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In the first of a new series of topical livestock nutrition articles, Rumenco
technical manager David Thornton highlights the declining feed value in grazed
grass at this time of year, and offers useful advice on how to keep cattle growing
on target right through to housing and the switch to winter rations.

The weather in September has been generally warm and fair – certainly for the first half
of the month – and the sight of cows still at grass while the sun shines has been a
welcome boost for many livestock farmers after what has been another disappointingly
wet summer.

However, although grass may still be visibly growing in early October and looking
plentiful in some areas of the country, its quality is definitely declining rapidly. Water
soluble carbohydrate levels drop when the days get shorter and solar radiation reduces.
Autumn grass is also usually wetter than summer grass and the extra bulk and dilution of
nutrients will limit intake and diet utilisation. Shorter days also mean fewer grazing hours
and this all can add up to cattle growth rates dropping off a cliff unless action is taken.

It’s true that many cattle producers recognise this nutritional fact and early October is
around the time that they start thinking about whether or not to feed concentrates to
grazing youngstock, in particular. However, many fail to recognise that there are pitfalls
in this approach.

Whilst growing cattle often need some supplementation around now, feeding even small
amounts of concentrates can cause substitution of grass dry matter intake, simply
because the rumen bugs needed to ferment either fibre (pasture) or starch
(concentrates) are quite different and don’t get on. The rumen can go out of synchrony
and the result is expensive and disappointing performance.

Cattle will eat concentrates in preference to grass, which is acceptable in a very dry
summer, but not particularly efficient in a green, lush summer as has been the case once
again this year when there has been plenty of grass available. Remember, grass is the
cheapest feed on the farm at around 1p/kg DM compared with rolled barley at 12p/kg
DM (based on £100/tonne), so it makes sense to utilise it fully. In fact, an ability to make
the most from grazed grass is what often separates the profitable livestock holding from
one struggling to make ends meet.

Keeping cattle growing is vital at this time of year. And to help producers continue to hit
growth targets, we often recommend the introduction of feed blocks where grass quality
is falling away – simply because this supplementary feeding method offers a whole host
of benefits.

Trial work with feed blocks has shown that they can promote an improved mean daily
liveweight gain (DLWG) of 0.24kg over feeding no supplements at all, fuller pasture
utilisation and heavier weaning weights (see trial summary).

Blocks are also more convenient than most other supplementary feed systems – another
valued benefit during what is usually a very busy period on many farms. Mixed farms, in
particular, have usually had all their focus on the cereal harvest just as the cattle growth
rates are dropping because of the lower quality grass. Diverting labour every day to feed
cattle often is just not possible.

Feeding blocks not only supplies more energy against declining grass digestibility, it also
provides supplementary protein, vitamins and minerals as well, which are so important
for health and thrive.

Block consumption also closely matches grass availability, results in very good pasture
utilisation and promotes less variation in individual performance within a group of cattle.
This offers tremendous advantages for producers selling batches of weaned calves and
dairy farmers wishing to serve batches of bulling heifers of a more even size and weight.

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