microelements Flashcards
when are deficiencies likely to occur?
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
sources of toxicities?
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)
how to assess mineral adequacy?
soil sampling forage sampling animal sampling -stores -circulating pool -fn supp & measurement
blackies vs texels: who accumulate Cu more?
texels - sample for Cu tox
sample blackies for Cu def
Se vs cobalt/vit B12: which need to sample more animals?
cobalt/Vit B13
Se more tightly controlled
does Cu have a long half life?
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
does cobalt/vitB12 have a long half life?
no - only hold reserves for 2-4wks
what is Se correlated to?
half life of RBCs
landmarks for sampling liver?
ICS 9/10
aim for opp elbow (45deg)
1/3 way down
standing (better) or LLR
what is the classic storage organ for Cu?
liver
which side is used for sampling liver?
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
what is vit B12 used for?
methyl transfer - TCA cycle, purine & pyrimidine synthesis
mineral of starvation
how is vit B12 absorbed?
protein produced in stomach binds to vitB12 which is then absorbed in SI
might be why sometimes assoc. btwn parasitism & vitB12 def
CS of cobalt
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
diagnosis of cobalt deficiency?
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
tx of cobalt def?
fertiliser/boluses/feed/inj (short/long acting) or mineral added to diet
what is selenium used for?
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
CS of Se def?
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
diagnosis of Se def?
serum glutathione perioxidase
tx of Se def?
boluses/oral dose/inj (depot)/fertiliser/mineral add to diet
what are the toxicities of Se?
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
CS of acute Se toxicity (supplementation)?
will occur w/i 24-48h toxic damage to CVS system dyspnoea salivation recumbency D+ death
CS of chronic toxicity (seleniferous plants)? more elusive
non-specific dullness ill-thrift anaemia rough coat brittle hooves (sloughing in extreme cases) joint paint- to the pt of immobility
CS of Cu def?
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
