CATTLE

CPD article

Mineral nutrition of lactating

dairy cattle
Accurate mineral supplementation for all categories of stock on a dairy unit is essential for optimal health and
productivity and to prevent toxicity from over-supplementation. This article will review the current recommendations
on mineral supply for the lactating dairy herd with practical advice on supplementation strategies and outline the
role which the practitioner can play in ensuring accurate supplementation in their client’s herds. 10.12968/live.2017.22.4.178

Julia Moorhouse BVM&S CertCHP MRCVS, Veterinary Nutrition Consultant, Evidence Group, Redhills, Penrith, Cumbria,
CA11 0DT

Key words: dairy | mineral | nutrition | macro-mineral | trace element | supplementation

I
n recent years, greater attention has been focused on excess
mineral supplementation in dairy herds, primarily due the Table 1. Macro-mineral requirements for
increase in diagnoses of copper toxicity (Bone et al, 2011). the lactating dairy cow
However, both over and under supplementation of minerals Macro-mineral Total daily require- Reference
on UK dairy units remains commonplace (Moorhouse, 2015). Ex- ment (% of dry
cessive supplementation is most common, with 88% of farms over matter)
supplementing phosphorus, 78% feeding excessive copper and Calcium (Ca) 0.7–0.8% NRC, 2001
selenium and all farms studied supplying excessive levels of io- Phosphorus (P) 0.32–0.42% NRC, 2001
dine (Moorhouse, 2015). The responsibility for ensuring accurate
Sodium (Na) >0.2% NRC, 2001
mineral supplementation lies with the herd owner. However, the
veterinary practitioner is well placed to coordinate this process, Magnesium (Mg) 0.25–0.3% Schonewille et al,
2008
particularly in herds that do not employ a nutritionist. The veteri-
nary practice also has a responsibility to ensure accurate mineral Potassium (K) 1.5% NRC, 2001
nutrition in cases where they are selling mineral supplements.
The macro-minerals are those for which the animal has a re-
quirement in grams per day, whereas the micro-minerals or trace Table 2. Trace Element requirements for
elements are required in smaller quantities. Daily macro-mineral the lactating dairy cow
requirements are commonly expressed as a percentage of the dry Trace Element Total daily require- Reference(s)
matter intake (DMI), which therefore takes into account produc- ment (mg/kg DM)
tion level. Trace element requirements are usually expressed as mil- Copper 13 Sinclair and Mac-
ligrams per kilogram of dry matter (mg/kg DM). Current macro- Kenzie, 2013
mineral and trace element requirements for lactating dairy cattle
Cobalt 0.2–0.35 NRC, 2001; Overton
are outlined in Tables 1 and 2. It is essential that those involved in et al, 2016
reviewing mineral supplementation on farms keep up to date with
Selenium 0.3 NRC, 2001
current relevant recommendations as research in this field is ongo-
ing. A review of the nutrient requirements of dairy cattle (NRC, Iodine 0.6–0.9 NRC, 2001; Overton
et al, 2016
2001) is currently taking place and is due for release in 2017.
Zinc 60–80 Overton et al, 2016
Macro-minerals Manganese 40–50 Weiss and Socha,
Calcium 2005
Calcium is the most common mineral in the body, with 99%
© 2017 MA Healthcare Ltd

stored in bone (Suttle, 2010). It has roles in blood clotting, mus- between 3–8 g/kg DM (McDonald, 2011), whereas maize silage
cle contraction and transmission of nerve impulses (Suttle, 2010). content is generally low averaging 1.4–3.0 g/kg DM (Suttle, 2010).
Lactational hypocalcaemia can be seen if calcium levels are inade- Forage legumes and brassicas have a higher calcium content; lu-
quate, particularly if magnesium supply is also deficient. Grass and cerne = 21.9 g/kg DM, kale = 21 g/kg DM (McDonald, 2011).
grass silage have a high calcium content; UK grass silages average Maize silage based rations therefore require greater levels of sup-

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plementation. Additional calcium is usually supplied as calcium However, if other sodium salts are used, additional chloride may
carbonate either within a mineral supplement or added separately be required (NRC, 2001). Further research is required to establish
to the ration. recommendations for chloride requirements in dairy cattle.

