Research

Improving dairy cows’ health, fertility

AgResearch’s Dr Mallory Crookenden has received the 2020 Cooper Award, which is the Royal Society Te Apārangi Early Career Research Excellence Award for Technology, Applied Science and Engineering, for key advancements in the use of pragmatic solutions that support immune function around calving to improve animal health on New Zealand dairy farms.

Mallory’s work is focused on using applied methods to influence inflammation and immunological health, with the aim of reducing the risk of disease and improving fertility in NZ dairy cattle.

She uses her expertise in disciplines, such as biochemistry, immunology and molecular biology, to understand critical issues that affect livestock on NZ dairy farms and then provide practical solutions which can be readily applied on-farm.

Her PhD research was the first to describe seasonal changes in immune function in low-to-moderate yielding grazing animals, which had previously only been reported in highyielding animals in confinement systems.

This research created the opportunity to use applied technology to improve the dampening of harmful inflammatory immune reactions around calving, thereby improving animal health in NZ dairy systems.

It is estimated that $1.5 billion of revenue is lost annually in NZ as a result of health problems and mortality during the calving period.

Mallory’s research has investigated immune function and modulation during this time to better understand the mechanisms behind this increased risk of disease. For context, roughly 90% of metabolic disease and 75% of infectious disease occurs during the calving period, with a three to six-fold greater risk of death. This is, therefore, a critical period for potential intervention to improve cow health and welfare.

Mallory’s research post-PhD has continued to focus on methods to improve the health and welfare of NZ dairy cows by improving immune function around calving.

One such study involves the investigation of a feed additive, sodium aluminosilicate, more commonly known as Zeolite, to treat low blood calcium concentration (hypocalcaemia) in cows during the early post-partum period.

Hypocalcaemia is the most prevalent metabolic disorder at calving, due to the sudden increase in calcium requirements as lactation begins. An estimated 4065% of dairy cows undergo a state of subclinical hypocalcaemia at calving, while an additional 3-10% will experience clinical hypocalcaemia.

Feeding Zeolite results in a negative calcium balance that activates homeostatic regulatory mechanisms. The result is an increased efficiency of intestinal absorption of calcium and an acceleration of homeostatic mechanisms to mobilise stored calcium from bone, at which point zeolite is removed from the diet.

From a health perspective, this short-term management intervention reduces the risk of clinical and subclinical hypocalcaemia, with blood calcium concentrations remaining normal in cows that receive Zeolite. Her research confirmed the effect of Zeolite on plasma calcium concentrations and focused on downstream immune-modulating effects, showing a reduction in harmful inflammation.

This work has led to a subsequent, large-scale trial in over 1,000 animals (in progress).

Based at AgResearch’s Hopkirk Institute in Palmerston North, Mallory graduated with her PhD from Massey University in 2018. Her thesis was placed on Massey University’s Dean’s List of Exceptional Doctoral Theses Award.

A prolific author, from her first publication in 2015, she is now an author on 24 peer-reviewed articles, with eight as first-author. n

Focus on food sustainability

Several organisations are coming together to collaborate on the challenges of food transitions.

Anew postgraduate school focusing on food sustainability is to be opened in Canterbury.

The school’s aim is to support the transition to more future-focused, sustainable food systems and preparation in New Zealand, and is a joint project between the University of Canterbury (UC), Lincoln University (LU), Plant & Food Research, Manaaki Whenua Landcare Research and AgResearch.

The theme of the school is Food Transitions 2050. A new, official name will be gifted to the school at a later stage.

A collaboration at postgraduate and research level, the school will focus on creating solutions to complement existing food innovation initiatives in NZ.

It will have particular emphasis on zero carbon futures, water, international transportation, plant-based diets, rural economies, artificial intelligence and technical transitions.

Foundational students are already applying to the school, attracted by the transdisciplinary and Matauranga Māori research (co-designed with mana whenua) spanning food and future landscapes, food for a carbon-zero future, food consumer transitions and food governance.

