Hypocalcaemia & Milk Fever in Cows
Phil Rogers MRCVS
Grange Research Centre, Dunsany, Co. Meath, Ireland
| Hypocalcaemia | Causes | Remedies | Atypical Milk Fever | Remedies |
Physiological hypocalcaemia: A moderate fall in blood Ca at parturition is normal . It is associated with major hormonal and metabolic changes that occur at calving (the sudden demand for extra Ca for colostrum, fat mobilisation and reduced feed intake).
Severe parturient hypocalcaemia often is associated with milk fever, downers, uterine inertia,("lazy", prolonged, slow calving), dystocia, stillbirth/weak calves, RFM (retained foetal membranes), uterine prolapse, lameness, metritis and LDA (left displacement of the abomasum).
CAUSAL FACTORS: The following factors increase the risk and severity of parturient hypocalcaemia:
|Main causal factors||Comments|
|1. Age||More prevalent in third calvers and older|
|2. Genetics||More prevalent in certain breeds (especially Channel Island breeds) and certain lines of cow|
|3. Low Mg / high Ca intake prepartum||These reduce Ca turnover in bone and Ca absorption, respectively|
|4. General nutrition prepartum||Milk fever is more prevalent on high-K pasture than on silage and in overfat cows (Fat Cow Syndrome, fatty liver) and in thin cows|
|5. Stress||Many forms of stress, especially cold stress in subzero temperatures, induce hypocalcaemia|
|6. Low feed intake on day of calving||Reduces Ca intake and absorption|
|7. Intercurrent conditions||Lameness, back pain, severe deficiency of Cu, I, Se and/or Vitamin E may weaken the musculoskeletal system. This makes it more difficult for the cow to stand if she goes down at calving.|
REMEDIAL ACTIONS to reduce the risk and severity of parturient hypocalcaemia include:
|Routine actions||Correct detected causes (see 1-7 above)|
|1. Control body condition prepartum||Control prepartum energy intake: Feed cows to calve in good body condition (body score 3.0-3.5 on a 5-point scale), i.e. not too fat or too thin. Restrict energy intake of fat cows; supplement energy intake of thin cows.|
|2. Increase Mg intake prepartum||To ensure high turnover of bone Ca prepartum, include 10-20 g Mg/cow/d (say 15 g) in dry-cow supplements (about 15% Mg in mineral mixes fed prepartum).|
|3. Reduce Ca intake in late pregnancy||To ensure maximal
% absorption of Ca from digesta, reduce Ca intake
in the last 6 weeks prepartum. Avoid Ca supplements
prepartum, or keep them <6 g Ca/cow/d. Dry Cow minerals with
0% Ca are advised in herds with a milk fever history. Avoid
mineral mixes prepartum if the Ca level is >6%.
Total prepartum intakes of 25-50 g Ca/ day are ideal but are unattainable, as most common prepartum diets of herbage or silage supply >55 g/cow/d. [Irish herbage and silage have Ca levels c. 0.65 and 0.69% DM, respectively. An intake of 10 kg DM of such feed would supply 65-69 g Ca/d, respectively]. However, if this is appropriate, considering cow body condition and forage-quality on offer) one can reduce prepartum Ca intake somewhat by feed restriction and/or the use of low-Ca feeds (such as maize-silage, grains and roots).
HOWEVER: (a) if one can predict calving date accurately, one SHOULD switch from a low- to a high- Ca intake 1-5 days BEFORE calving, but (b) if calving is delayed for several more days, the cow will adapt by reducing her % absorption of Ca. In that case, the high-Ca feed will increase the risk of hypocalcaemia.
