The New Zealand dairy industry accounts for approximately 25% of national greenhouse gas (GHG) emissions. Dairy farms are heterogeneous in their management and production characteristics, resulting in varying emissions across farms. This variability in emissions leads to diverse abatement costs and GHG mitigation potential. This study aimed to explore farm heterogeneity in GHG emissions and identify key management and production factors associated with emissions and operating profits across New Zealand’s dairy farms. Unbalanced longitudinal panel data from DairyBase spanning 10 consecutive milking seasons (2012-13 to 2021-22) were used. Pearson correlation analysis was used to examine associations among GHG emissions, farm management and production indicators. Linear mixed-effects regression model was then applied to estimate the effects of key management and production factors on emissions and operating profits. The results revealed regional heterogeneity in farm characteristics and emissions across dairy farms. Total GHG emissions showed an overall increasing trend over the study period, with year-to-year fluctuations. GHG emissions per hectare showed strong positive associations with key production indicators, including milk solids production per hectare (r = 0.82), total feed intake per hectare (r = 0.76), pasture and crop intake (r = 0.75), and stocking rate (r = 0.72). Total feed intake, nitrogen fertilizer application, and irrigation showed significant positive effects on both emissions and operating profits. Transitioning from twice-a-day to lower milking frequency showed reduced emissions but mixed results for operating profit. The findings highlight that reduced use of nitrogen fertilizer and supplementary feeds corresponded with reduced emissions but also with reduced farm profits. Given the diversity in farm characteristics and emissions across dairy farms, further investigation through farm-level classification is needed to identify effective farm-specific GHG mitigation options.

Sheep or beef cattle (cattle) share of total farm feed consumed, measured in stock units (SU) on New Zealand farms, is often adjusted depending on the profitability of each enterprise. The impact of these adjustments on whole-farm productivity, profitability and predicted methane (CH4) output has not been recently explored. A system dynamics model of a representative North Island Hill Country sheep and beef farm was parameterised to evaluate whole-farm productivity, profitability and predicted CH4 output simultaneously, while varying sheep and cattle SU. Five scenarios were considered: 80%:20%, 60%:40%, 50%:50%, 40%:60% and 20%:80% sheep and cattle SU, respectively. For every 20% increase in cattle SU, on average, total liveweight and carcass weight equivalent (kg CWeq) sold increased by 0.5% and 3.3%, respectively, while cash operating surplus (COS) increased by 10%. However, predicted total enteric CH4 emissions increased by 2.2%, due to fewer lambs in the system, which have a lower emission factor, and farm economic emission efficiency (COS($NZ)/tCO2e) increased by 7.5%. Overall, the results show that to increase COS, farmers should increase cattle SU. Although when considering a transition towards a higher proportion of cattle SU in the mixed system, they should also consider pasture management and environmental implications.

The impact of increasing the weaning weight of lambs on the productivity and profitability of sheep enterprises on New Zealand sheep and beef farms has been investigated without considering greenhouse gas emissions. The study examined the impact of increasing the weaning weight of lambs on sheep enterprise productivity, profitability and predicted enteric methane (CH4) emissions in a case study farm using a system dynamic model. Under a fixed feed supply condition, weaning weights of all lambs were increased by 10% and 20% compared to a base scenario. Carcass weight equivalent per hectare rose from 79.9 to 81.7 kg/ha and 91.4 kg/ha, while cash operating surplus per hectare increased from NZD173/ha to NZD184/ha and NZD262/ha, respectively. Predicted enteric CH4 emissions declined marginally from 566.3 to 563.8 t and 561.0 tonnes of carbon dioxide equivalent (tCO2e), while predicted emission intensity reduced from 7.67 kg CO2e/kg to 7.53 kg CO2e/kg (2.0%) and 7.39 kg CO2e/kg liveweight sold (3.6%), respectively. Economic emission efficiency increased to NZD94/tCO2e and NZD135/tCO2e compared to NZD88/tCO2e, respectively. Increased lamb weaning weight improved productivity, profitability and economic and predicted CH4 emission efficiencies but did not significantly reduce predicted CH4 emissions under fixed feed supply conditions. This suggests no trade-off between profits and enteric CH4 emissions.

