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    Age-related changes in intestinal permeability and absorptive capacity in the domestic cat (Felis catus) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Manawatū, New Zealand
    (Massey University, 2025) Patterson, Keely
    Ageing reduces fat and protein digestibility in the domestic cat which might have implications for their health and wellbeing. Reasons for the reduction in digestibility are unknown, but could be related to changes in the structure and/or function of the gastrointestinal tract (GIT), including increased permeability. Increased intestinal permeability may affect nutrient absorption, promote inflammatory responses, and allow pathogens to be absorbed. Currently, the literature that describes the relationship between intestinal permeability and age is conflicting, with limited studies undertaken in the domestic cat. This thesis compiled the first literature review of intestinal permeability and absorptive capacity, focusing on the lack of meaningful information and a standardised methodology regarding these GIT parameters in cats. It is hypothesised that intestinal permeability is negatively affected by age, and that interventions, such as probiotics, can reverse this. In Chapter 2, the differential sugar absorption test (SAT), using lactulose, rhamnose, xylose, and 3-O methylglucose (3-OMG) as markers of intestinal permeability and absorptive capacity, was developed using liquid chromatography-mass spectrometry (LC-MS). By using this method in Chapter 3, a group of young cats were compared to a group of senior cats. The results supported the hypothesis that intestinal permeability increased in senior cats. There was no age-related change in absorptive capacity, but there was a trend where males tended to have higher absorptive capacity values than females. To further understand GIT health in ageing cats and test possible interventions to strengthen the weakened intestinal barrier, probiotic yeast Saccharomyces cerevisiae var. boulardii (S. boulardii) was supplemented to midlife – senior aged cats in a crossover trial in Chapter 4. S. boulardii supplementation did not affect the GIT health parameters measured. Secondary analysis showed that with increasing age, the cats faced reduced fat digestion and increased intestinal permeability. This study highlighted the variation in data sets obtained in senior cats which should be accounted for in future research. Additionally, future research should focus on the mechanism by which altered intestinal permeability decreases nutrient digestibility to promote better nutrition for senior cats.
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    Developing palatants for pet food from leather industry wastes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2024) Li, Bizhu
    The leather industry generates substantial waste streams, which are presenting a significant challenge in terms of both environmental sustainability and economic efficiency. Adding value to leather waste streams is a popular research idea. Most previous research has focused on recycling and reusing collagen from leather waste or turning leather waste into bioenergy. This project concentrated on turning one leather waste stream into ingredients for pet food because the commercial value of the pet food industry is increasing. Cats are strict carnivores, and they find ingredients from animal sources highly palatable. Therefore, the aim of this project is to produce and develop edible and palatable products which are attractive to cats and analyse these novel products in order to understand more about increasing palatability in cat food. Chapter 2 is the literature review. The first part of the review summarises and compares research into the utilisation of leather waste streams, especially in the food industry. The second part contains basic information on palatability, and how improvements in cat food manufacture and methods for testing palatability have been made. The final part of the review considers methods for food flavour instrumental analysis especially to characterise key factors associated with palatability. Chapter 3 details attempts to explore collagen hydrolysis. Collagen hydrolysed by water mixtures were produced for in vivo testing by cats using two-bowl palatability tests. However, the hydrolysed collagen solutions only had the same levels of palatability as water for cats. Chapter 4 describes further palatability sample development and production processes. A series of samples were prepared and tested by cats using the same method in Chapter 3. The best performing of these was a raw sheep skin sample hydrolysed by phosphoric acid at 105°C and then adjust its pH to 5.5, which showed that a novel palatable product for cats can be produced from leather waste. This sample was further analysed in Chapter 5. Proximate analysis, volatile compounds characterisation, total amino acid, free amino acid and fatty acid analyses were carried out. Those tests allowed full nutritional mapping of the sample. The future work chapter indicates the remaining gaps in the finished lab work and the suggests further work that needs to be carried out.