|4. P supplements prepartum?||If low-P forages (such as beetpulp, fodderbeet etc) are fed, up to 20 g P /cow/d may be added. Herbage and grass-silage are the most common prepartum diets for cows. Mean P levels in Irish herbage and silage are 0.38 and 0.31% DM respectively. These have ample P for dry cows. Prepartum P supplements have little effect in preventing parturient hypocalcaemia, except at impractical levels (30-50 g P or more/cow/d).|
|5. Decrease stress at calving||Minimising stress reduces adrenalin release and fat mobilisation at calving, thereby reducing their adverse effects on blood Ca levels. Comfortable calving boxes and provision of shelter and warmth at calving help. Closed-circuit TV monitors and careful use of calving jacks help to keep interference to a minimum.|
|6. Increase feed and Ca intake at calving||Give palatable feed (such as molassed concentrates + good silage or hay) to raise the intake of DM and Ca as soon as the cow shows signs of calving ("pins-down" or "water-bag" visible).|
|7. Give Ca +/- P supplement on the day of calving||If
hypocalcaemia or milk fever occurs at calving in spite of the
methods suggested above, dose or feed susceptible cows with a
very high Ca supplement on three occasions close to calving. Common
Ca supplements include feed-grade limestone flour (Ca
carbonate, 34% Ca) and Dical ( dicalcium phosphate, 22% Ca,
18% P). Give 125-150 g limestone flour (42-51 g Ca) 12-24h
prepartum; repeat just after calving, and at 12h later.
If low blood P levels coexist with low blood Ca levels, give 3 doses of 180 g Dical instead of the limestone flour.
|8. Ca and P supplements postpartum||High yielders need total daily Ca and P intakes of circa 90-120 g Ca and 60-80 g P/cow/d after calving. Dairy nut, fed at circa 7 kg/cow/d should have circa 0.8-1.0% Ca and 0.5-0.7% P. It is important to have the higher levels of Ca and/or P in dairy nut if cows are on feeds low in Ca and/or P (roots, maize-silage, high cereal diet). Lactation minerals, for inclusion at 120-140 g/cow/d in 7 kg of home-mixed concentrate feeds, usually contain 12-14% Ca and 9-11% P, but feeds low in Ca or P need special mineral balancers.|
|9. Cull susceptible cows?||Consider culling of susceptible cows on grounds of genetics and age.|
|10. Anionic diet prepartum||Under Irish conditions, a combination of methods 1 to 7, above, usually prevents hypocalcaemia. Should they fail, one may consider feeding S- and Cl- supplements to make the prepartum diet more acidic (anionic). Foreign research indicates that, by increasing Ca turnover in the body, anionic diets reduce the risk of hypocalcaemia. The supplements, however, are unpalatable and may restrict feed intake.|
|11. Veterinary products to prevent milk fever||Vitamin
D3, or its synthetic analogues (cholecalciferol etc): Injection
within 8 days prepartum was claimed to improve Ca absorption from
the gut, to increase Ca mobilisation from bone to blood, and to
reduce the incidence of milk fever. The claims are controversial.
Results are mixed; adverse side effects may arise, and milk
fever may be delayed, only to arise 10 days later. The method is
expensive but may be used together with the methods described above
in valuable cows with a history of milk fever in previous calvings.
Gels of Ca-salts: Oral gels containing Ca chloride, or other Ca-salts may be considered. They are expensive and may not be more effective than method 7, above.
ATYPICAL MILK FEVER IN COWS (See the notes on typical milk fever, above)
Atypical hypocalcaemic syndrome occurs >2 days before, or >2 days after calving. It is difficult to control, as the key causes largely are unknown. Older cows (parity >2) and certain genetic lines are particularly susceptible.
Low blood Mg and high Ca intake prepartum restrict Ca release from bone. Under- or over- nutrition and stress can induce hypocalcaemia.
Effective preventative measures are unavailable. However, try the following:
total Ca intake should be as low as possible (25-70
g/cow/d). To optimise bone turnover of Ca, avoid Ca
Postpartum total Ca intake should be high (80-140 g/cow/d). From calving to peak lactation, give high Ca supplements (20-40 g Ca / cow/d). These amounts are supplied by 57-114 g calcium carbonate or 91-182 g dicalcium phosphate.
|Mg supplements||To optimise bone turnover of Ca, give a supplement of 10-20 g Mg/cow/d (say 15 g) prepartum, 10 g Mg/cow/d postpartum, and 20-40 g Mg/cow/d (say 30 g) in the tetany season.|
|Optimise feed intake postpartum||If possible, optimise feed intake postpartum to match production but aim to avoid over-fatness (fatty liver) or very poor body condition.|
|Minimise stress||If possible, minimise stress to reduce adrenalin release and fat mobilisation and their adverse effects on blood Ca levels.|
|Culling?||Hypocalcaemia is partly controlled genetically; cull affected cows?|