Trace Elements

Define “trace element”

Micronutrients/micro-minerals required in very small quantities but essential for normal function

List the 4 important trace elements (TE) limiting production in NZ

Limiting TE in temperate grassland production:

1. Cobalt

2. Selenium (vitE overseas)

3. Iodine

4. Copper

Grazing ruminants rely on pasture for TE (derived from soil) → Unknown true TE intake

Define “primary TE deficiency” and describe 4 contributing factors

Definition: Soil/plant deficiency influenced by

1. Certain districts

2. Different plants (ability to take up TE)

3. Different environment (eg. pugging changes TE concentrations)

4. Use of fertiiser

Define “secondary TE deficiency” and produce an example

Definition: Lack of TE absorption in animal (i.e. ingestion sufficient, but absorption is limited)

Example: Animal ingests sufficient Cu, but absorption is limited as Cu binds to Mo, S and Fe in the rumen

3 Types of TE problems seen on farm

1. Failing to supplement when needed → Poor production

2. Unnecessary supplementation → Wasted cost

3. Excessive supplementation → Toxicity (Se and Cu) and residues

TE deficiency can result in poor production BUT can also be an excuse for poor production

3 Reasons to assess TE on-farm

1. Diagnose deficiency when animals are performing poorly (+ clinical signs consistent with TE deficiency)

2. Ensuring sufficiency to ensure animals have sufficient reserves

   • Best approach → Proactive prevention of TE deficiency

3. Monitoring to ensure supplementation programme is adequate

5 Diagnostic steps to assess TE on-farm

1. History

2. Clinical findings

3. Relate changes in animal performance to liver/blood TE concentration (response relationship)

4. Soil/plant TE testing

5. Supplementation trials → Excellent data BUT time/$-consuming

2 Considerations when TE sampling a herd

1. Is the TE stored in the body?

   • YES → Sample storage site (liver) = Cu ± Co

   • NO → Sample blood = Se + Co

2. Is there significant TE variation within the herd?

   • YES → Need lots of samples = Cu ± Co

   • NO → Only few samples required (Se)

Selenium: 2 Functions

1. Helps protect cells against free radicals (antioxidant) from:

   1. Metabolism

   2. Inflammation

   3. UV light

   4. Air pollution

2. Maintains resistance to infection

Selenium deficiency: Predilection

• Signalment

• Season

• District

No species/season/region predilection (any species, any time, anywhere)

Selenium deficiency: 6 Clinical signs

OBVIOUS

1. White muscle disease

   • Rare in NZ due to awareness of Se deficiency

   • MoA: Free radical damage to active muscle → Calcification → Loss of function and stiffness

   • Clinical Signs: Stiff heart, neck, diaphragm muscles (active muscles)

SUBTLE

2. Poor GR (always consider Se deficiency as a DDx)

3. Diarrhoea

4. Early embryonic death (sheep)

5. Decreased milk production

6. RFMs (dairy cattle)

Selenium deficiency: Sample selection

• Number

• Sample type

• 2 Test options + indications

• Correlation with production response

Number: 3 - 5 samples

• Little variation between animals (ewes, hoggets, calves) assuming grazing same area and similar grazing management

Sample: Blood sample

• EDTA (whole blood) = RBCs samples have a mixture of new RBCs (new Se levels) and old RBCs (Se levels over time)

• Red top (serum)

• ± Liver

Test:

1. Glutathione peroxidase (GSH-Px) within RBCs

   • GSH-Px is a selenium-dependent enzyme located in RBCs

   • Because RBCs have a ~3 month lifespan, RBCs reflect long-term Se status

   • Sample: EDTA

   • Indication: No supplementation → Determine long-term Se deficiency of herd

2. Selenium within serum OR whole blood

   • Sample: EDTA OR red top

   • Indication: More reliable in determining when further supplementation is next required or identifying toxicity (short-term)

Correlation: For BOTH GSH-Px and blood Se, reliable RR correlated with production responses → Determine if Se supplementation will likely result in GR response

Cobalt deficiency: Predilection

• Signalment

• Season

• District

Signalment: Lamb > Adult sheep > Cattle

• Lack of good data for deer

Season: Spring and summer (lower [Co] in pasture due to higher growth rates → Dilution of Co)

District: Bay of Plenty (volcanic soils)

• Lake Taupo ash blown over the Bay of Plenty → Young volcanic soil with Co deficiency)

Cobalt: Function and source

Function: Constituent of vitB12 which is part of the co-enzyme in the propionate → glucose pathway