A system dynamics model of a sheep enterprise on a New Zealand sheep and beef farm was used to concurrently evaluate productivity, profitability, and predicted enteric methane outputs, allowing farmers to make informed decisions about improving mature ewe weaning rates (lambs weaned/ewe mated) or breeding hoggets. Mature ewes were bred at 125%, 140%, and 165% weaning rate scenarios, while hoggets were bred at 0%, 60%, and 80% weaning rate resulting in various combinations (i.e., 125-0, 125-60, or 125-80). Improvements in the weaning rates of mature ewe or breeding hoggets improved kg lamb carcase weight equivalent per ha, and cash operating surplus per ha, due to an increased number of lambs weaned and sold, reduced enteric methane intensity (g methane/kg of product), and increased economic emission efficiency (profits/tCO2e). Compared to hogget breeding, achieving a high weaning rate, that is, 165% in mature ewes, provided greater improvements in all indicators than alternatively achieving 140% and 60% or 125% and 80% in mature ewe and hogget weaning rates, respectively. Considering poor weaning rates in hoggets and management complexity, farmers may find it easier to focus on achieving higher weaning rates in mature ewes, rather than breeding hoggets to improve profitability and enteric methane emission efficiency.

Limited data on native shrubs has hindered direct comparisons with pine radiata as afforestation options for steep slopes on New Zealand hill country sheep and beef farms. This study updated a native shrub sub-model (NSM) with new research data and developed a radiata pine sub-model (RPM) for integration into a bioeconomic model using STELLA Architect. The model assessed asynchronous afforestation of 10% of effective farm area with either option, comparing impacts on feed supply, sheep dynamics, and farm economics. NSM was updated with growth curve, foliage biomass, and carbon stock data from two New Zealand sites. RPM used literature for growth curve, carbon, and log production data. Simulations included a pasture-only (base) and afforestation with either species at 10% and 20% planting rates. Native shrubs reduced feed supply by 2.5% and 4.0%, while radiata pine reduced it by 7.0% and 7.4% at 10% and 20% planting rates. Reduced feed led to smaller flocks and lower cash flow. Radiata pine generated surplus through carbon and log income, offsetting reduced sheep flock cash flow, while native shrubs did not. Carbon prices of 64.2 and137.4 NZD/NZU would be needed for viability in the best- and worst-case scenarios. Native shrubs are potential land use option on steep slopes but require policy intervention to lower establishment costs and carbon prices.

In New Zealand (NZ), the metabolisable energy requirements (MER) of ruminants can be estimated using nutritional models from Nicol and Brookes (2017), CSIRO (2007), and NZ’s Agricultural Inventory Model (AIM) of the Ministry for Primary Industries [MPI] (2022). The aim in this study was to calculate the total MER of a ewe, beef breeding cow, lamb, and a calf/yearling in a pasture-only system in NZ under the same assumptions to assess the extent and reasons for variations among the three commonly used nutritional models, and the implications for a given farm/s. The study utilised MER models from the three sources above using a factorial method. This method determines the MER for each physiological phase of an animal, to estimate total MER for each animal. The AIM (MPI 2022) model relative to Nicol and Brookes (2017), and CSIRO (2007) models respectively, estimated 13.4 % and 8.0 % higher MER for a ewe, 16.3 % and 16.6 % for a cow, 1.1 % and 2.0 % lower for a lamb, and 9.2 % and 9.2 % higher for a calf/yearling mainly due to a higher maintenance MER compared to the other models. This has implications for feed budgeting and stocking rates (SR) for a given farm, as the AIM (MPI 2022) model leads to a lower SR than the other two models for a given level of feed available. Energy balances and productivity could be negatively impacted if a model underestimates MER. This also yields different greenhouse gas (GHG) profiles, especially enteric methane, for a given farm and could potentially have financial consequences for farmers if an Emissions Trading Scheme was introduced. For consistency in ME estimates and GHG reporting, further research (feeding trials) is required to compare these model estimates to actual requirements of ruminants under NZ conditions. This could help identify the model that most accurately reflects MER for ruminants in the country.

