What to do with those High SCC cows? Identify and make a plan

The BMSCC target by the end of August should be below 150,000 and holding steady or declining. When it is high or lifting there is cause to take action to protect the milk quality for the remainder of the season.

Start with checking the basics. Is the plant operating within the optimal range settings. If in doubt Hamish, Mat (Oamaru), or Ewan (Waimate) can visit during milking to do a dynamic machine check and at the same time trouble shoot for other apparent issues.

By late September/start October many herds will be doing their first herd test for the season. There is an opportunity here to review the ISSC results and order LIC’s Mastitis Multiplex PCR test on the high cell count individuals. This identifies 3 of the most common mastitis pathogens including Staph aureus as well as a gene for penicillin resistance. Testing must be pre-booked but there is no commitment to test until our vets have reviewed the herd test results and recommend cows for testing. The cost is $19/cow submitted.

Identification of cows carrying Staph at the start of the season can be managed (run in the last herd or set on draft and milked last). By doing this you will limit the spread of this hard-to-treat infection and protect your uninfected cows.

As a reminder though, while you wait for your first herd test – we also have in clinic quadratic plate cultures with an AI plate reader with a rapid turnaround on results.

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.