There are many complex interactions and influencing factors affecting both the uptake and utilisation of trace elements at the soil, plant and animal level.
All these factors, along with the farm's history and fertiliser use, should be considered before administering copper, selenium or vitamin B12 products to animals. After all, treatment without being aware of the farm's mineral status is not only wasteful but also potentially harmful to your livestock. Both blood and tissue (liver) sampling can be used in conjunction with soil and/or plant analyses to develop a trace element supplementation programme if required.
It is best to obtain livers from cattle for the analysis of copper status in the autumn time. This allows us to make decisions about whether to supplement cattle before the winter and spring when the availability of copper from the soil and pasture decreases. The animals' requirements for copper are highest at this time of the year, particularly in young, or heavily pregnant animals. Blood serum samples are only useful for the diagnosis of copper deficiency when liver reserves are depleted and animals are showing clinical signs. Soil analysis, because of the complexity of interactions and influencing factors, is not considered useful for the diagnosis of copper deficiency.
There is generally a good relationship between the level of selenium in the soil, plant and animal. Therefore, if the selenium in the soil is known to be low, then the likelihood of having selenium deficiency in your livestock will be high. In saying this, soil and plant analysis will not tell us the amount of selenium being absorbed through the animal's gut, and therefore animal tissue sampling or blood are best in order to make predictions as to whether supplementation is required. These can be taken from cattle (or ewes) at the same time as for copper, in the autumn time.
COBALT (Vitamin B12)
Severe cobalt deficiency (vitamin B12 deficiency) in lambs, particularly in Manawatu, is rare. This is because most areas are adequate to marginal in cobalt. In the marginal areas, we do not generally see a response to vitamin B12 supplementation unless there has been severe erosion (weathering), leaching, and/or repetitive cropping or fertiliser use. Clinical signs (anorexia and poor growth rates) will be most easily noticed in lambs - if not then it is very unlikely that adult sheep or cattle on the property will be deficient.
Weaning time is a convenient time to collect liver or blood samples from lambs for analysis of vitamin B12. However, because there is little change in vitamin B12 or cobalt status from birth to weaning, vitamin B12 deficiency can, therefore, be diagnosed (via a blood sample) in newborn lambs. The advantage of this is that if lambs are found to be deficient at a very early age, the benefits of supplementation at docking (as opposed to weaning) are greatly improved. By supplementing lambs deficient in vitamin B12 at docking time, a one to four kilograms live weight advantage at weaning could be expected depending on the severity of the deficiency.
Lambs can be tested for vitamin B12, selenium and copper at weaning using just one sample (blood or tissue), however, because sheep have lower requirements for copper (unless they are Finns!), the latter may not be necessary depending on the farm's history.
Liver samples can be either taken from the live animal by your vet (liver biopsy) or at the freezing works at the time of slaughter. Live liver biopsies in cattle are often better because these livers are more likely to come from cattle that are representative of the herd. Liver biopsies or livers collected from lambs at the works are generally equally meaningful.
If you wish to have samples collected at the works, or would like to have some biopsies taken by your vet, please contact your nearest clinic to make the necessary arrangements. Together we can then make informed decisions regarding the treatment options available.