microelements

Question 1

when are deficiencies likely to occur?

Answer 1

deficient soils
antagonists: soil pH, moisture & other elements & chemicals; plant e.g. goitrogens
performance animals @ grass: growing lambs/NZ type dairy systems
animals being fed unconventional diets/grazed in certain microenviron

Question 2

sources of toxicities?

Answer 2

soil
reclaimed land from mining
land w spoil heaps/slag or ash
certain plants can accumulate Se/Cu to toxic lvls
pig slurry
iatrogenic - feeding inapprop. feed to sheep (cattle feed has higher lvls of Cu)

(Se tox most likely in dry environ w high pH)

Question 3

how to assess mineral adequacy?

Answer 3

soil sampling
forage sampling
animal sampling 
-stores
-circulating pool
-fn 
supp & measurement

Question 4

blackies vs texels: who accumulate Cu more?

Answer 4

texels - sample for Cu tox

sample blackies for Cu def

Question 5

Se vs cobalt/vit B12: which need to sample more animals?

Answer 5

cobalt/Vit B13

Se more tightly controlled

Question 6

does Cu have a long half life?

Answer 6

yes, animal can hold Cu in liver for years
if blood sample adequate now doesn’t mean diet is adequate now
also consider age of animal sampling

Question 7

does cobalt/vitB12 have a long half life?

Answer 7

no - only hold reserves for 2-4wks

Question 8

what is Se correlated to?

Answer 8

half life of RBCs

Question 9

landmarks for sampling liver?

Answer 9

ICS 9/10
aim for opp elbow (45deg)
1/3 way down
standing (better) or LLR

Question 10

what is the classic storage organ for Cu?

Answer 10

liver

Question 11

which side is used for sampling liver?

Answer 11

RHS
rumen predominantly on LHS of animal - displaces liver to R
liver is just tucked underneath diaphragm, if go towards caudal ribcage should hit liver

Question 12

what is vit B12 used for?

Answer 12

methyl transfer - TCA cycle, purine & pyrimidine synthesis

mineral of starvation

Question 13

how is vit B12 absorbed?

Answer 13

protein produced in stomach binds to vitB12 which is then absorbed in SI
might be why sometimes assoc. btwn parasitism & vitB12 def

Question 14

CS of cobalt

Answer 14

results in vit B12 def (pine)
starvation w appetite suppression, ocular discharge, anaemia & fatty liver: anaemia from starvation; nutrients accumulating in liver & not moving on, will tend to get friable & fatty liver
lambs > adult sheep > cattle

Question 15

diagnosis of cobalt deficiency?

Answer 15

vit B12 blood in sheep, but not cattle
liver, milk vit B12 or methylmalonic acid (chemical which accumulates in liver bcs cannot be processed) in serum
vit B12 req for metabolising methymalonic acid

Question 16

tx of cobalt def?

Answer 16

fertiliser/boluses/feed/inj (short/long acting) or mineral added to diet

Question 17

what is selenium used for?

Answer 17

selenoproteins: glutathione peroxidases - resp for controlling reactive species (similar to antioxidants)
transforming thyroxine (T4) to triiodothyronine (T3): affects thyroid hormones - will have def in T3 if have def in Se, body slow down

Question 18

CS of Se def?

Answer 18

oxidative damage: white muscle dx - fast growing animals on diets w high oxidative stress; get ischaemia of muscle, fibrosis if serious & can be fatal; will affect myocardium as well as skeletal muscles
reduced growth, esp wool
reduced immune fn & fertility (not simple rs)
reduced ovine neonate survival bcs less T3

Question 19

diagnosis of Se def?

Answer 19

serum glutathione perioxidase

Question 20

tx of Se def?

Answer 20

boluses/oral dose/inj (depot)/fertiliser/mineral add to diet

Question 21

what are the toxicities of Se?

Answer 21

direct inhibition of cellular oxidation/reduction rxn by depleting glutathione & S-adenosylmethionine reserves
pdtn of free rads that cause oxidative tissue damage (antiox @ low lvls, but metabolised to free rads - low therapeutic index)
replacement of S/S-containing amino acids in body w Se/seleno-amino acids

Question 22

CS of acute Se toxicity (supplementation)?

Answer 22

will occur w/i 24-48h
toxic damage to CVS system
dyspnoea
salivation
recumbency
D+
death

Question 23

CS of chronic toxicity (seleniferous plants)? more elusive

Answer 23

non-specific
dullness
ill-thrift
anaemia
rough coat
brittle hooves (sloughing in extreme cases)
joint paint- to the pt of immobility

Question 24

CS of Cu def?

Answer 24

ataxia (swayback) - 2 forms = neonatal/delayed & atypical (stand transfixed w head quivering due to cerebral oedema)
steely wool-crimp loss
depigmentation
D+
anaemia, infertility & poor growth
#s in adults

Question 25

diagnosis of Cu def?

Answer 25

blood sample: liver store, serum
if bloods norm then biopsy

(molybdenum/iron & sulfur antagonise Cu absorption)

Question 26

what are the fn of Cu?

Answer 26

repro
erythropoiesis 
bone dvlpment
connective tissue dvlpment
skin pigmentation
growth

Question 27

how does fn of Cu relate to Cu deficiency signs?

Answer 27

foetal death - repro
anaemia - erythro
reduced mineralisation of cartilage - bone dvlpm
aortic rupture/reduced bone collagen strength - CT dvlpment
coat depigmentation - skin pigmentation
spinal cord dysfn (swayback)
D+

Question 28

tx of Cu def?

Answer 28

fertiliser (not in Eu): CuSO4 but environ damage
drench/bolus/ruminal needles (dissolves in rumen wall after puncturing into it)
genetic selection
be careful of accumulation!

Question 29

causes of Cu tox?

Answer 29

presents as acute haemolytic crisis dx but usually chronic w acute crisis
cattle feed to sheep (higher Cu content)
red clover
oversupp.
grazing land w hx of pig slurry
breed: HF vs jersey (jersey more suscep?)
distillers by-products: high lvls of Cu because produced in Cu stills
deg of indiv. = high liver lvl of Cu w no crisis vs crisis & death w low liver Cu lvls
dairy cows @ risk of excess Cu c.f. beef cows @ risk of low Cu lvls

Question 30

tx of Cu tox?

Answer 30

ammonium tetrathiomolybdate x3 every other day
only drug that strips Cu from liver - now illegal in Eu
NaSO4
penicillamine

Question 31

categories of iodine def?

Answer 31

primary

secondary to goitrogens: subdivided into plant chemicals & inorganic goitrogens (humans)

Question 32

CS of iodine def?

Answer 32

goitre
scant wool
sometimes high mortality in absence of goitre is due to starvation/hypothermia (esp neonates)

Question 33

diagnosis of iodine def?

Answer 33

PM: ratio of thyroid weight:BW (<0.4g thyroid:1kgBW) = long-term iodine def/functional iodine def
plasma inorganic iodine (PII) - contemp iodine intake: good estimate of sufficiency = good instantaneous measure of sufficiency of diet atm, but not good for long-term bcs good @ storing iodine in thyroid
can measure lvl of iodine intake & diet, can do blood free iodine. good measure of instantaneous dietary iodine intake

Question 34

tx of iodine def?

Answer 34

IM inj of iodised oil pre-mating
oral dosing: 280mg K iodide 8 & 4 wks before lambing
sustained release ruminal boluses: I, Se, Co
pour-on (cattle) - lick themselves hence easily just lick off coat & restore lvls