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Context: Wild dogs, including dingoes and dingo cross-breeds, are vertebrate pests when they cause financial losses and emotional costs by harming livestock or pets, threaten human safety or endanger native fauna. Tools for lethal management of these animals currently include aerial baiting with poisoned baits. In New South Wales (NSW), Australia, aerial baiting was previously permitted at a rate of 40 baits km^-1 but a maximum rate of 10 baits km^-1 was subsequently prescribed by the Australian Pesticides and Veterinary Medicines Authority. The efficacy of these baiting rates has not been quantified in eastern Australia, undermining the value of the policy and rendering adaptive management efforts difficult, at best.

Aim: To quantify the mortality rate of wild dogs exposed to aerial baiting at historic and currently approved rates, i.e. 40 baits per kilometre and 10 baits per kilometre, respectively.

Methods: Wild dog mortality rates were measured at sites in mesic north-eastern NSW, where aerial baiting was applied to control wild dogs and contrasted with sites and individuals where no baiting was undertaken. In total, 132 wild dogs were trapped and fitted with GPS-VHF telemetry collars before annual aerial baiting programs. Collars were used to locate animals after aerial baiting and to determine the fates of individuals.

Key results: 90.6% of collared wild dogs exposed to aerial baiting at 40 baits km^-1 died, whereas only 55.3% of those exposed to 10 baits km^-1 died (Welsh's t = 4.478, P = 0.004, v = 6.95). All wild dogs that were not exposed to toxic baits survived during the same periods.

Conclusion: Managers using aerial baiting to maximise wild dog mortality in mesic south-eastern Australia should use 40 baits km^-1 rather than 10 baits km^-1.

Implications: Wild dog population reduction for mitigation of livestock and faunal predation requires the application of efficacious control. The currently prescribed maximum aerial baiting rate of 10 baits km^-1 is inadequate for controlling wild dog populations in mesic forest environments in NSW.

Infectious laryngotracheitis virus (ILTV) is thought to exit the host in respiratory aerosols and enter by inhalation of these. High levels of ILTV DNA have been detected in excreta, raising the possibility of alternative routes of shedding from the host. However, it is not known whether or not the ILTV DNA in excreta represents infective virus. This study investigated transmission of wild type and vaccinal ILTV from infected to susceptible commercial meat chickens. Airborne- and excreta-mediated transmission of two field isolates of ILTV (Classes 9 and 10) and three vaccine strains (SA2, A20, and Serva) were tested. To test airborne transmission, air from isolators containing infected birds was ducted through a paired isolator containing uninfected chickens. To test excreta transmission, aliquots were prepared from excreta containing a high level of ILTV DNA within the first week after infection. Chicks were infected bilaterally by eye drop. Clinical signs were monitored daily and choanal cleft swab samples for ILTV detection by quantitative PCR were collected at 4, 8, 15, 22, and 28 days postinfection (DPI) in the airborne transmission study and at 7 and 14 DPI from the excreta transmission studies. There was no transmission of ILTV from excreta, suggesting that ILTV is inactivated during passage through the gut. All strains of ILTV were transmitted by the airborne route but only to a limited extent for the vaccine viruses. The field viruses induced clinical signs, pathology, and greatly elevated ILTV genome copies in swabs. In summary, these findings confirm the suspected airborne transmission of ILTV, demonstrate differential transmission potential between wild type and vaccine strains by this route, and indicate that excreta is unlikely to be important in the transmission of ILTV and the epidemiology of ILT.

A common strategy to reduce predator attack on livestock is the deployment of guardian alpacas. However, little research has been conducted on the behaviour of this species while housed with other livestock. This study monitored two male alpacas cohabitating with 180 lambing ewes in order to quantify field behaviour in two phases. Phase one assessed diurnal patterns of alpacas and lambing ewes using Global Navigation Satellite System (GNSS) collars recording data over 41 days, in combination with observational recordings. Phase two developed an alpaca behavioural ethogram through continuous observations from 05:30 to 19:30 h over a 3-day period. The two alpacas shared similar behaviours with commonality of distance travelled, and both species exhibited an increase in activity level based on speed between the times of 05:00 and 17:00 h. The GNSS data indicated that the alpacas flocked with the ewes at night sharing the same resting location, however, would spend time during the day on the outskirts of the paddock. Alpacas were observed to spend the majority of the observation period in two behavioural states: grazing (57%) and resting (27%). As a result of this study we were able to catalogue a range and frequency of field behaviours which alpacas exhibit while cohabitating with lambing ewes. However, further research is needed to determine in more detail how these behaviours correspond with the effectiveness of this species as a livestock guardian.

