Optimal Mineral Nutrition of Cattle and Sheep on Irish Farms

Phil Rogers MRCVS, Agricultural Research Unit, Teagasc National Office

A seminar for Teagasc Livestock Specialists, Teagasc Office Portlaoise, July 22^nd, 2003

 Executive Summary | Introduction | Mineral Targets for cattle & sheep | High-spec mineral mixes for cattle & sheep | Mg supply re grass tetany | Ca supply re milk fever | Optimal supply of N, P, K and S | Ca, P, Mg and Na nutrition to prevent urinary calculi | Optimal supply of Cu, Co, Se and I | Cu toxicity in sheep and calves | Se toxicity  | Pb toxicity | Where to look for technical data | Aide Memoire | References | Questions

Executive Summary

Irish ruminants ingest minerals from four main sources:  

Mineral levels in Irish forages depend on many factors, only some of which are under the farmer’s control. Factors that influence forage mineral levels include:  

Table 1 shows the mean mineral levels in Irish forages (pasture and grass silage) in the early 1990s (3). Values highlighted in yellow indicate abnormal national means for that element.

Table 1: Mean mineral levels in Irish forages (pasture and grass silage) in the early 1990s.  

*Sd (standard deviation): 95% of values fall in the range (mean +/- 1*Sd), i.e. 95% of Irish herbage Ca values lay between 0.47 and 0.83 %DM; 99% of values fall in the range (mean +/- 2*Sd), i.e. 99% of Irish herbage Ca values lay between 0.29 and 1.01 %DM.  

The main imbalances found in Irish pasture (3) were:

• N, K and S and Mo were high in 65, 32, 80 and 42% of samples, respectively
• P, Mg, Na, Cu and Zn were subnormal in 32, 49, 19, 65 and 25% of samples, respectively
• Se and I were subnormal in 94 and 97% of samples, respectively
• High Se was found in 1.2% of pasture samples; endemic Se toxicity occurs on circa 50 farms in the Republic
• Mn deficiency was not a problem; only 2% of samples were subnormal
• Co levels are not shown, because much Co found on pasture (or silage) analysis is surface contamination from soil. However, Co deficiency is common in Irish herbage.

From these national data, it follows that optimal mineral nutrition of Irish cattle and sheep on forage-based diets involves routine supplementation to ensure balanced inputs of the essential major- and trace- elements to ensure that neither deficiencies (primary or secondary) nor toxicities occur.

We will discuss the following topics:

• Mineral Targets for cattle and sheep
• Typical high-spec mineral mixes for cattle and sheep
• Mg supply in relation to grass tetany
• Ca supply in relation to milk fever
• Optimal supply of N, P, K and S
• Use balanced Ca, P, Mg and Na nutrition o prevent urinary calculi (typically Mg phosphate) in concentrate-fed sheep
• We will also discuss optimal supply of Cu, Co, Se and I
• Finally, we will discuss Cu, Se and lead (Pb) toxicity

Introduction

Useful background data are in the Teagasc Manual, “Control of Mineral Imbalances in Cattle & Sheep: A Reference Manual for Vets and Advisers” (1). Siobhan Kavanagh has some spare copies of the manual, or you can download it from the Teagasc Web Pages (1). Other details of most topics covered in this seminar are available on the Teagasc Webpages – see the references at the end of this paper, especially references 2, 3, 4, 5, 6, 7, 8.

Mineral Targets for cattle and sheep

Table 2 summarises the range of values of major- and trace- elements in TDMI that are classed as “normal” for cattle and sheep.

Table 3 summarises the range of values of trace elements in TDMI that are classed as “normal” for cattle and sheep.

When assessing the adequacy of total feedstuffs, values outside of these ranges can be regarded as abnormal (undesirable). The tables also give the Recommended Optimum Dietary Level (RODL). This usually is at or above the “mid-normal range”, but physiological and species differences influence RODL. For example, dairy cows milking on spring grass need more Mg and P than dry cows in winter; sheep need more Co and less Cu than cattle.

Table 2: Major element levels (%TDMI) classed as “normal” and the RODLs for cows and ewes.

*           Excessive K and S is undesirable;

**          Extra Mg (usually 30-50g/cow/d and 10-20g/cow/d) is needed during tetany-risk periods and the last 4-6 weeks prepartum, respectively;

**          Extra Mg (usually 3-7g Mg/ewe/d) is needed during tetany-risk periods. If Mg supplements are given routinely prepartum, they should not exceed 2g/ewe/d; excess Mg in late pregnancy can increase the risk of hypocalcaemic paresis (“Lambing Sickness”).

Table 3:            Trace element levels (mg/kg TDMI) classed as “normal” in feed, inclusion rates permitted under EU Feed Regulations, and the RODLs for cows and ewes in Ireland.

