During drought cattle diets may be deficient in protein, energy and minerals. The extent of the deficiency of these nutrients depends on the severity of the drought, the fertility
of the soil, the nutrient requirements of various classes of cattle.
If supplementary feeding is considered necessary, the following points should be considered:
- energy content
- protein content
- type of supplement
- some common fodders
- other roughage
- chemical residues
- animal health
- handling and storage.
The energy content of a feed is referred to as metabolisable energy and is expressed as megajoules per kilogram (mj/kg) The available energy in the fodder depends chiefly on the dry matter content and the digestibility of the fodder. The available energy in fodders rises as the digestibility and dry matter content rises, for example 1 tonne sorghum is equivalent to about 10 tonnes of pumpkins on an as-fed basis.
Table 1 shows the comparative protein content and energy values of some common fodders on a dry matter basis, and on a 'fresh' (as-fed) basis together with the calcium and phosphorus content. The fresh basis figures will vary slightly as moisture content varies. However, the figures are adequate to compare feeds and their cost.
While energy is the critical nutrient for the survival of cattle during drought, the total supplement must have adequate protein and minerals for the most efficient use of the energy.
Pregnant, lactating and growing cattle will require a higher level of protein than other classes of cattle for tissue and milk production.
Grains and good quality hay generally have sufficient protein for survival feeding, whereas molasses will need to be fortified with urea and/or vegetable protein meal to lift the protein content.
Type of supplement
Seasonal nutritional deficiency supplements may be fed to overcome nutritional deficiencies that occur each enter/dry season. Supplements are generally fed at less than 1 kg / head for a long period, usually three to four months. They are usually less expensive, on a per head per day basis, than drought supplements.
Drought supplementation is generally when the producer decides that cattle are not to lose any more weight. This supplementation is usually not necessary until late in the dry season when paddock feed quantity and quality is at its lowest point. Drought supplements are generally fed at greater than 1 kg / head / day,for a shorter period than seasonal supplements such as commercial blocks, and are more costly on a per head per day basis.
Table 1 also shows the crude protein content and energy values of some common fodders.
|Fodder||Metabolisable energy content||Crude protein||Ca|
|dry matter basis (MJ per kg)||fresh basis (MJ per kg)||dry matter basis (%)||%||%|
|Good quality lucern hay||9.5||8.6||18.0||0.91||0.33|
|(paddock for comparison)|
* these feeds require additional protein.
Probably the most important consideration is cost. The landed cost on the property (purchase price plus freight), per kilogram of energy, is a convenient method of comparing fodders. It must be remembered that at the same landed price, highly digestible fodders (e.g. grain) are more valuable than fodders of low digestibility (e.g. coarse hay). Similarly, fodders with high dry matter contents (e.g. grain) are more valuable than fodders with low dry matter contents (e.g. pumpkins).
Drought fodders can be categorised as palatable and unpalatable. Wheat, sorghum, maize, molasses, cottonseed meal and good quality lucerne hay are palatable, whereas stubble hay and coarse grassy hay are much less palatable.
Problems likely to be encountered when feeding palatable fodders are cattle chasing vehicles carrying feed, cattle bossing each other and poor feed distribution among the cattle. Vehicle chasing leads to unnecessary waste of energy and sometimes mismothering of calves.
Poor distribution of fodder among cattle results in a big variation in body condition within the group. Dominant cattle will be in good condition and cattle low in the dominance ranking, which eat less fodder, will be in poor condition and could die. These problems can be minimised by dehorning, drafting according to size and condition, providing adequate trough space, feeding less frequently than might be anticipated, and by the addition of unpalatable ingredients to slow down the rate of feed intake (e.g. the addition of salt to a dry lick or urea to molasses).
The acceptance of unpalatable fodders can be improved by the addition of palatable ingredients such as grain, molasses and in some cases salt.
The information in Table 2 is a guide to the feed value of most common hays.
|- with nuts||very good||10||no|
|Soybean, some seed||good||10||no|
|Navy bean straw||poor||1-3||yes|
|- cut at flower||good||10||no|
|- cut when mature||fair||2-5||yes|
|Winter cereal stubble||fair||2-4||yes|
|Winter cereal hay||good||7-9||no|
|Native pasture (mature)||poor||2-4||yes|
Medium to high protein hays (6%+) can be fed at the rate of 1 to 2 kg /head / day when there is plenty of paddock feed available.
When paddock feed becomes scarce, feeding rates for maintenance are as shown in Table 3.
|Feed||Weaners||Pregnant breeders||Dry cattle|
|Early||Late||over 18 mths|
|Treated stubbles (sorghum, wheat or barley)||2.0||3.5||3.0-6.0||3.0|
Raising protein content of hay
The protein intake of cattle fed poor quality hay can be lifted by:
- feeding a protein supplement to the animal
- treating the hay 12-24 hours before feeding with the following mixture. Do not feed this mixture direct to any livestock.