Mobile applications (apps) can be of great benefit to the way farmers record and access information, make more informed decisions, combine with other precision agriculture technologies, and play an important role in the delivery of farmer extension. There is little peerreviewed empirical information on Australian or international farmers' adoption and use of agricultural apps. Despite their widespread use, the literature also suggests that farmers have lower uptake of mobile device and app use than the general population.

The first objective of this thesis was to review the current technology adoption and extension models and assess their relevance for the adoption of app technology for the livestock industry, particularly the sheep sector. The next objective was to establish the levels of technology adoption of smartphones and agricultural app use for Australian livestock farmers and what farm or farmer characteristics influence adoption. The next task was to assess the motivations or incentives for farmers to adopt agricultural apps in their farm businesses and finally evaluate the attitude of farmers towards the role of apps in extension and on-farm decision-making. Overall, the research project aimed to identify factors of importance to farmers that influence their decision-making processes for agricultural app uptake through directly asking farmers. Another aim was to identify factors and processes important to developing agricultural apps that underpin successful adoption. These results can form the basis of a development framework to guide the creation of agricultural apps targeting farmers as their end-users.

This study uses a mixed-methods research methodology. Online quantitative surveys were conducted to establish smartphone ownership and agricultural app use levels and evaluate farmer attitudes towards the role of apps in farmer extension and decision-making. The study also identifies factors of importance to livestock farmers and other factors influencing app adoption. I held semi-structured key informant qualitative interviews with app development team members from industry research and development (R&D) and private sector organisations. Analysis of the interviews identified key success factors for app adoption.

An initial online survey (Survey 1) was completed by 392 respondents, including app users and non-app users, where 79% were sheep farmers. Subsequent surveys (Surveys 2–4) were completed by a total of 150 respondents, targeting the users of three Australian agricultural apps—RamSelect, Lifetime Ewe Management and Good Bulls—where 84.7% of respondents were farmers (sheep and dairy). Survey respondents generally had high smartphone and tablet ownership levels of between 91.9% and 97.9%. Mobile app use was also high among survey participants, with 83.4% for Survey 1 and 90.8% for Surveys 2–4. However, significantly lower rates of agricultural app use suggest either a lack of relevant, useful and easy to use apps for agriculture or an issue with the value proposition for app adoption.

Survey 1 found that farmer age, use of advisers and farmer network participation significantly influenced farmer app adoption. However, when asked, farmers ranked networks and advisers of low influence when deciding to use an agricultural app. Older age brackets had lower levels of app adoption, but the level of adoption was still relatively high. Thus, age should not be viewed as a barrier to adoption or overlooked in R&D and marketing. Developers and marketers of agricultural apps should also be wary of how they use farm advisers and farmer networks in their adoption plans. Although there was a positive relationship with higher levels of adoption, it may not be for previously thought reasons.

All surveys revealed a strong positive farmer attitude towards using apps in farmer extension. The vast majority of participants see apps replacing some traditional extension methods or that apps would be useful tools to incorporate into programs. Participants demonstrated a similar positive attitude for the role of apps in on-farm decision-making. The combined response signifies a strong positive attitude to using apps in the livestock industry.

Participants were asked to rank the importance of app attributes and reasons for app use. Participants identified usefulness, ease-of-use and a better way of doing something already done as the most important app attributes. Survey participants highlighted that making more informed decisions, increasing efficiency, accessing and recording important information and saving time were the most important reasons for agricultural app use. The top reason for not using an agricultural app was apps taking too long to set up and learn how to use.

