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.

Spontaneous Humeral Fractures in Heifers

Humeral fractures (upper front leg) in heifers are no laughing matter. Every year we have many farms affected in this practice, sometimes losing up to 10% of their heifer line. We see two peak periods of these fractures. The first, +/- one week of calving and the second coinciding with peak lactation (we have found heifers that break legs at peak lactation are in the top 10% producers at the first herd test).

We know that the bones of these heifers have osteoporosis (thinned), and this is likely due to excessive mineral loss in late gestation and peak lactation. Heifers that are in a surplus dietary calcium status will not need to mobilise bone calcium. If dietary limeflour is supplied in excess of requirements through the last month of pregnancy and also the early lactation period (up to mid-November) at about 100g/heifer day. Avoid providing heifers high dose anionic salts (mag sulphates and mag chlorides) as these may enhance the release of bone minerals.

These heifers also have a high copper consumption, so it is important to support this with good supplement levels going into the winter.

Brassica Feeding over the Dry Period – The Good, the Bad and the Ugly

Next to fodder beet, brassicas (rape, kale, turnips and swedes), are the other mainstay of the winter diet. It helps to understand some of their properties to get the best from them.

The Good

• In kale, the upper 2/3rd of the plant has quite good ME – being about 12.5MJ. The lower part of the plant (the stalk) will be lower and is only about 7ME close to the ground. The overall ME is about 11-11.5MJ/kgDM. The ME of all other brassicas are closer to 12MJME.

• Generally speaking, brassicas have good levels of crude protein for a dry cow – 14-18%. This makes it quite a good crop to finish the winter on if you have had cows on a low crude protein fodder beet through the early part of the dry period.

• Kale/Rape have high levels of calcium – about 3 times what is in grass and 9 times what is in fodder beet bulbs. This makes it handy for replenishing bone stores in dairy cows.

• A tall grazing face can form good shelter for cows if being grazed in a southern direction.

The Bad

• Kale crops often have bad utilisation in bad weather – it can be as low as 50%. Make sure you allow for this.

• Best practice is to work on 80% utilisation in good conditions. If it is higher than this, cows are probably being underfed. Make sure you factor this in on your daily allocation.

• All brassicas are low in effective fibre (and yes that includes those chewy looking stalks). This is the reason that as a minimum 25% of the diet needs to have a long fibre source – e.g. straw, hay or baleage.

• Animals often ingest quite a bit of mud while on crop – this will deplete copper stores. Selenium is also consumed/depleted soaking up ‘free radicals’ created by a high content of poly-unsaturated fatty acids.

• Swedes can be quite hard, making it tough for calves and heifers to eat. It can tend to be lower in crude protein as well.

The Ugly

• The lack of effective fibre and if fed frozen can make cattle prone to frost bloat (a free gas bloat). The cold temperature shocks the rumen disabling the ability to belch. Wait for the frost to come off before feeding.

• Brassicas will bind up Iodine which can result in still births in calves – particularly out of heifers. Dosing a trough with stock iodine on a daily basis in the last month of gestation may reduce this risk.

• Nitrate poisoning is a real danger - particularly in rape followed next by kale. Its most likely to occur after periods of cold, low light conditions, where leaf loss has occurred from previous breakouts, and when animals go onto a frozen crop with an empty belly.

• Like fodder beet, swedes can cause acidosis. A transition period is also important.

Achieving an Optimal Outcome at Drying-Off

1. Reducing Milk Production Before Dry-Off

Lower milk production reduces udder pressure and leakage post-dry off, minimizing mastitis risk.

• Gradually reduce feed intake to about 150 MJME/day and less than 16% crude protein in the week before dry-off week.

• For 3 days before and after dry-off, provide a diet of about 90 MJME/day and 12% crude protein.

• Remove top 10% ISCC cows from supply in the last 3 days before dry-off to avoid BMSCC grades

• Feed cows straw for 2 days before dry-off to firm up faeces and reduce splatter.

• In preparation for dry-off, identify and leave some rough residual paddocks (ie. 1700-1800kg DM/ha) to return cows to on the days before and including dry-off, to minimise grass intake and keep the cows environment clean.

