Many regions across New Zealand experience cold, wet winters with low pasture growth. Consequently, farmers often rely on winter forage crops to feed cows, resulting in challenges with animal welfare, environmental damage and operational difficulties. Despite the potential of off-paddock facilities to overcome negative outcomes of crop wintering, only 15% of New Zealand dairy farmers have off-paddock facilities. This study aimed to document farmers’ experiences when planning, building and using off-paddock infrastructure and involved interviews with five dairy farmers who had recently built infrastructure. Early, strategic planning to include sufficient time for thorough consent preparation, establishing values, visiting farms with infrastructure, financial planning and alignment with farm operations was essential for success. Siting considerations, such as visual appearance and proximity to housing, were important for community acceptance. Farmers should consider appropriate long-term supply of feed and bedding materials, understand effluent management and allow for flexibility in use. Finally, selecting a reputable project team with strong communication and problem-solving skills was vital. The findings highlight the importance of comprehensive planning and stakeholder involvement from the outset. Insights from the project can help farmers “build it once and build it right,” avoiding costly mistakes with financial, environmental, social and animal welfare implications.

The assessment of greenhouse gases (GHG) and nitrogen (N) emissions is essential for climate change mitigation. The Intergovernmental Panel on Climate Change (IPCC) provides guidelines for GHG quantification at both national and global levels. However, the IPCC Tier 1 (T1) and Tier 2 (T2) estimates, mostly used in national inventories, rely on generic emission factors (EFs) and empirical equations that are not suitable for case-specific assessments on individual farms. Thus, a more advanced Tier 3 (T3) methodology is needed to reflect the impact of key factors on emissions and reveal the effect of emission mitigation measures. Here we compare the IPCC T1 and T2 estimates to results from a cascade of process-based (PB) models referred to as T3 approach, for farm-level emissions. The results showed that the estimates from PB models differ significantly from those of the IPCC T1 and T2 estimates and allow more capability to predict variation. Moreover, PB models account for temporal changes and the underlying mechanisms responsible for GHG and N emissions. These models can be adopted for case-specific GHG assessment and project future mitigation strategies under different climate scenarios, regional contexts and on-farm management. Additional to the known applicability of PB models to estimate enteric methane (CH4)and soil emissions, the present study demonstrates for the first time in Germany and Europe the effectiveness of Manure-DNDC model in simulating ammonia (NH3) and CH4 barn emissions, highlighting the potential for using PB models in case-specific GHG and N assessments for the whole manure management chain. Overall, this study presents options for a methodology in case-specific GHG assessment that can capture the effect of climate change and mitigation measures.

Context For dairy cows housed indoors, ambient temperature and relative humidity are key drivers of heat stress, whereas for cows kept outdoors, solar radiation and wind speed are also important. Solar radiation directly increases the heat load on cows, whereas wind speed affects their ability to dissipate heat through convection and evaporation. Aim We aimed to determine whether climate-driven changes in these variables affect heat stress risk where cows are outdoors during summer and shoulder seasons, particularly in pasture-based farming systems such as in New Zealand. Understanding outdoor-specific factors is crucial for accurately assessing and mitigating heat stress in grazing dairy cattle, because their management needs differ substantially from those in housed systems. Methods Using daily climate projection data from 2006 to 2098, peak daily values of the temperature–humidity index (THI) of Thom and the grazing heat-load index (GHLI) of Bryant were calculated and used to map predicted changes in both the annual (June–May) number of days with heat stress risk and also the annual accumulated heat stress exposure (the sum of effective degrees Celsius above the threshold) for dairy production regions of New Zealand. Key results The results illustrated the limitations of using THI in the context of outdoor use, where solar radiation and wind speed are shown to be more important than relative humidity. The GHLI predicted that the risk of heat stress is already high in the Waikato (69 days), Bay of Plenty (69 days) and Canterbury (80 days) regions in the 2020s. Canterbury was also notable for having high heat stress exposure within day compared with other regions (i.e. heat stress days were particularly intense), attributable to the combined effect of high air temperatures, high solar radiation and low wind speeds. Conclusions According to climate projections, regions already experiencing high numbers of heat stress risk days and heat stress exposure in the 2020s will experience the greatest increases in heat stress risk to the 2050s. However, dramatic increases in the number of heat stress days are not anticipated. Implications This allows research and development to focus on mitigation practices in these regions where dairy farming systems must adapt to a changing climate. Mitigation strategies may include provision of shade, access to sprinklers, genetic selection for heat stress resilience, modifying feeding regimes to reduce heat load, or development of new solutions and technologies.