- 9 kg urea
- 45 L water
- 18 kg (13 L) molasses.
One litre of this mixture contains 150 g urea, which is sufficient to treat a 20 kg bale.
To treat a bale, stand it on its side with cut ends upwards, cut the top string and pour the mixture evenly over the surface. Round bales can be treated by pumping the mixture into the bale with a spear.
While silage is a valuable form of roughage, there is no magic in the ensiling process. The resultant silage is only as good as the crop it was made from, unless other nutrients were added during the ensiling process.
When purchasing or feeding silage it is important to make allowances for the moisture content, which can vary from 30% to 70%. This means that if you are buying silage for $150/tonne with 50% moisture you are actually paying $300/tonne of dry matter. This is particularly important when carting silage long distances.
During times of drought a wide variety of roughage and crop residues are fed to livestock. The nutritive value of these feeds varies considerably, many are little better than fill. It is important to check the chemical residue status of these feeds before they are purchased.
It is not recommended to feed sugar cane tops to cattle.
As feed is often in short supply during times of drought, cattle often graze paddocks they would not normally graze or are fed crop residues that are not usually used. This can lead to an increase in the problem of chemical residues.
The following points may help to minimise the risk from chemical residues:
- Contamination can occur by using banned chemicals, by incorrect use of registered chemicals or by not observing correct withholding periods and export slaughter intervals. Use registered chemicals and veterinary drugs according to label instructions.
- Do not feed stubble or other residue from crops that have been grown on land previously treated with organochlorines.
- Feed stubble or other residue from crops treated with pesticides only after the withholding period has expired.
- Purchase fodder from a reputable source. If possible, obtain an enforceable guarantee that it is free from residues and/or a vendor declaration.
- Beware of grain storage facilities with concrete or earth bases, particularly those that have been treated with organochlorines. These areas may be a source of contamination.
- Clean up loads of grain containing a significant amount of dust. They may have very high levels of contamination.
- Do not hold cattle in yards treated for white ants, particularly where organochlorines have been used.
- Pay careful attention to disposal of old chemical containers and prevent cattle from entering disposal areas.
- If there is any doubt about the chemical status of feed or soil, have tests carried out before cattle are fed or grazed. Contaminated soil can cause residues in grazing cattle as the cattle will eat dust on plant material.
The fodder must not be toxic or harmful at the desired feeding levels. Table 4 shows some of the common health problems associated with feeding drought fodders, and the methods of minimising these problems.
|Grain poisoning (acidosis)||Introduce grain gradually, make changes gradually. Feed only survival levels unless a decision has been made to feedlot fatten. The addition of bentonite and sodium bicarbonate reduce acidosis. The order of safety with common grains is maize, sorghum, barley, wheat.|
|Urea poisoning||Introduce urea gradually. Mix urea thoroughly. Prevent rain water contamination. Feed safe levels of urea. Keep antidote (vinegar) on hand.|
|Plant poisoning||Avoid fodders containing poisonous contaminants.|
|Mouldy hay||Avoid feeding mouldy hay.|
|Digestive system obstructions||
Feeding whole vegetables can cause obstructions in the gut. It may be necessary to chop whole vegetables into pieces.|
Feeding scrub for prolonged periods gives rise to impaction of the digestive system with dry stems and leaves. This can cause a slowing of the digestion and sometimes a blockage. The problem can be minimised by feeding supplements such as molasses and by cutting more scrub thereby increasing the proportion of leaf to stem in the diet.
Baling twine and plastic bags, if left in the feeding area, can also cause gut obstructions.
|Gossypol poisoning||The feeding of high levels of whole cottonseed may cause toxicity. The general recommendation is not to feed more than 1% of body weight.|
|Pulpy kidney||Pulpy Kidney (enterotoxaemia) is often associated with drought feeding. Cattle should be vaccinated with 5-in-1 vaccine.|
|Pesticide residues||Extreme caution needs to be taken with `high risk' fodders. These are those fodders that have been grown where there is a history of pesticide use (especially organochlorines). The onus is on the vendor not to sell contaminated fodders.|
Botulism has been caused by the ingestion of fodders contaminated with dead birds and animals, or parts of dead birds and animals (for example, poultry, cane toads, rats, snakes). Care should be taken to avoid fodders likely to contain these contaminants.|
In high risk situations, animals should be vaccinated.
Handling and storage
High level feeding programs for large herds require the handling of a surprisingly large quantity of fodder. Bulk handling is the most convenient method of handling large quantities of fodder and is likely to be the method that will use the least amount of labour.
In the case of molasses, storage and handling is facilitated by the use of a large, centrally located, elevated storage tank and a smaller tank on a vehicle or trailer for paddock distribution.
Most fodders require that a realistic monetary value be added to the landed price for handling and storage.