The interviewing of agricultural app development teams helped identify key factors within the app development process that led to apps being more likely to achieve successful adoption. These factors include beginning the process with a verified end-user 'pain point', validating the app solution, clearly defining the app value proposition, having end-users engaged throughout the whole development process and implementing advanced systems to utilise feedback to enable customer success continual product improvements. Furthermore, some areas of R&D organisation product development and funding models hinder the success of app adoption that had a commercialisation goal.

This study contributes to the literature by establishing both levels of technology adoption of agricultural apps and key determinants of app adoption in the Australian livestock industry. While the study was conducted in Australia, there is limited peer-reviewed information on agricultural app adoption more broadly. This study adds value to the small number of existing international studies. The study considers farm and farmer characteristics that influence agricultural app adoption and uniquely identifies what motivates and influences farmers to adopt from a farmer perspective, as well as their attitudes towards the role of apps in farmer extension and on-farm decision-making.

While many aspects of existing DST adoption frameworks and established technology adoption models are still relevant to adopting agricultural apps, no single model or framework effectively encapsulates the factors and processes needed, or the new app-specific findings reported in this study. On this basis, a framework is proposed based on the research conducted, identifying why farmers use agricultural apps, factors that influence app adoption, and the factors and processes within app development that lead to apps being more successful in the marketplace. The agricultural app adoption framework is intended for app developers and providers, with farmers as their target users, particularly livestock producers, to reach greater levels of adoption success. The framework can also inform funders, extension agents and policymakers on the crucial elements to be considered in developing successful apps for farmers.

This study also highlights areas for further investigation, such as the need to better understand the relationship between farmer network participation and adviser use with higher levels of technology adoption and how best to incorporate apps into new and existing farmer extension programs. There is also potential for using other product development and funding models within R&D organisations to improve commercialisation success and higher levels of app adoption.

This study analyzed pig traders in Mukono district in Uganda. The main objective was traders' characterization in terms of trading activities, seasonal fluctuations, networking, and business constraints. A second objective was comparison of results across sampling sources, and to assess the extent to which these sources influence research results. Data on traders was collected through a survey questionnaire. The survey employed samples from 3 separate sample frames: traders identified by each of retailers, farmers, and local authorities.

The results indicated a limited number of intermediaries (actors), in the pig value chain in the locality studied. A large proportion of traders are also involved in the retailing function (principally as butchers). Farmers/producers remain the main suppliers to pig traders, whereas retailers/butchers, and in lower proportion small scale producers, are the main customers of these traders. Pig traders are facing many constraints in their day-to-day operations. Limited funds, transport costs and poor transport facilities are the most-cited constraints to traders' buying activities. Business environment constraints (lack of customers, high competition between traders, unpredictable market conditions, etc.) are the most frequently-cited constraints to selling activities.

Traders were segmented into two groups in the basis of their sampling list origin: a first group composed of those drawn from the producers' or retailers' lists, and a second group composed by traders drawn from the local authority's list. Results indicated that the former group is mainly composed of young and inexperienced traders, in contrast to the second group which is composed of aged and experienced traders. Traders groups' constraints analysis showed that the two groups of traders are experiencing different constraints, especially the young and inexperienced traders who cited a large number of problems. These results highlight the importance of the sampling source.

The application of ultraviolet (UV) light in poultry production is garnering increased interest with the drive toward improved poultry welfare and optimized production. Poultry can see in the UV spectrum (UVA wavelengths: 320-400 nm) thus inclusion of these shorter wavelengths may be viewed as more natural but are typically excluded in conventional artificial lights. Furthermore, UVB wavelengths (280-315) have physiological impact through stimulation of vitamin D pathways that can then improve skeletal health. However, better understanding of the effects of UV supplementation must occur before implementation practically. This non-systematic literature review aimed to summarize the impacts of UV supplementation on the behavior, welfare, and production of laying hens, meat chickens (breeders and growers), and other domestic poultry species including directions for future research. The literature demonstrated that UVA light has positive impacts on reducing fear and stress responses but in some research, it significantly increases feather pecking over age during the production phase. UVB light will significantly improve skeletal health, but an optimum duration of exposure is necessary to get this benefit. Supplementation with UVB light may have more distinct impacts on egg production and eggshell quality when hens are experiencing a dietary vitamin D3 deficiency, or if they are at the terminal end of production. The relative benefits of UVB supplementation across different ages needs to be further verified along with commercial trials to confirm beneficial or detrimental impacts of adding UVA wavelengths. Further research is warranted to determine whether adding natural light wavelengths to indoor poultry production is indeed a positive step toward optimizing commercial housing systems.

