Milk Fever Prevention – There is no set recipe

/

The causes of milk fever are multifactorial. Having a good understanding of what these risks are on your farm and in your herd, can enable a sensible preventative plan to be put in place.

  • Cows of 6 years and greater are at much greater risk.

  • Fat cows. Risk of milk fever increases by 40% as cows shift from BCS 5.0 to 5.5.

  • Bone calcium stores/reserves from the previous lactation and dry period. High production cows from the previous lactation that were not calcium supplemented, then spent a winter on e.g. fodder beet will likely have low calcium bone reserves.

  • Energy intakes of springers – more energy drives more colostrum, more colostrum more calcium draw.

  • High DCAD diets – these create a metabolic alkalosis in the cow. In a high pH environment inside a cow, the cells necessary for releasing bone calcium reduce their activity.

  • High calcium diets as a springer will switch off the Parathyroid gland (PT). This gland regulates blood calcium by triggering increased bone calcium resorption, increased intestinal absorption and reduced kidney calcium excretion when blood calcium levels fall. Ideally, we want an activated PT gland at both before and after calving.

  • High dietary potassium will increase the DCAD but it also has a direct competitive effect with the absorption of both calcium and magnesium.

  • Low magnesium diet will make the PT gland less responsive, whereas excessive magnesium diets can compete with calcium. It is important to provide ‘just enough’.

Preventative strategies

1. In cows with good bone calcium stores/reserves as a result of plentiful supplementation in the previous lactation and dry period, a good preventative strategy would involve the following components:

  • A low calcium springer diet (under 0.4% for 10-14 days)

  • A low DCAD diet (aim below 200 units). Maize is good, as well as high doses of anionic salts (must be for 10-14 days).

  • With a low DCAD diet success can be measured by a lowering of urinary pH (<6.5 but >5.5). It is easy to collect urine from springer cows and test them with cheap electronic pH meters. Normal cow urine is about pH 8.0 when on pasture only.

  • Modest magnesium supplementation (blood Mg of 0.75-1.1)

  • Plenty of fibre (hay straw)

2. In cows with poor bone calcium reserves, there is little benefit from using low DCAD diets (and or springer transition minerals) and/or restricting calcium intake as a springer. This is because those two strategies are attempting to promote release of bone calcium. This may be of limited use if there is reduced available calcium in the bone. Consider the following:

  • Although it seems counter intuitive if springer cows are offered a very high calcium intake (think 400g/day of limeflour), the cow is no longer reliant on her bone supply or kidney retention. Her dietary intake saturates all needs.

  • For this method to work cows MUST have a consistent daily supplement routine – i.e. you can not afford to miss a day! It is imperative that you discuss this strategy with your Prime Vet before undertaking it.

3. Some herds will just sit in the middle ground with risk. In this situation we need to place a ‘bob each way’. Things to consider:

  • Place on low DCAD/low K pastures (i.e DCAD less than 500 units)

  • Supplement magnesium with a baseline through water. MgSO4 is a bit more preferred to MgCl. Dose at 70g/cow/day.

  • Limit grass intakes to springer to ~3-5kgDM/day

  • Ensure cows are not fed more than 120MJME/day in springers

  • Fed plenty of long fibre (i.e. straw or hay)

  • Feed springers cows ‘Springer Transition’ mix ~300g/day. Also consider Gypsum (CaSO4) at ~200-250grams/day.

  • Feed colostrum cows ad-lib ‘Colostrum cow’ mix.

  • Identify high risk cows for a calcium bolus immediately postcalving (>6yrs, >BCS 5.0)

  • Shift breaks in springers at about 5am (i.e. before the coldest part of the night). Give springers at least 2 feeding opportunities in a day.

  • Pause collars on freshly calved Halter cows

  • As soon as calved get onto high dose (~400g/day) of limeflour for first four days and then reduce to 200g/day for up to six weeks.

Contact your Prime Vet for more details or your TM for products mentioned in this article.