South Waikato veterinary Services

Trace Element Monitoring


Monitoring trace elements is an ideal way to assess your herds status, giving you critical information to help tailor your mineral supplementation programmes.

Generally we recommend taking blood samples from 10 randomly selected cows and liver biopsies from 5. It is a good idea to include at least 2 first calvers as their mineral requirements are often slightly different to adult cows due to the extra demand of growth.

The cows we sample need to be well fed on the day of the biopsies. This is so the full rumen holds the liver nice and firm against the cows diaphragm, making it straightforward to biopsy.

The ideal times to sample your herd is at least one month prior to mating (blood tests only) and again prior to drying off (blood tests and liver biopsies). This allows us time to correct any significant deficiencies well before your herd is dried off or mated. We also recommend sampling the herd at the start to calving to monitor the cows trace elements after the dry period and to ensure they are getting a good level of Magnesium supplementation.

Why take both blood and liver samples?

Whilst we can measure blood Copper levels easily, this only tells us what an animals Copper status is on an individual day. It unfortunately tells us nothing about the animals copper stores. Copper is stored in the liver thus taking liver biopsies is the best way to analyse what your herds Copper stores are. Copper supplies will naturally decrease over winter (especially if the herd is wintered on crops or a property without an inline water dispenser.) Therefore it is especially important we check your herds Copper status prior to drying off. Other trace elements such as Selenium, B12 and Magnesium are more accurately measured in the blood. By taking samples from at least 8-10 animals we can get an accurate picture (at an affordable cost).

Do you need special equipment for liver biopsies?

To take a liver biopsy the cow must be restrained in either a head bale or narrow race with access to the right hand side. The vet will clip hair and scrub a small area approximately 2 by 2 inches and instill local anaesthetic into the skin and muscles. They will make a small 1cm incision which they place a special liver biopsy needle (this is why you need to book to have liver biopsies taken as vets don’t always have these in their cars) through to get a small sample of liver. There is no need for antibiotics or pain relief after the procedure - although we do like to use some purple spray to cover the wound.

What about young stock?

Young growing calves often require regular supplementation of Selenium and B12 as they are growing. Selenium is especially important to growing animals as low levels will significantly increase a calf’s susceptibility to disease. It is important we monitor the trace element levels in young mobs of calves as overdoses of some trace elements can be deadly. Both bloods and liver biopsies can be performed on young stock - however usually we only take bloods as the facilities on the run off do not permit us safely collect liver biopsies.


The South Waikato Veterinary Services team is committed to providing top quality and extensive professional services to the Tokoroa, Putaruru, Whakamaru, Mangakino, Tirohanga and Atiamuri areas.

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2 Satco Drive, Tokoroa

75 Tirau St, Putaruru

108 State Highway 30, Whakamaru

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