There is a limited number of studies examining the economic impact of sand and dust storms (SDS), which are frequent hazards in Western Asia and the Middle East. This research aims to review the sectors affected by SDS in Kuwait, estimate the resulting economic costs, and offer guidance on identifying and collecting missing data. Between 2006 and 2022, the average annual economic impact of SDS in Kuwait was estimated at US195 million (in 2022 dollars). Annual losses ranged from US14 million to US698 million, depending on the number of SDS events each year, which varied from 1 to 22 in the period under study. The most significant impact was observed in the oil production and export sector, given its prominent role in Kuwait’s economy. The airline industry and public works also incurred substantial costs due to SDS. In contrast, agriculture did not appear to be significantly affected, possibly because of greenhouse production and seasonal timing of certain crops that avoids peak SDS periods. However, no comprehensive assessment has been conducted on the effects of SDS on crop cultivation or pastoralism in Kuwait. Other sectors, including education, construction, healthcare, and defense reported qualitative impacts from SDS events, but it was not possible to estimate these costs due to the absence of quantitative data. The research recommends further comprehensive analysis of SDS effects on Kuwait’s economy, utilizing surveys and/or interviews as well as enhanced sectoral data identification and collection to map risks and expected impacts.

Reducing greenhouse gas (GHG) emissions from dairy farming is crucial for mitigating climate change and enhancing the environmental credentials of New Zealand's dairy exports. This paper aims to explore potential GHG mitigation measures and their interactive effects when combined within New Zealand context, emphasising the practicality of these combinations, particularly focusing on recent studies of pasture-based dairy systems. The review assesses various mitigation options across animal, manure management, feed-based, soil-related, and system-related interventions and identifies immediately applicable mitigation options based on specific criteria. It also discusses the implementation costs, implications on emissions, and the combined effects of these options when applied as bundles in pasture-based systems using a combination matrix. It is indicated that mitigation options on New Zealand's dairy farms can yield diverse outcomes and costs based on farming characteristics. By analysing different combinations of short-listed, it was found that although most mitigation options are compatible, some may have a lower overall reduction potential because of interaction effects. Integrating lower N fertiliser use, low-emission feed, and reduced stocking rates with high-performing animals provides a practical approach for GHG reductions and potential cost savings. However, implementing compatible mitigation bundles requires better quantification of their interactions, economic viability, and compatibility with existing farming systems which need further research.

In New Zealand, willow and poplar are used on hill farms for erosion control and to supplement pasture during low pasture periods. Some native shrubs are browsed by wild herbivores but remain unexplored for farmed ruminants. We evaluated the seasonal nutritional composition of five native New Zealand shrubs (Karam & umacr;, P & amacr;p & amacr;uma, Karo, Whauwhaupaku, and Houhere) and compared them with willow (Kinuyanagi). Leaf and edible stem were analysed for nutritional composition and in vitro digestibility following AOAC procedures. Results showed that except Houhere, all other native shrubs leaves had lower crude protein (CP) (11 MJ/ kg DM) than Kinuyanagi. Kinuyanagi leaves were comparable to Houhere in ME and CP in spring but had lower CP in summer. Stem nutritional composition was similar across all shrubs. Acid and neutral detergent fibres in edible portions were comparable to those in common pastures, fodder crops, and forages in New Zealand. The findings suggest native shrubs could supplement low ME in summer pastures or winter herbage scarcity, but further research is needed on animal preference and intake.