Phosphorus Magnesium
The second most abundant mineral in the body is phosphorus, Of the body’s magnesium 60–70% is locked up in bone but it is
with the majority stored in bone and teeth (Suttle, 2010). Its pri- also one of the most abundant minerals within soft tissues (Suttle,
mary role is in the formation and remodelling of bone, but it also 2010). Magnesium is absorbed from the rumen by a combination
has essential functions in a range of other areas. These include of passive and active transport mechanisms (Suttle, 2010). Magne-
roles in nerve myelination, energy transfer via ADP and ATP and sium is essential for a wide range of enzymatic functions including
as a component of deoxy- and ribonucleic acids (Suttle, 2010). the formation of ATP. It also plays an important role in muscle
Phosphorus is expensive to supplement and reduction in the in- contraction, cell membrane integrity, nerve impulse transmission
clusion in mineral supplements represents an opportunity for cost and is present in red blood cells (Suttle, 2010). The magnesium
savings on many UK dairy units. Mild phosphorus deficiency can content of forages varies with plant species and season and when
cause reduced yield and fertility. There are high levels of phospho- concurrent changes in potassium content occur this can lead to a
rus in cereals and rape, therefore diets with a high inclusion of high risk of grass tetany (Suttle, 2010). Magnesium content in pas-
these raw materials will require minimal supplementation. Rumi- tures is low in the spring when potassium content is high, particu-
nants are able to utilise phosphorus present in grains as phytates larly in heavily fertilised pastures, resulting is a high risk of clinical
due to the presence of phytase in the rumen (Suttle, 2010). Ru- hypomagnesaemia. Legume silages, e.g. lucerne and clover, have
minants will selectively graze phosphorus rich swards (Jones and a greater magnesium content than grass silages (Suttle, 2010).
Betteridge, 1994). Considerable recycling of phosphorus occurs, Absorption of magnesium is inversely correlated with the potas-
with secretion of large quantities in the saliva which flows into the sium content of the diet, with the interaction being dependent on
rumen and is subsequently absorbed. Excess phosphorus is excret- diet type. In cattle the absorption coefficient, at a given potassium
ed in the urine and faeces and can leach into water courses where content, is reduced when feeding a forage plus concentrate diet
it causes eutrophication and algal blooms. Over supplementation compared with feeding forage alone (Suttle, 2010). To maintain
of phosphorus is therefore both costly to the farmer and to the magnesium absorption, an increase in magnesium supply of 4 g
environment. Recent research has suggested that the recommen- per day is required when dietary potassium intake increases by 10
dations for phosphorus requirements, particularly in high yielding g/kg DM (Schonewille et al, 2008).
dairy cattle, should be reduced (Valk and Beynen, 2003). No ben- Magnesium salts used as supplements vary in their magne-
efit on lactational performance has been found from increasing sium content and availability. Magnesium oxide (calcined mag-
dietary phosphorus content above 0.42% DM (NRC, 2001). Sup- nesite), has the highest magnesium content (approximately 50%
plementation is usually in the form of di-calcium phosphate, but Mg), but variable availability. Absorbability varies with origin,
mono-sodium phosphate and mono-calcium phosphate which particle size and processing temperature with coarse particle size
have a higher solubility can also be used. and low temperature leading to low apparent absorption (Adam,
1996). Magnesium chloride and magnesium sulphate have a
Sodium and chloride lower magnesium content but may have higher availability com-
Sodium and chloride are essential for the maintenance of blood pared with magnesium oxide. Excess supplementation of mag-
and body fluid volume and control of acid–base balance (Suttle, nesium is unpalatable.
2010). They have roles in nerve impulse transmission and the ab-
sorption of nutrients. Addition of salt (sodium chloride), to a ra- Potassium
tion improves the palatability of the diet. Salt is commonly offered UK rations usually contain sufficient potassium as it is abundant
to cattle as free access rock salt blocks. When sodium or chloride in common feed ingredients and readily absorbed (Suttle, 2010).
levels are low, cattle may drink urine or lick inanimate objects During heat stress, additional potassium may be required to com-
(Suttle, 2010). Forages generally have a low sodium content and a pensate for the reduction in DMI, losses through sweating and for
higher chloride content (Suttle, 2010). The majority of grain and maintenance of acid–base balance (NRC, 2001).
plant protein sources have a low sodium content (with the excep-
tion of sunflower), whereas root crops have a high sodium content Trace elements
(Suttle, 2010). Spring grazing is often deficient in sodium, particu- Current recommendations for trace element requirements for lac-
larly when high levels of potassium fertiliser have been applied. tating dairy cattle are outlined in Table 2.
Drinking water is highly variable in sodium content but can be Trace elements have a wide range of role within the body in-
a valuable source of the mineral. Recommendations for sodium cluding cellular protection, antioxidant effects (e.g. copper and
© 2017 MA Healthcare Ltd