*           Mo levels >2mg/kg DM antagonise Cu absorption by cattle/sheep;

**          These high Cu, Se and I levels in feed are advised for beef and dairy cows for at least 5 months (1 month pre- to 4 months post- calving)

***        Avoid Cu supplements for sheep except on specific veterinary advice  

Typical high-spec mineral mixes for cattle and sheep

For more details on the composition of high-spec cattle and sheep Mins, see references 1, 10, 11, 13. Note that cattle need at least 7 different formulations:

(1) Dry Cow Mins;

(2) Dairy/Beef Cow Winter Mins;

(3) Tetany Control Mins (for lactating cows at grass in risk periods);

(4) Calf and grower/finisher Mins;

(5) Fodder Beet Balancer Mins;

(6) Maize silage Balancer Mins;

(7) Balancer minerals for cattle on ad libitum concentrates.

Table 4 gives examples of top-class formulations for mineral mixes for COWS AND OTHER CATTLE on grass silage or herbage as the main forage. Different formulations are needed for cattle on high intakes of special feeds, like fodder-beet silage, maize silage, or ad libitum concentrates.

Table 4:           Examples of top-class formulations for mineral mixes for COWS AND OTHER CATTLE on grass silage or herbage as the main forage.

⁽¹⁾ Never feed cattle minerals to sheep, and vice-versa. Cattle minerals may cause copper toxicity in sheep. Never feed cow minerals to calves, as scouring and urinary stones and copper toxicity may follow.
⁽²⁾ If recommended daily allowances are above or below those shown, adjust the trace-element and vitamin levels down or up, accordingly. One would normally feed 150-180 g minerals in home-mixed lactation diets. Special minerals are needed if silages based on whole-crop maize or fodderbeet are fed.
⁽³⁾ To prevent urinary stones in drystock, feed low levels (0-3%) of Mg in mineral mixes.
⁽⁴⁾ Some authorities double these amounts of Mn for breeding females, especially in groups with severe infertility and suspected Mn deficiency
⁽⁵⁾ The maximum Se supplement was reduced to 5 mg Se/cow/d, as from January 1 1996. Do not feed high Se minerals to cattle within 5 miles of a known Se-toxic farm unless blood test indicates no risk of Se toxicity.
⁽⁶⁾ The higher Vit E levels are 4-6 times higher than usual (underlined values are more usual). Research in USA and elsewhere shows that high levels of Vit E improve immunity and reduce mastitis incidence.

In theory, sheep also need a wide range of mineral formulations to cater for different physiological states (pregnancy, lactation, tetany-risk, lamb fattening minerals, etc). However, because the total mineral market for sheep is so small relative to that for cattle, the trade does not provide the optimum range of formulas and reaches a compromise with a smaller range.

Mg supply in relation to grass tetany: See references 1, 9, 10, 11 for more details.

Oral Calmag: The target supplement in the risk period is 30-50g Mg/cow/d, as 60-100g Calmag (50% Mg)/cow/d, and 10% of that for ewes (3-7g Mg, as 6-14g Calmag).

Soluble Mg via the water supply: The target supplement during the risk period is circa 20g Mg/cow/d, as circa 200g Mg chloride (10% Mg)/cow/d. Do not recommend Mg sulphate (scouring and drop in water intake) or Mg acetate (too dear). Water medication is unreliable for sheep.

Pasture dusting with Calmag: (Paddocks: 17 kg powdered Calmag/ha every week; Set Stocked: 34kg/ha every 2 weeks) also is very effective. Best done on damp grass, with at least 6” of grass cover.

Free-choice DIY 50/50 Calmag/Molasses lick, or High-Mg Blocks usually are effective but intake cannot be guaranteed, and some cows may not be protected.

Mg Bullets: Forget the old Mg bullets by Pfizer. They released too little Mg (only 1g/d each). To prevent tetany, cows would need at least 6 bullets every month. This would be too dear and give only 20% of the Mg in 2oz Calmag. The newer Optimags release 3g Mg/d each; to prevent tetany cows need at least 2 of these every month. That is still too dear, and it will not keep blood Mg normal. Bullets are not as reliable as 2-3 oz Calmag/cow/d. However, dosing bullets that release 3g/ewe/d (and repeating the dose after 4 weeks) would be a useful, if expensive, way to control tetany in ewes.

Ca supply in relation to milk fever: The main points to remember are to keep Ca inputs low before calving, supplement with 15g Mg/cow/d in late pregnancy, and avoid calving cows too fat or too thin.

