By Mary Young, livestock nutritionist, SAC Consulting

Late summer the quantity and nutritional quality of grass begins to decline. Animal growth rate can start to decline on a grass only system (particularly if being set stocked), therefore, some supplementation may be necessary in order to maintain animal performance.

However, there is a careful balance as too much concentrate can cause animals to substitute this for grass, causing little improvement to performance. Be careful not to fall into the trap of using concentrates as a substitute for good grassland management.

The target sward height for growing/finishing cattle between August – September is 7-8cm on a set-stocked system. On a rotational grazing system, you should aim to have the cattle in at 10-15cm and out at 7-8cm. Monitoring sward heights is the key to ensuring there is sufficient grass and if there isn’t then adding concentrates may be worthwhile. On a well-managed system where grass is plentiful, store cattle can achieve at least 0.8kg/day, without supplementation.

Where grass supply is limited in autumn or during a dry spell, supplementing with concentrates should start at a low rate and built up to 2-3 kg depending on your growth targets. For finishing cattle that are gaining upwards of 1kg/day they will need supplemented now, in this scenario you may also want to consider finishing cattle inside. Another option if ground conditions are favourable is to introduce an ad lib hopper outside, on this kind of specialised system introduce feed slowly and make sure cattle are not introduced on an empty belly as they may gorge on feed resulting in acidosis. Care should be taken to balance the cereals with protein and minerals and starting with a digestible fibre feed (e.g. soya hulls or sugar beet pulp) will make it safer as cattle transition onto a high cereal-based ration. Having a ring feeder full of straw available is also advisable particularly if grass is poor or in wet weather. If you are unsure contact your nutritionist to look at the options available.

The concentrate should complement the grass and be high in energy and moderate for protein (13-14% fresh weight). If grass is plentiful then concentrate can supplemented at 0.5kg per 100kg liveweight but where grass supply in the autumn becomes poorer you may need to increase the level of supplementation to 1kg per 100kg liveweight. If higher levels are required, then housing stock may be a better option. You may find that native breeds, especially heifers can be finished on grass alone. However, they can still benefit from cereals such as barley in late summer as quantity of grass starts to decline.

There is no one size fits all option to maintaining cattle performance on grass, it depends on your system, the type of cattle, target growth rates and the growing season and grass available. Monitoring the grass in front of stock whether by using a plate meter, sward stick or welly boot is a vital management tool to let you plan and make decisions on how best to keep cattle thriving. Concentrates can be used as a tool to boost performance and production, but nothing beats good grassland management.

Mary Young, Livestock Nutritionist, SAC Consulting