Northern Ghana is a semi-arid region characterised by a unimodal rainfall pattern, and hot and dry weather conditions. Heavy reliance on rain-fed agriculture and the lack of resources for irrigation, makes smallholder farmers in the region increasingly vulnerable to climate-related crop failures. In recent years, climate-smart technologies (CSTs) such as changing planting dates (PD), compartmental bunding (CB), mulching (M), and transplanting (TP) have been recommended to minimise yield losses. However, there is limited information on the most risk-efficient CSTs for crops cultivated in the region. This study used a stochastic dominance approach to identify the most risk-efficient CSTs for maize, rice, and sorghum. The stochastic modelling process employed the Aqua-crop model to simulate climate-related yield variability using Ghana climate data, and gross margin variability with crop budgets from literature sources. From the study's findings, changing planting date from April to May was the most risk-efficient choice for maize and sorghum under farmers' and recommended practices. In contrast, transplanting was the most risk-efficient technology for rice farming in the study area. The study also highlights the importance of considering the risk-averse nature of smallholder farmers when selecting CSTs. By identifying the most risk-efficient CSTs, the study can help improve the resilience of smallholder farmers. These findings have important implications for the development and adoption of CSTs in northern Ghana.

Finishing of dairy-origin calves in an accelerated 'New generation beef' (NGB) beef finishing system for slaughter up to 14 months of age has potential co-sector benefits. These include production efficiencies and a reduced number of dairy calves slaughtered at a very young age. In the present study, a NGB system and an 18-month Bull-Beef system were first modelled separately, both purchasing three-month-old Friesian bull calves. Then Mixed systems with varying proportions of both NGB and Bull-Beef animals were modelled. Production, feed balance and profitability were compared, using cash operating surplus (COS) as a profit indicator. In the NGB scenario, double the number of animals were finished compared with the Bull-Beef scenario; however, monthly feed demand was less synchronous with predicted pasture supply, requiring more feed transfer via pasture baleage. The COS for the NGB system was $-571/ha, with less income and greater costs than the Bull-Beef system (COS = $2026/ha). Break-even prices for NGB animals were up to 74% above current prices, but break-even prices were less in Mixed systems with a greater proportion of Bull-Beef animals. Without high price premiums, challenges remain for the NGB systems appeal to beef finishers due to their low slaughter weights and sale prices.

New Zealand sheep producers generate most of their income from sheep sales, particularly lamb sales. To increase revenue from lamb sales producers have two choices, increase the number of lambs weaned or increase the weight of lambs produced and sold. Lifting the number of lambs sold requires an increase in lambs born per ewe, however this comes at a cost as these lambs are typically smaller and may not reach optimal slaughter weight within the desired timeframe. Alternatively, increasing the weight of lambs, while maintaining total feed supply constant, means that the number of breeding ewes carried on the farm may have to be reduced. This study utilises an existing bioeconomic model to examine the impact on farm productivity and profitability of increasing lambing percentage from an average of 133.5% to 140, 150 or 160%, or increasing lamb weaning weight from 30 kg and 25 kg for singles and twins respectively, by 10, 20 or 30%, or alternatively a mix of the two, i.e., 140% lambing rate and weaning weights of 33 and 27.5 kg for singles and twins, respectively. The results show that lifting lamb weaning weight, by 10, 20 or 30%, increases enterprise cash operating surplus (COS) from $291/ha to $342, $392, or $444/ha, respectively, which is more than the increases in COS from lifting lambing percentage by 10, 20 or 30%, which increased COS to $313, $345, or $368/ha, respectively. The alternative of lifting lambing percentage by 10% and lamb weaning weight to 33 kg and 27.5 kg, increased COS by $74/ha. Overall, increasing pre-weaning lamb growth was more profitable than increasing lambing percentage. Therefore, if a producer has a lambing percentage of 140% or above their focus should be on improving pre-weaning lamb growth rates rather than lifting lambing percentage.

