Recently completed B+LNZ research projects | Beef + Lamb New Zealand

Recently completed B+LNZ research projects

The B+LNZ research portfolio is diverse and supports several projects and larger programmes across animal health, productivity and genetics, environmental health and mitigations (greenhouse gas) and landscape management. Read about our recently completed research projects.

The objectives of this project were to:

1) quantify the benefits of deferred grazing
2) establish criteria to help farmers identify when deferred grazing is appropriate in their farm system. 

This was achieved by comparing standard rotational grazing and deferred grazing in replicated plot studies at two sites:   

  • Mataiwhetu Station – a summer wet property   
  • Otorohaea – a summer dry property.  

The deferred treatment was not grazed between mid-October and the end of summer / early autumn (depending on the farm) but was rotationally grazed after the deferred period for the remainder of the study.   

Comparing the effect of standard rotational grazing and deferred grazing in a replicated split-paddock study on three sites:

  • Mataiwhetu Station – a summer wet property   
  • Otorohaea – a summer dry property  
  • Pukekauri Farms – a summer wet property.


‘Deferred grazing’ is a management tool used to maintain pasture quality and rejuvenate paddocks on pastoral farms. In the deferred paddocks, perennial ryegrass produces seeds, new tiller buds that form at the base of existing plants remain dormant over summer and develop into new tillers in autumn. The deferred pastures are grazed to low residuals at the end of the deferred period over one or two grazing’s (e.g. to 1500 kg DM/ha) so that the ryegrass seedlings and new ryegrass tillers have access to light. The previously deferred pastures are treated as renewed pastures and are grazed carefully with light stock for short periods. 

Deferred grazing has been used by some hill country farmers in the mid Northern North Island New Zealand for more than a decade. These farmers could see benefits for both the deferred pastures and for the rest of the farm and wanted to quantify those benefits through a science-led project. 

Key results

Compared to standard rotational grazing, deferred grazing improved pasture performance by increased:

  • ryegrass ground cover and tiller densities
  • topsoil moisture
  • anaerobically minerablisable nitrogen (the amount of nitrogen potentially available for plant uptake) and reduced:
  • facial eczema spore counts 
  • weed content.

There was reduced nutritive value in the deferred paddocks during the deferred period, but pastures rapidly recovered after the deferred period. Decline in quality of the deferred pastures was not enough to offset overall farm-scale profitability.

When compared to standard rotationally grazed pastures, the deferred pastures grew less during the deferred period but more after the deferred period, so dry matter production was similar in both over the experimental period.

FARMAX modelling carried out on one of the farm sites showed there was an 8% increase in total farm and per-hectare gross margins when 15% of the farm was deferred. 

Benefit for farmers

This project provided science-based evidence for the benefits of deferred grazing compared to standard rotational grazing, on three farms in the Bay of Plenty and Northern Waikato. Information from this project has been disseminated in a handbook and a fact sheet including a checklist for farmers on how to defer paddocks. 

Timeline and investment

This was a three-year study with investment by B+LNZ of $180,000 over the duration.


Farmer events

  • Farmer field days throughout the project.

Popular press articles

Scientific publications

B+LNZ resources

  • Handbook for farmers including decision ‘rules’ to help farmers identify when deferred grazing is appropriate in their farm system. 
  • B+LNZ factsheet.


This was a Ministry for Primary Industries Sustainable Farming Fund project led by AgResearch and co-funded by B+LNZ, Ballance Agri-nutrients, Bay of Plenty Regional Council with in-kind support from the Waikato Regional Council, Plant & Food Research and AgFirst.  

Lead Scientist: Katherine Tozer (AgResearch).  
Farmers involved: Allen Coster, Rick Burke, Jon Sherlock, Brian Thomas. 
B+LNZ point of contact: Maria Shanks and Cara Brosnahan.

The aim of this study was to provide an understanding of introducing refugia into a lamb finishing operation that had a triple drench resistance issue. Refugia, introduced through lambs with susceptible parasites, was compared to the more conventional practice of quarantine drenching.


Resistance of parasites, or worms, to all classes of drench is a major concern in New Zealand farming systems. Intensive finishing and hogget grazing systems are at high risk of developing triple drench resistance, as are areas on farm predominately utilised for grazing young stock.

There is an opportunity to better understand drench resistance on farm. This project harnessed the power of relationships between a group of Wairarapa breeding and finishing properties, their vets and industry experts to have an in depth look at the impact lambs supplied from the group breeding properties had on a large scale finishing farm receiving their store lambs, including the development of triple drench resistance on this farm.

Key results

Know your worms. It is important to have a recent faecal egg count reduction test (FECRT) from the farm you are buying lambs from prior to arrival to your farm. By doing this, you know if you are introducing parasites that will be susceptible to drench and can introduce refugia on your farm, or drench resistant parasites that will increase the likelihood of drench resistance on your farm. In this study, the group of farmers shared their recent FECRT results and explored how their results impacted the next farm their stock traveled to. The project enabled them to reduce cost and gain efficiencies by cutting out ineffective quarantine drenches, improved the relationship between breeding and finishing farms and showed a start to reversing triple resistance status of the finishing farm involved.