REMEDIAL ACTIONS to reduce the risk and severity of bovine hypocalcaemia at calving include:

Optimal dietary supply of N, P, K and S: Table 5 compares the Recommended Optimum Dietary Level (RODL) for these elements (%DM) with the mean levels found in Irish forages in the early 1990s:

Table 5.           Comparison of Recommended Optimum Dietary Level (RODL) of N, P, K and S (%DM) with the mean levels found in Irish forages in the early 1990s

Pasture, especially young lush pasture, usually had excessive amounts of N, K and S for optimum dairy cow nutrition. This can be associated with loose faeces and impaired absorption of other elements by cows, notably Mg, I, Cu and Se.

Silage usually had suboptimal N and P for dairy cows, and the K levels were somewhat too high. The S levels were also high, probably due to use of unnecessary S fertilisers and/or Cosil silage additive.

There is little that one can do to reduce the N, K and S levels in pasture or silage without running the risk of decreasing grass production or having poor silage fermentation. Therefore, we may have to accept these anomalies. However, there is a clear case for giving protein and P supplements to silage-fed dairy cows in lactation.

Use balanced Ca, P, Mg and Na nutrition to prevent urinary calculi in concentrate-fed sheep

See reference 22. Ovine urinary calculi are typically Mg phosphate, precipitated in an alkaline urine.

Causes of urinary calculi: Calculus formation has many causes, of which the mineral (P, Mg, Ca, Na) level in feed is only one factor. It involves: reduced water intake, reduced urine output, cold environment, alkaline urine pH and genetic susceptibility. Other possible factors are: urinary infection; mucilaginous material in urine; low roughage intake and saliva secretion; increased P retention; vitamin A deficiency; excess intake of fluoride, oxalate, sodium bicarbonate and silica. However, precipitation of magnesium phosphate is the basic cause in intensively fed sheep. Urolithiasis is very rare if the total feed contains P < 0.46% and/or Mg < 0.23% DM respectively. The higher the P and Mg levels, the greater the risk. Low Ca/P ratios increase P absorption. Mg availability is high on cereal-based diets. Lambs on concentrates need less Mg, possibly 50% less, than lambs on grass diets.

Control and prevention of urolithiasis (urinary calculi) in lambs:

1. Eliminate as many of the causes as possible.
2. Maximise water intake. Lambs are finicky drinkers. Water intake can fall severely where water bowls/drinkers/troughs are not cleaned out frequently. Intake falls also in cold weather, especially in freezing conditions (frozen pipes, cold water). Use of thermostatically controlled heating-elements in water tanks to raise the temperature of drinking water to 10 degC may help to increase water intake in very cold weather.
3. Maximise saliva production by including some roughage, coarse mix or grass-meal.
4. Replace the concentrate feed, pending its analysis for P, Mg, Ca, Na. For least risk of urolithiasis, the DM of the total feed⁽¹⁾ for concentrate-fed lambs should contain < 0.46% P and < 0.23% Mg, 1-2% salt (or 0.39-0.78% Na). These levels of P and Mg are 10% or more above those which some experts would allow. A Ca/P ratio of 2/1 or more is desirable to reduce P absorption.
5. Salt and Ca/P ratio in feed: At levels >0.45% P and/or >0.22% Mg in TDMI, rations should contain:
• >1-2% salt (exclude sodium bicarbonate!) to enhance water intake and increase urine output (diluting the Mg and P level in urine), thus reducing the risk of formation of Mg phosphate crystals;
• and the Ca/P ratio should be 3/1 (high Ca reduces P absorption).
6. Acidify the urine?: On concentrate- (but not forage- or grass-) based diets, inclusion of ammonium CHLORIDE (0.5-1.5% of feed DM) reduces crystal formation but increases the risk of demineralisation of the skeleton. This could be important in pedigree stock to be kept for breeding or showing, but may be unimportant in lambs fed for slaughter.

Optimal supply of Cu, Co, Se and I: It is important to advise adequate supplements of these trace elements as an insurance against deficiencies. Cattle should get all four of these routinely. Mn and Zn usually are added but are not as important nationally as the other four. The most important ones to remember are those for cows and ewes: See Table 3, above, for the RODLs.

Table 6 shows the recommended trace element supplement (mg/head/d) for cows and ewes. Note that ewes get 10% of the cow dose, except for Cu [use only on vet advice] and Co, where the top dose for ewes is 20% of the top cow dose.

Table 6.           Recommended trace element supplement (mg/head/d) for cows and ewes.

The lower levels are for routine continuous use. With the following exceptions, the higher levels are advised for national use in the Teagasc 5-month mineral programme for cows (1 month prepartum to 5 months postpartum), or as needed in groups of cattle or sheep at risk of severe deficiency,

^ Some authorities advise much higher Mn supplements (up to 980 mg/cow /d) in herds with severe infertility due to suspected Mn deficiency. A pro-rata dose for ewes would be up to 98 mg Mn/d.

* Give Cu to sheep only on veterinary confirmation of Cu deficiency.