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    Energy partition and nitrogen utilization lambs fed Willow (Salix alba) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Animal Science at Massey University, Manawatu, New Zealand
    (Massey University, 2025) Yan, Ziyu
    Willow (Salix spp.) has gained attention in recent years for its potential to enhance livestock nutrition and mitigate environmental impacts, particularly in the context of reducing methane (CH4) emissions from ruminants. This study investigated energy metabolism and nitrogen (N) utilization of Romney lambs under two treatments: summer pasture and willow + summer pasture. All lambs were placed in metabolic crates for three days where feed intake, faecal excretion, live weight changes were measured, and feed, faecal, and urine samples were analysed for nutrient composition. The contents of dry matter (DM), organic matter (OM), crude protein (CP), fat and lignin in willow were higher than those in summer pasture (366.8 g/kg willow vs. 357.5 g/kg pasture; 918.0 vs. 905.8 g/kg DM; 133.6 for 100g/kg DM; 44.8 vs. 34.8g/kg DM; 91.2 vs. 50.8 g/kg DM; respectively), while the ash, neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents were lower than those of summer pastures (82 vs. 94.2 g/kg DM; 303.2 vs. 562.6 g/kg DM; 223.7 vs. 324.4 g/kg DM; respectively). The apparent digestibility of willow (DM: 63.7%; OM: 65.1%; CP: 50.8%; fat: 61.6%; NDF: 51.6%) was higher than that of summer pasture (DM:57%; OM: 59.1%; CP: 50.2%; fat; 54.5%; NDF: 51.2%). It was found that the use of willow as a supplementary feed in summer resulted in improved apparent digestibility, energy utilization and N balance in lambs. Willow supplemented lambs had lower urine N loss. However, willow supplementation did not reduce the live weight loss of lambs, which may be related to the insufficient proportion of willow in the mixed diet, the inadequate adaptation of rumen fermentation to willow and the detoxification process caused by secondary compounds in willow. Although willow supplementation led to an increase in faecal N, and an increase in estimated CH4 emissions in the predicted model, willow reduced the proportion of energy loss in the faeces, urine, and methane. Willow is a potential feed that provides a higher metabolizable energy (ME) intake and apparent digestibility during the summer months, reducing energy loss and improving energy utilization and N balance in lambs.
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    Alternative methods to predict the nutritive value of broiler chicken diets : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, Manawatū, New Zealand
    (Massey University, 2024-11-28) Thiruchchenthuran, Sivajanani
    Feed represents the major cost of poultry production accounting for up to 70% of the total. Accurate estimation of the chemical composition and nutritive value of the feed ingredients and diets is essential to reduce costs and optimise diets. Undersupply of nutrients will have a strong negative impact on the performance of birds and oversupply will have a negative impact on the environment as well as cost of production. Traditional methods of feed evaluation are time-consuming and costly. Both in vivo and in vitro techniques have several limitations. Therefore, there is a need for rapid and accurate analysis of feed samples for their chemical composition and nutritive value in real-time for optimal formulation of diets. Prediction equations and Attenuated Total Reflectance Fourier Transform Mid-Infrared Spectroscopy (ATR-FT MIRS), however, could offer a much faster approach to predict the chemical composition and nutritive value of broiler diets. Therefore, this thesis aimed to develop and validate prediction equations to be applied in practical conditions and to investigate the potential of ATR-FT MIRS in predicting chemical composition and nutritive value of broiler diets. The first study (Chapter 3) was designed to develop prediction equations using stepwise regressions. Bootstrap was used to select the variables as well as to confirm the stability of the models. The results indicated that prediction models for coefficient of apparent ileal digestibility (CAID) and ileal digestible content (IDC) of nutrients could be developed using the stepwise regression and bootstrapping approach. To ensure the practical application of each equation with greater confidence and to alert users to potential risks, Chapter 4 was designed to validate the proposed prediction models developed in Chapter 3. The validation revealed that some equations could not be used in all situations (CAID of nitrogen (N), fat, starch, and calcium (Ca) and IDC of Ca), and some could be used as a general guide (CAID and IDC of phosphorus (P)). The equations developed for CAID of energy and dry matter (DM), and IDC of N, starch, energy, and DM could be used with good results in terms of R2 and CCC in the validation study. The 5th, 6th, and 7th Chapters investigated the potential use of ATR-FT MIRS in predicting the chemical composition and nutritive value of broiler diets using various approaches. Many of the wet chemical compounds in broiler diets, ileal digesta, and excreta were predicted well. The results also revealed that the nutritive value of broiler diets can be predicted from the diets itself, ileal digesta, and excreta spectra as well as the combination of diet and ileal digesta spectra or diet and excreta spectra. Overall, the results of this thesis indicated that prediction equations and ATR-FT MIRS can be used as a rapid real-time technique to evaluate the nutritive value of broiler diets. The findings of this thesis regarding ATR- FT MIRS are novel and can be used for further update and development of MIRS calibration models, which could substantially reduce the cost of wet chemical analysis in future.
