Salt lick is usually given to ruminant animals to supplement for essential minerals needed by their body.
Most of the feeds being consumed by ruminants do lack certain minerals especially those that are fed solely on grasses. It is therefore necessary that they are supplied these minerals through salt lick.
Which one is better to use as salt lick: iodized salt or compact mineralized salt lick? The truth of the matter is that most compact mineralized salt lick contains more than sodium and chlorine (sodium chloride) whereas it is only sodium chloride that is contained in iodized salt.
So in my own opinion, I will prefer the use of mineralized salt lick for them. In fact it is less cumbersome to use mineralized salt lick than iodized salt. It can be placed in their feeding trough from where they can be able to lick it.
With regards to how often the salt lick should be used for the animals, as good as the salt lick is for the animals, it is not expected to be administered daily to the animals.
I do recommend once a week for those using iodized salt whereas for those using solid mineralized salt, daily licking is okay for them as the quantity licked at a time cannot be too much for them.
Definition of Salt Lick (Mineral Lick)
A mineral lick (also known as a salt lick) is a place where animals can go to lick essential mineral nutrients from a deposit of salts and other minerals. Mineral licks can be naturally occurring or artificial (such as blocks of salt that farmers place in pastures for livestock to lick).
Natural licks are common, and they provide essential elements such as phosphorus and the biometals (sodium, calcium, iron, zinc, and trace elements) required in the springtime for bone, muscle and other growth in deer and other wildlife, such as moose, elephants, tapirs, cattle, woodchucks, domestic sheep, fox squirrels, mountain goats and porcupines.
Such licks are especially important in ecosystems with poor general availability of nutrients. Harsh weather exposes salty mineral deposits that draw animals from miles away for a taste of needed nutrients. It is thought that certain fauna can detect calcium in salt licks.
How useful are blocks and dry licks for livestock in a drought?
Use of licks for grazing livestock is still a relatively common practice, but how much benefit do ruminant animals really derive from their use? Several reasons are commonly cited for their use:
- Animals need salt.
- Stock are licking patches of soil, so they must be lacking in something.
- There is a need to provide extra vitamins and minerals.
- Licks help prevent specific diseases and conditions in the animals.
- Animals will eat what they need.
- Licks provide energy and protein.
Usually, either these reasons are not valid at all, or there are far more efficient ways of achieving improvements in animal health and performance than by providing blocks or licks.
The need for salt
Only when ruminant animals are under full hand feeding with high levels of grain will they require supplementary salt in their diet. Under these circumstances it is far better and more efficient to simply add 0.5% of fine salt to the feed than it is to provide salt blocks. Since stock actually like the taste, salt is also often used in feed mixes to improve palatability.
Stock licking soils
Stock will sometimes acquire cravings for certain flavours and it is certainly not uncommon for them to lick soil along creeks and dam banks. Also, stock will usually readily eat salt whether they need it or not. Taken on the balance of evidence, it is unlikely that the behaviour of stock is a good indicator of their need for extra nutritional supplements.
Stock will even readily eat substances that are detrimental to their health; the grazing of poisonous plants is a good example of this. As a livestock manager you should always ensure that animals have adequate energy, protein and good quality water before looking to finetune their diet with added minerals and vitamins.
Which minerals and vitamins do ruminants really need?
It is suggested that as many as 40 mineral elements may have some role in animal metabolism. However, only seven of these are required in quantities sufficient to be considered major essential elements. These are calcium, phosphorus, potassium, sodium, chlorine, sulfur and magnesium. The more important minor mineral elements include iron, iodine, copper, manganese, zinc, cobalt, selenium and chromium.
While these elements may be essential, it is also true that they are only required in minute quantities. In typical ruminant feeds and pastures, most minerals are present in sufficient quantities to supply the needs of stock.
Under dry or drought conditions, calcium and sodium deficiencies are the most common. These are most likely to occur in diets based on cereal grains. In this case it is far more efficient to add lime and salt to the feed ration than it is to allow free access to licks. When added to the ration, animals will consume the additional minerals they need in proportion to the feed they eat.
