Copper Metabolism in Cattle Flashcards
Copper introduction
- first shown to be essential for growth/development/haemoglobin production in lab rats in 1920s
- grazing ruminants with chronic wasting diseases found to respond to copper therapy (e.g Sawyback - ataxic disease of newborn lambs, neuromuscular condition unable to stand)
- copper deficient soils affecting livestock and vegetation
Is copper a trace element
What is a trace element
Yes
required in small quantities (mg/kg DM) cattle need 15-30mg/kgDM of copper
What is an enzyme co-factor
a chemical compound required by an enzyme as a catalyst
cytochrome c oxidase role
can copper be used as an antioxidant
enzyme that requires copper for respiration in the electron transport chain as an electron acceptor
responsible to generate energy for all tissues
antioxidant - prevent tissue damage from free radicles and get rid of waste produced during respiration
Copper in transport of other minerals
Hepheastin - transport of iron from intestines, influx of iron across basolateral membrane into cells of intestinal tract
Peptidylglycine monoxygenase
- copper dependant enzyme required for generation of appetite regulating hormones
gastrin and CCK
serum/tissue of - activity in PAM rats positively correlated with dietary intake of copper
Copper Metabolism - absorption
- occurs in duodenum
- enters enterocytes ACTIVE transport from lumen
- exits by active transport into blood
- Cu2+ to Cu by brush boarder metalloenzymes at apical surface then transported across apical membrane of enterocyte by CTR1 (high affinity copper transporter
- Cu transported into golgi network = synthesis of metalloenzymes (e.g hepheastin) OR shuttled by atox1 to ATP7A into bloodstream
Where does copper go after absorption
to the liver(copper homeostasis main organ)
Cu bound to serum albumin with transcuprien and histidine
Liver role
storage organ
regulates copper excretion in bile
secrete copper into blood for transport to tissues
Copper storage and excretion
- liver
- Cu uptake into hepatocytes mediated by CTR1
- Cu binds to cytosolic copper chaperones for intracellular transport
- after transfer across gut = enter portal vein
- free intracellular copper stored in vesicular copper pools
- liver fluke infestations can limit how much Cu liver can store
Three pools of Cu in liver
- storage (mainly in MT)
- excretion (transpored into bile)
- transit (enters enzymes)
What happens if there is excess in copper supply
ATP7B translocates to the cell membrane and pumps copper out of cell
Copper transport
Ceruloplasmin (CP)= main transport protein - binds 6 Cu ions
consists of 90% plasma Cu
CP produced at steady rate
however studies in mice found after gene deletion for CP still metabolise copper
Clinical copper deficiency in ruminants signs
- visible
- economic
- pathological
- change coat colour (black to white wool), swayback in lambs
- infertility (anoestrus, lack of oestrus behaviour), Reduced growth rate poor FCR (feed conversion efficiencies)
- uneven bone growth = osteochondrosis
- connective tissue dysfunction (e.g. lesions in ligamentum nuchse supporting neck lead to dislocation causing head to drop and create a ‘hump’
- heart func, immune func,
- RBC formation (haemoglobin synthesis declines)
Causes of copper deficiency in ruminants
- primary - lack of Cu in diet (unlikly problem in UK, tolerate low Cu)
- Secondary - antagonists affecting Cu metabolism (e.g. molybdenum, sulphur, iron, zinc) lead to copper responsive disorders
Suttle (1990) concluded Mo+S interactions main cause of Cu deficiency
Why use term copper responsive disorder rather than clinical deficiency
may look clinically well and give it copper supplementation and its health may improve
if clinically or sub clinically deficient, respond to copper treatment
What do molybdenum and sulphur combine to create
Thiomolybdates (MoS4)
prevents absorption of copper
can cause copper deficiency
- sulphide formed by ruminal microorg from dietary sulphate/organic sulphate compounds
molybdenum only exerts limiting effect on copper retention in presence of sulphur
Thiomolybdates
- what forms them
- types and effects
- Mo and S form monothiomolybdates (TM1) - breakdown acidity of abomasum
- become TM3
- become TM4 (tetra-thiomolybdates) collect copper, dont allow absorption
- further along sequence = more stable
- more Mo and S in diet = further along sequence TM formed
What can happen to TMs
- excreted in faeces
- absorbed into blood and excreted through bile or stored in liver. exert systematic effect on Cu metabolism in excess
- go into tissues - thiomolybdate removes Cu, inactivates enzymes = toxic
What is the haemolytic phase
mass release of Cu into the bloodstream, excess copper induce production of superoxide radicals which cause RBC membrane damage
mass hepatic degeneration, liver breaks down, metabolic shut down
Clinical signs of haemolytic phase
- jaundice (excessive breakdown of rbc leading to bile accumulation)
- dark urine
- blood dullness
- death
Why are younger animals more susceptible to copper toxicity
higher copper absorption in young
decreased copper absorption in adults
can still look clinically heathy with build up of copper
How much copper fed to a cow to avoid deficiency
10-15 mg Cu/kg DM
Sources of copper
- pasture/food/crops depending on soil Cu, drainage, herbage species
- normal pasture range = 4-8mg/kg DM
- low in milk
Copper toxicity
- another name
- dependent on..
