Hypocalcemia in Large Animals

Question 1

production dz’s tend to be…

Answer 1

metabolic in origin

Question 2

Expression of production dz (P) =

Answer 2

F (GxE)
* Fxn of genotype and environment
* aka mismatch of genetics & environment of animal

Question 3

many prod’n effects are

Answer 3

subclinical (iceberg phenomenon)

Question 4

List Production dzs

Answer 4

• hypocalcaemia
• hypomagnesaemia
• ketosis
• acidosis

Question 5

Specific production diseases are related to…

Answer 5

mastitis, lameness, reproductive dz’s (RFM, etc)

Question 6

Metabolic dz of cattle

Answer 6

“manifestation of cow’s inability to cope w/ metabolic demands of increased production”

Question 7

metabolic dz predominantly dz of…

Answer 7

dairy cattle, preg ewes

Question 8

Demands +/or unsuitability to conditions leads to

Answer 8

economic loss + animal health/welfare concerns

Question 9

Periparturient hypocalcaemia is aka…

Answer 9

• periparturient paresis
• Milk fever

Question 10

Definition of Milk Fever

Answer 10

“a metabolic dz occurring around the time of parturition caused by HypoCa”

Question 11

Milk fever is characterised by…

Answer 11

• general muscle weakness
• depression of consciousness

Question 12

Explain Ca storage & usage in Dairy cow

Answer 12

Most of Ca is stored in bone fluid (~9-15g) and bone (~8 kg). This piles into the extracellular pool of Ca (8-9g) which fluctuates with serum concentrations (3-3.5g). During lactation the serum concentrations feed ~2-2.3 g/kg in colostrum and ~1g/kg in the milk. A cow producing 10 kg of colostrum may lose up to 23 g of Ca per a single milking which is 7x the serum concentrations available leading to deficit quickly if not adequately supplied as most Ca w/i the skeletal system is slow to unlock.

Question 13

What plays into Ca homeostasis?

Answer 13

• PTH - reabsorb Ca from kidneys & is necessary for restoring Ca lvls back to normal
• Bone - osteoclastic, bone fluid more readily available
• Vit D - osteoclastic behaviour, increase gut absorption of Ca

Question 14

Explain Ca homeostasis

Answer 14

A decrease in plasma concentration signals PTH secretion. To balance this, PTH secretion travels to kidneys to increase Ca reabsorption where 25 Hydroxy Vit D is converted to 1,25 Dihydroxy Vit D. This travels to the bone reserves which are concerted to mobilisation of Ca. The bone reserves also receive PTH secretion affects and influence PTH secretions as well. The kidneys influence the Gut by increasing active Ca absorption. Kidneys also influence PTH secretion. This all returns the body to normal calcium.

Question 15

Risk factors for Ca homeostasis

Answer 15

• Age
• Breeds (Channel island breeds esp.)
• overconditioning
• genetics

Question 16

Dietary causes of HypoCa

Answer 16

• increase in Ca in the dry cow diet (demand is 30 g/d); Silage increases in Ca; overwinter & pasture herds in IE have issues
• suboptimal Mg in dry cow diet (reduces tissue sensitivity to PTH, reduces PTH secretion in response to HypoCa)
• XS DCAD [= (Na + K) - (Cl - S)]; (grass silage increased in K, drives balance upwards, acid-base status in serum altered)

Question 17

Explain DCAD & Mg

Answer 17

• like enzymes that degrade.
• mild acidosis (7.35): PTH & receptor work well together; Mg is cofactor for rxn so must be present in suffic. amts for rxn to occur
• mild alkalotic (7.45): receptor changes shape, incomplete binding of PTH, marginal Mg status or just Mg status marginal on its own, then rxn does not occur
• pH plays large role on ability of rxn to occur normally

Question 18

Morbidity & Mortality of HypoCa

Answer 18

• Morbidity: ~5-10%
• Mortality: v. low if found quickly & txt’d; subclin may be towards 15%

Question 19

Clin signs of HypoCa

Answer 19

• recumbency w/i 24 hrs of calving
• tachycardia - muffled heart sounds
• flaccid bloat - paralumbar fossa on L side, depressible
• Biochemistry - reduction in serum iCa (impacts NMJ, myofibril contraction)
• recumbency, vasodilation -> tachycardia; reduced CO -> tachycardia (toxaemia); ruminal atony -> flaccid bloat

Question 20

Stage 1 of HypoCa

Answer 20

Excitement phase 0.5-2 hrs
Vocalisation
Inappetant
Restlessness
Paddling

Question 21

Stage 2 of HypoCa

Answer 21

Sternal recumbency (8-12hrs)
* dull, depressed, ‘calf sleeping’ posture, lateral cervical kink (swan neck)
* unresponsive to stimuli, pupils dilate, poor PLRs, sluggish responsiveness
* temp norm to sub norm; no/slow anal reflex; anus relaxes; subnorm cold extremities
* reduced gut motility -> faeces at rectum
* RR <10, grunting during respiration
* pale mm, tachycardia (80-100)
* heart difficult to hear
* atonic reticulorumen

Question 22

Stage 3 of HypoCa

Answer 22

lateral recumbency - EMERGENCY
* Tympanitic - full bloat
* inhalation of ruminal contents possible
* comatose
* death w/i 12-24 hrs

Question 23

Relationship between hypoCa with hypophosphataemia

Answer 23

Seems that hypoPO4 will correct itself if HypoCa is corrected
Can help to supplement PO4 in short-term

Question 24

Relationship between HypoCa with HypoMg

Answer 24

• mild-mod tetany & hyperaesthesia persisting beyond Stage 1
• HR > just HypoCa
• Convulsions precipitated by sudden sound, etc.

