Minerals Flashcards
How can mineral deficiencies occur?
Low mins. in diet
Low absorption
Thru mineral interactions (formation of unabsorbable compounds; comp. for metabolic pathway)
Storage & function of minerals?
Held in different compartments (central reserve plus one or more reserves)
Many have multiple functions
Most have catalytic function
Some have physiological function (Na, Ca, Cl, K)
Some have regulatory function (Zn)
A bit about Calcium
Most abundant min in body (in bone)
Essential for: bone/tooth dev.; enzyme systems for normal muscle & nerve function; blood clotting
Blood calcium homeostatic range?
80-120 mg/L
Good sources of calcium?
milk
green, leafy crops
animal products containing bone
limestone
Factors that affect calcium:phosphorus ratio?
High P binds Ca -> - Ca absorption
Low vitamin D -> - Ca utilisation
Recommended Ca:P ratio?
1:1 or 2:1
Feed with best Ca:P ratio?
Oaten hay
Feed with highest Ca content?
Lucerne hay
A bit about vitamin D
2 forms - D2 & D3 Found in cut forages Produced by skin under UV light Stored in liver Works with PTH -> maintain plasma [Ca]
Good sources of vitamin D?
Sunlight & sun-cured forages
Consequences of Ca deficiency/ P excess…?
Rickets - young animals
Milk fever
Developmental orthopaedic disease (DOD) young horses
Osteomalacia & osteoporosis - older animals
Effects of -Ca and ++P?
Hyperparathyroidism -> bone demineralisation (as bone minerals mobilised -> +fibrous connective tissue -> bone enlargement (eg big head)
Symptoms & clinical signs of hypocalcaemia?
Clinical hypocalcaemia -> Milk fever/parturient paresis/paralysis
Inappetence
Lat recumbency
Coma & death
What constitutes hypocalcaemia (mm/L)?
Ca < 1.4mm/L
T or F - Ca is the most common mineral-related problem of the transition cow
True
Mineral availability in digesta occurs as…?
Easily absorbed - metallic ions in solution (Na/K)
Some absorbed - constituents of metallo-organic substances
Not absorbed - parts of insoluble substance
T or F - Minerals can not be converted between different forms
False - they can, depending on pH
Availability of minerals from other sources?
P as phytic acid
In milk > solid food
Chelated minerals
Incidence of hypocalcaemia?
Aus: 1.6 - 5.4% (>20% some herds)
US/UK: 6% (US - up to 70% clinical/subclinical hypocalcaemia)
Ca increase in Ca homeostasis…?
Dietary vit D2 & D3 & Ca -> +calcitriol (kidney) -> + Ca pool (3g plasma & 10g extracellular)
Parathyroid gland secretes PTH -> +calcitriol (kidney) & + bone breakdown -> +Ca
Ca decrease in Ca homeostasis…?
Thyroid gland -> calcitonin -> bone mineralisation -> -Ca pools
Kidney calcitonin -> +Ca excretion in urine
Milk/foetal losses
Faecal losses
Factors that cause hypocalcaemia after lactogenesis?
Inability to absorb Ca from gut & mobilise Ca from bone during lactogenesis
Ca requirement doubles during lactation (23g) in 10kg of colostrum
How long does it take for Ca mobilisation to occur to increase absorption?
3-4 days (most hypocalcaemia occurs soon after calving)
Nutritional causes of hypocalcaemia?
- Ca (diet & maternal reserves) K Mg P Na
Low Ca intake pre calving stimulates what?
Calcitriol
K properties &
pastures may contain 4-5% [K]
Effects of excess K…?
Excess -> metabolic alkalosis -> decreased sensitivity of bone & renal tissue to PTH
-> prevents upregulation of 1,alpha-hydroxylase
Hypomagnesaemia effects on Ca homeostasis?
Decreased mobility of Ca
PTH & calcitriol activity retarded
Phosphorus causes what?
hypocalcaemia -> PTH action on renal tissue
Keep <35g/day pre calving
Na properties and potential effects…?
Stronger cation than K
May cause metabolic alkalosis
Dietary options for reducing milk fever?
Ca & vit D
Manipulating DCAD (feeding anionic salts)
Replenishing Ca reserves
DCAD stands for…?
Dietary cation-anion difference
Why is DCAD important? How?
Lowering DCAD -> lowers pH -> improves Ca homeostasis
Also -> reduces risk of metabolic acidosis
Common anionic salts
CaCl2; CaSO4; MgCl2
DCAD should be at what value to prevent MF?
-10 ideally
T or F - DCAD can not be manipulated without anionic salts
False