- danger level
- what does it cause
- enzymes
- breed susceptibility
- EU maximum Cu
- cumulative poison (excess Cu ingested)
~ species dependent - pigs = highly tolerant, cattle ok, sheep = low tollerence and susceptable to copper poisoning esp on concentrated diets - gradual accumulation until 100mg/kg fat free DM
poisoning occurs in areas where herbage contains 10-20mg/kg DM Cu and low molybdenum levels
~necrosis of liver cells, jaundice (high bilirubin levels), loss appetite, death (from hepatic coma) ~ high Cu damages liver without symptoms - leakage of enzymes from damaged cells into blood, sudden lelease of Cu and haemolysis as a result of stressor (parturition, infection)
~ scottish black face = least susceptable, Texel = most - EU max = 15mg/kg DM Cu
~ care with antiprotozoal compounds = eliminte protozoa that produce sulphide that lowers CU availability (e.g. monesin)
Teart and molybdenum levels in teart soil compared to normal
= condition in cattle that causes scouring and unthriftyness
- 20-100mg/kgDM (norm = 0.5-3.0)
Crimp wool
- Cu present in enzyme for disulphide bridge formation to 2 adjacent cystine molecules
- copper absent = protein molecules in wool dont form bridge and wool stringy
Nutritional anaemia and falling disease
- produced experimentally in young pigs by diets low in Cu
- arise easily in animals just fed milk
- unlikely in older animals = copper supplementation unnecessary
- copper deficincy in cattle
- austrailia
- progressive degeneration of myocardium
Cu role in
- ceruloplasmin
- erythrocruorin
- superoxide dismutase
- pigments
- (protein) role with release of iron from cells into plasma. Deficient = impairs ability to absorb iron, mobilise from tissues and utilise in haemoglobin synthesis
- (protein) occurs in erythrocytes (RBC) role in oxygen metabolism = oxygen carrying haemoprotein complexes
- part of cells antioxident system, breaksdown harmful oxygen molecules
- ## Turacin = pigment of feathers
Cu deficiency symptoms
- anaemia
- poor growth
- bone disorders
- infertility
- depigmentation
- gastro-intestinal disturbances
- scouring
- lesions in brain stem and spinal chord = associated with muscular incoordination (lack of control), occurs especially in young lambs
Enzoonotic ataxia
- pastures with low copper content (2-4mg/kg DM)
- prevent = feed copper salt
- study in 1977 (smith et al) determine which stage in foetal or postnatal development produces ataxic lambs
~ EA detected 99 days of foetal age
~ no lesions if ewe received supplementary copper during pregnancy
~ primary events responsible for EA development take place after mid term
Swayback
- forms
What causes variable Cu absorption efficiency
- causes complete paralysis and/or staggering gait on hind limbs
- 2 forms ~ congenital (signs apparent at birth) irriversible but prevented only by ewe enough Cu in diet
~ onset of clinical disease dlayed for several weeks - parenteral injection of copper complexes in small doses - not always caused by dietary deficiency as been known on high Cu pastures
- efficiency of copper absorption variable
~ 10x variation in efficiency with Scottish blackface ewes absorbing Cu from autumn pasture (1.2%) and from leafy brassicas (13.2%)
~ genetics influence conc of Cu in blood/brain/liver of sheep - swayback affected by genotype
lambs given Cu supplemented diet and fishmeal retained Blackface = 6%, Texel = 13%, Suffolk = 8-9%
McCaughern, Mckenzie and Sinclair - starch
- 2020
- found feeding higher starch conc in diet increased hepatic Cu concentration
- so if deficient, could be a viable option
- increased serum ceruloplasmin activity = release iron into plasma from cells