** Within 5 miles of known Se-toxic farms, reduce the Se supplement to about 50% of the lower level, unless blood test confirms Se deficiency in the group.

*/** Ionophores (monensin etc) increase the retention rate of Cu and Se by ruminants. If ionophores are fed, avoid the higher levels of Cu and Se supplements, unless blood test suggests that higher levels are needed.

*** Zn supplement of up to maximum is advised if high-Ca diets are fed.

See the Teagasc Manual (1) for the daily targets for recommended trace element supplements for other classes of stock, and for vitamin supplements for all classes.

Copper toxicity in sheep and calves: Excessive Cu inputs can poison all breeds of sheep. Island breeds and crosses ( Texel , Ronaldsay, Soay etc) and some continental breeds (Charolais, Rouge) are very susceptible. Poisoning has occurred in sheep on pasture which had been fertilised with high-Cu pig slurry. In very rare instances, Texels have been poisoned at pasture with as little as 14 mg Cu/kg DM, and no other known source of Cu intake. Young calves also can be poisoned by excessive Cu inputs. Once clinical signs arise, seriously affected sheep usually die. One can use a cocktail of Cu-antagonists (mainly Mo, Fe, Zn & sulphates) to strip Cu from the tissues of comrade sheep at risk. Remedial actions during an outbreak of Cu poisoning are given elsewhere (21). Also see reference 1 for more detail.

Under current EU Legislation, complete sheep feeds must not exceed 15mg Cu/kg in total feed (17mg Cu/kg total feed DM). Assuming a maximum DM intake of 2 kg/ewe/d, the EU permits a maximum oral intake of about 34mg Cu/ewe/d (less, pro-rata, for lighter sheep). To be safe (in the case of susceptible breeds), stay below the maximum permitted by the EU.

Prevention of Cu toxicity:

1. Ensure 8-15 mg Cu/kg TDMI in sheep diets. Avoid high-Cu byproducts in the diet; insist on a miller’s/manufacturer’s certificate of the Cu level in the feed or in straights fed to sheep; apply high-Cu pig slurry to bare pasture only.
2. Do not feed cattle rations/cattle minerals to sheep.
3. Sheep should get no Cu supplement unless a vet has diagnosed Cu deficiency in the flock by blood test and/or on clinical/postmortem findings. Even then, it is safer to give Cu supplements to sheep only as directed by a vet. Oral slow release Cu is safest. If sheep need a Cu supplement, oral CuO capsules or Cu-containing glass boluses are safer than Cu via feed, or drench, or injection. For example, a CuO capsule can be given at doses of 4g (ewes), 2g (store lambs) or 1g (lambs 1-2 months of age). Dose once or twice/year, as needed.  

Selenium toxicity (selenosis): This may affect all livestock, especially cattle and sheep. Several plant species such as Astragalus (loco weed and milk vetch), Onopisis (goldenweed) and Zylorhiza (woody aster) are Se accumulators.  

Acute selenosis may follow a single consumption of very highly seleniferous plants. This occurs in USA but is unknown (?) in Ireland. Symptoms are severe and death usually occurs within hours. Signs are abnormal movement, dark watery diarrhoea, elevated temperature, weak and rapid pulse, laboured respiration, bloating and abdominal pain, mucous membranes are pale and blue, and pupils are dilated. There is no known treatment for acute poisoning, and the animal often dies before a diagnosis can be made. Cattle and sheep are the most likely species to be affected, but horses, goats, and swine can also be affected. The minimum acute lethal dose for cattle may be as little as 3 mg/kg LW, while for horses the dose may be 3.3 mg/kg of LW; 1.2 mg/kg of LW has killed pigs in 5 days.  

Chronic selenosis occurs in prolonged ingestion of toxic but lower Se levels than in acute selenosis. It has two forms - Blind staggers and Alkali Disease. The latter is the form more usually seen in Ireland but the former has occurred occasionally. It could arise in the future if high Se supplements were used in animals already exposed to endemic Se toxicity. Cattle are more susceptible than sheep.  

(1) Blind staggers occurs when animals ingest water-soluble Se compounds found naturally in accumulator plants. The signs occur in 3 stages. Stage 1 shows wandering, stumbling over objects, anorexia, visual impairment. Stage 2 is a more severe form of stage 1, in which the front legs seem unable to support the animal. Stage 3 shows blindness, tongue paralysis, inability to swallow, rapid and laboured respiration, salivation, and low temperature. The animal dies within a few hours of the onset of Stage 3. The toxic action in Blind Staggers may show a delay between the stages. Stages 1 and 2 may go unnoticed. Weeks later, the animal may show signs of Stage 3 and die. It is more difficult to diagnose in sheep because the stages are not as well defined as in cattle. Toxic amounts of Se can also cause birth defects in offspring from dams fed such levels.  