• No Co → No B12 → No enzyme for gluconeogenesis → Hypoglycaemia

Source: Co is incorporated into vitB12 by rumen microbes

• Co administered ORAL only (parenteral administration → MUST be vitB12)

Cobalt deficiency: 4 Clinical signs

1. Ill-thrift and poor growth rates in lambs (post-weaning #1)

   • DDx: Parasitism, nutritional deficiency, Se or Co deficiency

   • Poor GR reported in cattle BUT very uncommon (Co supplementation often excessive in cattle but NOT harmful as vitB12 is NOT toxic)

SEVERE

2. Eye discharge

3. “Washy” wool

4. Anaemia

Cobalt deficiency: Sample selection

• Number

• Sample type

• Correlation with production response

Number: 10 samples (reasonable variation in population)

Sample: Serum (red top) → Test for vitB12

• Although most vitB12 stored in liver, serum is easier to collect AND equally as useful

Correlation: Test RR has good correlation with expected production response

Iodine: 3 Functions

Used to synthesise thyroid hormones which are important for:

1. Energy metabolism

2. Development of foetal brain, lungs, heart and wool follicles

3. Stimulate production of foetal lung surfactant

Iodine deficiency: Predilection

• Signalment

• Season

• District

Signalment: Newborns #1 (foetal intake depends on dam's daily intake)

• Goats > sheep > cattle (rare and no supplementation required)

Season: Winter/spring

• Brassicas ± clover contain goitrogens which interfere with iodine uptake in the thyroid gland → Iodine deficiency

• eg. Pregnant ewes grazing brassicas in Southland → Prevent with iodine supplementation during gestation

District: Manawatu, Canterbury planes, Otago Southland

Iodine deficiency: Clinical signs

1. Goitre

2. Increased perinatal mortality due to

   1. Reduced ability to generate energy/heat

   2. Difficulty standing

   3. Heart and lungs do not form

   4. Cannot retain heat

Iodine deficiency: Sample selection

• Number

• Sample type

• 2 Types of tests

Number: ≥15 dead lambs

Sample: Thyroid (gm) : BWT (kg) ratio

• Individual/mean > 0.7 - 0.8 → Goitre

• Mean > 0.4 → Subclinical deficiency

Tests:

1. Lamb PM → Thyroid : BWT ratio

2. Ewe serum for iodine

   • -ve: Only measures intake over last 2 - 3 days

Copper deficiency: 5 Reasons why Cu is a complex TE

1. Interaction between Cu and other elements (secondary Cu deficiency much more common than a primary deficiency)

2. Large variation in animal levels/responses

3. Clinical signs of marginal deficiency are vague

4. No reliable production response RR

5. Toxic in overdose (chronic OR acute)

Copper deficiency: 5 Factors affecting Cu absorption

1. Age (high milk, low pasture = more Cu absorption eg. young cattle on milk)

2. Feed type

3. Season

4. Species/breed/individual variation (Texel sheep are very good at storing copper while Finn are poor)

   • Cattle/deer > sheep (Cu deficiency less common)

5. Mo, S and Fe → Bind Cu in rumen and prevent absorption = #1 driver of Cu deficiency on-farm

   • Mo #1 in NZ due to application of lime to pasture → Increased pH to optimise pasture growth

   • Mo levels peak in spring

Copper: 4 Functions

Function: Essential part of >12 enzymes involved in many functions

1. Myelin formation (neurological function)

2. Elastin and collagen synthesis (joints and bone strength)

3. Erythropoiesis (anaemia)

4. Pigmentation

Copper deficiency: Clinical signs

• Cattle (7)

• Deer (3)

• Sheep ()

Cattle

1. Ill-thrift

2. Diarrhoea

3. Loss of coat colour and pigmentation

4. Skeletal defects (spontaneous fractures)

5. Anaemia

6. Decreased milk production

7. Decreased reproductive performance (reduced calving rates)

Deer

1. Swayback = Hypomyelination in adult deer >9 months → Reduced function of hindlimbs

2. Osteochondrosis in young deer → Severe lameness

3. Reduced GR?

Sheep: Uncommon Cu deficiency → Vet-only supplement (do NOT prescribe unless confident of deficiency due to risk of toxicity)

1. Swayback in lambs (congenital OR delayed)

2. Bone fragility

Iodine deficiency: Sample selection

• Number

• Sample type

• 2 Types of tests

Number: ≥16 samples ideally (>7 recommended)

• High variation BUT $$$ sampling

Sample: Liver biopsy = Stab incision between ribs with biopsy probe

• Collection at meatworks or PM

Tests:

1. Liver biopsy #1 to assess sufficiency AND monitor

2. Serum okay to confirm deficiency but does NOT indicate Cu store in liver

Copper deficiency: Predicting response to Cu supplementation

• No production response RR

  • Cu supplementation in “deficient” herds → No detectable production response

• Decision to supplement based on risk assessment (combination of history, clinical signs, management system etc.)