- main effect of starch, no effective antagonist
- pH = lower recticular ph from maize diets compared to grass
- once fed in morning = rapid decrease in ph (metabolise nutrients, release VFA)
- protein yield increase with high starch conc (greater FME, greater growth of microbes, to abomasum where broken down into amino acids passed onto mamary glands)
- DMI = suplemented diets decreased (high sulphur
Individual farm Cu intake in 2012 - results
sinclair and atkins
- 50 farms involved
measured Cu levels where cattle exposed (mixed ration, water0 - Only 6/50 farms fed at or below 2011 UK guideline maximum of 20mg/kgDM
- no farms feeding below requirements
- EU limit Cu to dairy cow was = 40mg/kgDM
- 2016 brought down to 34mg/kgDM = 10 farms above limit
- mean intake of Cu = 258% of NRC 2001 value (12mg/kgDM)
- most farms have tendency to oversuplement CU
Kendall et al 2015 - liver Cu conc in cull cattle in Uk
and why dont get toxicity
- separated into animal classification = beef cows, dairy Holstein, other dairy breeds
- measured liver Cu conc above AHVLA reference range = 508mg/kgDM (%)
- 38% Holstein dairy cull cows had higher toxic liver Cu conc which were higher than reference range
- beef cows (lower proportion of concentrates, housed short periods, exposed to higher sulphur/molybdenum) 17% higher toxic liver Cu higher than reference range
- Holstein breed has high tolerance for Cu toxicity (just seem dull, lethargic) rarely copper toxic clinically
Why care about copper toxicity (health complication)
- increased risk of cancer (urinary tract)
- enter food chain and impact human health
Reasons for over supplementation of Cu
- decreased fertility with suboptimal Cu supplementation = safe than sorry to prevent reduced fertility
- copper come from variety of sources (miscommunication form nutritionist, mineral sales person sell boluses
- high conc of sulphur/molybdenum in forage in some farms
Effect of forage type and antagonists on hepatic Cu retention
- forage vs maize
- forage with naturally high sulphur and molybdenum, nutritionists analyse
- increase copper conc in diet
- avoid deficiency and no toxicity due to high S/Mo conc
- if grow maze for lactating dairy cows (high S/Mo) increase Cu to compensate
- cows with maize drop dead of Cu toxicity = lethargic, reduced intakes/fertility/yeilds, outbreaks of Tb
Effect of forage type and antagonists on hepatic Cu retention
(study)
- Sinclair et al 2017
- 56 cows
- see differences between maize diet vs grass based
- 75% maize/25% grass and then 25% maize/75% grass
- 4 treatments = maize with/wo antagonists, grass with/wo antagonists
- antagonists = extra S/Mo to simulate farms with naturally high cons
- feed diets for 14 weeks each
- monitor changes in hepatic copper conc and performance over time
- liver sample at start of diet, at 14 weeks (calculate change per day)
- with normal maize/grass diets both hepatic conc increased by 0.7 and 0.9 respectively
- expect conc to go down same extent in antagonist diets due to S/Mo
- grass based diet = di happen
- maize = still increased in copper by 0.2mg/kgDM = S/Mo not really affect in maize
How dairy cow diets changed and why
- now in uk, increased milk yields for dairy cows
- fed higher energy diets = substituted grass for maize
- ## maize has more energy to drive higher milk yields
What’s wrong with equations for calculating Cu needed for diets
- initially based on smi purified grassbased diets in sheep
- dont apply to maize diets
Why differences in Cu metabolism between dairy vs beef cattle
- not taking account of maze inclusion in lactating dairy cow diets = should give lower quantities of copper
