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The measurement and prediction of pasture intake in extensive grazing systems, typical of northern Australia, remain elusive after 50 years of research. The aim of this paper is to review research conducted over the past 50 years, highlight advances in understanding, discuss remaining challenges and consider future developments with digital technologies. While the fundamental components of voluntary intake are well understood, their measurement is difficult, particularly in extensive grazing systems, which has limited the development of predictive models that adequately address the interplay of factors influencing intake from the bite to the landscape scale. Ongoing research by the authors is used as an example to highlight the potential application of digital technologies to overcome limitations in measurement and prediction. Digital technologies offer the opportunity for monitoring factors that control voluntary pasture intake at scale and under commercial conditions. However, our ability to ground-truth novel indices of intake remains limited without ongoing development of physical methods. This will limit the accuracy and precision of predictive models incorporating digital technologies that can be applied to the extensive grazing conditions of northern Australia. The advent of precision livestock management for extensive cattle production is essential if the industry is to remain viable in the future where production is transparent, ethically sound and environmentally defensible as well as profitable. Feed intake is fundamental to animal performance and efficiency. Yet, for the cattle industry of northern Australia, our understanding of pasture intake is limited. While much is known about the components of feed intake, it remains difficult to integrate this knowledge into a dynamic and responsive estimation of voluntary intake under typical grazing conditions. This paper reviews the state of understanding, highlights gaps in knowledge and discusses the potential impact of digital technologies that will offer new solutions to old challenges. [ABSTRACT FROM AUTHOR]

Data concerning the practices and policies of collaborating properties for nutritional, breeding and health management of herds were captured by survey of herd owners/managers (n = 78) at the commencement of a large observational study conducted across northern Australia to identify and quantify the effect of major animal-, management group- and property-level risk factors on measures of reproductive performance. The cooperating herds in this study were considered to be broadly representative of north Australian beef breeding enterprises in terms of geography, size and ownership. Using four broad regional categories, this paper presents descriptive summaries of the management practices and nutritional conditions of cooperating herds in what was known as the Cash Cow project. Property sizes were largest within the Northern Downs and Northern Forest, and smallest within the Southern Forest. The expected average annual growth of yearling steers was >50 kg less in the Northern Forest, compared with the other country types, which also appeared to be associated with the identified production system and turnoff animal. Despite the exacerbated nutrition and environmental challenges and likely increased time required for new managers within the Northern Forest to attain an in depth understanding of the cattle and property dynamics, this region had the greatest incidence of management changes. The nutritional information summarised in this study highlights that available phosphorus during the wet season, as indicated by faecal levels in proportion to dietary energy, was likely to limit animal production within the Northern Downs and Northern Forest. During the dry season, pasture digestibilty and protein levels were likely to be approaching maintenance for cows on ~50% of properties in each country type and that responses to rumen degradable protein were also likely on 50% of properties. Despite this finding, low use of dry season supplements was observed for the Northern Downs, which was partially explained by the high incidence of the management systems based on segregating cows on lactation status and pregnancy. In all country types, the ratio of bulls to cows was higher than the 2.5% recommended for extensively managed situations, while limited use of vaccines to control infectious causes of reproductive loss was also observed. The major conclusion of this study is that there was marked variation in the adaption of interventions to specific businesses, indicating considerable opportunity exists for further adaptation in the region. A large epidemiological study known as the Cash Cow project was conducted in commercial beef breeding herds across northern Australia between 2007 and 2011 with the aim of determining and quantifying the effect of management, nutritional and environmental factors on reproductive outcomes. This paper describes results from survey questionnaires examining their nutritional, breeding and herd health management practices and policies completed by herd managers/owners of participating properties at the commencement of the study. [ABSTRACT FROM AUTHOR]

Context: The accuracy of estimated breeding values (EBVs) is an important metric in genetic evaluation systems in Australia. With reduced costs for DNA genotyping due to advances in molecular technology, more and more animals have been genotyped for EBVs. The rapid increase in genotyped animals has grown beyond the capacity of the current genomic best linear unbiased prediction (GBLUP) method. Aims: This study aimed to implement and evaluate a new single-nucleotide polymorphism (SNP)–BLUP model for the computation of prediction error variances (PEVs) to accommodate the increasing number of genotyped animals in beef and sheep single-step genetic evaluations in Australia. Methods: First, the equivalence of PEV estimates obtained from both GBLUP and SNP-BLUP models was demonstrated. Second, the computing resources required by each model were compared. Third, within the SNP-BLUP model, the PEVs obtained from subsets of SNP were evaluated against those from the complete dataset. Fourth, the new model was tested in the Australian Merino sheep and Angus beef cattle datasets. Key results: The PEVs of genotyped animals calculated from the SNP–BLUP model were equivalent to the PEVs derived from the GBLUP model. The SNP–BLUP model used much less time than did the GBLUP model when the number of genotyped animals was larger than the number of SNPs. Within the SNP–BLUP model, the running time could be further reduced using a subset of SNPs makers, with high correlations (>0.97) observed between the PEVs obtained from the complete dataset and subsets. However, it is important to exercise caution when selecting the size of the subsets in the SNP–BLUP model, as reducing the subset size may result in an increase in the bias of the PEVs. Conclusions: The new SNP-BLUP model for PEV calculation for genotyped animals outperforms the current GBLUP model. A new accuracy program has been developed for the Australian genetic evaluation system which uses much less memory and time to compute accuracies. Implications: The new model has been implemented in routine sheep and beef genetic evaluation systems in Australia. This development ensures that the calculation of accuracies is sustainable, with increasing numbers of animals with genotypes. The accuracy of estimated breeding values is routinely provided to breeders as part of genetic evaluations in Australia. A new method to approximate accuracies using genomic information has been developed and is presented in this paper. The new model has been implemented in Australia's routine sheep and beef genetic evaluation systems. This development ensures that the calculation of accuracies is sustainable with increasing numbers of animals with genotypes. [ABSTRACT FROM AUTHOR]

