Hugh Fearnley-Whittingstall has written a brilliant book called The River Cottage Meat Book which has loads of information about all the different types of meat and poultry, and there is a section on Suckler Herds. The following in an extract taken from this book, which we though summed things up quite nicely:

“Herds of cattle raised solely for beef are called suckler herds, because the calves are allowed to suckle their mothers, usually in an extensive grazing environment, for the first six to nine months of life. After weaning, they usually remain in family groups, grazing extensively throughout their lives (though some farmers will sell some of their weaned calves at about nine to twelve months as store cattle, to be finished on a more intensive system). Depending on the quality of the pasture, the breed in question, and the time of year they are sent to slaughter, suckler beef cattle may be finished exclusively on grass or with a supplementary feed of cereals and/or legumes (peas and beans), either indoors or out.

The best suckler herd beef cattle are traditionally fully matured animals of two to four years old. Since BSE, the legal maximum age for beef cattle has been thirty months, and the most conscientious beef breeders will take their steers as close to this as possible...

...There are some who will try to persuade you otherwise, but to my mind the best beef you can buy, not only in terms of eating quality but also as far as general welfare standards and traceability are concerned, will always be from a good suckler herd of a British beef breed. It’s hardly surprising when you consider that for centuries this has been precisely the intention of the enterprise.”

(Fearnley-Whittingstall H [2004] The River Cottage Meat Book Hodder & Stoughton pp 68-69)