Dairy cows have to calve every 12 months or so in order to maintain milk production. The snag with that is that, while half of those calves are valuable heifers that will go on to become replacements for the milking herd, the other half are bulls.

At one time the national dairy herd was mostly British Friesians that were big, sturdy cattle that produced bull calves capable of growing into reasonable beef animals. Sadly, the drive towards higher yields encouraged farmers to switch to more extreme dairy-type Holstein Friesians that are thinner, "scrawny" looking animals, that produce bull calves with limited beef potential.

It's not that beef from such animals doesn't taste good, but rather that the yield of beef from their carcases is much less than that from a beef-type animal. That's reflected in the prices paid for Holstein Friesian, or Black & White (B&W) bullocks as they are generically called.

A typical prime, beef-type bullock might sell at auction for around 220p per kg of live-weight, while a B&W will probably only fetch about 145p. That price differential makes it very difficult to make a profit from rearing and fattening B&W bull calves, particularly when beef prices are depressed at a time when feed is expensive. Sadly, the end result is that many B&W bull calves are virtually worthless and put down at birth.

About 30 months ago when prices of milk were high and dairy farmers were making good profits, they were keen to breed more heifer replacements to expand production. That led to more B&W cattle being bred pure rather than crossed with beef bulls, and the end result was more B&W bull calves being born.

As is the way with farming, nothing stays the same, and a global glut of milk led to dramatic reductions in the price paid by processors.

Milk surplus to the requirement of processors that is traded on the spot market fell to such low prices that some introduced an "AB" pricing system. That's where the farmer is paid the full liquid price for a pre-determined amount, and anything supplied over and above that amount is paid at a much lower price based on the spot price. At one stage the B price was nearly half the A price, which itself was below the cost of production.

Farmers aren't stupid, and rather than more-or-less give milk away, decided to use it to cheaply rear those unwanted bull calves in the hope of generating additional, badly-needed income from them.

There are basically two ways of turning B&W bull calves into beef. The first, more traditional method, is to castrate them and rear them as bullocks along with the heifers, turn them out to grass for a season to allow them to cheaply grow bigger, before bringing them indoors for a period of fattening at 18-months to 2-years of age.

The key to success is to keep a tight control of costs - particularly feed. One way of reducing feed costs in the fattening period is to feed cheap root vegetables like potatoes, turnips, carrots and parsnips that have been rejected by supermarkets, as well as cabbages and sprouts.

In addition, there are things like waste bread that is delivered in bulk lorry loads.

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 in cattle rations.

Another method of rearing B&W bull calves for beef is not to castrate them, but to rear them intensively, indoors as bull beef for slaughter at around 12-months of age, when they weigh about 500kg live-weight and yield carcases of about 265kg. Again the key to success is to strictly control costs, with the big advantage of the system being that the calves were virtually worthless and the milk that reared them was of little value.

Dairy breeds like our traditional Ayrshires don't grow fast enough or big enough to be profitable under a bull beef system, but some canny producers are rearing them in batches in straw-bedded pens for slaughter at just over 8 months of age as rose veal. - pink-fleshed, tender meat.

That's much more welfare-friendly than the system of rearing veal calves in individual crates that has been banned across the EU since January 2007.