Animal urine and urine patch characteristics are important drivers of nitrogen leaching in pasture-based dairy systems and their manipulation offers opportunities to mitigate these losses. We developed a model, based on previous work, to investigate the effect of applying tactical management strategies to reduce nitrogen leaching from urination events during different times of the year. Our model predicted that reducing pasture height or decreasing the volume per urination event to increase the spread of urine in the critical summer and autumn months (January to May) had minimal effect on nitrogen leaching at paddock scale. In contrast, diluting the nitrogen concentration of urine by decreasing dietary nitrogen intake by 30% or increasing total daily urination volume by 40% (while keeping daily nitrogen excreted constant) during these critical months reduced nitrogen leaching by 28% and 13%, respectively. When these dilution strategies were applied for the whole milking season (August to May) reductions of 40% and 22% were achieved. This demonstrates that management strategies can be applied tactically during key times of the year and still achieve considerable nitrogen leaching reductions. This is important for dairy producers who can add substantial reductions to nitrogen leaching from their farm systems, while reducing the management effort and costs by focussing on one key urine characteristic, nitrogen concentration, and only during a limited time of the farm season.

Producers in New Zealand’s pasture-based, seasonal dairy sector are striving to reduce nitrogen (N) losses to the environment whilst maintaining or increasing farm profitability. This study examined the cost-effectiveness of stacking different combinations of five N leaching mitigation strategies within the whole farm system; 1) reduced N fertilizer input, 2) off-paddock infrastructure, 3) recycling N by growing maize silage on a dedicated area on the farm using effluent as a fertilizer source followed by a catch-crop, 4) dietary salt supplementation to dilute urinary N, and 5) applying a nitrification inhibitor (NI) to slow the release of nitrate in the soil. The reference point (baseline) was a typical current dairy farm (CF) system in the Waikato region of New Zealand. We modelled four Future Farm scenarios by stacking mitigation strategies as follows: baseline plus reduced N fertilizer input, reduced stocking rate, and off-paddock infrastructure (FF); FF plus a dedicated maize block (FFP); FFP plus dietary salt (FFPS); and FFPS plus NI (FFPSNI). These systems were modelled using the Whole Farm Model coupled with the Urine Patch Framework, and APSIM models, using observed climate and economic input data over five consecutive years from 2013-2018. Relative to CF, the FF system achieved a N leaching reduction of 31% with a reduction in profit of 16%. The FFP system had a smaller N leaching reduction (22%), but the reduction in profit was smaller (11%). The fully stacked system (FFPSNI) demonstrated the largest leaching reduction of 33%, but also the largest profit reduction of 27%, compared with the CF. Stacking these five N mitigation strategies can achieve substantial N leaching reductions at the farm-scale. Including a dedicated, effluent-fertilized maize block followed by a catch-crop as part of the stack can reduce the negative impact on profitability but has a trade-off in N leaching. Farmers will have to weigh up these compromises between profit and leaching, considering risk factors not modelled here.

