Autumn is the perfect time to review your trace element and mineral programme and to make a testing and supplementation plan for your farm with your veterinarian.
Most farms will have a trace element supplementation programme of some description, but regular testing is needed to make sure it is working and that you are getting the best return on your investment by not under- or over-supplementing. Even if you think your plan is fine and it seemed to work well last season, we all know that no two seasons are ever the same, and there can be vastly different feed and environmental challenges and stressors which may have a large impact on your stock’s trace element demands and reserves. Without testing and a discussion about which trace elements have been supplemented, and when, for each age group, it is impossible to know if your plan is working. All too often during this discussion, it becomes apparent that trace element and mineral programmes may not be adequate, let alone optimal, e.g. ill-thrifty calves or heifers, a high number of retained membranes/dirty cows at metrichecking, or perhaps reproductive performance not as good as expected?
Copper and selenium are the key trace elements to test for in the autumn, but other trace elements and minerals (e.g. magnesium, calcium, iodine, cobalt/B12) are also important, whether it be under certain feed/ environmental conditions, at other times of the year, or for different stock ages.
Copper plays a key role in cow health by supporting growth, milk production, fertility, immune function, and calf viability. Copper levels decline over the winter due to reduced availability from pasture and crops, reduced feed intake, inconsistent or absent supplementation, and increased copper demand from the foetus in late gestation. This means that, unless we ensure copper levels are optimal in autumn, they can be low or even deficient in the spring when the mineral is needed the most! This is why we advise that liver biopsies are taken in autumn to check that cows have enough copper stores to get them through the winter.
Selenium is another important trace element for cow health. It is also involved with milk production, reproduction and calf viability, but probably most notably it has a very important role in immune function, helping to reduce the incidence of disease during periods of stress, e.g. the peri-calving period. Selenium levels can be highly variable between farms, and they are dependent on soil and pasture levels as well as the amount of supplement being fed. Testing is the only way to be sure about your cows’ selenium levels, and autumn testing is also a great time to ensure levels will be optimal at calving.
Liver biopsies are the most accurate way to determine copper storage levels in your herd prior to winter, because the liver is where copper is stored in the body. It is possible to test blood samples for copper levels; however, the usefulness of those results is limited to telling you if your cows are truly deficient. Sufficient blood levels will not give you any information about the amount of copper a cow has stored in her liver. There is no correlation between blood copper levels and liver copper levels until deficiency is reached, i.e. a cow with blood copper level of 18umol/L does not necessarily have higher liver levels than a cow with a blood level of 10umol/L. The liver acts like a tank, releasing copper into the blood supply to maintain sufficient levels, so, while a cow may have sufficient blood copper levels, her liver could be on the verge of running out with no stores to get through the winter. It is very difficult, therefore, to make recommendations about copper levels, how long the supply will last, and what supplementation is needed from blood copper results alone. The liver biopsy is the “fuel gauge” of the liver, telling you if you have enough copper in the tank to get to your destination (spring).
We know that some farmers are concerned about the impact of liver biopsies on their cows, and therefore might prefer to test the livers from cull cows at the works; however, these results may not reflect the true copper status of your herd, as many of these cows are empty cows or low producers due to underlying illness, which will affect their liver copper levels. You also never really know if the livers tested are actually from your cows. Liver biopsies are simple and safe procedures and far less invasive than you might think.
Selenium is not stored in the body, therefore blood samples correlate well with their recent selenium intake and are an effective and simple way of checking the status of this trace element. The other trace elements can also be added to the blood samples taken to test selenium.
It is recommended to take livers and bloods from cows representing both older and younger animals in your herd as well as different mobs, especially if they are managed differently.
And do not forget about your youngstock!
While much of the focus with trace elements is on cows in the herd, heifers and yearlings are often forgotten about, despite regularly being the most deficient groups. Heifers at grazing have been exposed to different pastures and soils as well as different trace element supplementation regimes, so their trace element status can be very different from that of the herd. We often find they have significantly lower copper and selenium levels and therefore may need their own supplementation plan. Your yearlings should also be tested for copper, selenium +/- B12 heading into their first winter.
Supplementing without need or at incorrect levels is either a waste of money or means you will not be achieving the desired results. If you are not giving enough, then you will not see the production and reproduction benefits you expect, and if you are giving too much, you run the risk of toxicity in your herd. Just as testing indicates when levels are low and more supplementation is required, it also indicates when levels are optimal and no further supplementation is required and when levels are getting high and that supplementation should be reduced to avoid toxicity.
While we are usually looking to correct deficiencies, it is becoming increasingly common to see high levels of trace elements (especially copper in herds feeding PKE). Both copper and selenium can be fatal in excess. Testing, therefore, is an absolute necessity.
Alongside this testing is ultilising your veterinarian’s expertise and knowledge to formulate a plan, specific for your farm, which involves more than just giving trace elements but also takes into account other factors such as previous supplementation, age groups, recent conditions/events specific to your farm or region, time of year/ upcoming events, and supplementation options.
Give your local Vetlife veterinarian a call to lock in your autumn trace element testing and supplementation plan review. Your cattle will be both healthier and perform better with appropriate supplementation of key trace elements.
And do not forget about follow-up testing in the spring pre-mating!
