- ROUGHAGE FOODS – HAY
Average Composition %
- C.P. – 5.0
- T.D.N – .44
- D.C.P. – 1.5
- Fiber – 39
- Calcium – 0.25
- Phosphorus – 0.20
Veld hay is usually poor quality hay. Generally it is low in protein, high in fibre and low in phosphorus, and is also low in calcium and minerals other than silica. The average yield is about 1 ton per hectare. Its poor quality makes it an unsuitable feed for high-producing animals, particularly dairy cows. A common practice is to treat it with urea and molasses, which greatly increases its feed value and palatability. When so treated, it is very useful for over-wintering cattle and sheep on the veld.
|Early flowering (good quality)
|7 – 8
|3.5 – 4.0
|Very mature (poor quality)
|Lignification: the tendency of the stem of some kinds of grasses to become woody or to have the qualities of wood.
The nutritive value of hay is dependent on three main factors. Of these, the stage of growth at which the hay is cut is of the foremost importance. Very young herbage has the highest feed value regarding a dry matter, but the yield of nutrients per hectare should also be taken into account. In most instances, the yield of digestible protein per hectare rises to a maximum at early flowering, whilst the yield of T.D.N. per hectare peaks at seed-setting. To obtain a good product, without sacrificing too much quantity, cutting at the early flowering
stage is advocated. At this stage very little lignification has occurred. Therefore the hay constituents rapidly decline.
The nutritive value is affected to a small extent by the botanical composition of the herbage. For example, the improved pasture hay is usually superior to veld hay. However, the presence of a clover or legume in the mixture markedly improves the feed value, especially with respect to protein.
The third factor which affects hay quality is the losses incurred
during hay making and storage. For a considerable time after cutting, the living cells respire, oxidising carbohydrates to carbon dioxide and water. This loss has been estimated at between 5 and 10% of the original dry matter. If drying is rapid, death of the cells is hastened and so, in Southern Africa, the lower figure is more applicable. Mechanical losses have been estimated at 5 to 10%, but they may be considerably higher if the leaf becomes brittle and shatters easily. Hence, unless some care is taken, this loss in Southern Africa may be as high as 30%. Further, it involves a loss of the more nutritious
part of the plant. Leaching losses are variable and entirely dependent on the amount of rain falling on the crop during the hay-making. If subjected to heavy rain, almost all the soluble carbohydrate, protein and soluble minerals are lost. The other ‘climatic loss’, is due to bleaching which may cause an appreciable loss of carotene; 66% losses have been reported and may be higher if excessive bleaching occurs. Finally, losses occur in the stack or bale. These have been estimated at 5 to 10% but where moulding or overheating occurs this loss is greater due to a decrease in digestibility.
Legume hays are excellent roughages provided they are cut at the appropriate stage and made without appreciable rain spoilage and loss of leaf. The optimum stage of cutting is the early pod stage when the crop is one- third in flower. However, it appears that changes in the composition of many legumes, once they have reached hay-cutting stage, are relatively small. Hay made at the late stage will have slightly lower protein content and a higher fibre and lignin content, which will decrease its digestibility. On the other hand, certain legume hays, e.g. Jack bean and soybean, increase in digestible nutrient content as they mature because of the accumulation of oil in the seed. As mentioned earlier under Grass Hays, rain spoilage causes loss of soluble carbohydrate, protein and soluble minerals. Unfortunately, the loss of leaf from legume hay tends to be high in Southern Africa. The rapid drying conditions cause the leaf to lose water quickly and become brittle before the stem is sufficiently dry for the hay to be stacked or baled. Hence on collection of the hay, and later while feeding, the leaf shatters and a considerable amount is lost. The protein content of the leaf is approximately twice that of the stem and so the loss of protein may be considerable. A rough estimate indicates that it may be as high as 50%. Furthermore, the hay leaf is generally more nutritious and digestible than the stem. To summarise, legume hays, if well made, are rich in protein, calcium, carotene and vitamin D. They also have a high-fibre content. The following table gives their composition:
|Average Composition of Legume Hays
|Dolichos bean hay
Jack bean hay
Velvet bean hay
15 – 18
|Cut early (before flower)
Good Average Quality
Mature and stemmy
Lucerne hay possesses to a high degree the nutritive characteristics of legume forages. It is exceptionally rich in calcium with an average content of 1.50%. The average phosphorus content is 0.25%. Good Lucerne hay is unparalleled as roughage for dairy cattle, and for pigs not on pasture, it is especially valuable as a vitamin supplement.