2. Avoid giving antibiotic DCT to low volume cows

Low volume cows have a higher risk of causing Inhibitory substance grades the next spring if treated with DCAT.

• Do not treat cows with DCAT if they were producing <5L a day in the week before dry-off. These cows should receive ITS only.

3. Identifying Cows Unsuitable for Internal Teat Sealant (ITS) Only

Certain cows are at higher risk of losing the sealant or developing mastitis.

• Avoid ITS-only treatment for older cows (≥4 years) producing more than 15L at last herd test, cows with teat end lesions, poor udder conformation, or recent clinical mastitis. These may be better suited to combination therapy.

4. Keeping Cows Calm on Dry-off Day

Calm cows are easier to handle, reducing stress and contamination risk when inserting DCT.

• Supplement calcium and magnesium in the week before dry-off (avoid oversupplementing magnesium).

• Provide plenty of a low energy, high fibre diet to keep cows satiated on dry-off days. Use straw or other high dry matter high fibre feeds

5. Ensuring Clean Teat and Udder Skin

Clean skin reduces the chance of introducing bacteria during dry-off procedures.

• Trim tails at least a month before dry-off and keep them free of dags.

• Firm up faeces through diet and avoid muddy grazing conditions.

• Apply teat spray by hand-wand to every teat at every milking for the last five days before dry-off.

• Avoid walking cows on mucky laneways on the last day.

6. Correct Teatseal Insertion Technique

Proper placement ensures the sealant stays in place and is effective.

• Hold off the top of the teat during insertion to trap it at the base of the teat.

• Do not overheat the product as it may float up into the udder (20°C is optimal).

• Insert ITS or DCAT soon after cup removal to minimize contamination risk.

7. Reducing Risk of Teatseal Loss After Administration

Loss of sealant increases mastitis risk.

• Do not let cows run immediately after treatment; walk them slowly to a clean, close paddock.

• If moving cows to a run-off, do so within 2-24 hours or wait at least 7 days.

• Continue low energy, low protein feeding for 3 days post dry-off.

Transport of Cull Cows

We all have to do our bit to ensure that cull cows are transported in such a way as to maintain animal welfare, so they arrive at the other end fit and healthy.

• Only select animals that are fit for transport.

• A BCS of at least 3.0, ideally more.

• No signs of ill health.

• No visible signs of wounds, bleeding disease or deformity.

• Can bear weight evenly on all 4 legs.

• Horns: Not ingrown or recently removed. They must be inside the ears and not sharp enough to damage each other in the truck.

  • If you are unsure have them assessed to see if they can qualify for a transport certificate by a vet. When we write a transport certificate we can only certify them for 7 days and it must be to the nearest works. Make sure you have this all organised prior to booking us in to see them.

  • Download the Fit for Transport app from MPI for more information.

Massey University has done research looking at what caused cows to go down when they went to works. They found:

1. 80% of down cows had milk fever (low blood calcium levels).

2. Most cows that went down were still lactating.

3. The further cows were transported the greater the risk of going down.

What can you do to reduce the risk of cows going down?

• Where possible, fully dry cows off before transporting to slaughter. Transporting in full milk is high risk. Milk any lactating cows as close to transport as possible.

• Cull cows should be transported for the shortest time possible and ideally processed at the nearest works. Discuss options with your stock agent. The risk of injury or going down increases with travel time and distance.

• Supplement with extra calcium and magnesium

  • Lime flour 250- 300g per cow

  • Magnesium 60- 70 gm Mag Chloride or Mag Sulphate in water and 30gm Mg Oxide mixed with hay or straw.

• Take cows off green feed (lush pasture) for a minimum of 4 hours and a maximum of 6 hours if they are still lactating, (12 hours if dry) prior to pick-up time.

• Provide ad-lib roughage and water until loading with the calcium and magnesium added.

• A grazed-out paddock is recommended to give cows the opportunity to rest before the journey. Don’t stand them on concrete.

• Cows may be held in yards overnight at the processing plant, so the total time off feed is longer than just the journey time.