As the public interest in improving animal welfare increases, industries must align their practices with consumer’s expectations. Environmental enrichment can promote positive welfare, however research regarding pasture-based cattle is limited, likely as is assumed they can perform all desired behaviours as they are housed in ‘naturalistic’ environments. Therefore, Chapter 1 of this thesis introduces the concept of enrichment and its impacts on animal welfare, and identifies potential enrichments for beef cattle housed at pasture.

Chapter 2 examines cattle’s preference for a bare pastured paddock compared to a feedlot environment. The study demonstrates that some cattle were still attracted to the feedlot environment, suggesting enrichment should be explored for extensively managed animals.

Chapter 3 determines enrichment preferences of beef steers when housed at pasture. Overall, enrichments allowing for grooming showed the most promise for inclusion in extensive systems, based on both continued use and a relatively high number of displacements.

Chapter 4 determines the impacts of enrichment during yard-weaning for beef cattle born at pasture. The study shows that enrichment influenced short-term behaviours and affective state, but did not have any long-term impacts on body weight or temperament, although external factors such as increased mud and regrouping may have impacted results.

Chapter 5 examines the impact of enrichment loss on beef cattle. The study demonstrates that welfare was impaired when brush access was blocked, although this varied between individuals according to the degree of initial brush use.

Finally, Chapter 6 provides an overall conclusion which summarises the finding of the thesis and suggests that enrichment could be a valuable tool for improving pasture-based beef cattle welfare, although further work is required before it is readily adopted by industry.

Increased beef output resulting from adoption of on-farm innovations and demand for local beef of high value and hygiene in Nusa Tenggara Barat (NTB) province, in eastern Indonesia, is a potential opportunity to increase beef traders' livelihood and the safety of local beef products for consumers. Innovative intervention is essential to improving local slaughtering and processing procedures, currently carried out traditionally on the floor, to be more hygienic and to benefit from this new value chain. However, there is a lack of baseline information on the beef quality and hygiene associated with the NTB local traditional beef processing system. Understanding the market needs and local production management and constraints is crucial to determine the best intervention strategies for beef processing improvement.

This study evaluates motivations for consumers to demand more hygienic beef, quality and safety characteristics and willingness to pay for safe premium beef that contributes to adding value to processing (Chapter Three); analyses critical points for beef hygiene in the existing slaughter conditions (Chapter Four); quantifies the microbiological profiles of beef and processing environment (Chapter Five); characterises the management and social constraints around hygienic beef production in NTB (Chapter Six); and identifies knowledge, attitude, practice and aspirations of abattoirs for hygienic production of beef.

A consumer survey (Chapter Three) in Mataram City, the capital of NTB Province, found that a potential segment of consumers (27 % of the sample population) are willing to buy for characteristics of beef hygiene, premium cuts, vacuum packaging, beef freshness, and free-pathogen produce. As these consumers intend to cook safe local premium beef for international dishes using fast-cooking methods, the meat greatly relies on hygienic produce. This preference for safe premium beef could be an opportunity for the local beef production sector to meet this niche consumer demand. This potential target market may lead to improvement of the safety and quality of local beef products, and the implementation of good processing hygiene for local abattoirs. In this regard, assessment of factual conditions of local beef processing is crucial to allow the implementation of effective and affordable interventions for produce safety and quality improvement, which led to the conduct of observational study of abattoirs (Chapter Four) and microbiological profiles of current processing condition and carcass (Chapter Five).

Overall, the current condition of abattoirs (Chapter Four) is critical of hygiene and sanitation aspects involving abattoir structures, facilities, slaughtering and processing procedures and personnel sanitation. Infrastructures are poorly equipped with standard hygiene facilities, clean water sources, food safety control mechanisms, standard sanitary operational procedures (SSOP), cleaning and sterilisation tools, personal hygiene rules, and other technical facets. Amongst all the issues identified, the most crucial aspects that need urgent interventions in the first round include on-the-floor slaughter, water sources, cleanliness and hygiene behaviour of workers, and cleaning and sterilisation of equipment.