inclusion in dairy cow diets in the US are much higher than those selenium) and synthesis of enzymes, hormones and vitamins (e.g.
in the UK (usually 0.5–0.6% DM). An increase in inclusion has cobalt). Full discussion of their individual function is beyond the
been recommended in hot weather in the UK, but requires ex- scope of this article. Deficiencies of trace elements in lactating
cellent water availability. When sodium chloride is used to meet dairy cows are uncommon but toxicity is increasing, particularly
sodium requirements, the chloride requirement will also be met. copper toxicity (Bone et al, 2011).

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Copper Where selenium supplementation is necessary, it can be in-

The primary function of copper is its role as a component or activator corporated into in feed minerals as sodium selenite. In ruminants
of numerous enzymes, co-factors and proteins (Suttle, 2010). Cop- there is little difference between organic and inorganic supple-
per deficiency can be either primary (low copper supply) or second- ments because the inorganic selenium is incorporated into se-
ary, due to a high level of copper antagonists in the diet (primarily lenoamino acids in the rumen (in the same way as it is in yeast
molybdenum, sulphur, iron and zinc). Molybdenum rich swards (>2 cultures) (Suttle, 2010). Both sources are equally effective in pre-
mg/kg DM) are rare, occurring in discrete geographical areas (Suttle, venting the symptoms of deficiency (Suttle, 2010). Selenium is the
2010). Therefore a total diet containing high levels of molybdenum most toxic of the essential trace minerals and care must be taken
overall (when diluted with other diet components) is very rare. Even to ensure accurate supplementation to avoid toxicity.
in these circumstances, when copper availability is poor a lactating
dairy cow (yielding 40 litres milk) will require only 20.8 mg/kg DM Iodine
copper in the diet (Suttle, 2010). For this reason a maximum total Iodine is required for the production of thyroid hormones which
dietary inclusion of copper of 20 mg/kg DM (Bone et al, 2011) has regulate energy metabolism. Thyroxine production increases dur-
been recommended. The total dietary content of copper should only ing lactation and iodine requirement increases accordingly (NRC,
exceed this with agreement from all parties involved — this includes 2001). Iodine deficiency can be primary or secondary (when high
the practising veterinary surgeon. However, this figure far exceeds levels of goitrogens are present in the diet, e.g. brassicas). Cyano-
the requirements of lactating dairy cattle in most circumstances with genic goitrogens, found in, for example, beet pulp and white clover,
13 mg/kg DM being the requirement to maintain liver copper stores interfere with iodine uptake by the thyroid gland. Their effects can
(Sinclair and MacKenzie, 2013). Diets should therefore be formulated be easily overcome by increasing dietary iodine supply and a safety
to meet requirements not to exceed requirements. In the absence of factor to account for commonly used sources is used in the recom-
significant levels of antagonists, which is the case for most of the UK, mendations (NRC, 2001). Pro-goitrins and goitrins, found in kale,
copper will accumulate in the liver when feeding 16–17 mg/kg DM cabbages and turnips, inhibit hormone synthesis. Their action is
total dietary copper (Sinclair et al, 2013). Jersey cattle appear to be not easily overcome by increasing iodine intake and therefore their
more susceptible to copper toxicity than Holstein cattle (NRC, 2001). inclusion in rations should be minimised or avoided (NRC, 2001).