  • No hard cut off like other three TE

• Over-interpretation of SERUM copper concentration is dangerous

  • Liver samples #1 prediction

• Must consider time of year and whether depleting (over winter) or repleting (spring)

• Decision of supplementation ≠ Diagnosis of deficiency

Copper deficiency: Targets for Cu concentration in liver

• Sufficient concentration

• Aim in autumn/early winter (+ 4 reasons why)

• Toxic concentration

Sufficient: Liver > 95µmol/kg = Adequate

Aim: Liver > 300µmol/kg in autumn and early winter as Cu levels are the lowest in spring (deplete over winter) due to

1. Soil dynamics in winter changing availability of Cu to animals (change in pH, water-logging)

2. Reduced feed intake in winter (ingest less Cu)

3. Eat more soil in winter due to mud splash and low grazing residuals (ingest more competing elements)

4. Cu demands increase in spring due to gestation and lactation

Toxic: Liver ~3000 - 4000µmol/kg

EXAMPLE: Beef cows in July

Question: Is supplementation necessary?

YES! Early winter → Expect Cu levels to decline more over winter → Deficiency in spring

• Aim > 300µmol/kg

9 Options for TE supplementation

1. Oral dosing

2. Injection (short-acting & long-acting)

3. Addition to fertiliser (Co, Se)

4. Addition to water supply

5. Rumen boluses

6. Pour-on (Se; cattle)

7. Pasture foliar sprays (Co)

8. Mineral licks?

9. Anthelmintics (most contain TEs BUT only useful for Se in animals being regularly drenched)

6 Options for Co supplementation (+ advantages and disadvantages)

Method	Advantages	Disadvantages
Cobalt sulphate fertiliser	Once per year (low labour input) No extra animal manipulations	$ Short period of effect (strategic timing required) Must supplement whole farm, but only benefits proportion of stock (vs. Se which benefits ALL stock classes)
Short-acting vitB12 injection	Cheap Target treat animals which require it	Repeat doses as only raises levels for 1 month Extra labour and animal manipulations
Long-acting vitB12 injection	Adequately raise levels for 8 months Target treat animals that require it	$
Cobalt sulphate pasture foliar spray	Cheap Target areas where lambs graze No extra animal manipulations	Appropriate equipment (tractor with boom sprayer) required Land with appropriate contour Labour Short period of activity
Oral bolus	Adequately raise levels for 3 - 4 months 1 - 2 doses required Target treat animals that require it	$$$ Only licensed for sheep >40kg More effort to administer
Oral dosing	Cheap Target treat animals that require it	Regular treatments required → Adequately raise levels for 3 - 7 days High labour input Multiple yardings and manipulations of animals

EXAMPLE:

History:

In early April Matt contacts you as he is unhappy with the growth rates of his 750 ewe hoggets, which are 3kg below target. They haven't been weighed since weaning in December, at which stage their weights were on target.

• Matt tells you that the ewe hoggets have not received any specific trace element supplements although he has been drenching them for worms every 28 days with a mineralised drench. He had some trace element testing done about 10 years ago but he can't remember the results, however he thinks they were OK.

Questions:

1. 2 Potential TE deficiencies involved

2. 4 History questions

3. Sampling: For each TE, justify the sample selection

Cobalt and selenium deficiencies?

History:

1. Knowledge of location (known soil deficiencies?)

2. Copy of previous testing results? If not, which vet practice performed the testing

3. Soil or herbage testing performed?

4. Change in management this season? (eg. change in fertiliser type or application or other minerals)

Sampling:

1. Cobalt = 10x serum (red top tube) for vitB12

   • Reasonable variation in population

   • Ensure recent yarding as time off-feed artificially increases vitB12 levels

2. Selenium = x3 - 4 whole blood (EDTA) for GSH-Px

   • Little variation in population

   • Matt has recently drenched with mineral anthelmintic → Ensure drenching is keeping Se level adequate

   • Consider whole blood Se if no drenching was performed

EXAMPLE: How would you interpret the results? Are they relevant only to the ewe hoggets or can they also be extrapolated to other livestock on the farm?