Plant & Food Research chief executive officer David Hughes says that by bringing together all of these organisations it was creating a new platform for integrative research that will create impact for many years to come.

“We are really excited to be part of collaboration involving two universities and three crown research institutes that will enhance the opportunities for postgraduate scholars to tackle food transitions – one of the most important challenges of our time,” Hughes says.

“Science that is looking hard at our future food systems is essential to protect the future wellbeing of our species and the environment that we depend on.”

AgResearch chief executive Dr Sue Bidrose says they were thrilled to be part of this new postgraduate school concept. Manaaki Whenua Landcare Research chief executive Dr Richard Gordon, AgResearch chief executive Dr Sue Bidrose and Plant & Food Research chief executive David Hughes watch Lincoln University acting vice-chancellor Professor Bruce McKenzie and University of Canterbury vice-chancellor Professor Cheryl de la Rey sign a new collaboration agreement to establish a new school focusing on food sustainability.

“We’re fortunate at AgResearch to have highly experienced scientists who are experts in their fields, and through this new virtual community, our scientists will be able to mentor and help develop a host of talented researchers of the future,” she says.

LU acting vice-chancellor Professor Bruce McKenzie says the school will be instrumental in attracting and growing talent in the land-based sector.

“We are effectively enhancing postgraduate research volume and quality and encouraging more people to study and work in the land-based sector to meet industry demands for skills and capability, increased productivity and tackle future technical changes,” McKenzie says.

Collaborating with the other institutes allowed them to make the most of their collective expertise in how food is produced in Canterbury and beyond, Manaaki Whenua chief executive Dr Richard Gordon says.

UC vice-chancellor Professor Cheryl de la Rey echoed that sentiment.

“Our new postgraduate school highlights this partnership’s bold vision of working toward securing the future of food, and the joint contribution our researchers can make in the areas of food equity, food intelligence and food innovation,” she says.

LU assistant vice-chancellor of Māori and Pasifika Dr Dione Payne says the inclusion of Vision Mātauranga, a key component of the project and PhD proposal process, was a great step forward.

“Although we are at the beginning of our journey, it is clear there is a commitment to ensuring authentic engagement with Māori and that Mātauraka Māori is valued amongst all the partners,” Payne says. n

New tech to manage giant buttercup

By Gerard Hutching

Giant buttercup is a weed that is well established on New Zealand dairy farms, costing farmers millions of dollars in lost milksolids.

Dairy farmers have been handed two new hi-tech tools in the fight against the invasive giant buttercup, which is estimated to cost the industry about $200 million a year in lost milksolids production.

The buttercup is a weed with potential to make a serious dent in farm profits.

For farmers with 12% of the ground cover being in giant buttercups, it could reduce their farm’s profit by $1,040/ ha. Researchers have developed a new tool that could deliver considerable productivity and economic gains.

A native of Europe, the giant buttercup successfully established itself in New

Zealand at the beginning of pastoral farming and is now widespread on dairy farms in South Auckland, Hawke’s Bay,

Southland, Taranaki, Wairarapa, West

Coast and Tasman District.

The plant is particularly aggravating in Golden Bay, where AgResearch principal scientist Dr Graeme Bourdôt and colleagues have worked closely with farmers to develop the two tools as the components of a science-based decision support system. The system enables better informed decisions on controlling the weed with herbicides and managing herbicide resistance.

Downloaded onto a smartphone, the first of the two tools, the Grassland Cover

Estimator (GCE) app, enables a farmer to figure out how much giant buttercup there is in a paddock.

“To determine if a giant buttercup infestation is worthwhile controlling, the farmer must first know how much of his paddock is covered by the buttercup.

Is there enough to make it worthwhile controlling?” Bourdôt asks. AgResearch principal scientist Dr Graeme Bourdôt with the giant buttercup plants being used in a study on the genetics of herbicide resistance in the weed.

