Linking Retained Membranes, Milk Fever & Minerals

It’s calving time again and farmers are being urged to have their emergency calving kits on hand. Amongst these kits are down cow treatments including oral, subcutaneous, and intravenous calcium and magnesium options. With clinical milk fever rates estimated at 2% in NZ Dairy herds, that’s over 9000 down cows treated every year in Taranaki alone. Similar estimates of 1.7% are touted for Retained Foetal Membranes (RFM’s). Industry targets for both these diseases are <1%, so there’s plenty of opportunity to improve on the current situation.

As the title suggests, RFM’s and Milk Fever are linked. Mineral balance plays a significant role in both these diseases, but I’ll get to that later. The risk of RFM’s in cows increases with advancing age and number of births, occurrence of clinical milk fever, and increased milk yield. Studies have shown that a Milk Fever cow is 3.2 times more likely to retain her placenta than a cow that has not had Milk Fever.

So how do we prevent clinical Milk Fever and RFM’s? Because apart from being expensive to treat, by the time we see clinical Milk Fever cases, 20 additional cows are sub clinically affected and so is our production potential. Historically magnesium, starter drenches and pre-calving selenium have been common strategies used. Is this enough?

Not necessarily. While starter drenches may be successful in preventing cows from going down it doesn’t change the fact that the causative factors are still acting on them. And while most of us are familiar with the importance of selenium in preventing RFM’s, it’s not the only nutritional risk factor. If you’re supplementing with selenium and still getting RFM’s then it’s worth taking a closer look at what might be going on.

True prevention comes from removing the risk. Nutritional management is one of the best ways to prevent and decrease the incidences of RFM’s and Milk Fever. This is where the minerals come in. Deficiencies of trace minerals other than selenium can contribute to increased risk of RFM’s. Dietary imbalances in macro minerals including Ca, Mg, K, P and Na can predispose the herd to Milk Fever and RFM’s. Similarly, an energy or protein deficiency, or deficiency of vitamins A, E and D are also risk factors.

Interestingly, one international study has shown that the incidence of RFM’s is significantly greater on land applied with high levels of nitrogen fertilisers than the places with lower application rates. What’s the link? Well, high dietary nitrogen (crude protein) levels, along with high potassium levels will interfere with magnesium absorption and therefore calcium status of the cow. No surprises that these are also risk factors for milk fever. A simple strategy in this case would be to reduce your nitrogen and potassium inputs if practical or adjust the timing of application to avoid high nutrient levels over calving.

So, if less than 1% is the goal, how do we get there? Start by sampling and analysing your pastures to know your dietary mineral levels and risks. This will give you the confidence to make decisions that can help reduce any risk factors and achieve your targets. Sample today and you can make changes straight away so you can reap the rewards this season.