(2) Alkali Disease, the most common manifestation of selenosis in Ireland , occurs when animals ingest protein-bound water-insoluble Se in plants or grain. Alkali disease is more chronic than Blind Staggers, taking longer to manifest, perhaps even years in some cases. It can affect all livestock, especially cattle and horses. Poisoning in cattle rarely occurs unless the feed Se levels exceed 3mg/kg DM; in 50% of documented cases in Ireland, feed Se exceeded 6mg/kg DM. Signs include lack of vitality, anaemia, emaciation, stiffness of joints, lameness, rough coat, loss of long hair, and hoof sloughing and deformities. Hoof deformities are a classic sign of selenium and can cause lameness and severe pain; food and water must be provided because affected animals may be hesitant to walk.  

The most effective means to prevent selenosis is to remove the animals from the seleniferous areas. Dilution of high Se feeds with low Se feeds in a mixed ration will help to prevent toxicity. Recognition of seleniferous plants, proper land management, and grazing control are all necessary to completely prevent selenosis. In the early stage of an outbreak, dosing with a high-S cocktail may halt the progression of the disease. For details, see reference 29.  

Treating the soil with sulphates, to increase the S:Se ratio in forage, rarely depresses Se uptake by accumulator plants enough to guarantee their safety. Feeding a higher protein diet may reduce Se toxicity; animals fed the same amount of toxic selenium but fed a higher protein diet lived for a few more days than those animals fed a low protein diet. See reference 1 for more details.  

Lead toxicity (plumbism): Cattle and sheep ingest large amounts of soil (cattle 5-15% of TDMI; sheep 15-35% of TDMI). If the soil has high levels of heavy metal (Cd, Pb, Zn) ingestion of the metal via soil can be high enough to poison the animals. Soil near abandoned lead- or zinc- mines or smelters may have high Pb levels. Ingestion of Pb-contaminated soil has poisoned cattle in Ireland and UK . That has happened many times in UK/Ireland on “rehabilitated mine waste”. Plant Pb levels in such cases often have been normal.  

However, ingestion of Pb from contaminated silage (battery chopped in!), or licking painted timber/boats (red-lead paint is banned now but timber painted with it can remain toxic for decades) are common causes of poisoning. Other Pb sources are: putty, tarpauliin, sump-oil, and contaminated herbage near motorways.  

Pb toxicity can kill cattle, even adult cows, very quickly. If diagnosed, the source of Pb must be found and removed from the cattle. Affected cattle usually can be saved if the Pb source is removed and Pb-chelation therapy is started immediately.  

Where to look for scientific/other technical data: See a range of search options at http://homepage.eircom.net/~progers/search.htm  

Teagasc subscribes to Dialog & DataStar, a selection of scientific databases that are accessible via a web-based interface. These databases contain the abstracts/summaries of articles on every aspect of Teagasc’s research interests. To access the databases, click on http://www.dialoghosting.co.uk/Teagasc/ after getting your Login Codes (User ID & Password). To get these codes, check with your IT Manager, or Phil Rogers.

The Teagasc Intranet has useful notes on how to search the Abstracts Databases to best advantage. To find these notes, search under the keywords “Lendac” and “OVID”. Note that the files on the Intranet refer to OVID/WebSpirs5. We have moved to DataStar & Dialog recently, but have not mounted the data specific for those databases yet. However, the files on Lendac are a useful introduction to focused searching.  

Also, you can access PubMed Medline [ http://www.ncbi.nlm.nih.gov/PubMed/medline.html ] free, without passwords. It has vast amounts of data on animal nutrition and disease.  

Google Advanced Search [ http://www.google.com/advanced_search ] is very useful to locate nutritional articles on the WWW, for example from other research institutes and university sites. It is also useful for sourcing veterinary products and nutritional supplements.  

BABELFISH Online Translation is a most useful free service. It allows one to paste about 150 words of text from any of several languages into the system and it outputs a reasonable translation. See notes on its use at http://www.tnet.teagasc.ie/hq/staff-dev/InternalTrainers/translation.asp

AIDE MEMOIRE

To summarise the main points of this seminar, and to impart the basic principles of balanced mineral nutrition of ruminants to their clients, advisers should remember the “MOST FARMS” mnemonic:

Signs (SIGMARA - the S in MOST, above)  

Note that the Teagasc recommendations for supplementary trace element inputs to cattle and sheep are 2-4 times higher than those recommended in most other countries. This is because Irish research over >30 years has confirmed that our ruminants NEED these high inputs. If, to follow foreign advice, we reduce our levels of supplementation, the blood mineral status of our herds and flocks will fall accordingly.  