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    Investigations on black soldier fly (Hermetia illucens L.) production and nutrition : a sustainable solution for poultry feeding : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science, School of Agriculture and Environment, College of Sciences, Massey University, Palmerston North 4442, New Zealand
    (Massey University, 2024-08-20) Mahmoud, Amira Elsayed Abdalla
    Black soldier fly (BSF; Hermetia illucens L.) is renowned for efficiently converting organic wastes into valuable biomass rich in protein and fat. This makes it a profitable and sustainable method for waste management and a useful feed source for animals like poultry, fish, pigs, and pets. Using BSF reduces the dependence on traditional feed ingredients such as soybean and fish meal, which are often imported and add to the carbon footprint. Despite growing interest and large-scale production of BSF meals, knowledge gaps hinder the widespread adoption of this technology, especially in small and medium-scale operations. The overall aim of this multidisciplinary research was to better understand the biology and rearing methods of BSF, processing of insect meals, and their utilisation by broiler chickens. The thesis research specifically investigated: (1) methods and techniques that optimise BSF breeding and meal processing relevant to small and medium-sized operations, (2) the impact of substrate type, moisture, and compaction on the non-feeding stages of BSF, (3) disease management in BSF colonies to ensure healthy population dynamics, including the first record of red mites as a parasitic case within BSF colonies, and (4) the nutritional value of the larval and pre-pupal stages of BSF as replacements for soybean meal (SBM) in poultry feeds. Firstly, the thesis provided a practical guide to establishing and managing a BSF colony, covering the entire process from egg production to larval and pre-pupal meal processing. The procedures were based on the experience of producing 450 kg of BSF larvae (BSFL) and pre-pupae (BSFP) over the course of doctoral research. Secondly, a study examined the impacts of substrate type, moisture levels, and compaction on BSF pupation success, adult emergence and morality. Among the six substrates evaluated (sand, wood shavings, topsoil, vermiculite, spent wheat middlings, and potting soil), spent wheat middlings presented as the most cost-effective and readily available option. Moisture level was found to significantly affect substrate performance, with 10% moisture providing the best outcomes for pupation and reducing mortality while avoiding mould growth. Mild compaction did not negatively impact pupation development, suggesting that moderate compaction could enable small farmers to reuse substrate and lower the cost. Thirdly, an infestation of poultry red mites (Dermanyssus gallinae), causing noticeable skin discoloration and anatomical damage to the BSFL and BSFP, was identified. The mites repeatedly bit and fed on the BSF bodily fluids, causing distress. The implications of mite infestation on colony health and viability are discussed, emphasising the need to maintain colony hygiene. Lastly, the apparent metabolisable energy (AME) and standardised ileal digestibility coefficients (SIDC) of amino acids (AA) of full-fat BSFL and BSFP meals for broiler chickens were determined. The AME and SIDC of BSFL and BSFP were higher than those reported for SBM, the commonly used protein meal in poultry diets. The findings demonstrated that BSFL and BSFP meals are better sources of energy and digestible AA, and are potential substitutes for SBM. Although the principles behind BSF bioconversion technology may seem straightforward, effective implementation requires deeper understanding of its complex stages. The present thesis provided a thorough overview of BSF technology, including rearing methods, optimising pupation conditions, the identification of a novel ectoparasite affecting BSF colonies, and the potential use of BSFL and BSFP into broiler chicken diets. By addressing these key aspects, the research contributes valuable insights for optimising BSF production and utilisation, particularly for small and medium-scale operations.