This perspective paper provides industry leaders, researchers and policy developers strategic approaches to ensure that the welfare of dairy cattle is protected at the same time as the industry increases its resilience to climate change. Farm systems and practices will evolve in response to the direct impacts of climate change and/or from responses to climate change, such as mitigation strategies to reduce dairy's greenhouse-gas (GHG) emissions. The five domains framework (nutrition, physical environment, health, behaviour, mental state) was used to assess the potential impacts on animal welfare and strategies to minimise these impacts are outlined. Given that the future climate cannot be certain these approaches can be applied under a range of emissions pathways to (1) ensure that the effects of GHG mitigations on animal welfare are considered during their development, (2) engage with end users and the public to ensure solutions to the effects of climate change and weather variability are accepted by consumers and communities, (3) identify and measure the areas where improved animal health can contribute to reducing GHG emissions from dairy production, (4) ensure those supporting farmers to develop and manage their farm systems understand what constitutes a good quality of life for dairy cattle, (5) ensure effective surveillance of animal disease and monitoring of welfare outcomes and farm-system performance in response to climate change and GHG mitigations. Overall, these strategies require a multi-disciplinary co-development approach to ensure that the welfare of dairy cattle is protected at the same time as the industry increases its resilience to the wider impacts of a changing climate.

Feed management decisions are crucial in mitigating greenhouse gas (GHG) and nitrogen (N) emissions from ruminant farming systems. However, assessing the downstream impact of diet on emissions in dairy production systems is complex, due to the multifunctional relationships between a variety of distinct but interconnected sources such as animals, housing, manure storage, and soil. Therefore, there is a need for an integral assessment of the direct and indirect GHG and N emissions that considers the underlying processes of carbon (C), N and their drivers within the system. Here we show the relevance of using a cascade of process-based (PB) models, such as Dutch Tier 3 and (Manure)-DNDC (Denitrification-Decomposition) models, for capturing the downstream influence of diet on whole-farm emissions in two contrasting case study dairy farms: a confinement system in Germany and a pasture-based system in New Zealand. Considerable variation was found in emissions on a per hectare and per head basis, and across different farm components and categories of animals. Moreover, the confinement system had a farm C emission of 1.01 kg CO2-eq kg(-1) fat and protein corrected milk (FPCM), and a farm N emission of 0.0300 kg N kg(-1) FPCM. In contrast, the pasture-based system had a lower farm C and N emission averaging 0.82 kg CO2-eq kg(-1) FPCM and 0.006 kg N kg(-1) FPCM, respectively over the 4-year period. The results demonstrate how inputs and outputs could be made compatible and exchangeable across the PB models for quantifying dietary effects on whole-farm GHG and N emissions.

Evaluating the ability of perennial ryegrass to continue underpinning New Zealand’s low-cost dairy production systems under future climate change scenarios requires a modelling approach. In this study, climate projections for different climate change scenarios were used in the BASGRA pasture model to predict changes in annual yields and seasonal pasture growth rate patterns of perennial ryegrass. These predictions, including uncertainty, were made for the years 2010-2014, 2040- 2044 and 2090-2094 in 14 dairy-dominant subregions in the Upper North Island of New Zealand. The suitability of perennial ryegrass is expected to decline in the future across all subregions, with worse outcomes expected under higher atmospheric greenhouse gas levels. Winter is expected to be the season least affected by climate change and summer the most affected. Late-winter/spring is predicted to become the main growing season, followed by late-autumn/early-winter. The ability offarmers to adapt their farming practices is essential in remaining profitable and internationally competitive.

A two-year dairy study was conducted under irrigation at Lincoln, Canterbury, comparing 1. Moderate stocking rate (MSR, 3.9 cows/ha; comparative stocking rate (CSR) of 89 kg live weight (LWT)/t DM (dry matter) offered; 150 kg nitrogen (N) fertiliser/ha/year; grain supplementation of 0.55 t DM/cow/year; wintering cows off- farm); or 2. Low stocking rate (LSR, 2.9 cows/ha; CSR of 91 kg LWT/t DM offered; grazing diverse pasture (Italian ryegrass, plantain, red- and white clover); 103 kg N fertiliser/ha/year; wintering cows on-farm). The Lincoln University Dairy Farm (LUDF; 3.4 cows/ha; CSR of 76 kg LWT/t DM offered; 169 kg N fertiliser/ha/year) was the benchmark. Milk yield, pasture production and quality data were modelled in FARMAX and OverseerFM to estimate financial and environmental performance of each farm. Performance was similar for MSR and LUDF. LSR gave the best environmental outcome across 2018/19 and 2019/20, leaching approximately 31% less N compared with MSR and LUDF. However, annual milk solids per ha were 28% less for LSR relative to MSR and LUDF. Correspondingly, the annual operating profit per ha was 35% less for LSR compared with LUDF. These financial losses can be mitigated in an LSR system if the farmer adopts more complex pasture management.

