Our advice as vets is to check your stock’s trace element levels before mating, even if your mineral supplementation hasn’t changed or you tested cull cows at dry off.
Unfortunately each season is different and results can change. This season, for example, has been very abnormal...
We had cull cows which were very high in some minerals, but then the levels in bloods taken from cows on-farm were low (so the cows tested at the works were NOT the ones from this farm)!
We experienced unusually high levels of magnesium in springers, which caused a lot of down cows.
We saw high levels of fatty acids (from fat break down) in springers who had good body condition scores, indicating there’s too much fat loss happening, which can cause trouble at mating time.
We took blood and liver samples from once-a-day and twice-a-day milking farms where the milk production ranged from 300MS/cow to over 500MS/cow, to compare what the mineral levels were like. And yes, even the high producers also had issues!
So, let’s take a look at the types of trace element issues you might face.
Copper deficiency
Copper deficiency can have many negative effects. One of the more concerning ones for farmers is that each litre of milk contains a standard amount of copper, so deficiency leads to lower milk production.
A copper deficiency is often the result of a lack of copper itself, but it can also be because of an overload of copper antagonists.
For example, copper does not get absorbed well when there is too much molybdenum and sulphur present, and absorption is also negatively affected with high iron, high manganese or even high zinc levels. As the molybdenum or sulphur applications in your fertiliser can change year by year, copper levels need to be monitored yearly.
Copper is stored in the liver and the body tries to maintain serum copper levels in the blood at the same level. Therefore, liver biopsies (taken from live animals on-farm) will show us the storage levels of copper and can show deficiencies before the serum levels go down and visual symptoms arise.
Magnesium deficiency
Magnesium deficiency is serious and it can cause grass staggers and milk fever.
We all know it’s important to supplement magnesium at calving time, but low or marginal levels around mating can also cause issues. Cycling cows move more than usual and this activity requires more minerals to support body functions. So, if cows with poor levels cycle, there is a higher possibility of them going down.
Too much magnesium is also an issue. This can happen because an individual cow has simply had a higher daily intake or because there is too much supplementation for the herd in general.
We have to ask questions about management and test to be able to make a distinction between the two. Magnesium is not stored in the body, so the level in the blood is an indication of the intake in the last 24-48 hours.
Selenium deficiency
Selenium deficiency is very common across our farms.
Besides being required for immunity, selenium is also required for fertility and growth – it’s a very important trace element. High somatic cell counts, more mastitis cases, and having to treat mastitis for longer, can all be part of a deficiency in selenium.
Cows with low levels of selenium can have a normal submission rate, but the conception rate will be reduced. Unfortunately, you will only find that out at pregnancy testing time, which is too late to change anything.
Be proactive instead of reactive. If you call us out to do some blood tests to check your cows’ levels now, and treat if needed, then you should have fewer empty cows to cull.
In summary, we highly recommend getting some blood and liver samples taken to check if your results are normal. At the same time, you can also check your levels of calcium, NEFA (fatty acids) and/or BOHB (beta-hydroxy butyrate – ketone produced by the liver). Make sure your herd is at their best for reproductive success.
Remember, you can’t improve what you don’t measure!