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    Use of triaxial accelerometers and machine learning algorithms for behavioural identification to assess the effectiveness of a joint supplement in old domestic cats (Felis catus) : a thesis presented in partial fulfilment of the requirements for the degree of MSc (Animal Science), Massey University, Palmerston North, New Zealand
    (Massey University, 2024) Liu, Yuting
    Osteoarthrosis has a 90% prevalence rate in older cats and adversely affects quality of life. Long-term administration of non-steroidal anti-inflammatory drugs is usually required, but can have adverse effects such as vomiting, diarrhoea and kidney failure. Nutraceuticals have been shown to relieve joint pain in cats without such side effects, however, due to differences in dose rates and formulations there is no consensus within the academic community as to their efficacy. Most studies have utilised subjective measures such as veterinary or owner-assessed changes in activity, which are not very sensitive. Accelerometers can provide objective data on cat activity and have recently been shown to identify specific behaviours (Smit et al., 2023). In the present study, triaxial accelerometers (ActiGraph®, Pensacola, FL, USA) were fitted to the collars of the cats for 20 weeks to assess activity and behaviour. Two groups (n=8 per group) of old cats (aged 11-16 years; Massey University, Palmerston North, NZ) were fed the same diet (Chef: Kraft Heinz Wattie’s Ltd., Hastings, NZ) for four weeks to collect baseline acceleration data. The 16 cats selected for the main study were then divided into two groups balanced for physical activity. The test group received a joint supplement added to the baseline diet while the control group were fed the diet unsupplemented for 16 weeks. The commercial joint supplement contained glucosamine, chondroitin sulphate, curcumin and green-lipped mussel (Tandem, Wellington, NZ). The aim was to assess the effectiveness of the joint supplement in maintaining or promoting activity and specific behaviours in the cats. Overall physical activity was not different between groups at baseline but was higher over the study in the test group compared to the control animals (P<0.03). Grooming, as identified by the algorithm, showed a tendency (P=0.051) to be higher in the test group than in the control. These results suggest that the supplement had a positive effect on both overall activity and more specifically on grooming behaviour in old cats.
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    The influence of lipid types and lipid levels on the performance parameters, apparent metabolisable energy and ileal nutrient digestibility in day 1-21 broilers fed maize-soybean based starter diets : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Palmerston North, Manawatū, New Zealand
    (Massey University, 2023) Hou, Sydney
    The current study investigated the influence of different lipid sources and lipid inclusion level, and their interaction on ileal nutrient digestibility (N, DM, fat, starch, GE), apparent metabolizable energy (AME), and performance parameters (BWG, FI, FCR, and mortality) of broilers fed maize-soybean diets for 21 days post-hatch. A completely randomized design was used with 2 x 3 factorial arrangement of 6 treatments with 8 replicates, and 8 birds per replicate to study the effect of two lipid levels: High (H) and Low (L) and three lipid types: Crude Palm oil (CPO), Soy Oil (SO) and Poultry Fat (Sirona, PF). Six experimental diets (POH, POL, SOH, SOL, PFH and PFL) were formulated using maize and soybean as the main feed ingredient. The inclusion levels of the main feed ingredients and lipid vary between the diets achieving different levels of energy and nutrient density. Other ingredients that were included in the diets show only a slight variation. The lipid sources provided the birds with similar levels of AME within the same lipid inclusion level. High diets were formulated with more lipids than the Low diets, which provided an extra 100Kcal AME (H = L + 100Kcal/kg). Low diets were formulated to contain 6% of crude fat with lower AME. All the lipid type x lipid level interactions are not significant for all the performance parameters, AME, and ileal nutrient digestibility. However, both lipid types and lipid levels significantly (P < 0.05) affected body weight gain of broilers. Birds consumed poultry fat source diets had the highest BWG, with similar level in soy oil diets and lowest in diets consist crude palm oil. Diets with low lipid inclusion level resulted significantly better (P < 0.05) BWG. Feed intake was influenced (P < 0.05) by lipid inclusion level in diets that low lipid inclusion resulted improved feed intake. Feed conversion ratio is significantly impacted (P < 0.05) by lipid type, where the soy oil had the best efficiency followed by poultry fat, and diets that included crude palm oil had the highest FCR. AME was significantly higher (P < 0.05) in diets containing plant-based oils and increase lipid level contributed to the significant difference (P < 0.05) between AME in diets. Ileal digestibility of DM, fat, and GE was significantly higher (P < 0.05) in soy and crude palm oils than poultry fat. In general, the result showed that the performance parameters, AME, and ileal nutrient digestibility of broilers are influenced by the various fatty acid profile and the amount of unsaturated and saturated fatty acids in the different sources. Lipid inclusion level affected the AME and performance parameters of broilers.