Anthropogenic nutrient input is one of the greatest causes of freshwater and coastal eutrophication worldwide. In many catchments, nutrient losses must be reduced to meet the water quality outcomes sought by communities and regulators. To achieve this, policy makers must find an acceptable balance between the economic value of land use activities and sustained health of the receiving ecosystem. We evaluated abatement policies for an intermittently closed and open lagoon catchment ecosystem in the Southland region of New Zealand. The objective was to assess the cost-effectiveness of different policies aimed at reducing nutrient loads entering the lagoon while minimizing reductions in farm operating profit by considering production losses and costs of mitigations. We developed an economic-environmental optimization model that selects farm system (e.g., reduced fertilizer input and stocking rate) and edge-of-field (e.g., constructed wetlands) mitigations most suitable to each pastoral farm (dairy, dairy support, sheep and beef). Three optimization strategies, either with a focus on nitrogen (N), phosphorous (P), or both, were evaluated: a differentiated strategy considering nutrient loss and profitability differences between farms; a uniform strategy requiring a similar proportional reduction for all farms; and a nutrient cap strategy requiring all farms to achieve losses below a set cap in kg ha-1 year-1. Results indicate that it will be a challenge to achieve the currently recommended target of 50% reduction in the load of both nutrients. When N was the focus, the best outcomes achieved around 50 and 30% reduction in N and P loads respectively, but it required a reduction in total farm income, before interest and tax, of 22 to 38% (approximately NZ$5-9 M year-1 at current prices). The catchment-wide differentiated policy was the most cost-effective from a farmer and economic point of view, but still required land retirement for approximately 30% of the farm businesses. A double nutrient cap strategy of 40 kg ha-1 for N and 0.8 kg ha-1 for P, resulted in 30-35% reduction in both nutrients at around 17% reduction in profit (NZ$4 M year-1). The work demonstrates the importance of evaluating the cost-efficiency of nutrient loss mitigations at farm scale when evaluating different abatement policy options at catchment scale. It demonstrates utility for other similar sites by showing how the focus can be on individual farm businesses, while searching for balanced environmental and economic outcomes at the larger scale.

Developing resilient, profitable, and robust dairy farm businesses in response to multiple drivers of change (e.g., water quality regulations, a low carbon economy) is challenging. This study explored methods for working with dairy farmers and stakeholders from the West Coast of New Zealand to evaluate options for system change. Physical, financial, and environmental data from the study farms were analysed and benchmarked to provide farmers with information on how their financial and environmental performance compared with others. The most profitable farm had the lowest purchased nitrogen (N) surplus. However, high pasture production and utilisation resulted in higher methane emissions for this farm. FARMAX and OVERSEER models were used to apply principles of the top performing farm to two selected study farms.These study farms largely succeeded in reducing N surplus and methane emissions, but operating profit was reduced, suggesting a complete system rethink is needed including focusing on growing and harvesting more home-grown feed with less N input, and scrutiny of farm working expenses. This study showed that benchmarking, farmer participation and modelling has the potential to create a positive environment thatmotivates farmers to review their current performance, extract solutions from their local peers and partner with researchers.