- feed greater quantities of copper easier
- lots of sources of copper
Copper statistics
- uk dairy herds feeding above industry limit 20mg/kgDM Cu
- uk female dairy herd had toxic/high liver Cu conc
- 64%
- 40%
Affect of diets on rumen ph and dietary starch
- maize silage diets = reduce pH to greater extent compared to grass based diet
- rumen pH may have effect on type of TM formed
- feeding maize alters dietary starch concentrations
- dietary starch related to rapidly fermentable carbohydrates, rapid fermentation results in volatile fatty acids (esp propionic acid
- generation of propionic acid decreases pH of rumen = affect TM formation = affect copper absorption
Sulphur metabolism in rumen and affect on DMI
why is there a change in intake for high starch diets
- inorganic or organic (containing amino acids)
- acted on by sulphur reducing bacteria = release hydrogen sulphide (HS)
- HS 2 pathways in rumen ~ dissociate to form bisulfide or remain as hydrogen sulphide where migrate to gas cap of rumen is eructated and inhaled, absorbed into blood streem and cauases brain damage (polioencephalomalacia)
- sulphur acts of smooth muscle lining the rumen and slows down contraction, feedstuff retention time increases, cant eat as much full for longer, decrease intake
- lower ruminal ph = greater proportion of hydrogen sulphide migrate to gas cap (high starch diets)
Where does the interaction of S and Mo occur
ruminal fluid
What happens when sulphur is lost from the system (rumen)
less sulphur around to complex copper in TM and prevent absorption
Low starch vs high starch - hydrogen sulphide pathways
low = hydrogen sulphide turns to bisulfide S combine with Mo to form Thiomolybdates which results in HIGHER pH
high = hydrogen sulphide enter lungs and LOWER pH
Measuring copper status
- diet
- liver biopsey ~ local anesthetic, 11th intercostal space, probe inserted, very invasive
- blood ~ identifies Cu deficiency, liver enzymes enter blood when hepatocytes rupture
- ICP-MS = measures dietary minerals (Cu, S, Mo) other factors can influence such as diet
Why is it difficult to diagnose Cu status, toxicity and deficiency
What does diagnosis rely on
- clinical signs of copper deprivation cant be relied on for diagnosis (e.g. various nutritional stresses cause loss of crimped wool in sheep
- presence of clinical symptoms OR sub clinical loss production
- biochemical evidence of subnormal tissue or blood copper
- improvement after treatment with copper compares to untreated cattle
- find def/toxicity
- try to correct it and alter supplementation strategies
- track performance
How to measure Cu status from blood samples
- plasma copper = icp-ms
- ceruloplasmin = ELIZA
- liver function enzymes e.g. AST, ALT = ELIZA
- measure Mo levels in plasma (More Mo absorbed via intestinal wall = indicate more Cu absorbed and Mo not complex with copper ~ not in blood, removed in faeces
How to measure Cu status in liver samples
- liver Cu conc = ICP-MS
- Adv = most accurate
- DIs = invasive, expensive, time consuming
- big range in deficiency and toxicity = changes with fertility and immunology even within middle range (20mg/kgDM - 508mg/kgDM
Ways to prevent Cu deficiency
- Cu containing pasture fertilisers
- inorganic dietary supplement sources
~ salt licks containing 0.5-1.9% CU
~ Cu solution in water (small doses can cause rapid clinical response due to some Cu bypassing rumen) or forage to maintain a Cu:Mo ratio of >3 - Organic dietary sources
~ Calves given 10mg/kg DM Cu as glycinate complex in corn-based diets containing 2 and later 6mg/kg DM Mo = up to 44% greater responses in plasma and liver Cu
