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Vaccinations Parasite Management Using drenches Trace Elements Farm relevant concerns

A heifer's health plan needs to adapt to her age and grazing farm, especially if she moves farms within her first two years. This plan should cover five areas: biosecurity, vaccinations, parasite management, trace elements and minerals, and region-specific concerns like liver fluke or facial eczema. Vaccinations are vital for all incoming animals, and there are mandatory vaccinations for diseases like bovine tuberculosis and Leptospirosis. Parasite management should be customised for each farm's parasite presence. Trace element deficiencies, like copper and selenium, need to be monitored. Regular consultations with a vet ensure the health plan remains relevant and effective.

Heifers have unique health needs specific to their age and the farm that they are grazing. If heifers move farms during the first two years of life, it is likely that they will need a health plan that adapts with their movement.

Heifer health plans have five elements:

  1. A biosecurity process
  2. A vaccination programme.
  3. A parasite management programme that limits drench resistance.
  4. A trace element and mineral programme.
  5. Address regional or farm relevant concerns (e.g. liver fluke, facial eczema, etc.)

Animal health plans need to be specific to the farm where the heifers are grazing as disease exposure, parasite presence, mineral deficiencies and biosecurity risk vary on each farm. The more stock movement between properties, the more comprehensive preventative measures should be.  A vet can help assess the appropriate animal health plan.


All animals that enter the farm should be appropriately vaccinated and disease tested. Protecting your animals and safeguarding your business against disease risks are for everyone’s benefit.

Diseases that must be managed by law are bovine tuberculosis (TB) and Leptosperosis (Lepto). All vaccines listed below are most effectively administered once animals are 12 weeks of age or older.

Optional vaccinations

Clostridia is the most common optional vaccine in heifers with farmers knowing it as 5-in-1, 6-in-1, or 10-in-1. Vaccination for Clostridia is very effective in preventing disease. Clostridia are a group of toxin-producing bacteria that are implicated in diseases such as: blackleg, pulpy kidney, malignant oedema, tetanus and black disease; which result in sudden death.

Salmonella infections are a higher risk for heifers because of their developing immune system and changing farms. Risk factors like stress from transport and sudden diet changes while moving farms, as well as BVD infections means grazing managers should consider vaccinating. Salmonella bacteria colonise in the intestinal tract and can cause an infectious diarrhoea that, if untreated, may result in death. Salmonella are zoonotic organisms, so can cause disease in people as well. Whenever Salmonella is suspected extra hygiene precautions should be taken to prevent them from spreading. If cases of salmonellosis are infrequent, or never seen, then vaccination is unlikely to be warranted.  Vaccination is not completely protective but will lessen the frequency and severity of the disease when it is present.

Bovine viral diarrhoea (BVD) is a highly infectious viral disease which can spread via bodily fluids. It causes reduced growth rates, reproductive losses, an increase in disease in general, and lowers milk production. There is no treatment for BVD, prevention via vaccination is the only option. Find out more about BVD.

Parasite management

Parasites are farm specific and the farm owner/manager should select the drench types that are most effective at controlling the parasites on their farm. As part of the biosecurity process quarantine drenches should be administered on animal arrival and animals retained in a quarantine paddock, this prevents the transfer of parasites between farms.

There are three categories of cattle endoparasites: roundworms, tapeworms and flukes. Roundworms (nematodes) have the greatest economic impact and can cause reduced weight gain, weight loss, diarrhoea and death. Reduced weight gain is the first sign of parasites. Ninety percent of the parasite population is on pasture, not inside animals, so managing roundworms on pasture is as important as managing them in the animal.

There are three approaches to managing roundworms:

  • reducing larval intake (preventing infection)
  • helping the animal cope with roundworms (building resilience)
  • killing the adult roundworms inside the animal (drenching).

Find out more about managing internal parasites on the Wormwise website.

Listen on:

Using drenches

When it comes to drenching, it is common for stock owners to select and administer drenches. This should be done in consultation with the grazing farm manager/operator so that drenches are relevant for the parasites present on their farm.

Based on current information, it is clear that many New Zealand farmers are using drenches in a manner that will result in drench resistant parasites and drench failure. There are four ways to limit drench resistance, one method can be applied or a suitable combination of methods for your farm.

  1. Grazing management
  2. Good drench practice
  3. Selective drenching or refugia
  4. Fecal egg counting

If using parasite drenches, drenching should not occur more frequently than every 28 days and should be based on heifer growth and fecal egg counting. When conditions are cool and/or dry drenching should be spelled for longer. A heifer’s immune system will start to suppress roundworm egg production at about 8 months of age, which makes fecal egg counting less accurate, but the stronger immune system of the heifer should offset the measure.