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Deficiencies in phosphorus are common on red soil scrub country in the Western Division of NSW
Under these circumstances a dry lick or block lick formulated from safe phosphorous sources remains the most practical solution to phosphorus deficiencies in stock (see Primefact 273 Making your own protein blocks for cattle).
Sulfur deficiencies often occur in cattle grazing forage sorghum and Sudan grass crosses. Sulfur supplementation has been shown to improve cattle performance by up to 40% when grazing Sudax. Access to salt blocks containing at least 8% sulfur should alleviate deficiencies in cattle grazing these crops.
Magnesium and selenium deficiencies
Other common deficiencies specific to certain environments and seasonal conditions include those of magnesium and selenium. A magnesium deficiency leads to grass tetany, and a selenium deficiency leads to white muscle disease.
Both problems need to be treated with specific supplements to ensure uniform treatment. Selenium deficiency is often treated with ‘bullets’ placed in the rumen, or by specially formulated selenium drenches.
Overdosing with minerals such as selenium, zinc, manganese, iodine, copper, molybdenum and cobalt can have toxic effects. For this reason voluntary-intake licks and blocks often contain very low levels of these elements to ensure that these toxic effects will be avoided even if animals gorge themselves.
Unfortunately this means that typical dosage rates will be below required levels if the element is deficient in the paddock feed. It is invariably better to treat animals for the specific deficiency than to try to treat them with a ‘shotgun’ approach.
Unlike minerals, vitamins are organic compounds. They are required by animals for normal growth and maintenance. Animals’ vitamin requirements are very small, and vitamins or their precursors (provitamins) are relatively widespread in pasture, cereal grains and other feed supplements.
Vitamins are generally unstable compounds which are easily oxidised, so their inclusion in blocks and licks is not really an ideal method of supplementation.
Two vitamins that may become deficient in drought circumstances are vitamins A and E. It is far better to treat these deficiencies with drenches or injectable preparations that supply sufficient levels to last stock up to 6 months.
Animals will eat what they need
The use of ‘free choice’ supplements to enable animals to select what they need presupposes some level of ‘nutritional wisdom’ on the part of the animals.
While there is some evidence that, given the choice, animals will select a diet that is balanced for protein and energy, the same cannot be said for mineral and vitamin supplements. It is highly unlikely that animals will freely choose the correct type and quantity of supplement to ensure a balanced intake of these micronutrients.
Prevention of diseases
It is often suggested that calcium blocks and licks be used to try to offset the effects of metabolic disorders such as pregnancy toxaemia and milk fever. There is often confusion about the causes of these diseases.
Pregnancy toxaemia (hypoglycaemia) occurs due to a lack of dietary energy in heavily pregnant ewes. This causes the animal to mobilise body reserves too quickly, causing a build-up in ketones that causes damage to the brain and nervous system.
On a flock scale, the only cure for this disease is providing feed of adequate quantity and quality no amount of blocks or licks in the paddock can alleviate this problem.
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Milk fever (hypocalcaemia) is the manifestation of low blood-calcium levels, but this is often not the result of a diet low in calcium. Many interactions occur between mineral elements in the metabolism of animals, and the most obvious solution is often not appropriate.
Hypocalcaemia is often related to intake of high-oxalate plants such as sorrel and oxalis, but may also be related to grass tetany and low magnesium levels. Dietary intake of calcium can be a factor in animals fed cereal grain diets; in this case, ground limestone should be added to the grain at 1.5% w/w.
On lush green grass pastures and cereal crops, it would be more beneficial to supply extra roughage than to supply a calcium block. (For more information on cattle health issues in a drought, refer to Primefact 333 Preventing animal health problems during drought.)
Provision of energy and protein
The key dietary elements for ruminant animals are energy and protein. For most efficient use, these must be in balance. Blocks and licks do not provide appreciable levels of energy to animals. The majority of the block make-up contains no energyat all.
If the principal deficiency in the diet of animals is energy, then provision of blocks or dry licks will serve little purpose and will add considerable expense. Blocks that contain urea and protein meals do provide a source of protein for livestock grazing protein-deficient dry pastures.
However, proprietary blocks are not usually the most cost-effective way of supplying supplementary protein to grazing animals. Based on their ‘cost per kilogram protein’ value, blocks are typically 2.5 times the cost of lupins
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