For years now dairy cows have been growing in stature, however, according to Andy Dodd, AHDB Dairy Technical Manager, that trend needs to be arrested to ensure efficiency.

Mr Dodd explained that a maintenance value had been added into the most commonly used breeding indices to try and stop UK dairy cattle getting any bigger. In time the value should see fewer very large cows being bred.

While breeding indexes such as Profitable Lifetime Index (£PLI) and the Spring Calving Index (£SCI) have always included key traits such as fertility, longevity and production, maintenance has been a more recent addition. Using the genetics of the terminal sire it estimates the mature weight of the daughter compared to the average heifer, which means farmers should be looking for a negative result.

Mr Dodd said: "We don't necessarily need cow size to reduce, we just need them to stop getting bigger and bigger. The maintenance value will estimate how far above or below the average weight the daughter of the sire is likely to be, and to keep size at a reasonable levels we want farmers to select those which are likely to be lighter than average.

"Maintenance is really about efficiency. Historically farmers bred bigger animals to produce more milk, but we know smaller animals can produce just as much, so often bigger cows simply cost more to feed. There is also a concern on many farms about cows outgrowing the cubicles in both sheds and parlours and incurring extra costs there."

The same arguments apply to beef cows. To maximise profit, beef cows need to be smaller, eat less, live longer and be more fertile. The best performing beef herds have less forage costs per cow, less purchased feeds per cow and a higher stocking density of cows.

According to The John Nix Farm Management Pocketbook, the feeding of cows is expensive, particularly during the winter months. Whereas feed used by calves for growth or dairy cows for milk production generates a financial return, 70-75 per cent of the total energy consumed by a herd of beef cows is used for maintenance, which produces nothing -it simply maintains the cow's body condition. This maintenance requirement is significantly altered by a cow's mature size.

A large cow weighing about 700kg, as opposed to a medium sized cow of about 600kg, will require the energy equivalent of an additional 540kg of moderate quality silage over a 175-day winter housing period to meet maintenance requirements. In a 150 cow herd, this is an additional 12 acres of first cut silage, or 20 acres of second cut silage that is used only to maintain cows. In addition, as the size of the cow increases, so do protein requirements, increasing the possibility of having to supplementary feed cows to prevent loss of condition.

With the increasing cost of silage production, along with the high cost of supplementary feed, it is clear to see how excessively large beef cows could reduce stocking density and eat away at a herd's profit.

One definition of a biologically efficient cow is one that will produce the heaviest calf possible whilst requiring minimal inputs herself. Generally speaking, bigger beef cows are much less efficient than smaller ones.

Not so long ago it was fashionable to breed big cows because they bred calves that grew big and were worth more at slaughter. Things have changed, and demand from retailers is for smaller carcases that yield smaller cuts. Most meat companies have reduced their preferred carcase requirements from a maximum of 420kg to 380kg, and impose price penalties on overweight carcases.

Such a change in the market requirements has played into the hands of smaller, native beef breeds like the Aberdeen Angus.

Another of the advantages of such native breeds is that they tend to have shorter gestations than big, continental-types, and that is one of the reasons their calves are smaller. Small calves are preferable to big calves as cows find it easier to give birth to them, meaning the stockman doesn't have to assist with the calving.

Smaller, easier to maintain beef cows will be the future in a post-Brexit world where there will probably be a lot less support from the taxpayer.

Indeed, there may well be a rosy future for our hardy, native hill breeds like the Galloway, Highlander or Luing that can produce the finest beef with minimal inputs.