Milk fever: A vet's tips for prevention and cure
Jersey cows are proven to be twice as susceptible to milk fever compared with Holstein cows.
That on-call ringtone is a sound embedded into my subconscious; even when I hear it in shops, I always reach for my pocket, and my heart rate begins to rise. It’s that natural adrenaline rush of not knowing what crisis is at the other end of the phone.
I was talking with a colleague during the week, and we concluded that on-call is where you see the most interesting cases while also having to think on your feet.
Last week I had my first out-of-hours milk fever case of 2024, I answered it upstairs whilst sitting at my desk and the call was a welcomed break from tedious admin.
This call was to an older lady in a large dairy herd who had calved the evening before and had now gone down in the cubical house.
The main questions I always ask farmers on the phone are; when did she calf? Is she lying flat out? And lastly, what treatment has she received? It gives me an idea of the case I am about to arrive at on the farm and also how serious a condition I will find the cow in.
To meet that increased need for calcium, reserves in their bones and teeth are utilised, as well as regulating the absorption from the gut from the food they digest.
The cow uses a hormone called the parathyroid hormone to raise blood calcium, the issue is that this hormone needs to be downregulated in the dry period to have the desired effect post-calving. This is why the diet before calving is low in calcium and supplementation is left until the point of calving to not interfere with the parathyroid hormone function.
A classic clinical milk fever can present as a down cow unable to rise with cold extremities, an S-shaped neck turned into face her body and overall loss of muscle tone which can lead to fatal bloat.
The target for any farm would be to have <5% clinical milk fever cases in one year. It is well-researched that for every case of clinical milk fever, there are up to six cases of subclinical cases that are going under the radar but low calcium has an effect on their immune systems can be impacted causing a string of secondary diseases such as mastitis, ketosis and metritis. Poor rumen contractibility and smooth muscle dysfunction due to low calcium can lead to issues such as left displaced abomasums two to three weeks post-calving.
It may seem a little counter-initiative that to prevent milk fever, calcium is the last thing a cow requires during the dry period. On the other hand, magnesium in the dry period is our friend for milk fever prevention as it also helps to prime the parathyroid hormone to jump into action when the cow calves.
Magnesium in mineral supplementation is key for at least the last six weeks of the dry period, a minimum of 20g per dry cow per day is optimal. This may need to be discussed with your vet or nutritionist in light of silage results as a high potassium (K) silage will bind magnesium causing it to be unavailable. If your silage results come back with a result over 1.8% K then additional magnesium supplementation may be required to prevent milk fevers at calving.
If you are getting cases of early milk fevers this spring, all is not lost. Magnesium is the first issue to address and then it is looking at supplementation at calving with calcium. The higher-risk cows to focus on would be; the older, higher-yielding, over-conditioned cows that perhaps have a history of milk fever.
They should supply at least 40g of calcium per bolus and calcium carbonate should not be the main ingredient as it is absorbed too slowly. We plan on using the new head gate in the calving shed to make the bolus job easier and safer.
All my cows get a fresh cow drink at calving to firstly boost their calcium intake but also to supply fluid therapy and energy, “The tea and biscuits” of the bovine maternity ward.
Since focusing on magnesium dry cow mineral supplementation, the targeted use of calcium boluses and blanket use of the fresh cow drink at calving we have dropped our incidence of milk fever to perhaps 1-2 cases a year which is well under the 5% target.
The on-call cow was exhibiting classic milk fever signs, down in the cubical shed with her legs splayed behind her in an attempt to rise, I always check their udders for mastitis, their temp and check for a calf (I found a twin once in a down cow).
She was given a bottle of Calcium under the skin before my arrival, I administered a bottle IV slowly and gave a bolus after as she was sitting upright and could swallow. It is important not to give too much calcium IV or Subcutaneously to cow as it can stitch on a hormone called calcitonin which excretes calcium from the body which would be very counterproductive.
After treating the cow on the farm that night, I advised her to wait a while for the calcium to take effect as trying to move a cow too quickly could cause her to fall and stress only makes matters worse.
I left the farm with the hope that she would be up within the hour and I was so glad when the farmer texted to say she was up, and honestly, it was one of the best feelings.
We have lots of bad days on the farm both as farmers and vets, not everything gets better which makes these milk fever wins even sweeter.
