L11: Mineral Nutrition I (principles and Ca) Flashcards Preview

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Flashcards in L11: Mineral Nutrition I (principles and Ca) Deck (22)
1

What is a macromineral?

required in greater amounts

2

What is a micromineral?

Required in smaller amounts

3

What are the general functions of minerals?

  • structural (bone, muscle)
  • enzymes/cofactors
    -catalytic function Ca + P = bone
    -regulatory (Zn)
  • regulating osmotic pressure
  • pH
  • nerve and muscle function (physiological)
    -Na, Cl, K
    -facilitated transport
  • vitamin, blood and hormone synthesis

4

*Describe generally how mineral deficiencies occur and how form in digesta effects availability

Describe generally how mineral deficiencies occur

  • Insufficient in diet (liebigs law of minimum
  • low absorption -need continual exposure or supplementation
  • Mineral interactions 
    -formation of unabsorbable compounds
    -competition for metabolic pathways
    -induction of metal binding proteins
  • Toxic accumulation

5

*Describe generally how mineral deficiencies occur and how form in digesta effects availability

Availability -in digesta, minerals occur as?

  • Easily absorbed -metallic ions in solution eg Na, K
  • Partially absorbed -chelated
  • Not absorbed -parts of insoluble substances

6

The conversion of minerals between different forms (active or inactive) is .... dependent

pH

7

Give examples of mineral availabilty

  • P often present as phytic acid -need phytases (enzymes) to access, is then easily absorbable
  • Chelated minerals
    -exist as cyclic compound w/ organic molecule
    -protects from reacting with other elements eg when passing through GIT
    -enzymes can change this coating

8

*Describe the functions of Ca in the body 

  • Most abundant mineral in body, [ ] in bone
  • essential for:
    -bone and teeth
    -enzyme sys. for normal muscle and nerve function
    -blood clotting
  • Blood calcium homestatic at ~80-120mg/L
    -hormonal regulation by calcitonin

9

*List good dietary sources of Ca

  • milk
  • green, leafy crops (legumes)
  • animal products containing bone
  • limestone
  • Grains LOW source

10

*Describe how Ca deficiency can occur and the potential consequences

What is the recommended Ca:P ratio?
What happens if there is excess P?

  • 1:1 or 2:1
  • excess P binds Ca reducing absorption

11

*Describe the role of Vitamin D

What are the two bioactive forms of VD?

How is VD produced?
Where is it found (source)?

Where is it stored and what does it work with and why?

  • bioactive forms are VD2 and VD3
  • Produced in skin by exposure to UV light
  • Found in cut forages, sunlight, sun-cured forage
  • Stored in liver
  • works w/ PTH to maintain plasma Ca [ ]

12

*Describe role of VD in calcium homeostasis and how Ca hom. is maintained

  • See lecture for diagram
  • VD from sun or diet enters body, goes to liver, passes to kidney where it is paired with PTH
  • stimulates intestines to increase Ca absorption
  • Stimulates Ca uptake into bones by calcitonin if Ca in excess
  • Or stimulates Ca release into blood

13

*Describe how Ca deficiency can occur and the potential consequences

 

  • Lack of sunlight or dietary supplementation, grazing on high P pastures
  • Consequences:
    -big head
    -osteoporosis (brittle bone)
    -Osteomalacia
    -rickets
    -DOD
    -Milk fever (hypocalcemia)

14

What is the most common mineral-related problem of the transition cow?

MILK FEVER (HYPOCALCAEMIA)

15

*Describe how milk fever occurs and how dietary management can prevent it

What are the symptoms of clinical milk fever?
Plasma [ ]?

  • symtpoms include inappetence, lateral recumbency, coma, death
  • Plasma [Ca} <1.4mmol/L or <56mg/L

16

*Describe how milk fever occurs and how dietary management can prevent it

What are the symptoms of subclinical milk fever?

Plasma [ ] ?

  • can reduce subsequent production
  • Plasma [Ca} 1.4-2mmol/L

17

*Describe how milk fever occurs and how dietary management can prevent it

What causes milk fever?

  • Inability to absorb from gut and mobilise from bone enough Ca to meet sudden demand imposed on plasma Ca pool by lactogenesis
  • Low diet levels and reserves
  • Binding by high P
  • Ca req. doubles in lactation
  • Takes at least 3-4 days to increase Ca mobilisation from bone and increase absorption

18

*Describe how milk fever occurs and how dietary management can prevent it

Describe dietary management of milk fever

  • Dietary supplementation of Ca and VD
    -VD injections
  • feeding anionic salts (DCAD manipulating)
  • efficiency of absorption declines as diet [Ca] increases
  • Low Ca intake (low Ca diet) pre-calving stimulates calcitriol synthesis
    -means better able to respond to Ca plasma drain at lactogenesis

19

What is the role of Potassium (K)?

What does an excess of K cause?

  • Helps retain Ca in blood -decreases loss through urine
  • excess causes metabolic alkalosis
  • PTH increases, no Ca release
  • Reduces bone sensitivity and renal tissue to PTH

20

What is the role of Magnesium?

  • Poorly absorbed from diet, 0.2-0.4% needed for maintenance level
    -needs to be supplemented
  • High dietary K can reduce plasma [Mg]
  • Hypomagnesaemia means less able to mobilise Ca from bone

21

What can excess P cause?

  • Increased mobilisation of Ca from bone regardless of [Ca] in diet
  • induce hypocalcaemia
    -inhibits PTH action on renal tissue
  • Keep diet P to <35g/d pre calving

22

What is DCAD?

  • Dietary Cation-Anion Difference
  • lowering reduces blood and urine pH
    -improves Ca homeostasis