Abamectin withholding periods have changed

The milk withholding periods for abamectin-only pour-on products are changing from nil to 35 days to comply with the lower maximum residue level (MRL) for abamectin in milk. This will come into effect in September 2022, but because the MRL is being lowered to address an existing trade risk, farmers are urged to start observing the 35 day milk withholding period now to avoid unacceptable abamectin residues and ensure future compliance to the new MRL. Please check the supply of drenches in your sheds and don’t be caught out - if in doubt check with your vet.

What is the impact on farm?

Farmers are urged to start observing the 35-day milk withholding period now to avoid unacceptable abamectin residues and ensure future compliance to the new MRL. They are also urged to check the supply of drenches in their sheds to avoid the risk of having to dump milk. By avoiding abamectin use during the lactation period from the start of the milking season farmers will have a 5-6 week lag time ahead of the change coming into force.

It is important to note that any milk produced in the weeks ahead with abamectin residues could still trigger a trade issue or stoppage of trade, so moving away from the use of abamectin during lactation now will help reduce that risk.

How serious are the trade issues around abamectin?

China and the EU both expect exported dairy products to contain no detectable levels of abamectin residues, with international limits of detection as low as 0.002 mg/kg. A previous detection of abamectin residues in dairy products in 2020 resulted in a negative impact on trade, leading to New Zealand Food Safety taking this action to prevent any issues or stoppages in the future.

What impact does the 35-day milk withholding period have on detection of abamectin residues?

The 35-day milk withholding period can be expected to conservatively ensure a lack of detectable residues in order to manage the trade risk. This change to single-active-ingredient abamectin pour-on products will bring them in line with all other products containing abamectin, which already have milk withholding periods of 35 days or longer.

What actions have been taken by MPI/NZ Food Safety?

Members of the ACVM team at NZ Food Safety have proposed the setting of a new Maximum Residue Level (MRL) that is aimed to ensure residues in milk are below the limit of detection and satisfy concerns from overseas markets. Consultation on the proposed changes to the Food Notice: Maximum Residue Levels for Agricultural Compounds closes on 12 August, with the finalisation of changes being planned for September. Once the new MRL is in place, a nil withholding period will not be enough to prevent non-compliance with the MRL.

Are registrants of abamectin products also aware of and preparing to act on this change?

Yes. As an example, one registrant has already updated their label and marketing to include the statement 'Milk intended for sale for human consumption must be discarded during treatment and for 35 days following the last treatment'. Registrants are also required to inform their supply chains as the change is finalised for each individual product.

Trace elements

The important trace element deficiencies of livestock in New Zealand are cobalt, selenium, copper and iodine. In heifers, the efficiency of uptake of trace elements from pasture changes as the rumen develops. Find out more about trace elements.

Trace minerals for dairy heifers

Deficiency impact Risks for deficiencies

Poor weight gain

Poor mating results

Lighter coat colour

Broken bones


Low copper content in feed source

Grazing on heavy soils with Molybdenum Ingesting soil during grazing, particularly on crops

Treating for facial eczema with zinc


Poor weight gain

Poor mating results

Low Selenium levels in the soil

Grazing in the Central Plateau of the North Island or on peat soils in the Waikato

Cobalt/ vitamin B12 Ill-thrift Grazing in the Central Plateau of the North Island
Iodine Goitre (A swelling in the neck due to the enlargement of the thyroid gland) Calf death at calving Low iodine levels in feed, like a brassica based diet


Farm relevant concerns

Mob specific animal health plans should be agreed to by the grazing manager, even if the stock owner is the one implementing the animal health treatments.

When starting out in a grazing relationship all the key elements of animal health plans should be addressed. These questions can help develop a health plan:

  • What are the stock movement levels on the property and potential disease exposure?
  • What is the historical presence of Salmonella, theileria, facial eczema, etc.?
  • What are the parasites present on farm? What is the farm management that will reduce parasite pressure (e.g. grazing management, cropping regimes, and stock classes)?
  • What have been the historic trace element deficiencies? What pasture species, crop types, supplement, soil types, and fertiliser history will the heifers be grazing on that might impact the trace element presence and concentration in their diet?

Once a health plan has been discussed and implemented over the season, consider:

  • How effective was last season’s health plan and are there any changes to be made?
  • What has changed or are there any new risks to be aware of?

Other heifer mob level animal health issues to be aware of and incorporate into the health plan are in Table 1.

Illness Primary risk factors
Facial eczema

Dead and decaying plant material in pastures

Weather conditions that are warm and humid

Liver fluke

Cattle less than 12 months old

Spring grazing conditions Humid, moist environments with a nearby water source (poorly drained paddocks)


Stressful incidents (travel, handling, poor stockman ship, poor hygiene)

Underweight at trucking Recently weaned off milk or significant feed changes

Animals raised indoors or with poor ventilation Poor health (poorly fed or other illnesses)


Wild animal entering the farm area

Exposure to cattle that are infected with Theleria

Last updated: Sep 2023
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