The Vitamin B12 levels are in the low to marginal range and this is almost certainly playing a role in the poor growth rates of these hoggets. Young growing sheep have the highest requirement for cobalt so it is likely that any other lambs/hoggets on the farm will also be affected. Adult sheep are unlikely to be affected. Cattle have a much lower requirement for cobalt than sheep and are very unlikely to be affected.

GPx levels are well into the adequate range and rules-out selenium deficiency as being a contributor to the poor growth rates in these ewe hoggets, at least over the past couple of months. The hoggets have been getting drenched every 28 days with mineralised anthelmintic which will raise their Se levels so we can't extrapolate these results to other livestock on the farm (except for those that have also been getting regularly drenched with mineralised anthelmintic).

EXAMPLE: Cobalt deficiency

Matt has 2,600 ewes which produce 3,200 lambs. 750 ewe lambs are retained as replacements while the remainder of the lambs are sold to slaughter between December (weaning) and August. He also runs 500 R1 and R2 dairy grazers.

The farm contour is a mix of steeper hill, medium hill and rolling hill. The ewes and ewe hoggets are mainly grazed on the steeper and medium hill country while the finishing lambs and dairy grazers are mainly grazed on the medium and rolling hill country.

The lambs/hoggets are the stock class on this farm which require supplementation.

Question: What supplementation option/s would you recommend to Matt? Justify your choices (note there are not necessarily any right or wrong answers).

1. Copper sulphate fertiliser is contraindicated as only the hogget lambs and ewes require the treatment and they make up a low proportion of the stock units on the farm. Because they will eventually graze the whole farm, the whole farm must have copper sulphate which becomes very expensive considering how small the proportion of their stock class is. Timing of fertiliser application must also be consistent

2. Short-acting vitamin B12 injections are cheap and target animals requiring supplementation. BUT repeated injections are required (good for lambs to slaughter soon after weaning, but not for smaller lambs that are kept for longer or replacements)

3. Long-acting vitamin B12 injections target animals which require supplementation and last long so repeated doses are unnecessary. BUT they are $$$. They are a good option for lambs going to be on farm for a long time (eg. replacements and small lambs that will take a long time to reach slaughter weight)

4. Pasture foliar spray is cheap and you can target-treat lamb paddocks. Because animals are not individually treated, it is less labour and stress of handling BUT it is not feasible on Matt’s farm due to undulating contour and requires a high labour output

5. Oral bolus is contraindicated as ewe hoggets and lambs have not yet reached this weight. In fact, by the time the lambs reach this weight, they will be almost ready for slaughter

6. Oral dosing is cheap and can be individually-targeted but the period of action is short which makes it contraindicated due to excessive labour and animal manipulations required

EXAMPLE:

In March you are contacted by Anaru and Christine who have recently purchased a local sheep and beef cattle farm along with the livestock already resident there. The farm is rather run-down and known to have poor production due to poor management and low inputs. Anaru and Christine are very motivated to improve the livestock performance on the farm and have asked you to come to the farm to develop an animal health plan.

Currently the farm is used as a breeding property. There are 4,200 ewes producing 4,300 lambs - 1200 ewe lambs are retained as replacements and the remainder are sold as store lambs at weaning in December. There are 260 breeding cows producing 215 calves. 60 heifer calves are retained as replacements while the remainder are sold at weaning which is next month, in April.

Question: The aim for this farm is to ensure TE sufficiency. In order to accurately do this, animal testing is required. Fill in the table below.

TE	Ideal Livestock Class to Test	Ideal Time of Year to Test	Ideal Sample to Collect	Ideal Number of Samples to Collect
Co
Se
Cu
I

TE	Ideal Livestock Class to Test	Ideal Time of Year to Test	Ideal Sample to Collect	Ideal Number of Samples to Collect
Co	Lambs	Pre-weaning or at weaning	Serum vitB12	10
Se	ANY (assuming no recent supplementation and all grazing similar parts of the farm)	Anytime	GSH-Px whole blood	3 - 5
Cu	Older cattle (R2 heifers and adults) Avoid calves as largely on milk (sufficient Cu)	Slaughter pre-winter from non-pregnant cows	Liver biopsy	5 - 7
I	Lambs	Spring	PM thyroid (gm) : BWT (kg)	≥15