The aim of this project was to model combinations (“stacks”) of cost-effective nitrogen (N) leaching mitigations within a dairy system that could reduce N leaching by 40-60%, whilst minimising losses in profitability. A FARMAX and OverseerFM combination was used to model a baseline farm representing a typical Canterbury system, and seven sequentially “stacked” mitigated systems. The mitigations were combined and stacked in the following order based on mechanism(s) of action, practicality, and cost-effectiveness: 1) reduced synthetic N fertiliser input (from 190 to 100 kg N/ha/year); 2) including Italian ryegrass in the pasture sward; 3) including plantain in the pasture sward; 4) earlier calving and drying off (by 10 days); 5) wintering on pasture and baleage; 6) standing cows off-pasture;7) using new-generation nitrification inhibitors. The most cost-effective stack combined mitigations 1 to 5. We estimated that N leaching was reduced by 57% relative to baseline, with an 8% reduction in operating profit. Greenhouse gas emissions were reduced by 8%. The largest single reduction in N leaching was from stack #5, and it coincided with no/little change in milk production pasture eaten and had no capital cost. A careful selection of complementary mitigations could achieve significant reductions in N leaching without compromising greenhouse gas emissions and, to any great extent, profitability.

The objective of this study was to predict the future performance of perennial ryegrass in the Upper North Island, New Zealand. The Basic Grassland model, BASGRA, was used with historic, current and future daily climate data as input, and soil water holding capacity, to predict changes in perennial ryegrass performance in space and time. The study focussed on land of ≤7° slope north of the town of Tokoroa and considered two potential warming pathways to the end of the 21st century. Persistence was defined as the time in years for the ryegrass sward to decline to 50% ground cover. The results for the two climate pathways were largely consistent with each other. Persistence should remain in the medium category (2.5-3.4 years, 10-12 t DM/ha) for the rest of this century for Bay of Islands, Whangarei, South Waikato/Tokoroa, and Rotorua. Persistence is predicted to change from medium to predominantly low (0-2.4 years, <10 t DM/ha) for Far North, Dargaville, DairyFlat/Rodney, Waiuku/Pukekohe and northern and central parts of Waikato. Coastal regions of Bay of Plenty were predicted to be poorly suited to perennial ryegrass and to remain so into the rest of the century. Large parts of the Upper North Island that are currently borderline for perennial ryegrass are predicted to become unsuitable for the species.

Context Due to high protein concentrations in pastures, dairy cows offered a pasture-based diet often consume excess nitrogen (N), which leads to high ruminal ammonia concentrations and excessive urinary N excretion, thereby contributing to pasture N leaching. Aims To study the effect of administration of natural zeolite on ruminal pH and ammonia production and N excretion in lactating cows offered an all-pasture herbage diet. Methods In a metabolism stall trial using a crossover trial design, rumen-cannulated Friesian cows were administered either zero (Control, n = 16) or 400 g/day of zeolite (Zeolite; n = 16). Zeolite was divided into two equal portions and administered directly into the rumen before feeding fresh-cut ryegrass-clover herbage at 07:30 and 15:30 hours. Cows were kept in the metabolism stalls for two measurement periods of 5 days each, with each period preceded by an adaptation/washout period of 2 weeks. Feed intake, milk yield, total urine and faecal outputs were measured daily. During the last day of each measurement period ruminal fluid and blood were frequently sampled. Key results Zeolite administered at 2.2% of dry matter intake (DMI) did not affect daily DMI. Moreover, milk yield and milk composition, including milk urea, were not affected by zeolite administration. In cows administered zeolite the mean 24-h ruminal ammonia concentration was reduced by 1.5 mmol/L (9%) and the ruminal pH pattern in zeolite-administered cows over 24 h was above that of Control cows, but the overall effect on pH was not significant. Zeolite had no effect on plasma urea, total urinary N excreted or faecal N. Of the total N excreted across the groups, 21.7, 50.6 and 27.7% was excreted into milk, urine and faeces respectively. Conclusions Zeolite administration reduced ruminal ammonia concentration but this did not result in reduced urinary N excretion in dairy cows offered pasture. Implications Dietary supplementation with zeolite may help to improve aspects of ruminal function in cows consuming pasture, but is unlikely to be an effective tool for reducing N leaching from pastures.

