DIETARY COMPONENTS

THE nutrient content of dry matter is assessed in terms of its crude protein (CP), crude fibre (CF) and metabolisable energy (ME). Metabolisable energy is energy from feed that an animal can convert into live weight gain, milk and wool. Energy that is not converted as above may be lost as: Undigested material in faeces Production of urine Formation of methane gas Production of heat

The diet of every animal will differ depending on many factors including type, age, sex and growth stage. Some of the options available to the farmer include the following:

COLOSTRUM

Feeding colostrum in the first few days of life is highly beneficial to the new-born animal. Colostrum or ‘biestings’ is the first of the mother’s milk and as well as being highly nutritious in terms of vitamins and mineral content, it has other benefits:

It stimulates bowel movements with the expulsion of meconium — ‘the first faeces’, which cleans out the digestive tract.

It contributes to the immunity of the animal as it contains antibodies, which help to fight infection.

It has a warming effect which is important for animals born outdoors, especially for lambs which are susceptible to lamb-chill.

MILK REPLACER

A formula of dried milk that may be used for up to three to four months, depending on the ease at which the animal is weaned onto meal.

BULKY FOODS

Provide the bulk of the diet of ruminant animals such as cows and sheep, these foods are rich in water and/or cellulose which ruminants can digest. Water prevents dehydration, while fibre prevents constipation. Examples of bulky foods include:

Fresh grass: The cheapest form of food available to the farmer, but for maximum nutritive value to be gained, desirable species and an efficient grazing system is essential. Ryegrass dominated swards, grazed rotationally, provide a fully balanced complete feed, capable of supporting high levels of production.

Silage/hay: Two forms of grass conservation, which differ in their biochemistry — dehydration in the case of hay and fermentation in the case of silage. The nutritive value of each depends on many factors, including growth stage at cutting and preservation technique. In general, good quality silage is considered to have a higher nutritive value however than hay. Haylage is grass cut just like hay, but it is baled when the moisture content is still relatively high. Maize silage is a popular alternative to grass silage as a feed while maize straw can be used for bedding.

Root crops: Although they compare favourably with grass in terms of energy content, root crops are low in protein and are labour intensive unless grazed in situ, for example turnips for feeding sheep.

Forage crops: Rape and kale are high in protein, unlike other forage crops but their intake should be limited as excess amounts may interfere with the utilisation of iodine through the production of goitrogens. An iodised mineral supplement may be included in the diet to counteract this.

CONCENTRATES

These form an essential part of the diet of non-ruminants such as pigs which cannot digest any significant amounts of fibrous material and examples. As concentrates are high in dry matter, they are a high energy food. In addition, low dry-matter diets can lead to loose dung and the build-up of dung on the hide of the animal which may contribute to the spread of disease. Examples of concentrates include the following:

Cereal grains and cereal grain by-products: Used widely as sources of energy, the structure of the cereal grain makes it somewhat difficult to digest, particularly in the case of barley and oats. The presence of a tough fibrous coat inhibits the digestive juices from reaching the starchy interior. As a result, two processes ie rolling (which flattens the grain and breaks the fibrous coat) and grinding (which crushes the grain), greatly improve the digestibility of cereal grains. Cereal grain by-products such as bran and pollard are also used in animal feed.

Molasses: A thick, black liquid, molasses is a by-product of sugar beet production. Its sticky texture makes it suitable for pelleting animal feeds. In addition, its sweetness improves the palatability of the feed and it is often used as an additive in silage-making. A second by-product of sugar beet production known as beet pulp is similar in nutritive value to barley and is fed to cattle and sheep. Its high crude fibre content makes it unsuitable for feed to non-ruminants such as pigs.

Animal products: Meat and bone meal, and fish meal contain large amounts of protein, including essential amino acids which must be provided in the diet of pigs and poultry.