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    Effect of different dietary amino acid profile on growth and chemical composition of Black soldier fly (Hermetia illucens L.) larvae : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Manawatu, New Zealand, School of Agriculture and Environment
    (Massey University, 2023) Wang, Mengxuan Marryana
    With increased focus on food security worldwide, including alternative proteins in manufactured animal feed and human diets is an increasingly popular topic among diverse groups. Black soldier fly (BSF) (Hermetia illucens L.) larvae have gained significant attention in recent decades. The larvae provide good-quality proteins; however, the rearing procedures and rearing substrate for this species vary considerably. It is essential because the body composition of these insects is highly dependent on the rearing substrate in terms of all essential nutrients and other substances, such as heavy metal residue. The current study looks at the dietary amino acid influence on the body composition of BSF larvae. This research aimed to find out whether the BSF larvae require a list of essential amino acids as the monogastric animals do and whether they need an ideal amino acid profile for their efficient production. Answering these questions can shine a light on the mass production efficiency of this species of insect and aid the production of BSF with a relatively constant nutritional profile so they can be reliably incorporated as feed ingredients. Earlier literature indicates that the growth of BSF larvae is affected by ambient conditions such as temperature and culturing substrates. The chemical composition of the substrates is directly related to the content of the larvae, and amino acid requirements, being the foundation of the proteins, are important to understand. Two distinct diets were formulated and presented in two treatments in the current study. Ten replicates of 50-week-old larvae in each treatment were established and reared for 14 days. The larvae and their feeding substrates were then sent for chemical, including amino acid, analysis. My findings suggest that BSF larvae can synthesise a relatively stable amino acid profile regardless of the amino acid composition of the diet. However, for optimal growth performance, balanced diets are essential. There are only a few amino acids that are most likely essential for BSF larvae, namely valine, leucine, lysine, and taurine.
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    Feed not food : alternative feedstuffs for growing-finishing pigs : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Manawatu, New Zealand
    (Massey University, 2023) Nguyen, Thanh
    Conventional diets used in the swine production sector, which rely heavily on soybean meal (SBM) and cereal grains, do not align with sustainable development goals. Hence, exploring alternative feedstuffs that are inexpensive, environmentally friendly, and do not compete with human food sources is essential to meeting future expectations around sustainability. As pigs are omnivores, they can efficiently convert many types of feed into a nutritious protein source for human consumption. Therefore, research and development in alternative feedstuffs for pigs are ongoing, and farmers are encouraged to adopt these options to enhance the sustainability of their operations. However, incorporating alternative feedstuffs in the diets of grower-finisher pigs requires proper risk management as they can contain high levels of insoluble fibre and other anti-nutritional factors that may affect pig growth performance, pork quality, and welfare. This thesis aimed to investigate alternative ingredients for inclusion in growing-finishing pig diets. The first experiment (Chapter 3) examined the effect of replacing barley, SBM and soybean oil with dried distiller’s grains with solubles, canola meal, wheat middlings and tallow on pig growth performance and meat quality. There were no negative effects of the alternative diet on overall pig growth or carcass performance, however, skatole levels of backfat were significantly lower in pigs fed the alternative diet. The second experiment (Chapter 4) investigated the effect of lucerne as an ingredient in grower-finisher diets and as manipulable enrichment material on pig growth performance and behaviour. Feeding the lucerne diet reduced average daily feed intake, live weight gain, feed intake per feeder visit, and feeding rate, but increased feed efficiency. Despite these effects, overall performance was not significantly different between treatments when considering feed conversion ratio, final slaughter weight, dressing out percentage and backfat thickness. The third experiment (Chapter 5) investigated the effect of replacing SBM with Poultry by-product meal (PBM) in growing-finishing pig diets on growth performance, carcass yield and meat quality. Four experimental diets were formulated, in which SBM was replaced with PBM at the increasing level of 0%, 33%, 77% and 100%. The diets were then fed to growing-finishing pigs. The results clearly demonstrate that PBM can be used as