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Minerals and other supplements
Published 1 February 10
As well as providing the right combination of energy, protein and fibre, dairy rations need to be well-balanced for a range of macro-minerals, trace elements and vitamins to support high levels of Performance. There are also a number of feed supplements promising a range of benefits from the provision of specific amino acids, protected fats and other digestive aids.
This Chapter will look at:
- Mineral and Vitamin Supplements
- Other Supplements
Although most fresh and conserved forages provide good levels of the most important minerals and vitamins, some feeds are naturally low in specific ingredients and may require supplementation in the ration.
Since compound feeds are generally well supplemented with minerals and trace elements, the many farms on which around 40% of energy intake comes from such feeds are unlikely to encounter deficiency problems.
While TMR-fed herds are theoretically more vulnerable to mineral induced problems, enough use is probably made of proprietary mineral mixes on most units for few difficulties to arise in practice. To avoid metabolic disorders like milk fever and hypomagnesaemia extra calcium (Ca), phosphorus (P) and magnesium (Mg) may be required at specific times.
Rather than avoiding deficiency problems, the main challenge with other major minerals like sodium (Na), potassium (K) and sulphur (S) is more often to avoid high levels or imbalances which may reduce the utilisation of other nutrients or induce metabolic disorders.
While many of the key trace elements - especially copper (Cu), cobalt (Co), selenium (Se), zinc (Zn) and iodine (I) - are likely to be adequately supplied in most diets, it is always advisable to check rations and balance them as required. Such checks are particularly important in areas with a history of trace element deficiency and where no specific veterinary measures are being taken to address the problem.
The combination of protein from feeds and microbial protein from the rumen will provide a perfectly adequate source of amino acids for most low and moderate yielding cows. Shortages of the essential amino acids lysine and methionine may, however, arise with high yielding cows. The relative expense of supplements providing these amino acids means they should only be used sparingly and limited to cows likely to show a performance response rather than fed across the whole herd.
As a rich source of energy, small quantities of fats or oils offer the opportunity to increase the energy density of rations markedly, providing they do not impair rumen efficiency by coating the fibre and restricting its fermentation. The solution offered by a number of supplements is to effectively protect the fat from breakdown either naturally or through some form of treatment. The value of such supplements depends upon the extent to which this protection is effective while still allowing the fats to be available for digestion in the omasum and small intestine. Again, the most cost-effective response is likely to be seen from high yielding cows in early lactation.
Commercial yeast products are claimed to improve performance by helping to stabilise rumen conditions and allow optimum fibre digestion. Although they may be beneficial in some feeding systems, it is difficult to independently quantify likely levels of response and so calculate whether inclusion is cost-effective. Introducing a yeast product for one month in a period when the milk output is expected to be stable would allow any response to be detected.
Bicarbonate of soda is an alkaline product which can be fed to help maintain rumen pH at levels for optimal fibre digestion in the rumen. Cows' tremendous rumen buffering ability - particularly through saliva production - means bicarbonate supplementation is likely to be unnecessary in most circumstances. However, in situations where the diet is very acidic by virtue of a high content of fermentable ingredients it can be valuable.