REFERENCES  

MANUALS ON CATTLE/SHEEP MINERAL NUTRITION & FURTHER READING RE LAB TESTS

MINERAL SUPPLEMENTS FOR FARM ANIMALS

  COMMON PROBLEMS RELATED TO MINERAL IMBALANCES

GENERAL INFORMATION AND SEARCH OPTIONS

 QUESTIONS  

1. Beef finishers (550 kg) on:

40 kg of 20% DM silage/head/d with Cu levels of 9 mg/kg DM,

+ 4.5 kg of 88% DM beef-nuts with Cu levels of 60 mg/kg DM,

+ one 24g CuO (80% Cu) bolus, said to have an active release over a period of 150 days:

Assuming a recommended total input of 550 mg Cu/head/d, is the mean daily Cu input (a) too low, (b) OK, or (c) too high?  

(Hint: calculate the DAILY inputs from each component, then the total DAILY input, and compare that with the RECOMMENDED daily intake)  

2. Cycling dairy cows (600 kg) on:

70 kg of 20% DM grass/head/d with I levels of 0.2 mg/kg DM,

+ 3 kg of fertility-nut with 8 mg I/kg,

+ one Ionox bolus containing 2700 mg I, said to have an active release over a period of 150 days:

Assuming a recommended total input of 64 mg I/head/d, is the mean daily I input (a) too low, (b) OK, or (c) too high?  

(Hint: calculate the DAILY inputs from each component, then the total DAILY input, and compare that with the RECOMMENDED daily intake)  

3. Of wether lambs on ad-libitum lamb fattening nut, 20% developed urinary calculi over a 10-day period after the onset of sub-zero temperatures in January. The label stated that the nut contained 0.84% Ca, 0.55% P, 0.32% Mg and 0.22% Na. The pipes are not frozen but water intake has fallen a lot since the cold weather began. Is the problem due to:

(a)    Excess Mg in the diet?

(b)    Excess P in the diet?

(c)     Not enough Na in the diet?

(d)    Not enough Ca in the diet relative to P?

(e)    Decreased water intake?

(f)      All of the above in combination?  

4. Adjusted for a DM content of 88% in grain/concentrate diets, EU Feed Regulations lay down maximum permitted levels of trace elements in diets for adult cattle as follows: Cu 39.7, Se 0.57, I 4.55 and Co 11.4 mg/kg DM. 

1. Assuming that a lactating Friesian cow has a total DM intake 16 kg DM/d, calculate the maximum permitted intakes of Cu, Se, I and Co/cow/d.
2. Assuming that the cow is eating only 16 kg of grass DM, with Cu, Se, I and Co levels of 9, 0.1, 0.2 and 0.2 mg/kg DM respectively, calculate the actual intakes of Cu, Se, I and Co/cow/d from that grass
3. Calculate the shortfall between the actual and the EU-permitted total intakes of Cu, Se, I and Co/cow/d
4. The Teagasc Manual (Rogers & Gately, 1992, updated 2000) recommends optimum (maximum) supplementary intakes of Cu, Se, I and Co, respectively, of 450, 5, 60 and 10 mg/cow/d. Are those recommendations compatible with the total inputs allowed under the EU Regulations, as assessed by the answers in (a), (b) and (c), above?

5. A farmer who had turned out dairy cows in late March also had weanling steers (circa 300 kg LW) in a shed. In the feed store, he had a supply of two types of concentrate: (a) a special dairy grazing nut with 2.0% Mg, and (b) a beef nut with 0.2% Mg. He had been feeding both nuts at 2 kg/head/d.  

The farmer decided to take a 10-day break, starting on April 10th. He hired a relief worker to take over while he was away. The relief-worker fed nut (a) to the steers and nut (b) to the cows for 10 consecutive days. He got the feeding rate right (2 kg/head/d) but had switched the nuts in error. What did the farmer probably find when he came back after the week’s break?

1. that several cows had died of tetany?

2. that all of the steers were scouring badly?

3. that some steers had urinary obstruction due to calculi?

4. that the relief worker had skipped to London ?

5. all of the above?

6. After being dosed with one 4g capsule of CuO (80% Cu)/head before housing, a group of 200 intensively-fed lambs was fed a Co-Op fattening concentrate ration ad-libitum with 22 mg Cu/kg DM.  

Within 1 month, 20% of the lambs had died, or were showing the following symptoms: kicking at the belly, grinding the teeth, anorexia, weakness, jaundice and dark-coloured urine.  

Without telling the CoOp about the CuO dose given before housing, the farmer decided to lodge a claim for damages against the Co-Op.

1. Would the CoOp be likely to contest the claim in Court?

2. If no, why not?

3. If yes, would the farmer be likely to win the case outright? Why?  

4. If, on advice from a shrewd nutritional consultant, the CoOp lawyer induced the farmer to admit to giving the 4g CuO capsule/head before housing, would the judge be likely to cut the damages by up to 50%?