Future development pathways for irrigated dairy farms in Canterbury operating under stricter nitrogen (N) loss limits were compared in two farmlets over four years. One represented the traditional pathway of intensification via higher inputs of N fertiliser and supplementary feed ('higher input-high efficiency', HI-HE), while the other represented a lower input pathway using half the amount of N fertiliser and one quarter the amount of supplementary feed ('lower input-high efficiency', LI-HE). The stocking rate of both systems was matched to feed supply to achieve high utilisation (similar to 90%) of the pasture grown. Mean total annual N surplus and estimated nitrate-N leaching were lower in LI-HE than HI-HE, by 46% and 25% respectively. Milk production was lower for LI-HE (1,700 kg versus 2,240 kg milk fat + protein per ha/year). Estimated profit was the same for both systems at a milk price of $6.46/kg fat + protein, below which LI-HE was more profitable than HI-HE and vice-versa. Compared with the benchmark high-performing Lincoln University Demonstration Dairy Farm (LUDF) through the same period, LI-HE was 2% less profitable, but estimated N leaching was similar to 30% lower. Subsequent adoption of the LI-HE system by LUDF demonstrated that the system is scalable, and profitable.

The dairy cow model ‘Molly’ is a mixed discrete event-continuous system model that simulates feeding, metabolism and lactation of dairy cows. Decades of model development have resulted in a valuable tool in dairy science. Due to the deprecation of the ACSL (Advanced Continuous Simulation Language) programming language, Molly has been translated into C++. This paper describes the translation process and discusses the advantages of the new implementation, one of which is the ability to run Molly within RStudio, a popular integrated development environment (IDE) for data science.

The nitrogen (N) fertilizer application rate (kg ha−1 year−1) in pastoral dairy systems affects the flow of N through the soil, plant and animal pools of the system. With better understanding of the magnitude of these pools and their fluxes, dairy systems could be managed to improve N use efficiency, therefore reducing losses to the environment. A study with three levels of N fertilizer, 0 (N0), 150 (N150) and 300 (N300) kg N ha−1 year−1, was conducted in the Canterbury region of New Zealand from 1 June 2017 till 31 May 2018. Farm measurements, e.g. pasture and milk production, were used to calibrate three different farm-scale models, DairyNZ’s Whole Farm Model, DairyMod, and Overseer®. The models were used to extrapolate periodic farm measurements to predictions of carbon (C) and N pools and fluxes on an annual basis. Pasture and milk production per hectare increased from N0 to N300 by 70 and 58%, respectively. There was a concomitant increase in farm-gate N surplus (input–output) of 43%, resulting in predicted increases in N leaching and greenhouse gas emissions of 72 and 67%, respectively. By increasing N fertilizer from 0 to 300 kg N ha−1 year−1, 53% more feed N flowed through the dairy herd with surplus N deposited as urinary N increasing by 49%. Plant uptake and soil immobilization increased by 58 and 343%, respectively, but not enough to avoid substantial increases in leaching and emission losses. Carbon flux through the soil system increased through increased litter and faecal deposition, but with very little C sequestration because of accelerated microbial respiration rates.

Recent years have seen a decline in herbage production and tiller populations in New Zealand's perennial ryegrass (Lolium perenne) dairy pastures. One hypothesis is that modern genotypes are less suited to the warmer, drier weather experienced under changing climate patterns. In this study, a combination of long-term trial data (2011-2017) and a process-based pasture model (BASGRA) was used to explore the causes and possible mitigation of the observed production and population loss at three sites (dryland sites in Northland and Waikato and an irrigated site in Canterbury). Bayesian calibration was used to identify the model parameter sets that were consistent with the trial data and to identify differences in plant morphology and responses between sites. The model successfully simulated the observed differences in tiller numbers between the dryland sites, where populations and production declined rapidly after the second year and the irrigated site where populations and production were maintained. Analysis of the model calibrations along with preliminary scenario simulations suggests that increased tiller mortality associated with drought was the main cause of persistence failure at the dryland sites and that decreasing grazing pressure or breeding for tolerance to higher temperatures may not be successful in preventing this.