- ROUGHAGE FOODS – SILAGE
Average Composition %
- Dry Matter – 20 – 25
- C.P. on a dry matter basis – 7
- D.C.P. on dry matter basis – 4
- T.D.N. on a dry matter basis – 50
The nutritive value of grass silage is dependent upon the composition of the original material and the losses incurred during the process of ensiling. Such losses consist of the initial respiration loss, those which result from the fermentation and the loss caused by wastage at the side and top, and through seepage from the silo. All of these may be considerable unless the silage is well made. For well-made grass silage, the loss of original dry matter and T.D.N. is approximately 25%. Poor quality silage frequently results from either under-consolidation when very young wet, high protein grass, with a low content of fermentable carbohydrate is ensiled. With under-consolidation, overheating of the silage mass occurs, leading to excessive destruction of carbohydrates and a marked reduction in the digestibility of the protein. Hence, overheated silages have a low nutritive value but are very palatable.
The other type of poor quality silage which is often made from young high-moisture grass is the result of a slow rate of fermentation and acidification due to insufficient fermentable carbohydrate in the ensiled material. Butyric acid-forming organisms predominate, very little heat is produced and considerable hydrolysis of proteins to ammonia occurs. The resultant under-heated, butyric-type silage has an unpleasant odour. It is very unpalatable and has a lowered feed value because of protein losses.
|Dry Matter %
In Southern Africa a small quantity of lucerne is ensiled. For this method of conservation the crop should not be cut too young (optimum the early flowering stages). It should be wilted a little and molasses maybe added to the material whilst ensiling. When it is well made, lucerne silage is excellent high-protein forage which is especially suited to dairy cows.
|Dry Matter %
Maize is an ideal silage crop. If the green forage is cut at the appropriate stage of growth, chopped into small pieces and packed well into a suitable silo, it almost always makes good silage. The material produces enough acid to keep the silage from spoiling. The yield of silage per hectare varies widely with the soil and season but is usually in the range of 25 to 30 tons per hectare.
The best silage is made from maize cut when the kernels have reached the dough stage of growth and most of the leaves are still green. If the process is delayed longer, the silage is less palatable and there is a risk that it may mould unless water is added whilst ensiling. On the other hand, if the crop is cut earlier, there is a loss of potential nutrients and a tendency to produce sour silage.
Maize silage is excellent forage for cattle and sheep. Care should be exercised in feeding it to sheep for they will only consume silage of good quality. It is too bulky and fibrous to be a suitable food for pigs and poultry but it has given satisfactory results when fed to breeding sows. For ruminants, it is generally fed in combination with hay or dry food where it gives the best results when fed with legume hay. If maize silage is the only roughage in a fattening ratio care should be taken to balance the ration with an adequate amount of protein supplement.
|Dry Matter %
The sorghums make good palatable silage if ensiled when the seeds are hard and ripe. If harvested at an earlier stage the silage will be sour and relatively low in feeding value. Sorghum silage is suitable for dairy cattle, beef cattle and sheep, but its value per ton is considerably less than good quality maize silage.
As stated earlier, this is because of the lower proportion of grain, a considerable percentage of which passes through cattle undigested. The average yield of green sorghum per hectare is usually higher than that of maize with 45 tons per hectare or more of cut material may be expected from a good crop.
3. DRIED GRASS
Dried lucerne is very similar to dried grass in nutritive value, but it invariably has a higher protein and fibre content. It is a common constituent of pig and poultry feeds, where it supplies appreciable amounts of carotene and also tends to give a ‘good colour’ to poultry products.
The artificial drying of grass, causing its rapid dehydration, almost completely eliminates the losses of dry matter which occur during ensiling and hay-making. Thus dried grass made from fertilized swards and cut at the appropriate time compares favourably with many concentrates. Since the cost of drying is high, the aim should always be to use good quality grass. By doing so, the product obtained will be rich in digestible protein, minerals and carotene, unless overheating has occurred during the process. On an average, one-third of the carotene is destroyed if overheating has occurred.
Dried grass has a dry matter content of 90%, with an average T.D.N. value of 70%, and the digestibility of its protein is 70%.