Negative affective states such as anxiety and depression pose a risk to animal welfare, however, practical tests for assessing these states in animals are limited. In humans, anxious individuals are shown to pay more attention toward threatening information than non-anxious individuals, known as an attention bias. Previously, an attention bias test was developed and validated as a measure of anxious states in sheep, where more anxious sheep showed increased attention toward a threat (dog) and were more vigilant than Control animals. Studies in humans suggest that attention biases also occur in depressed individuals, with observations of attention biases toward threats, as well as biases away from positive stimuli. Given these findings, we hypothesized that an attention bias test for sheep could also be used to assess states of depression. We predicted that Merino ewes in pharmacologically induced Depressed (para-chlorophenylalanine) and Anxious (m-chlorophenylpiperazine) states would show greater attention toward a threat than Control animals (saline), but that the Depressed sheep would show relatively less interest in a positive stimulus (photograph of a conspecific). During testing, Depressed sheep paid more attention toward the threat and less toward the photograph than Control animals as predicted (Analyses of Variance, P < 0.05, n = 16 per treatment). Interestingly, Anxious sheep showed an attention bias in the opposite direction, paying more attention toward the photograph and less toward the threat than Control animals (P < 0.05). Both Anxious and Depressed sheep were more vigilant than Control animals (P = 0.002). These results suggest the attention bias test can be used to measure and differentiate states of depression and anxiety in livestock. The bidirectional nature of the attention bias identified between treatments highlights the importance of measuring multiple behaviors in the test and considering the context in which the test is applied. This will enable a clearer characterization of the affective state of an animal, as an aspect of its welfare.

Blowfly strike or cutaneous myiasis, caused principally by the Australian sheep blowfly Lucilia cuprina is endemic to Australian sheep producing areas and is a major cause of suffering and economic loss. This article reports incidence and control practices as determined by three cross-sectional surveys of Australian sheep farmers covering the years 2003 (n = 1365), 2011 (n = 575) and 2018 (n = 354) with more questions relating to blowfly strike in the latter two surveys. Breech strike was reported at a higher rate than body strike in all survey years. Reported annual incidence of breech strike ranged from 2.2 to 4.7% of sheep nationally with minor differences between ewes and lambs. The incidence of body strike ranged from 1.0 to 7.1% with higher incidence in younger sheep in all years. The use of fixed time routine preventative chemical treatments increased during the survey period (43%, 46% and 66%, in 2003, 2011 and 2018 respectively) with dicyclanil (54%-58%) and cyromazine (23-36%) the main insecticides used for control since 2011. The use of the Mules operation (mulesing) to remove skin wrinkles from the breech area as a preventative modification did not change between 2011 and 2018 (47% in both), however, the use of pain relief at mulesing of replacement ewe lambs increased substantially between 2011 (59%) and 2018 (87%). The most commonly used methods to assist with flystrike control were timing of crutching (clipping of wool from susceptible areas) and shearing, with few respondents destroying maggots from treated sheep (21-26%) and very low use of fly traps (5-8%). Phenotypic selection of ewes for reduced susceptibility to flystrike based on visual traits was practiced by 61% of respondents in 2011 and 56% in 2018. Selection of rams for reduced susceptibility using estimated breeding values increased from 10% in 2011 to 17% in 2018. Breeding for resistance was the most commonly nominated (21%) most important change made to flystrike management in 2018. The results indicate that concern for sheep welfare has increased with almost universal use of pain relief at mulesing. Increased use of selection for blowfly resistance indicates farmer commitment to planning for a future without mulesing, although the practice remains prevalent. An increase in the reliance on preventative chemical treatments increases the risk of insecticide resistance.

