Production Diseases: Microelements Flashcards
When are mineral deficiencies likely to occur
Deficient soils
Antagonists:
- Soil pH, moisture and other elements and chemicals
- Plant
- Ex. goitrogens
Performance animals at grass:
- Growing lambs
- NZ type dairy systems
Animals being fed unconventional diets or grazed in certain microenvironment
how do mineral toxicities occur
Soil
Reclaimed land from mining
Or land with spoil heaps/slag or ash
Certain plants can accumulate selenium/copper to toxic levels
Pig slurry (less common now)
Iatrogenic
how do you assess mineral adequacy
soil sampling
forage sampling
animal sampling
supplementation and measurement
why is soil sampling hard to interpret
Is it in the plants? Are the animals eating these plants? Are the minerals in the plants even available to the animal?
how is forage sampling interpreted
It is for sure in the plant but does the mineral get absorbed/available for the animal?
how are animal samples interpreted
Stores
Circulating pool
Function
One has to understand the at risk population and the variability within the population (sample size)
- Lambs/calves
The half life of the measured parameter, does handling of the animal prior to sampling affect the result?
Whether we are measuring a storage or transport pool or the function associated with the nutrient, which homeostasis will strive to maintain within confines
- Ex. Calcium vs cobalt
Most of all is the result interpretable?
what are the functions of cobalt
Vitamin B12 used in methyl transfer — so TCA cycle and purine and pyrimidine synthesis
Rumen microbes produce B12 from cobalt
what are the clinical signs of cobalt deficiency
Result in Vit B12 deficiency (pine)
Starvation with appetite suppression, ocular discharge, anemia and fatty liver
Lambs > adult sheep > cattle
how is cobalt deficiency diagnosed and treated
Vit B12 blood in sheep
Cattle:
- Not in blood so liver, milk vit B12 or methylmalonic acid in serum (not practical at all)
Fertilizer/boluses/feed/injections (short or long acting) or mineral added to diet
- Drenching every 2 weeks
- Not good at storing water soluble vitamins
what is the funciton of selenium
Selenoproteins:
- Glutathione peroxides responsible for controlling reactive oxygen species
Transforming thyroxine (T4) to triiodothyronine (T3)
what are the clinical signs of Se deficiency
Oxidative damage — white muscle disease
- Fast growing animals on diets with high oxidative stress
Reduced growth, especially wool
Reduced immune function and fertility (not simple relationships)
Reduced ovine neonate survival due to less T3
how is Se deficiency diagnosed
serum glutathionine peroxidase
how is Se deficiency treated
Boluses/oral dose/injections (depot)/fertilizer/mineral addition to diet
what are the toxic effects of Se (3)
Direct inhibition of cellular oxidation/reduction reactions by depleting glutathione and S-adenosylmethionine reserves
Production of free radicals that cause oxidative tissue damage
Replacement of sulphur/sulphur-containing amino acids in the body with selenium/seleno-amino acids
what is chronic Se toxicity associated with
Chronic is associated with geographical sources — no treatment (but possibly try sulphates and copper)
what are the clinical signs of chronic Se toxicity
Non-specific
Dullness
Ill-thrift
Anemia
Rough coat
Brittle hooves (sloughing in extreme cases)
Joint pain — to the point of immobility
what are the clinical signs of acute Se toxicity
Toxic damage to cardiovascular system
Dyspnea
Salivation
Recumbency
Diarrhea
Death
what are the clinical signs of copper deficiency
Ataxia
- Neonatal/delayed and atypical (stand transfixed with head quivering due to cerebral edema)
Steely wool-crimp loss
Depigmentation
Diarrhea
Anemia
Infertility and poor growth
Fractures in adults
what are Cu functions and deficiency signs
how is Cu deficiency diagnosed
liver store
serum - transport hemostasis
how is Cu deficiency treated
Fertilizer
Drench/bolus/ruminal needles
Genetic selection
Need to be careful
Sheep accumulate Cu and it accumulates year on year
what elements antagonize Cu
Remember molybdenum/iron and sulphur all antagonize copper absorption
what does Cu toxicity present as
Presents as acute hemolytic crisis disease but usually chronic with an acute crisis
what are causes of Cu toxicity
Cattle feed to sheep
Red clover
Over supplementation
Grazing land with a history of pig slurry
Holstein vs Jersey (Jersey more susceptible?)
Distillers by-products
Can have high liver levels with no crisis, or have crisis and death with lower liver copper levels
what is the function of iodine
Manage metabolic rate via T3
what can iodine deficiency be categorized as
Primary
Secondary due to goitrogens
how can secondary iodine deficiency due to goitrogens be subdiviced as
Plant chemicals (2 further subgroups)
- Glucosinolates — produce HCN which is converted to thiocyanates which inhibits absorption of iodine (extra iodine is protective)
- Thiouracil goitrogens prevent iodination of tyrosine in the thyroid (extra iodine is minimally protective)
Inorganic goitrogens — defined in humans but not animals
what are the clinical signs of iodine deficiency
Goitre
Scant wool
Sometimes high mortality in absence of goitre due to starvation/hypothermia
how is iodine def diagnosed
Can be difficult
PM
- Measure ratio of thyroid weight:body weight (<0.4g thyroid:1kg BW)
Plasma inorganic iodine (PII)
- Contemporary iodine intake
- Good estimate of sufficiency
how is iodine def tx
Intramuscular injection of iodized oil pre-mating
Oral dosing
- 280mg KI 8 and 4 weeks before lambing
Sustained iodine ruminal boluses
- I, Se, Co
Pour on (cattle)