5. If yes, why?  

MINERAL QUERIES SUBMITTED BY ADVISERS TO SIOBHAN KAVANAGH  

DAIRY

1.    What causes copper deficiency in dairy cows?: Irish forage is marginally deficient in Cu for cattle, but most serious Cu deficiency in cattle and sheep is secondary, due to the presence of Cu-antagonists, especially high ingestion of Mo, S and Fe. See Cu Deficiency in the Teagasc Manual (1).  

What to do in low lime / high molybdenum areas? What to do in high molybdenum areas?: Use lime, as needed, possibly reducing the application slightly, BUT provide Cu supplements to the cows at the TOP end of the Teagasc recommended rates (i.e. at 450 mg Cu/cow/d for at least 5 months (1 month pre- to 4 months post- calving). See Table 4 in the Teagasc Manual (1) and references (9, 10, 11, 13). In a few herds (<10 herds in 20 years), supplements of 500-700mg Cu/cow/d were needed to control severe Cu deficiency. Note that in one trial in a Cu-deficient herd in New Zealand , the cows got a supplement of 1500mg Cu/cow/d for 7 consecutive years without toxicity problems. However, that level of supplement would definitely exceed permitted EU inputs for cows.  

2.    Is skin application of tincture of iodine tincture on the inside of a cow’s leg reliable to prevent I deficiency?: Spraying of 8-9ml of 5% tincture of iodinw/cow/week on the thin skin of the flank fold maintains blood I levels in the normal range for c. 1 week. However, Plasma (and milk) I levels go very high (offscale) in the first day, and fall thereafter until the next application. Thus, they are not as stable as the I levels in blood/milk of cows fed 60mg I/cow/d via the feed or the water supply. The method is best reserved for SUCKLER cows that cannot be given I cheaply by any other way (in feed or in water, or in mineral licks).  

Are there any quality assurance issues with milk from cows treated in that way?: Yes! Medical researchers are concerned that milk should not contain excessive I levels. High I in milk can cause toxic goitre in milk-fed infants. Therefore, as milk I values can be very high 24 hours after skin-application of a high dose of I, the method is NOT recommended for lactating dairy cows.  

3.    Which iodine boluses are best?: At present, to supply I to cattle at grass, IONOX (Bayer) is the best bolus on the Irish market. It has 18mg I (plus generous amounts of Se and Co)/bolus. If no other I supplement is used, the recommended dose is 2-3 boluses/cow every 5-7 months.  

       However, when one considers that Cu and Mg (at least) must be supplied also, IONOX is an expensive way to give I, Se and Co. Provision of appropriate high-spec Min-Vit Mixes IN the feed or ON the feed, or provision of soluble minerals (Mg and trace-elements) via the water supply, are cheaper and more effective ways to control all the common mineral problems together.  

4.    How does one get minerals into dairy cows that are fed straight ingredients, e.g. citrus pulp, at grass?: (1) Add the correct amount of the desired mineral mix to the day’s allowance of straight ingredient. For example, a farmer may want to feed a DIY mix of 3 kg straights (2 kg rolled barley + 1 kg citrus)/cow to high-yield cows in May. He/she could add 130-150g high-Mg Tetany Control Mineral to each 3kg of straights, preferably including circa 5% molasses at the final stage to prevent the mineral from settling out of the mix.  

CATTLE

5.    What mineral specification is needed for high concentrate feeding? Will a general cattle mineral suffice?: Individual concentrates vary widely in their mineral content (see reference 4). Depending on their individual ingredients, high concentrate feeds for growing ad finishing cattle usually need extra Ca, Na and Vitamin E over and above the amounts in mineral mixes for use in forage-fed cattle. However, it is not possible to give a simple answer to the questions because optimum balance of ANY mineral in animals depends on its TOTAL input (and the inputs of its antagonists) from ALL sources, relative to the optimum Recommended Optimum Dietary Level (RODL) of each mineral. For example, RODLs of Ca, P, Mg and Na for cattle (dairy and beef), and their contents in some typical concentrates are:  

One should aim to have the content of each mineral the TOTAL feed DM at or near the optimal RODL for that mineral, as in Mineral Targets for cattle & sheep, above.  

6.    Is feeding of minerals needed if a herd/flock has good performance and no history of mineral deficiency?: As stated in the Executive Summary, because Irish forages have MULTIPLE mineral deficiencies, one can expect MULTIPLE mineral deficiencies in most unsupplemented Irish herds/flocks. However, NONCLINICAL deficiencies are very common in Irish herds/flocks. Mineral supplementation of such animals does NOT increase animal health/profitability in easily detectable ways. That said, I advise ROUTINE use of mineral supplements to prevent the possibility of subclinical or clinical deficiency; I see it as a form of “insurance policy”. All concentrate feeds for drystock should contain min-vit supplements, especially in autumn and winter.  