Copper content of pasture and forage is variable, depending on Iodine deficiency causes weak or stillborn calves, reduced fertility
plant species, maturity, soil conditions and fertiliser used (Suttle, and impaired growth. Iodine toxicity has been reported at levels as
2010). Generally, grass species have a lower copper content than low as 5 mg/kg DM, with symptoms including salivation, increased
legumes (Suttle, 2010). Distillery by-products (for example, dried nasal discharge and reduced milk production. Excess iodine is ex-
distillers’ grains or pot ale syrup) can be high in copper (Suttle, creted in milk and is a public health concern because humans are
2010). When copper supplementation is assessed as being neces- more susceptible to iodine toxicity than cattle.
sary, additional copper can be supplied by incorporating copper
sulphate into an in-feed mineral supplement. No advantage has Zinc
been demonstrated in using other copper salts or rumen protected Zinc is essential for the structure and function of a huge number
sources of copper (Suttle, 2010). of metalloenzymes and functional proteins with a wide range of
function within the body. Those of greatest importance in terms
Cobalt of health and production are those with roles in gene expression,
Cobalt is required for the synthesis of vitamin B12 in the rumen. appetite control, fat absorption and antioxidant defence (Suttle,
Rumen microbes will rapidly show signs of deficiency by reducing 2010). This leads to abnormalities in skin, hair and hooves, ano-
propionate production. The symptoms of cobalt or vitamin B12 rexia and skeletal disorders in zinc deprivation (Suttle, 2010).
deficiency in cattle are inappetance, poor growth rates and weight
loss (Suttle, 2010). The cobalt content of grazing and forages varies Manganese
widely and should be analysed (Suttle, 2010). Sources of cobalt for UK forages and water typically have a high manganese content and
supplementation in feed must be soluble in the rumen with cobalt therefore deficiency is uncommon. There is some controversy over
carbonate and cobalt sulphate being more soluble that cobalt ox- the recommended requirements for dairy cattle with suggestions
ide (which can be used in slow release oral boluses) (Suttle, 2010). that 18 mg/kg DM (NRC, 2001) is too low. A higher recommenda-
tion of 40–50 mg/kg DM has been advised (Weiss and Socha, 2005).
Selenium
The function of selenium is as an antioxidant in the form of nu- Mineral review: key steps
merous selenoproteins, for example, glutathione peroxidase (GPX) zzOne person should be in control of mineral supplementation
(Suttle, 2010). There is a complex relationship between water solu- for the herd
ble antioxidants such as GPX which have an intracellular action zzAnalyse all forages for mineral composition. Grass based
© 2017 MA Healthcare Ltd

and lipid soluble antioxidants such as vitamin E which act in cell forages will be more variable in mineral content than straw,
membranes (Suttle, 2010). Supplementation with selenium has been maize silage and wholecrop.
linked with a reduction in the incidence of metritis and cystic ova- zzA mineral review must take into account mineral supply from
ries and in combination with vitamin E with a reduction in the inci- the total ration (including trough ration and variable rate
dence of retained fetal membranes (Harrison et al, 1984). concentrate feeds, e.g. parlour cake) (Figure 1).

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Figure 1. Mineral supply from all rations must be taken into account when conducting a mineral review.

