The mild, wet winter has encouraged grass to keep growing. That has been a bonus for sheep that has kept then in fine fettle, but winter grass is not nutritious enough for the growing needs of pregnant ewes, as it's mostly water. The growth of lamb foetuses is very rapid in the last eight weeks of pregnancy and puts an ever increasing nutritional strain on ewes.

Lean, undernourished ewes can become weak and have difficulty giving birth. Their lambs are often small and weak, and susceptible to hypothermia in cold, wet weather. The surface area of their skin is large in relation to their tiny body mass.

Worse, lean ewes may not have enough colostrum, that vital, highly nutritious first milk that gets the stomach working and passes on immunity to various diseases from the ewe to her new-born lamb. Even if a ewe manages to fill her lambs with colostrum, she may subsequently fail to produce enough milk to successfully rear them.

Ewes that have little or no milk invariably abandon lambs. That's Nature's way of ensuring that the ewe survives.

Lean ewes are also prone to illnesses like twin fever, or milk fever - two metabolic disorders that can be killers.

To avoid all those problems, it is important to introduce pregnant ewes to supplementary feed at this time of year.

I firmly believe in feeding sheep the best. Second-rate feed may be cheaper per tonne, but at the end of the day probably costs more per ewe. It may not be as digestible, palatable or nutritious. As a result, the sheep won't perform as well as if they had been fed better quality feed, or you will have to feed more to get the same results. Either way, cheap feed invariably proves that you get what you pay for.

Sheep and cattle are ruminants - which simply means they chew their cud. They have four stomachs instead of one like pigs, poultry and us.

The first stomach, or rumen, is a big fermentation bag where fibrous food such as grass, hay, silage or straw is partly broken down into a more digestible form by bacteria.

That more digestible food then passes through another two stomachs before entering the fourth one, which is a true stomach like ours.

So sheep and cattle nutrition is different from non-ruminants like pigs and poultry.

When feeding ruminants it's important to remember that those bacteria in the rumen also have to be fed. Keeping those bugs healthy and well-fed allows sheep and cattle to digest roughages like fodder and hill grass more efficiently.

The secret to success is to get a feed with a good balance of different protein sources, plenty of energy and the correct levels of minerals and vitamins.

Soy bean meal, rapeseed meal, dried grass, peas, or distillers' dried grains are all good sources of vegetable protein, while processed grains, vegetable oils and sugar beet pulp are all grand for energy.

Sheep and cattle may be greedy and constantly on the lookout for hay, silage and concentrated feed, but that isn't natural. Their natural diet is simply grass and we have to train them to eat man-made foodstuffs.

Most learn fairly quickly, but some never eat from a trough. That's quite rare in cattle, but not uncommon in sheep.

It's hard enough teaching sheep to eat concentrated feed when they are enclosed in fields, but on an open, unfenced hill, that task is a different one altogether. Unless they were trained in fields as lambs, pregnant hill ewes would need to be gathered every morning - time consuming and no easy task.

One way round the problem is feeding blocks, a self-feed system developed about 50 years ago where food is compressed by the manufacturer into hard, 20kg blocks of concentrated feed. Those blocks are then left at strategic points on the hill, where sheep are most likely to find them. To prevent greedy sheep from scoffing too much, certain unpalatable ingredients such as urea are included.

Block feeding is not only convenient for shepherd and sheep, it can also be good for hill grazing management. Once ewes have learned to nibble blocks, they will seek them out. Placing them on under-grazed areas attracts them away from over-grazed parts.

Unfortunately it's not always possible to ensure only sheep enjoy blocks. Scotland's hills and glens are full of hungry red deer that are also partial to nibbling at them.