Male-sexed semen can be used in beef cow herds to increase the number of heavier and faster-growing male offspring. The use of sexed semen requires artificial insemination (AI) which has limited use in extensive beef systems due to practical constraints and the additional breeding costs incurred. The objective of this study was to use bio-economic simulation modelling to predict the profitability of using sexed semen via fixed time AI for a New Zealand hill country farm system based around a beef cow herd. When modelling self-replacing Angus herds male-sexed Simmental semen was utilised across 43% of mixed-age cows then follow up Simmental bulls were used for subsequent natural mating. To generate replacement Angus heifers, first time calvers and remaining mixed-age cows were bred with unsexed Angus semen and then naturally bred with Angus bulls if they did not conceive. All mixed-age cows in an AngusxHolstein-Friesian herd with a bought-in replacements policy were bred with male-sexed Simmental semen followed by Simmental bulls. First time AngusxHolstein-Friesian calvers were bred with unsexed Angus semen followed by Angus bulls. Sire breed was assumed to have the same effects on offspring production regardless of use through AI or natural mating. Herds using sexed semen were assumed to undergo synchronised fixed-time AI which resulted in a more condensed calving spread and 3% heavier average weaning weights due to calves being predominantly male and on average seven days older. Total breeding costs were higher for herds using sexed semen via AI at NZD 135-166 /cow compared with NZD 67-102 /cow for herds using only natural mating. Increases in breeding costs were relatively larger than any additional income for all herds using sexed semen via AI, resulting in lower COS (cash operating surplus) compared with herds using all-natural mating. The COS of using sexed semen via AI were 14% (COS = NZD 280 /ha) and 9% (COS = NZD 405 /ha) lower than all-natural mating using Simmental sires for the purebred Angus (COS = NZD 325 /ha) and AngusxHolstein-Friesian crossbred (COS = NZD 444 /ha) cow herds, respectively. It appears producing more fast-growing male calves through use of sexed semen via AI is not currently an economically feasible option for beef producers under extensive production systems. Future analysis could include benefits of access to higher genetic merit sires as the combination of superior genes and more male offspring may be more profitable than all-natural mating.

Information on the nutritive value and in vitro fermentation characteristics of native shrubs in New Zealand is scant. This is despite their potential as alternatives to exotic trees and shrubs for supplementary fodder, and their mitigation of greenhouse gases and soil erosion on hill-country sheep and beef farms. The objectives of this study were to measure the in vitro fermentation gas production, predict the parameters of the in vitro fermentation kinetics, and estimate the in vitro fermentation of volatile fatty acids (VFA), microbial biomass (MBM), and greenhouse gases of four native shrubs (Coprosma robusta, Griselinia littoralis, Hoheria populnea, and Pittosporum crassifolium) and an exotic fodder tree species, Salix schwerinii. The total in vitro gas production was higher (p < 0.05) for the natives than for the S. schwerinii. A prediction using the single-pool model resulted in biologically incorrect negative in vitro total gas production from the immediately soluble fraction of the native shrubs. However, the dual pool model better predicted the in vitro total gas production and was in alignment with the measured in vitro fermentation end products. The in vitro VFA and greenhouse gas production from the fermentation of leaf and stem material was higher (p < 0.05), and the MBM lower (p < 0.05), for the native shrubs compared to the S. schwerinii. The lower in vitro total gas production, VFA, and greenhouse gases production and higher MBM of the S. schwerinii may be explained by the presence of condensed tannins (CT), although this was not measured and requires further study. In conclusion, the results from this study suggest that when consumed by ruminant livestock, browsable native shrubs can provide adequate energy and microbial protein, and that greenhouse-gas production from these species is within the ranges reported for typical New Zealand pastures.