Precision Livestock Farming (PLF) is the application of process engineering principles to livestock management, utilising automation, sensor-based monitoring, and intelligent systems to augment the expertise of livestock producers, and to facilitate the continuous monitoring of livestock biological responses. Livestock vocalisations have been shown to contain a wealth of information pertaining to animal welfare and health, presenting a significant opportunity to facilitate the noninvasive observation of livestock. The automated detection of livestock vocalisations has been demonstrated in numerous applications, such as welfare monitoring, disease diagnosis, and reproduction efficiency.

Recent advancements in machine learning have accelerated the progress of acoustic identification technologies, and this thesis will explore their application to the problem of livestock vocalisation detection. An automated livestock detection algorithm is proposed, utilising novel features derived from a Discrete Wavelet Transform (DWT), combined with a Support Vector Machine (SVM) approach to machine learning. A computationally efficient energy-based thresholding method was employed to facilitate automated segmentation. To date, a complete end-to-end realtime vocalisation detection system has not been demonstrated in the literature. This thesis culminates in the creation of prototype real-time automated vocalisation detection hardware, deployed using a low-resource single board computer (SBC).

To investigate the plausibility of an automated livestock detection system, MelFrequency Cepstral Coefficients (MFCCs) were used as input features for an SVM model to accurately classify sheep vocalisations. To improve on the preliminary results obtained, compact DWT-based acoustic features were proposed. The developed features were compared to MFCCs, both in terms of classification performance and computational timing. It was found that DWT-based features provided similar discriminatory ability to MFCCs, but a marked difference in computational timing was observed. DWT-based features were consistently faster to compute, and less variable in computational time, make them an ideal candidate for real-time vocalisation detection applications. To test the algorithm’s ability to be rapidly applied to different livestock-related vocalisations, 3 datasets were used for performance evaluation, targeting sheep, cattle, and Mareema Sheepdog vocalisations. The high classification results obtained indicated that the algorithm is multi-purpose in nature and can be successfully retrained to detect different vocalisation types.

With the successful development of an accurate classification component, functionality was extended into automated segmentation using an energy-based thresholding approach to acoustic event identification. A sophisticated codebase was developed in the C-programming language, capable of operating in an offline capacity. 700 hours of field recorded audio data underwent automated segmentation to identify the periods of highest acoustic activity. A test dataset containing sound events temporally dissimilar to the training data was created, allowing for the evaluation of the algorithm’s ability to operate in a changing acoustic environment. Results obtained from the test dataset revealed a highly accurate vocalisation detection algorithm, capable of successfully extracting and identifying sheep vocalisations. Although the algorithm performed well at classifying negative acoustic events, it was found to struggle with sounds possessing a similar spectral content and envelope to the target class (e.g., crow vocalisations). Following the successful development of the automated detection algorithm, all field recorded data was processed to classify segmented sound events, revealing the ratio of sheep vocalisations contained within each period.

The codebase developed for offline operation was extended to real-time deployment using the Advanced Linux Sound Architecture (ALSA). Prototype real-time livestock vocalisation detection hardware was produced and tested using pre-recorded audio data playback at varying distances from the capture sensor. During experimentation, the real-time system demonstrated high performance in detecting sheep vocalisations, and correctly rejected the majority of non-vocalisation acoustic events. The system experienced no data losses and did not enter any error states, indicating that the developed algorithm is computationally efficient enough to run on lowresource SBC hardware.

There are increasing calls by stakeholders to raise the standards of animal welfare across the livestock sector. The beef industry needs a way to demonstrate improvements in animal welfare over time. The enforcement of minimum standards can be effective in preventing poor welfare, but the ability to recognise, exemplify and reward those at the top end of the welfare continuum is currently lacking. Our perspective article outlines the benefits and challenges of taking a voluntary, producer-driven benchmarking approach to recording and improving animal welfare in Australian pasture-based beef cattle. We discuss considerations when selecting measures for use in this benchmarking approach, including their validity, reliability, feasibility and value. The assessment of the human–animal relationship is discussed as a worked example of balancing these considerations in a way that suits the extensive Australian beef cattle production environment. We propose that careful consideration at the development stage is required to produce a benchmarking system that is robust and fit for purpose. This will also facilitate the collection of clear, meaningful data to allow for transparency and accountability throughout the industry. Demonstration of successful welfare benchmarking of extensive beef cattle may enable the approach to be expanded across the supply chain and to other sectors of livestock production.

