milk fever

DIETARY STRATEGIES TO PREVENT MILK FEVER IN DAIRY CATTLE

MILK FEVER

Parturient paresis syndrome in dairy cattle

as caused by hypocalcemia

CALCIUM METABOLISM

Intake

Feces

Absorption

Plasma Ca Bone

Urine Colostrum/milk/fetus

CLASSICAL DIETARY STRATEGY TO PREVENT MILK FEVER

-Low calcium intake (20-25 g/day) during dry period

-Normal calcium intake (80-100 g/day) around parturition and after that

Low Ca High Ca

Ca intake 47.5 83.7

Ca absorption

g/day 2.2 2.3

% of intake 4.6 2.7

Calcium absorption in dry cows when fed either

low or high Ca rations

MODERN DIETARY STRATEGY TO PREVENT MILK FEVER

-Feeding of ration with negative DCAD (- 50 mEq/kg DM) during dry period

-Change to ration with normal DCAD (> + 200 mEq/kg DM) around parturition

ADVANTAGE OF MODERN VERSUS CLASSICAL STRATEGY :

Ration with negative DCAD raises absolute

calcium absorption

DCAD = Dietary Cation-Anion Difference

DCAD = m Eq (Na + + K +) - (Cl - + S 2-) / kg DM

Effect of a negative DCAD on the incidence of milk fever

Reference DCAD(mEq/kg ds)

Incidence of milk fever(%)

Block, 1984 + 330 47.4

- 128

Oetzel et al, 1988 + 189

- 75

Goff en Horst, 1995 + 450

+ 150

- 150

0

17.0

4.0

47.6

50.0

10.5

n = 19 – 24 / treatment

Influence of NH4Cl on urinary pH

H+ + Cl-

Rumen

ileum

H+ + Cl-

Urine

NH4+ + Cl- NH3 + H+ + Cl-

Liver : urea

Influence of CaCl2 on urinary pH

2 H20 2 OH- + 2 H+

GI-tract

H+ Cl- (Urine)

Ca2+ + 2 Cl-

Ca2+ + 2 OH- Ca(OH)2Feces

Urinary pH and Ca excretion in cows fed rations with either a positive or negative DCAD

+ 276 -170

pH 8.7 7.9

Ca (g/day) 0.4 6.1

DCAD (mEq/kg DM)

Hypothesis : Ration with a negative DCAD increases Ca-absorption

(Schonewille et al, 1994)

Cation-rich Anion-rich

Grassilage (kg dm/day) 5.0 5.0

Cornsilage (kg dm/day) 1.9 1.9

Concentrate (kg dm/day) 1.0 1.1

Ca (g/day) 50 53

Na (g/day) 10 10

K (g/day) 175 175

Cl (g/day) 52 169

S (g/day) 20 24

DCAD (mEq/kg dm) +276 -170

COMPOSITION OF EXPERIMENTAL RATIONS

Cation-rich Anion-rich

(g/day)

Intake 50.4 52.8

Feces 48.6 47.8

Absorption 1.8 5.0*

Urine 0.4 6.1*

Balance 1.4 -1.1

(% of intake)

Absorption 3.6 9.5*

*P<0.05 ( n = 6 in cross-over experiment)

CALCIUM BALANCE AND ABSORPTION

HYPOTHESIS :

The extra flow of Ca through the body after feeding a ration with a negative DCAD, can be used to

maintain the plasma Ca concentration at the onset of milk production

CALCIUM METABOLISM

Intake

Feces

Absorption

Plasma Ca Bone

Urine Colostrum/milk/fetus

Experimental rations

Cation-rich Anion-rich

Grasshay (kg dm/day) 4.6 4.6Cornsilage (kg dm/day) 1.5 1.5Concentrate (kg dm/day) 1.1 1.0Ca (g/day) 37 37Na (g/day) 33 31K (g/day) 160 160Cl (g/day) 79 220S (g/day) 15 15DCAD (mEq/kg dm) +330 -230

Experiment:

- Induction of hypocalcemia by Na2EDTA (0.9 mmol/h) infusion.

- Infusions were finished when plasma Ca not bound to EDTA was about 1.0 mmol/l.

- Measurement of urinary Ca excretion during EDTA infusions (catheter in bladder).

- Concentrations of Ca in plasma and urine were measured colorimetrically in order to obtain the concentration of Ca not bound to EDTA

(Schonewille et al, 1999)

Urinary pH and Ca concentration before the infusion

of EDTA

+330 -230

pH 8.73 5.73*

Ca (mM) 1.8 11.5*

* P<0.05

DCAD (mEq / kg DM)

Plasma Ca

Plasma Ca not bound toEDTA (mM)start of infusion 2.44 2.36

end of infusion 0.99 0.97

Amount of EDTA infused (mmol) 249 303*

* P<0.05

+330 -230

DCAD (mEq / kg DM)

Urinary Ca excretion during EDTA infusion after feeding a ration with a negative DCAD

Uri

nar

y C

a ex

cret

ion

(m

mol

/hou

r)

0.0

1.0

2.0

3.0

4.0

5.0

0 to 1.5 2.3 to 4.1 4.5 to 8.3

Time (hours)

Rations with a negative versus positive DCAD :

- Increase Ca absorption and urinary Ca excretion.

- Increase of the Ca flow through the body; the extra urinary Ca excretion can be reduced when plasma Ca is stressed.

Practical relevance :

- Assume production of colostrum is 10 L. (2 g Ca/L.)

- Extra urinary Ca excretion after feeding ration with negative DCAD is about 6 g Ca /day

- The amount of extra available Ca around parturition is sufficient to support the production of about 3 L. of colostrum.

CONCLUSIONS :

-The reduction of milk fever as induced by a negative DCAD, is explained by an increased absolute absorption of Ca and by immediate availability of the extra Ca flow through the body.

-A negative DCAD can be achieved by the use of NH4Cl, CaCl2, MgCl2 an/or MgSO4.