Milk Fever
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Transcript of Milk Fever
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DIETARY STRATEGIES TO PREVENT MILK FEVER IN DAIRY CATTLE
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MILK FEVER
Parturient paresis syndrome in dairy cattle
as caused by hypocalcemia
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CALCIUM METABOLISM
Intake
Feces
Absorption
Plasma Ca Bone
Urine Colostrum/milk/fetus
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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
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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
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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
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ADVANTAGE OF MODERN VERSUS CLASSICAL STRATEGY :
Ration with negative DCAD raises absolute
calcium absorption
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DCAD = Dietary Cation-Anion Difference
DCAD = m Eq (Na + + K +) - (Cl - + S 2-) / kg DM
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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
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Influence of NH4Cl on urinary pH
H+ + Cl-
Rumen
ileum
H+ + Cl-
Urine
NH4+ + Cl- NH3 + H+ + Cl-
Liver : urea
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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
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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)
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Hypothesis : Ration with a negative DCAD increases Ca-absorption
(Schonewille et al, 1994)
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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
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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
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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
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CALCIUM METABOLISM
Intake
Feces
Absorption
Plasma Ca Bone
Urine Colostrum/milk/fetus
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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
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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)
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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)
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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)
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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)
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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.
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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.
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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.