The old saying "down corn, up horn" refers to the fact that the price of cattle tends to rise in those years when the price of grain is depressed. Traditionally when grain is cheap farmers convert it into expensive beef by buying half-grown, or store cattle as we call them, to fatten - bidding the price of them up.

Unfortunately, with money tight on most farms, and good store cattle already averaging about £1000 per head and more, that isn't happening to the same extent this autumn.

An alternative and cheaper source of cattle and sheep to fatten can be found in the "rough ring". That's where cull, or "cast" as we call them, cattle and sheep are sold.

Cast animals are those breeding cattle and sheep that are no longer suitable for breeding. They may have become too old, lost their teeth, have diseased udders that prevent them from producing enough milk, or they may be barren or infertile.

Cast cows and bulls are an important source of manufacturing beef that is made into pies, tinned stews, soups, burgers and the cheaper, dark-coloured mince found on supermarket shelves. In France, well-hung cow beef is regarded as a flavoursome delicacy.

Older culls may not be as valuable as prime beef, which, as the name implies are cattle slaughtered in their prime, but cast cattle are still an important source of income to those farmers who take care not to dispose of them as a by-product but sell them to best advantage.

Indeed, some astute beef finishers are buying cheap cull cows for further fattening instead of expensive store cattle. Much of Scotland's beef herd calves in the spring and is weaned, or speaned as we call it, in October, and that is when a lot of cows are pregnancy tested. Those that turn out to be barren - and there will be more than usual this year as a result of the dreadful summer - are usually sold in the rough ring rather than waste precious winter feed keeping them on.

Provided they are in good health and not too old, beef cows, particularly those off a poorer upland farm that have spent the summer rearing a calf, have the potential for substantial daily live-weight gains as a result for their capacity to eat lots of food. Daily gains are highest for lean cows where most of the gain consists of lean tissue rather than fat.

Although there are a lot of cows being sold in rough rings around Scotland just now, it would be time consuming for a farmer to go round them buying his requirements. That's best left to a cattle dealer who will source them for a modest fee.

As with prime cattle, there is no need to base the fattening ration of cull cows solely on feed grains like barley, as there are a number of cheaper alternatives for the canny fattener.

The first that springs to mind are stock-feed potatoes which are those rejected by supermarkets, or simply surplus when the market is oversupplied. That happened in late spring and early summer when some potato growers were almost giving away unwanted potatoes. Astute feeders acquired them for the cost of the haulage and mixed them with draff (the mash left behind in the brewing process that can also be a cheap feed) to ensile in their silage pits. That way the mixture was pickled and preserved in much the same way as grass is in the silage fermentation process.

Other cheap, waste root vegetables suitable for cattle feed regularly rejected by supermarkets include turnips, carrots and parsnips as well as cabbages and sprouts.

In addition, cattle feeders can also buy waste bread and confectionery waste such as broken-biscuits that are both delivered in bulk lorry loads, although biscuit-meal is currently more expensive than feed barley.

Surplus, unsold bread from bakeries and retail outlets is sent to a facility that removes the packaging before delivering it to farms. Such loads can also contain a proportion of buns, cakes and muffins that all help to make it a high-energy feed suitable for incorporating into cattle rations. Indeed cattle rumens (the first of their four stomachs) can digest bakery products more efficiently than cereals like barley because they have been baked.

The secret to success are the modern cattle feeders that mechanically mix ingredients like silage, roots, bread, grain and straw into a TMR (Total Mix Ration).