Mineral deficiencies and toxicities

Question 1

What nutrition do cows need?

Answer 1

• energy and protein
• water
• minerals and vitamins

Question 2

What are minerals and vitamins essential for?

Answer 2

• allowing chemical reactions in body to take place - important for growth, fertility, health and immunity

Question 3

where is copper stored in the body?

Answer 3

• liver

Question 4

How is vitamin B12 synthesised in ruminants?

Answer 4

• made in rumen by microbes, using cobalt from the ration

Question 5

What two types of disease may mineral/vitamin deficiencies cause?

Answer 5

• subclinical, eg poor performance
• clinical, eg grass staggers

Question 6

What type of food will ensure a better mineral and trace element supply?

Answer 6

• more varied feed in base ration

Question 7

function of vitamin A

Answer 7

• eye function and growth, reproduction + immune response

Question 8

function of vitamin D

Answer 8

• absorption of calcium and phosphorus

Question 9

function of vitamin E

Answer 9

• biological antioxidant, protects cells against oxidative damage

Question 10

What vitamin deficiency causes cerebrocortical necrosis?

Answer 10

• thiamine (B1)

Question 11

which animals have the greatest demand for trace elements?

Answer 11

• young, pregnant + lactating

Question 12

What causes trace element levels to vary in pasture?

Answer 12

• vary due to soil type, pH, drainage and fertilised application

Question 13

Why are Texels more susceptible to copper toxicity?

Answer 13

• heightened ability to absorb dietary copper

Question 14

What is the most common mineral condition seen in cows?

Answer 14

• hypocalcaemia (milk fever)

Question 15

CS of lead poisoning?

Answer 15

• anorexia
• rumen stasis
• colic and constipation followed by diarrhoea
• neurological signs with progression

Question 16

A farm keep a flock of sheep. They are extensively grazed and only housed ready for lambing in March. They have started lambing. Start of the year wet with 30% more rainfall than previous so sheep brought in earlier and fed bale silage harvested from improved grassland. Some lambs have recently been born with an ataxic condition manifesting as paralysis and severe weakness in the hindlimbs.

What is your top differential and why?

What else should be ruled out?

Answer 16

copper deficiency - hind leg weakness and paralysis indicating potential spinal cord lesion (swayback if ewes became deficient in copper mid way through pregnancy)

rule out selenium/vit E deficiency

Question 17

Why might high levels of sulphur in forage lead to weak lambs with swayback?

Answer 17

• copper binds to sulphur which makes copper less available if sulphur levels high

Question 18

why are enzymes useful in comparison to simple concentrations for mineral deficiency/toxicity blood data?

Answer 18

• helps to determine that the minerals we are interested in are biologically available + takes into account mineral that is bound/being transported and utilised

Question 19

What do plasma selenium concentrations show?

Answer 19

• The short term (<1 week) selenium content of the blood
• An indicator of recent selenium intake rather than body stores.

Question 20

What is plasma selenium bound to that may mean it is affected by nutritional status?

Answer 20

• lipoproteins

Question 21

What is superoxide dismutase (SOD) a measure of?

Answer 21

• a medium term (approx 6 weeks) measure of functional copper through enzyme activity

Question 22

What is caeruloplasmin (Cp) a measure of?

Answer 22

• a short term (<1 week) measure of functional copper via enzyme activity
• Can also be elevated during acute phase responses

Question 23

What is plasma copper a measure of?

Answer 23

• concentration reflects the short term (<1 week) copper content of the blood but does not indicate that this copper is biologically functional

Question 24

What is glutathione peroxidase a measure of?

Answer 24

• a medium term (approx. 6 weeks) measure of functional selenium through enzyme activity

Question 25

How might you tx multiple cases of swayback?

Answer 25

- supplement silage with copper or supplementation of ewe with copper mid-gestation

Question 26

How might you prevent swayback from occurring in the first place?

Answer 26

- regular monitoring of silage mineral concentrations alongside monitoring of liver copper concentrations from cull animals

Question 27

What is silage cut from improved pasture often high in?

Answer 27

- sulphur

Question 28

What causes high iron in silage that could lead to copper deficiency?

Answer 28

- high rainfall prior to ensiling

Question 29

Why might you not supplement Texel breeds with copper, and instead manage swayback through grassland management and monitoring of silage?

Answer 29

- texels more sensitive to copper toxicity

Question 30

You visit a cattle farm. They have been wintered indoors before being turned out to pasture a few months ago. The grazing is perennial ryegrass and the fields are looking lush. This morning, one of his best cows 7 weeks into lactation was found dead - only sign was scuffing of the ground around her feet + head pulled back on her body. You rule out anthrax as no evidence of bloody discharge from orifices and farmer would have witnessed changes prior. There is no obvious bloating or illness. What do you suspect problem is and why? What should we rule out that could also cause sudden death?

Answer 30

- magnesium deficiency -- lush grass = less magnesium -- scuffing around feet = paddling seizures - rule out copper deficiency

Question 31

What mineral do cows need to be supplied with daily?

Answer 31

- magnesium

Question 32

why might calcium also be low if magnesium is low?

Answer 32

- low levels of magnesium = can affect calcium absorption

Question 33

Are microminerals required in more or less abundance than macrominerals?

Answer 33

- less

Question 34

what is often the first sign of magnesium deficiency on farm?

Answer 34

- dead cow

Question 35

how might cows in early stage of magnesium deficiency appear?

Answer 35

- like down cows with milk fever but will be nervous, trembling, overly excited or staggering

Question 36

How might you determine magnesium deficiency?

Answer 36

- test blood magnesium live cows - test pasture magnesium levels - vitreous humour in dead cows (or CSF)

Question 37

Why does lush grass cause magnesium deficiency?

Answer 37

- rapidly growing so low in magnesium with greater water content which will increase transit and lower uptake

Question 38

What management of pasture increases risk of grass staggers?

Answer 38

- heavy fertilisation in spring with nitrogen and potassium - high potassium and nitrogen and low sodium = interfere with magnesium absorption from rumen

Question 39

Why might early lactating cows be more at risk of grass staggers?

Answer 39

- calcium deficiency as in higher demand = more severe cases of grass staggers when coupled with magnesium deficiency

Question 40

Which animals suffer most with grass staggers?

Answer 40

- beef cattle in peak lactation ->need constant source of magnesium to replace large amount lost from body in milk. - even when feed levels of Mg low, milk levels remain the same

Question 41

why is testing blood of dead cows for magnesium levels not useful indicator?

Answer 41

- levels return to normal after death