Triple combination drenches may not be effective quarantine drenches. This includes for hogget grazing blocks and stock purchases. To know what quarantine drench you need, you need to know your worms.
For the introduction of refugia onto the farm the eggs must develop into infective larva, be ingested by lambs and breed. The time of the year to best achieve this and not induce clinical parasitism, or disease, needs to be considered for each farm system.

In this study, an increase in efficacy of drench was shown on the farm by both refugia and quarantine drench procedures. Testing will continue on this farm over the next 2 years to compare refugia and quarantine drench to determine if one or the other is better to reverse the effects of drench resistance over time.

Refugia can come with risks. In this study there was an unintended introduction of barber’s pole worm in the refugia trial. Barber’s pole was not detected at the initial screening but was detected in the refugia farm when tested 28 days later.

The results from this study so far suggest that both quarantine drenching and refugia can be used as management tools to reverse triple drench resistance. However, due to the short period of this project (6 months) testing will need to continue over the next 2 years to reliably confirm these results.

Benefit for farmers

This study demonstrated that by knowing the status of the parasites both on your farm and the farm you are buying stock from, you can put in place effective management strategies to reverse triple drench resistance.

Timeline and investment

This was a six-month study with investment by B+LNZ of $10,000 over the duration.


This project was carried out by Inside New Zealand Ltd, PGG Wrightson, South Wairarapa Vets and funded by B+LNZ and Silver Fern Farms.

Project leads: Renee Hogg (Inside New Zealand Ltd) and Andrew Dowling (PGG Wrightson).
Farmers involved: Wairarapa Producers Group.
B+LNZ point of contact: Will Halliday and Cara Brosnahan.


The aim of this study was to analyse existing data sets from animal health laboratories around New Zealand and from animals at slaughter via meat processing companies to see if the prevalence and distribution of facial eczema (FE) in beef cattle could be quantified.


Facial eczema is a disease of concern in New Zealand known to affect sheep, cattle, goats, llama and alpaca. FE is attributed to the ingestion of a toxin (sporidesmin A) produced by strains of the fungus Pseudopithomyces chartarum which sits in the litter at the base of some pasture swords.

The damaging impacts of FE on sheep and beef farms include reduced production and income, stress on farmers and their animals, impacts on animal welfare and environmental concerns around zinc treatments. As the fungus prefers warmer temperatures, it is likely that an increase in temperatures due to climate change will increase the number and extent of FE outbreaks in New Zealand.

While it is known that FE affects beef cattle, it is unknown to what extent or where in New Zealand it mostly occurs.

Benefit for industry

Understanding the prevalence, distribution and impact this disease has in beef cattle allows an informed strategy for the resources needed for research and management.

Key results

The data showed presence of FE in beef cattle. However, due to the limitations of the data from the animal health laboratories and meat processing companies, this could not be quantified. The limitations of the data were:

  • the number of animals tested/affected were not consistently recorded
  • there was a lack of detail in the meat processing data on livestock type and origin available
  • there was a lack of detailed data from the lab on what test was used for diagnosis and if this was consistent across the different laboratories
  • it is suspected that not all farmers with suspected FE had their animals tested, so the data was not truly representative

Timeline and investment

This was a seven-month project with investment by B+LNZ of $8,000 over the duration.

B+LNZ investment: B+LNZ investment into this project is $8,000 over the duration of the project.


This project was led by Ken Geenty and funded by B+LNZ.

B+LNZ point of contact: Cara Brosnahan.

This project investigated the following:

  • the potential effect of long-acting drench products on the rumen microbiome.

This was done using 300 ewes in total that were given one of three different treatments (long-acting drench product, controlled release capsule and untreated control). The rumen microbiome of these animals was sampled three times throughout the trial 

  • the effect of parasites on ewe growth, Body Condition Score (BCS) and fecundity over the summer-autumn period.

This was done by assessing 300 ewes (as above) and three measures were taken: 

  • Ewes were weighed and their BCS were assessed at days 0, 36, 78, 182 and 320. 
  • Faecal samples were recovered from a sample of ewes from each treatment group at days 0, 36, 78, 182 and 320 to determine the parasite load, or worm burden. 

Pregnancy status was determined by scanning. During lambing, all dead lambs were collected, and weaning lambs weighed.  


Long-acting drench products can have activity against organisms other than parasites, for example fungi and bacteria. The effects of long-acting drench products on the microbes within the rumen (rumen microbiome) are largely unknown and may influence such things as animal performance and production of green-house gases. 

Long-acting drench products are administered as a pre-lambing treatment of ewes by about 80% of sheep farmers in New Zealand. Pre-lamb drenching is done as farmers expect that by treating ewes, both ewes and their lambs will be heavier at weaning and ewes will be in better condition. In particular, it is widely believed by farmers and veterinarians that poor condition in ewes (low BCS) is caused by parasites and that by focusing drench treatments on these animals, it will result in significant production gains.