       Is it advisable to have house- or car- insurance if there is no history of a need to claim on such insurance in the past? Most people take out insurance just in case … but hope never to actually need it!  

7.    Would high magnesium lime cut down on the risk of tetany?: Pure MgO has 60% Mg; Feed-grade Calcined magnesite (Calmag) is 85% pure MgO, i.e. has circa 50% Mg. In contrast, dolomitic limestone (“magnesium lime”) has maximum of 15% Mg. It should NOT be used in an attempt to prevent tetany, as plant uptake of Mg from fertiliser is poor. Anyway, most tetany is NOT due to primary Mg deficiency, but to the presence of Mg-antagonists (especially lush grass, high in K and N). Effective control of hypomagnesaemia in cattle and shhe depends on direct supplementation with adequate oral Mg. See Mg supply re grass tetany, above.  

SHEEP

8.    Some farmers use high selenium supplements to reduce lamb mortality. Is there a risk of these being too high?: Sheep are not as prone to Se toxicity as cattle, but can be poisoned if the Se inputs are high enough. This rarely happens due to farmer-error in supplementation, but has happened when high-Se drenches sludged because of inadequate mixing of the dosing-pack between sheep. See the section on Se toxicity and reference 29 above.  

What dietary Se levels are recommended?: The optimum range of dietary Se for Irish sheep and cattle is 0.20 to 0.57mg/kg TDMI, preferably in the upper end of that range. Se is especially advisable in late pregnancy and leading up to, and during, the breeding season.  

What are the EU limits on inclusion?: The EU permits 0.50mg Se in total feeds (88% DM) for adult cattle and sheep. This converts to 0.57mg Se/kg TDMI. As Irish forage has circa 0.09mg Se/kg DM, a supplement of up to 0.48mg Se/kg DM falls into the “permitted area” under EU regulations.  

9.    How available is dietary P for sheep?: This is not easy to answer, because the published research data are very variable – usually in the range 20-50% of P intake.  

If a lot of dietary P is excreted, could this reduce the need for P fertilisation at grass?: One should ignore much of the faecal P excreted by grazing animals when calculating the amount of P fertiliser needed for adequate pasture growth. This is because faecal deposition is very localised and faecal P does not travel far from the dungpats. Evenly applied slurry is more reliable – it gives much better coverage over the dressed areas. One can use slurry (and artificial P fertiliser) very effectively. One should aim for circa 0.30% P, or more, in herbage DM for sheep and suckler cows, and circa 0.35% P, or more, in herbage DM for dairy cows and rapidly growing young cattle.  

10.  Bioplex minerals for all categories of livestock – what is the thinking on these?: There is little solid evidence from independent research that bioplexed trace elements increase animal health or productivity more effectively than adequate supplements of inorganic trace elements. Bioplexed Se and Zn are absorbed 2-4 times more effectively than inorganic Se or Zn, and are incorporated more effectively into biologically active enzymes. However, the price differential is huge – for Se more than 105-times the cost of inorganic Se. Therefore, on the basis of their exorbitant cost, I do not recommend their routine inclusion in mineral mixes.

       One exception is in cow herds with non-responsive hoof lameness/laminitis with suspect Zn deficiency [very rare, and usually due to dietary Ca excess relative to Zn]. In that case, I would advise bioplexed Zn/Zn methionate for a few weeks. If this clearly improved the lameness, I would advise THAT farmer to use bioplexed Zn routinely.  

However, MOST lameness has NOTHING to do with Zn deficiency. See advisory notes on laminitis/lameness (25).  

11.  Most maize balancers are short on calcium, particularly at high inclusion levels of maize. How do you get over that without exceeding the EU recommended level for some of the other trace elements?: Simply add extra Ca as limestone flour (feed-grade Ca carbonate, 34% Ca). See also reference 13.  

DEER

12.  High copper levels in deer diets: what is the legislation on copper inclusion levels?: If their diets are deficient in Cu (and have Cu antagonists - Mo, S, etc), deer (like cattle) are very prone to Cu deficiency. Deer should receive Cu supplements at the same rate (mg Cu/100kg LW) as cattle, i.e. a deer of 60kg LW would receive a Cu supplement of up to 45 mg Cu/d (circa 10% of the Cu supplement of a 600kg cow). EU Animal Feed Regulations allow a maximum of 35mg Cu/kg in total feeds (88% DM) for deer; this is equivalent to 39.8mg Cu/kg TDMI.  

       Any quality assurance implications here?: To ensure optimal deer health and quality of meat, ensure that they receive an adequate Cu supplement.