By Karen Stewart, SAC consulting nutritionist

As summer progresses the quantity and nutritional quality of grass declines. This year, grass growth has fallen off quite considerably as soils run out of moisture.

In spring and early summer there was sufficient good quality grass for animal production and for conservation as silage or hay. By now and into early autumn, animal growth rate will be declining on grass alone. At some stage, it is necessary to supplement the grazing if to maintain cattle growth rates. However, too much and it will simply substitute grass intakes and make weight gain more expensive.

The level of grass supplementation will depend on:

* The type of cattle and target growth rates

* The amount of grass available

* What kind of grass growing season we get from July onwards

What are the aims for your cattle?

Finishing cattle targeting upwards of 1kg daily liveweight gain will now need supplemented at grass. If grass is in low supply or of poor quality, then consider putting out an ad-lib hopper with concentrates – take care to introduce feeding slowly and to cattle that have a full belly to avoid gorging and then make sure hoppers do not run out thereafter otherwise this process needs to be repeated.

If feeding ad-lib, it is advisable to have a ring of straw available as well as long roughage if grass is poor (or on a wet day!!) when cattle will tend to congregate round a feeder rather than graze.

Bringing them in the house to finish may also be an option. Certainly, some groups of cattle’s performance will have been disappointing over this extended dry spell.

If grass remains plentiful and of good quality then growing cattle could still be growing at up to 0.8kg/day gain. However, this requires good growing conditions and very well managed grazing.

Grass availability

It is best to check sward heights on a regular basis to ensure there is adequate feed for them. The table below is a guide to grass heights for cattle at grass. Other factors such as quality of grazing, stocking rates and weather will also need to be taken into account.

Month Set stocked grazing system Rotational system field entry grazing height Rotational system field exit grazing height

June/July 6-7cm 10cm 5cm

August/September 7-8cm 10cm 6cm

The critical point is when to exit a field on rotational grazing systems. But as quality declines, and the thatch of dead material increases towards the base of the plant asking cattle to graze lower will compromise performance, if not gut fill. Grazing to lower heights will also prolong recovery.

As a simple rule of thumb, later on in the season – where feeding concentrates alongside grass – if grass is reasonably plentiful then concentrates can be fed at 0.5kg per 100kg live weight. Where grass supply is moderate or poor, as is likely on dry fields now burning up and into the slow declining quality of autumn grazings, feeding concentrates at 1kg per 100kg live weight is more likely to be required. The composition of the concentrate should be high in energy and moderate for protein, around 13-14% crude protein on a fresh basis is sufficient and no more than 0.5kg per 100kg live weight is fed in a single feed.

This article has been funded by the Farm Advisory Service.