zzTake care when calculating the mineral content of concentrate (phosphorus, sulfur, and calcium), on the grazing preference of steers on a tropi-
feeds, e.g. the ticket from a parlour cake will declare the cal grass-legume pasture grown on a low phosphorus soil. Animal Production
Science. 1994; 34(3):349-53
added minerals, but the background levels contained in the McDonald P. Animal nutrition (7th ed.). 2011. Pearson, Harlow, England
raw materials must also be taken into account. Contact the Moorhouse J. A practical Approach to balancing mineral requirements for the dairy
herd. Cattle Pract. 2015; 23:237-41
manufacturer to obtain the total mineral content. NRC. Nutrient Requirements of Dairy Cattle. 7th rev. ed. 2001. National Academny
zzWhen calculating mineral supply from variable rate feeds, Press, Washington, DC.
e.g. parlour cake, calculate supply for the average cow in the Overton TR, Chase LR. Nutrient Recommendations for dry and lactating cows.
2009. https://ahdc.vet.cornell.edu/programs/NYSCHAP/docs/basicnutrition-
herd and then check for under- or over-supplementation assessment.pdf Accessed 20th March 2017.
by calculating supply for animals receiving the lowest and Schonewille JT, Everts H, Jittakhot S, Beynen AC. Quantitative prediction of magne-
sium absorption in dairy cows. J Dairy Sci. 2008; 91(1):271-8
highest allocations.
Sinclair LA, MacKenzie AM. Mineral Nutrition of Dairy Cattle: Supply v Require-
zzAdditional forms of mineral supplementation must also be ments. In: Garnsworthy PC, Wiseman J, eds. Recent Advances in Animal Nutri-
taken into account, e.g. mineral licks, boluses and drenches. tion. 2013. Context Books Ltd., Ashby-de-la-Zouch, UK:13-30
Sinclair LA, Hart KJ, Johnson D, Mackenzie AM. Effect of inorganic or organic
zzTotal mineral supply for the individual animal must then be copper fed without or with added sulfur and molybdenum on the performance,
compared with recognised targets. indicators of copper status, and hepatic mRNA in dairy cows. J Dairy Sci. 2013;
zzA bespoke mineral supplement can then be formulated where 96(7):4355-67
Suttle N. Mineral Nutrition of Livestock. 4th Ed. 2010. CABI, Oxfordshire
required. Valk H, Beynen AC. Proposal for the assessment of phosphorus requirements of
zzMineral supplementation should be reviewed every 6 months. dairy cows. Livestock Production Science. 2003; 79(2):267-72
Weiss WP. Macromineral digestion by lactating dairy cows: Factors affecting digest-
ibility of magnesium. J Dairy Sci. 2004; 87(7):2167-71
Conclusions Weiss WP, Socha MT. Dietary manganese for dry and lactating Holstein cows. J
Ensuring accurate mineral supplementation, where necessary, is Dairy Sci. 2005; 88(7):2517-23
Xin Z, Tucker WB, Hemken RW. Effect of Reactivity Rate and Particle Size of Mag-
essential for the health and productivity of a dairy herd. The vet- nesium Oxide on Magnesium Availability, Acid-Base Balance, Mineral Metabo-
erinary practitioner is well placed to review current evidence for lism, and Milking Performance of Dairy Cows1. J Dairy Sci. 1989; 72(2):462-70
recommended requirements for minerals and to assess the total
mineral supply to animals under their care. Taking control of this
important role on a dairy units will help to prevent both under and KEY POINTS
over supplementation of minerals. LS zzOver supplementation of minerals is common on UK dairy
farms.
References zzPhosphorus, copper, selenium and iodine are most
Adam CL, Hemingway RG, Ritchie NS. Influence of manufacturing conditions on
commonly over supplemented.
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the bioavailability of magnesium in calcined magnesites measured in vivo and in

vitro. The Journal of Agricultural Science. 1996; 127(03):377-85 zzRegular mineral reviews are essential to prevent mineral
Bone P, Payne J, Twigge J. Guidance Note for Supplementing Copper to Bovines.
2011. http://www.food.gov.uk/sites/default/files/multimedia/pdfs/committee/
toxicity or deficiency.
guidancesuppcopperbovines.pdf Accessed June 6th 2015. zzThe review must take into account mineral supply from all
Harrison JH, Hancock DD, Conrad HR. Vitamin E and Selenium for Reproduction
dietary components and supplements.
of the Dairy Cow1, 2. J Dairy Sci. 1984; 67(1):123-32
Jones RJ, Betteridge K. Effect of superphosphate, or its component elements

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