“To estimate the percentage of a paddock that is covered by the weed, the GCE app uses a method plant ecologists have used for years called point analysis. The app works by the user walking across a paddock and observing whether the weed is present or absent at the tip of their boot. The observations are recorded as present or absent by swiping one way or another, and the app uses these observations to calculate the percentage of the paddock covered by the weed.”

He describes it as a simple generic tool that is much better than guesswork for estimating the coverage of a plant in a pasture. While a farmer could stand on a fence post on the corner of the paddock and estimate buttercup cover, he would likely not be quite wrong.

“Unsurprisingly, to get a good estimate of the cover of the weed in a paddock, you need to make observations over a good proportion of the paddock. The advice is to cover as much of the paddock as possible. Every time you

swipe the app as present or absent it does a running calculation of the percent cover, and you can see that as you’re walking,” he says.

The app also stores all observations and their geographic coordinates and this data can be exported from the phone to a PC for more detailed analysis and mapping if required.

Once the percentage cover has been established, the next step is to go to the second tool, the Giant Buttercup Decision Support Tool web app for a four-step process.

First the percentage of buttercup is inputted, followed by the second step of inserting various values related to productivity of the paddock (dry matter grown and eaten, pasture conversion rate, pasture utilisation). At this step, the milksolids payout price expected over the three years following the intended herbicide control programme is also inserted.

The third step offers a menu of herbicide treatment options including all 49 herbicide products currently on the market in NZ with a label claim for use against giant buttercup in pasture. Depending on which options are chosen, the app shows the current price of the products in dollars per hectare and the cost of application. The user can go ahead with these default values or replace them with other values. The final step shows the range in net benefit (in $/ha) that can be expected for each of the herbicide products that have been selected for comparison.

“Based on all the information you’ve put in, it works out how many kilograms of extra milksolids you could expect from the paddock if you control the buttercup with a particular herbicide,” he says.

“In calculating the net benefit for a particular proposed herbicide treatment, the app uses the cost of N fertiliser to account for the loss in fixed N resulting from the herbicide’s damage to clovers. Some herbicides can bowl out the clovers for a long time.

“To determine if a giant buttercup infestation is worthwhile controlling, the farmer must first know how much of his paddock is covered by the buttercup.” Dr Graeme Bourdôt

“Others have less effect, and some have no effect.”

Bourdôt says that underpinning the Giant Buttercup Decision Support (DS) Tool is a unique peer-reviewed and published data set from a three-year scientific experiment in 18 different dairy pastures in Golden Bay. The experiment compared all herbicide active ingredients currently on the NZ market for their effect on giant buttercup and on other pasture plants including the N-fixing clovers. It showed that the herbicides differ substantially Scientists are researching giant buttercup in a bid to get rid of it from our dairy

pastures. in their effect on the weed and damage to clovers. These differences, along with variability in efficacy within each of the herbicides, are accounted for in the DS Tool, which calculates the expected range in net benefit for each herbicide in a selected comparison.

In the same experiment, other control methods were also investigated. One was to use a common fungus, Sclerotinia sclerotiorum that kills the giant buttercup in dairy pastures, turning the plants into a slimy, rotting mess.

Another method compared was to mow the pasture before grazing. Mowing neutralises the toxicity in the buttercup – its scientific name is Ranunculus acris, referring to the acrid tasting chemical in the plant which can become toxic and cause blistering of the lips and tongue, intestinal disorders, and potentially fatal ventricular fibrillation and respiratory failure.

“When you mow, the bitter chemical comes out of the mown giant buttercup foliage as a gas. The wilted foliage is no longer bitter or toxic and is readily eaten without harm to the cow,” Bourdôt says.

Because the giant buttercup has evolved resistance to some herbicides, pre-graze mowing is potentially an effective alternative option, even if it is more labour intensive. Mowing is currently not included as an option in the DS Tool.

The AgResearch study has been funded through the Sustainable Farming Fund, with support from the Ministry for Primary Industries, DairyNZ, and Ravensdown. n