to grow, compared to $2000/ha for kale. The higher yield potential of the beet means it can cost 12c/kg DM grown as against 15c/kg DM for kale. Note these are indicative figures which depend on your individual components.

However there is more to the story. Beet will require some supplement to get the best results from it, e.g. high-protein hay or silage. Kale might be a balanced diet by itself, but generally some supplement will be fed although at a lower rate than for beet.

It is recommended that beet be no more than 60% of a pregnant cow’s diet, so rough figures would be 9kg DM beet at 12c/kg DM and 6kg DM balage at 50c/kg DM comes to $4.08/cow/day for a beet based winter. Kale might be 12kg DM at 15c/kg DM and 3kg DM balage at 50c/kg DM to total $3.30/cow/day.