Beef-dairy crossbred cows (such as Angus-Friesian) have lighter mature cow weights while weaning heavier calves compared with cows in a typical self-replacing New Zealand Angus breed herd. The objective of this study was to quantify the potential profitability of farming an Angus-Friesian cow herd through modelling the potential changes in cattle numbers, feed demand, production, and beef enterprise economics. The Angus-Friesian cow herd was simulated as purchasing all replacement heifers and was modelled with different sire breeds (Angus or terminal such as Charolais or Simmental) and offspring sale policies (sold at weaning at six months of age or at 27 months of age). Total annual cattle feed demand was maintained at the same level for all modelled scenarios. Angus-Friesian herds had 8% to 79% higher beef enterprise cash operating surplus (COS) compared with the selfreplacing Angus herd (COS = NZD 255/ha). For the Angus-Friesian herds, selling all offspring prime (direct to slaughter) at 27 months of age resulted in 20% to 59% higher COS than selling all offspring store (sold at weaning) at weaning at six months old. Utilising terminal breed sires with the Angus-Friesian herd resulted in 10% to 12% higher COS compared with using Angus sires when selling all offspring store at weaning, due to the heavier sale weights and resultant higher per head sale values. However, when selling all offspring prime at 27 months of age the utilisation of Angus sires resulted in 10% to 11% higher COS than using terminal sires, as the lighter weights and thus total feed demand was lower for offspring born to Angus sires allowing for a greater breeding cow numbers (and therefore numbers of offspring sold). Scenarios in which offspring were retained onfarm until 27 months of age increased total feed demand of cattle destined for sale, necessitating reductions in breeding cow numbers to as low as 60% of the base system level, which may inhibit farmers' ability to manage pasture quality. Farmers considering a change to an Angus-Friesian crossbred herd of breeding cows can include the potential herd numbers, feed demand, production, and economic changes predicted in this analysis in their decision making, as well as the practicalities of the explored strategies for designing their farm system.

New Zealand farmers can choose to breed a proportion of their beef cow breeding herd with terminal breed sires to produce heavier offspring to sell for higher per head prices. However, the heavier weights of terminal offspring also increase their feed demand which may necessitate cow herd size reductions in a system with a fixed feed supply. This study used a bio-economic, system dynamics model to simulate cattle numbers, production, and beef enterprise cash operating surplus (COS) for a self-replacing beef suckler herd of Angus breed cows bred with only Angus sires to produce purebred offspring or a proportion of cows bred with European breed terminal sires (such as Charolais or Simmental). The herd was also modelled with varying calf weaning rates (84 or 90%), with offspring sales occurring either at weaning or at 27 months of age, and in a secondary analysis, with or without price premiums for sales of cattle of at least 75% Angus breed. Total annual beef feed demand was maintained at 40% of total farm feed supply (total farm area of 530 ha) in all scenarios, with the remainder consumed by the on-farm sheep flock. Beef enterprise COS was therefore divided by the beef herd proportion of farm area (212 ha) to derive a per ha COS value. Herd replacement rate was first modelled at 22% allowing for 43% of cows to be bred with terminal sires with a weaning rate of 84%. With a weaning rate of 90% the replacement rate was 18% allowing 60% of cows to be bred with terminal sires. The base scenario with a herd weaning rate of 84% using only Angus sires had a COS of NZD 255 /ha. Relative to the base scenario, use of terminal sires increased COS by the largest amount (COS = NZD 317 /ha), Angus premiums increased COS by a lower amount (COS = NZD 307 /ha), and the higher weaning rate of 90% increased COS by a slightly lesser amount (COS = NZD 302 /ha). Alternatively, these strategies could be implemented concurrently, which was predicted to have the highest COS at NZD 381/ha. These results can inform farmer decision making and farmers can consider the relative profitability potential and practicality of the explored strategies for their breeding herd.

Hoggets (ewe lambs aged 4 to 16 months) can be bred from approximately 8 months of age for potentially increased flock production and profit, however most New Zealand hoggets are not presented for breeding and their reproductive success is highly variable. Bio-economic modelling was used to analyse flock productivity and profit in four sets of scenarios for ewe flocks with varying mature ewe (FWR) and hogget (HWR) weaning rate combinations. Firstly, hogget breeding was identified to become profitable when break-even HWRs of 26% and 28% were achieved for flocks with FWRs of 135% and 150%, respectively. Secondly, relatively smaller improvements in FWR were identified to increase profit to the same level as larger improvements in HWR. Thirdly, a high performing flock with FWR and HWR both ≥ the 90th percentile currently achieved commercially, was the most profitable flock modelled. Fourthly, a FWR was identified with which a farmer not wishing to breed hoggets could have the same profit as a farmer with a flock achieving current industry average FWR and HWR. Overall, the relative profit levels achieved by the modelled flocks suggest that more farmers should consider breeding their hoggets, though improvements in FWRs should be prioritised.