the primary protein source in pig diets without compromising the performance of growing pigs, as long as the diets are properly formulated to meet their nutritional requirements. A meta-analysis (Chapter 6) was conducted to assess the impact of substituting SBM with alternative oilseed meal, including canola meal, camelina meal, cottonseed meal, sunflower meal and rapeseed meal, on the performance of growing-finishing pigs. The findings indicate that this replacement adversely affected pig's daily weight gain while maintaining daily feed intake, resulting in an increased feed conversion ratio for both growers and finishers. Furthermore, the use of alternative oilseed meals led to reducing carcass and loin yield, although there was no significant impact on meat quality. However, the heterogeneities of the analysis for most parameters were substantial, possibly due to the variation in the nutritive value of the alternative oilseed meal. Overall, the results showed that substituting conventional feed ingredients with alternative feedstuffs had no or minor impacts on pig growth performance and meat quality. Additionally, several benefits of using alternative feedstuffs ingredients in growing pig diets were identified: reducing skatole in pork from entire males and improving feed conversion efficiency. The present research indicates that using alternative feedstuffs can be a viable option for pig feed, with possible benefits for pig production, meat quality and animal welfare. The field of alternative feedstuffs for pigs has much to explore, with numerous undiscovered options, such as legumes, brassicas, insects, and by-products, which can offer valuable nutrients and support sustainable pork production. These alternative feedstuffs may have multiple benefits, such as improved gut utilization, support for pig health, lower production costs, and reduced environmental impact. Furthermore, using feed additives to enhance the utilization of low-nutritive-value alternative feedstuffs is a viable option. As such, further research should focus on integrating these feedstuffs into pig diets while promoting sustainable development.
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    Use of New Zealand native browse shrubs on sheep and beef hill country farms : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at the School of Agriculture and Environment, Massey University, Palmerston North, Manawatū, New Zealand
    (Massey University, 2023) Wangui, James Chege
    Sheep and beef cattle farming on hill country through the historic clearing of native vegetation for pasture has caused biodiversity loss and increased the risk of soil erosion. Exotic tree species such as poplar and radiata pine can be used to control erosion, but there is current interest in using native plants on the hill country for indigenous biodiversity restoration in addition to erosion control. However, there is limited information on the forage value, biomass, carbon stock, and potential economic impacts of native plants compared to exotics species. This thesis was aimed to address the lack of information available on native shrubs and their comparison to exotics trees and shrubs. The forage feeding value results revealed that native shrubs had consistent nutritional composition across seasons, higher metabolizable energy, and lower crude protein than the exotic shrub Salix schwerinii (Kinuyanagi). Findings on in vitro fermentation characteristics showed that native shrubs were highly digestible, yielded higher volatile fatty acids, microbial proteins, and greenhouse gases than S. schwerinii. Estimation of biomass revealed that the native shrubs were similar in aboveground biomass accumulation, but differed in allocation to foliage, branch, and stem. Melicytus ramiflorus (Mahoe) had lower foliage biomass while Coprosma robusta (Karamū) had lower branch biomass, among the evaluated shrubs. Estimated carbon stock accumulation was higher for Pittosporum crassifolium (Karo) due to a greater woodier portion (branch and stem) than M. ramiflorus and C. robusta but lower than exotic trees. The data from the native shrub studies was used in the bioeconomic model and showed that planting native shrubs or radiata pine on steep slopes equal to 10% of the farm area would reduce farm feed supply. This reduction would result in a decrease in sheep flock size and sheep flock net cashflow, particularly with higher planting rates and with of radiata pine. While radiata pine had a surplus overall farm net cashflow, native shrubs had negative cashflow due to high seedling costs and low carbon income, making their use on the farm currently unprofitable at the modelled prices. The study's findings suggest that replacing exotic trees with native shrubs can provide high-quality summer browse for livestock. The decision to plant native shrubs on steep hill country slopes would depend on the farmer’s financial situation and interest in biodiversity conservation and profits. However, reducing planting costs and increasing the carbon price would be necessary to make investing in native shrubs profitable and more attractive to farmers.