Question 25

Milk Fever clin path

Answer 25

* HypoCa * HypoP * hypo/hyper-Mg * PM: no specific findings, possibly inhalation of guts found

Question 26

DDx for Stage 1 Milk Fever

Answer 26

HypoMg tetany Nervous ketosis BSE

Question 27

DDX for Stage 2 Milk Fever

Answer 27

peracute toxaemic mastitis toxaemic metritis, peritonitis uterine haemorrhage (less common)

Question 28

3 M's of dull, recumbent ow post-calving

Answer 28

Mastitis, metritis, milk fever

Question 29

Clin signs of Subclin HypoCa

Answer 29

Uterine inertia (risk factor for perinatal mortality in calving/stillbirths) RFM displaced abomasum -> reduced DMI, LDA more commonly reduced feed intakes after calving mastitis delayed 1st ovulation after calving

Question 30

HypoCa consequences

Answer 30

Dystocia -> due to uterine inertia retained placenta Metritis Mastitis Reduced feed intake LDA Ketosis

Question 31

Milk Fever Txt

Answer 31

* 400 ml Ca borogluconate IV (12g Ca) slowly admin w/ flutter valve & 14G needle * auscultate heart during admin (arrhythmias) - if sudden increase in HR, stop txt -> can be fatal arrhythmia & cessation during systole * SQ borogluconate for stores afterwards * do not milk cow out * should be standing w/i 1-2 hrs and normal afterwards * Simmentals/sucklers * once standing, will immediately urinate due to distended bladder

Question 32

Prevention Principles for Milk Fever

Answer 32

* 15-20 g Mg/cow/d for last month pre-calving * silage low in K+ * Ca as low as possible in dry cow ration * avoid mineral mixes containing >6% Ca pre-calving * optimal BCS Pre-calving * avoid metabolic alkalosis by adding acidic salts in dry cow ration

Question 33

Milk fever prevention

Answer 33

* Vit D (8-2 d before calving) -> 25, (OH)D3 in liver -> 1,25 (OH)2 D3 in kidney -> Cabp & bone mineralisation **must be accurate w/ calving dates** * Bolus of Ca as preventative for at -risk cows

Question 34

Non-parturient hypoCa

Answer 34

* sporadic - affects individuals * may occur in non-lactating females/bulls * aka RUMINAL ACIDOSIS

Question 35

Non-parturient HypoCa is assoc'd w/

Answer 35

* lush pasture - D * sugar beet tops, carrots - oxalates * potatoes, barley poisoning * grain diets * cold cow syndrome? oestrogenic mycotoxicosis - Fusarium spp

Question 36

When is the highest Ca demand for sheep?

Answer 36

3-4 wks prior to lambing due to calcification of foetal bones

Question 37

Signs of Hypocalcaemia in sheep

Answer 37

unable to rise elevated RR consipation

Question 38

Treatment for hypocalcaemia in sheep

Answer 38

50-80 ml of 20% Ca borogluconate

Question 39

Downer cow syndrome can be sequelae to...

Answer 39

HypoCa (such as Milk fever)

Question 40

Other causes of downer cow syndrome

Answer 40

calving paralysis spinal/back injury

Question 41

Downer cow vs Down cow

Answer 41

* Down cow: recumbent cow for any reason * Downer cow: 'Any cow which is down in sternal recumbecny for >24 hrs w/ no evidence of a systemic dz, or clinically apparent structural injury, which would prevent the cow from rising' * Downer cows are a subset of Down cows

Question 42

Importance of secondary damage

Answer 42

* Muscle &/or n. damage caused by prolonged recumbency &/or attempts to rise due to mass of animal * muscle damage leads to crush-compartmental syndrom * pressure on sciatic n. caudal to prox. femur * muscle tearing & haemorrhage when struggling to rise * renal damage assoc'd w/ myoglobinuria

Question 43

Explain the crush-compartmental syndrome

Answer 43

increased pressure on muscle tissue -> decreased venous drainage -> drainage pressure > perfusion pressure -> anoxia causing ischaemic necrosis -> transudation into surrounding tissue -> increased pressure on muscle tissue

Question 44

Prognosis for downer cow depends on

Answer 44

* secondary damage * position * biochemical parameters (more specific prognosis) * qlty of nursing care

Question 45

If CPK levels in a downer cow on day 1 are >12,000, then prognosis is... & what should be recommended?

Answer 45

Poor Euthanasia

Question 46

Prognosis for downer cow >7 days

Answer 46

Poor

Question 47

Prognosis for downer cow in lateral recumbency

Answer 47

Poor

Question 48

Prognosis for downer cow in abnormal postures such frog legged

Answer 48

Poor

Question 49

Prognosis for downer cow creepers

Answer 49

Good prognosis

Question 50

Prognosis for hypomagnesaemia tetany downer cows

Answer 50

poor prognosis

Question 51

Downer cow nursing

Answer 51

* good footing w/ no slope/ditch/ stream in small, sheltered paddock OR inside w/ 0.3-0.5 m straw bedding * Feed/water BID at minimum * 2x/d teat disinfection to prevent mastitis * creepers -> barriers to keep from moving * regular cleaning of environment * move from side to side to minimise hypostatic congestion muscle damage * AB's if infection present * **NSAIDS** - Ketoprofen 10%