New Zealand hill country sheep and beef farms contain land of various slope classes. The steepest slopes have the lowest pasture productivity and livestock carrying capacity and are the most vulnerable to soil mass movements. A potential management option for these areas of a farm is the planting of native shrubs which are browsable and provide erosion control, biodiversity, and a source of carbon credits. A bioeconomic whole farm model was developed by adding a native shrub sub-model to an existing hill country sheep and beef enterprise model to assess the impacts on feed supply, flock dynamics, and farm economics of converting 10% (56.4 hectares) of the entire farm, focusing on the steep slope areas, to native shrubs over a 50-year period. Two native shrub planting rates of 10% and 20% per year of the allocated area were compared to the status quo of no (0%) native shrub plantings. Mean annual feed supply dropped by 6.6% and 7.1% causing a reduction in flock size by 10.9% and 11.6% for the 10% and 20% planting rates, respectively, relative to 0% native shrub over the 50 years. Native shrub expenses exceeded carbon income for both planting rates and, together with reduced income from sheep flock, resulted in lower mean annual discounted total sheep enterprise cash operating surplus for the 10% (New Zealand Dollar (NZD) 20,522) and 20% (NZD 19,532) planting scenarios compared to 0% native shrubs (NZD 22,270). All planting scenarios had positive Net Present Value (NPV) and was highest for the 0% native shrubs compared to planting rates. Break-even carbon price was higher than the modelled carbon price (NZD 32/ New Zealand Emission Unit (NZU)) for both planting rates. Combined, this data indicates planting native shrubs on 10% of the farm at the modelled planting rates and carbon price would result in a reduction in farm sheep enterprise income. It can be concluded from the study that a higher carbon price above the break-even can make native shrubs attractive in the farming system.

The liveweight of New Zealand beef cows has increased in recent decades due to selection for higher growth rates. Published data suggest that the efficiency of beef cow production decreases with increasing cow liveweight. Changes in beef herd size, feed demand, production, and cash operating surplus (COS) were simulated with average mature cow liveweight varied to 450, 500, 550, and 600 kg. With total annual beef feed demand fixed at the same level, in all scenarios cow numbers and numbers of weaned calves decreased with increasing cow liveweight. When the model was run with consistent efficiency of calf production across the mature cow liveweights (scenario A), heavier cows were more profitable. However, using published efficiency data (scenarios B and C), herds of heavier cows were less profitable. The likely most realistic scenario for New Zealand hill country farms (scenario B) had COS decrease from New Zealand Dollars (NZD) 456/ha with a herd of 450 kg cows to NZD 424/ha with 600 kg cows. Reductions in COS were relatively small, which may not deter farmers from breeding heavier cows for higher calf growth rates. However, the results of this analysis combined with indirect potential economic impacts suggest that the heaviest cows may not be optimal for New Zealand hill country conditions.

A strategy to increase wool income for coarse wool (fibre diameter > 30 µm) producers through a transition to higher value medium wool (fibre diameter between 25 and 29 µm) was identified, with previous analyses allowing sheep feed demand increases to impractical levels during the transition period. This study modelled a whole flock transition from Romney breed to a ¾Merino¼Romney flock through crossbreeding with Merino sires, with sheep feed demand constrained between 55% and 65% of total grown feed. Transition was complete after 12 years, and the final ¾M¼R flock had higher COS (cash operating surplus; NZD 516/ha) than the base Romney flock (NZD 390/ha). Net present value analyses showed the transition always had an economic benefit (up to 13% higher) over the Romney flock. In a sensitivity analysis with sheep and wool sale prices changed by ±10%, higher sheep sale prices reduced the economic benefit of the transition (NPV up to 11% higher) over the Romney flock, as sheep sales comprised a higher proportion of income for the Romney flock, and higher wool sale prices increased the benefit (NPV up to 15% higher) of the transition to ¾M¼R over the Romney flock. This study demonstrated a whole flock transition from Romney to ¾M¼R breed was profitable and achievable without large variation in sheep feed demand, although the scale of benefit compared to maintaining a Romney flock was determined by changes in sheep and wool sale prices.