Key results

  • Farmers may not be making money from pre-lamb drenching every year.  
  • If resistant parasites are already on your farm, then using long acting anthelmintics will make the issue worse.  
  • To improve profitability, considering ways of improving lamb drop and lamb survival is likely to be more important than drenching.  
  • There was a change in the rumen microbiome of drenched vs undrenched animals. This was the first study to investigate the influence of long-acting anthelmintics on the rumen microbiome and it provided baseline information for future studies to build upon. Future studies are needed to understand what the observed changes in the microbiome of the treated animals in this study may mean for ewe performance as well as methane production.

Benefit to farmers

This study suggested that a financial benefit resulting from the administration of these long-acting drench products pre-mating is unlikely. 

These results are consistent with earlier studies which indicate that 1) parasites are not a major cause of low BCS in ewes on New Zealand farms and 2) studies showing that the production responses to the use of long-acting drench products are, to an extent, temporary and tend to decline or even disappear completely after the products have expired. 

Timeline and investment

This was a 32-month project. B+LNZ investment was $190,000 for the duration of the project.


Popular press

Scientific manuscripts


This work was led by AgResearch and co-funded by AgResearch and B+LNZ with in-kind support from Pāmu.

Lead Scientist: Dave Leathwick.
B+LNZ point of contact: Suzanne Keeling.

This project measured the concentrations of ivermectin (a macrocyclic lactone) reaching target cattle tissues (abomasum and small intestine) and the target parasites (Ostertagia and Cooperia) when given to cattle orally, by injection or pour-on. 


While it is known that different routes of drench administration can result in variable efficacy against some parasite species it is not understood why this occurs or why different organs appear different. Despite evidence that pour-on administration is the least effective and most likely to select for resistant parasites, these products are the most common for the cattle market in New Zealand today. Solid evidence explaining why one route of administration is better or worse than others is required to understand if a change on-farm is required. 

Current data indicates that in cattle, oral drenches are more effective than injections or pour-ons and this is probably because orals deliver a higher concentration of active ingredients to the target parasites in the gut.  

Despite this information, most cattle farmers continue to use pour-ons because of their ease of application. This almost certainly results in failure to properly control Cooperia (with an associated production loss) and the likely promotion of drench resistance in Ostertagia.

Key programme results

Route of administration is likely to influence the exposure of ivermectin for different parasite species:

  • for most parasite species (e.g. Cooperia species), oral administration of ivermectin will deliver the highest exposure of parasites to the drug
  • for Ostertagia ostertagi, administration of ivermectin by injection is likely to be the preferred option for achieving maximum drug exposure.

Ivermectin concentrations were highest in the small intestine following oral administration.

Benefit to farmers/industry

This knowledge provides farmers and veterinarians with scientific evidence on the type of administration of drench that is most effective in cattle and that the most effective administration may differ depending on the parasite targeted. Changes to the most effective way of administering drench will help reduce the likelihood of drench resistance and improve productivity.


Scientific publication


  • Two B+LNZ field days.

Timeline and investment

This was a 20-month project. B+LNZ investment was $95,000 over the duration of the project.


This work was led by AgResearch and co-funded by B+LNZ and AgResearch.

Lead scientists: Dave Leathwick and Tania Waghorn.
B+LNZ point of contact: Suzanne Keeling.

The aim of this project was to develop an udder scoring system associated with udder health, lamb survival and lamb growth rates and can accurately be used by farmers.

To do this, the following was investigated:

  • recognise and describe the range of udder and teat defects found in commercially-farmed ewes
  • factors associated with clinical and subclinical mastitis in ewes
  • the impact of udder and teat defects and udder health on lamb survival and pre-weaning live weight gain.


Lambing percentages in New Zealand have increased over the past twenty years, putting increased emphasis on ewe udder health to enhance lamb survival and maximise pre-weaning growth rates.

Many farmers indicate that they examine the udders of their ewes and make culling decisions based on this. However, there is sparse information available, and therefore guidance, on what farmers should be examining and the impacts of various udder characteristics on lamb performance.

Without this knowledge, farmers may fail to cull ewes who will not rear lambs successfully or whose lambs will display poor growth rates. Conversely, they may incorrectly cull ‘sound’ ewes.

Key programme results

Udder scores can be used to determine culling decisions or identify ewes whose lambs had greater odds of failure to survive weaning.

Udder palpation, udder symmetry and clinical mastitis scores during lactation were associated with lamb growth rates.

Benefit to farmers

This project provided information and resources to more accurately assess ewe udder health and make sound culling decisions.

Lambs that are born to ewes with udder defects will have a reduced chance of survival and the lambs that do survive grow an average of 25g less per day than lambs whose dams had normal udders so for long term productivity, understanding udder defects is hugely important.


Six presentations

  • Six to farmer and industry audiences.

Popular press articles

Scientific publications

Timeline and investment

This was a four-year project. B+LNZ investment was $345,000 over the duration of the project.


This work was led by Massey University and funded by B+LNZ, Massey University, the C. Alma Baker Trust and Lincoln University.

Lead Scientist: Anne Riddler.
B+LNZ point of contact: Suzanne Keeling.