This thesis aimed to define a suitable definition of ewe longevity for the Australian sheep industry and determine the merit of incorporating the trait into the Australian sheep breeding objectives. Therefore, the fundamental requirements for incorporating ewe longevity in the Australian sheep breeding objectives, the genetic parameters and economic values were estimated for ewe longevity and stayability traits followed by an estimation of response to selection.

The first part of this thesis deals with the data exploration of the MERINOSELECT and LAMBPLAN maternal databases within the Sheep Genetics and the estimation of genetic parameters for the ewe longevity and stay ability traits in Merino and maternal breeds. The majority of the flocks submitting data to the MERINOSELECT and LAMBPLAN maternal databases do not have sufficient recording patterns to derive longevity. However, the contemporary groups with regular recording patterns were selected. The contemporary groups were defined as the site × flock × year of birth. These contemporary groups of ewes with regular recording patterns within the MERINOSELECT database were; 1) born since the year 2000, 2) had spent a minimum of 3 years in the flock, 3) had their own annual weight (weaning, postweaning or yearling) or wool record and reproduction record (from 2 yrs) up to 6 years of age, 4) contained at least 30 ewes, and 5) at least 70% of the animals were assigned a sire (chapter 3).The ewe longevity or time in flock (TIF) was defined as the period between birth and the last available production record. The stay ability traits were defined as the presence of a ewe in flock up to certain periods of time. The heritability estimates of the ewe's longevity and stayability traits were moderate if not corrected for the ewes’ production and reproductive performance. However, after correcting for these traits, the ewe's longevity and stayability traits were lowly heritable. The correlation between the ewes’ longevity and stayability traits was strong.

The correlation between ewe longevity and production and reproduction traits was estimated via a series of bivariate analyses. The analysed production traits were weaning weight (wwt), post-weaning weight (pwt), post-weaning C-site fat (pcf), post-weaning eye muscle depth (pemd), post-weaning faecal egg count (pfec), yearling weight (ywt), yearling Csite fat (ycf), yearling eye muscle depth (yemd), yearling faecal egg count (yfec), yearling greasy fleece weight (ygfw), yearling fibre diameter (yfd), adult greasy fleece weight (agfw) and adult fibre diameter (afd). The reproductive traits analysed were fertility (fert), litter size (ls), number of lambs born (nlb), ewe rearing ability (era) and number of lambs weaned (nlw). The ewes’ TIF was lowly heritable and correlated to the production and reproduction traits. Therefore, a breeding objective was to be formulated that considers longevity as an objective trait, which requires calculating the economic value of the ewes’ TIF trait.

The second part of this thesis deals with the estimation of economic value and response to selection. The economic value of the ewes’ TIF was large across the fine wool Merino, dual purpose Merino and maternal production systems. Ewe longevity has a positive correlation with the current breeding objectives suggesting that selection on the current breeding objectives will improve ewe longevity across the three production systems within the Australian sheep industry. However, including longevity trait in the breeding objectives will further increase the overall genetic gain, and particularly improve genetic gain for longevity. In the maternal production system, the genetic gain of the growth and carcase traits slows down a little after including the longevity trait in the breeding scenarios. The results showed a 2 to 3% increase in the total dollar response across the three production systems after incorporating the ewes’ TIF trait into the breeding objectives. However, incorporating genomic information of TIF into breeding objectives increased the overall response by 13 to 16% across three production systems. The results suggest that selection based on the current breeding objectives will improve ewe longevity within the Merino and maternal production systems but noticeably higher genetic gain can be attained if the genomic information of ewes’ TIF is incorporated into the breeding objectives.

The final chapter discusses the research findings and concludes with recommendations for future research areas. These recommendations include important encouragements like improving the data quality, the importance of recording culling reasons, estimating accurate genetic parameters of ewe longevity and the potential of incorporating the ewe longevity as a trait in the Australian sheep breeding objectives to achieve higher genetic gain. This thesis contributes significantly to define ewe longevity and using the genetic parameters in the Australian sheep breeding objectives.