Context: There are multiple reports of high annual cow mortality rates in northern Australia, but no reports clearly indicating the overall rates and the impact of primary risk factors. Aims: The research aimed to determine which measured region-, property-, management group- and animal-level risk factors are associated with missing pregnant females. Methods: Risk factors for the annual rate of pregnant-cow mortality were investigated in an epidemiological study using outcomes for 21 554 cows from 52 beef herds in 2009 and 2010 in four primary country types within the mostly-dry tropical north Australian environment. Modelling of 2001–2011 Australian beef-herd statistics was used to corroborate and further quantify findings. Key results: In the epidemiological study, the overall predicted annual mean incidence of missing pregnant cows, a surrogate for mortality, was 10.9%, including lost tags and unrecorded cow movement that were estimated to constitute up to 9% missing cows. Risk factors associated with higher pregnant-cow mortality were as follows: not having follow-up rainfall more than 30 days after the first wet-season storms (4 percentage point increase); <2 t/ha of available pasture biomass in the early dry season (2–6 percentage point increase); pasture dry-season biomass <2 t/ha interacting with less than moderate mid-dry-season body condition score (3–10 percentage point increase); and, calving between April and September (non-significant trend for a 1–2 percentage point increase). Feed-quality measures did not affect mortality rate. Population modelling of Australian beef herd statistics suggested an average annual cow mortality rate in the Northern Forest region of ~7% compared with 2% in more nutritionally endowed regions. Conclusions: The major risk factor for cow mortality is under-nutrition, related either to generally-low soil fertility, seasonally-dry conditions, or management that exposes animals to poor nutrition. Annual mortality of pregnant cows appears 6–9 percentage points higher in the low-fertility Northern Forest region than elsewhere. Implications: Beef cow mortality is a major business cost in northern Australia. The efficacy of targeted management to achieve high cow performance was demonstrated by losses in a third of studied businesses in the Northern Forest being kept to the same or lower levels as median loss in endowed regions. An epidemiological study was conducted in commercial beef-breeding herds in northern Australia to determine and quantify the major associations between measures of performance and risk factors for herd management, nutritional, environmental and individual cow attributes. This paper presents the findings from the study using 21 554 pregnant cows in 52 herds that determined the major risk factors associated with those that went missing. This was supported by an analysis to calculate mortality rates using contemporary statistical data for the Australian beef herd. [ABSTRACT FROM AUTHOR]

Context: Sound reproductive efficiency is a key determinant for the overall productivity and profitability of a beef breeding business. Failure of a cow to conceive results in either culling or the cost of carrying non-pregnant animals. Aims: This study aimed to determine and quantify the major factors associated with non-pregnancy in commercial beef breeding herds of northern Australia. Methods: A prospective population-based epidemiological study of the likelihood of non-pregnancy in cows after an annual mating in northern Australian beef breeding cows used data from 73 herds from four broad country types and 62 323 animal years; approximately 80 property-, management-group- and cow-level risk factors were considered. A multivariable model building process was employed to scrutinise the resulting dataset, so as to identify what herd management practices, nutritional, environmental, and individual cow factors were associated with non-pregnancy and estimate their magnitude of effect. Key results: Non-pregnancy was disproportionately high in the Northern Forest (32.1%), compared with the Northern Downs, Central Forest and Southern Forest where it was 17.1%, 16.0% and 13.2% respectively. Time of expected calving had the largest impact on occurrence of non-pregnancy. Parity also had a significant influence, with first-lactation cows typically having 5–12% higher non-pregnancy than did mature cows. Non-pregnancy decreased with an increasing body condition score at the branding/weaning muster for lactating cows. The difference in non-pregnancy when comparing availability of wet-season pasture phosphorus content and digestibility of pasture during the dry season was 13.2 and 10.2 percentage points respectively. Conclusions: This study demonstrated the substantial impact environment, herd management practices, nutrition and disease factors can have on the reproductive performance of females. Implications: To optimise the efficiency of females (through reducing the occurrence of non-pregnancy) under commercial conditions in northern Australia, production systems should support beef herds calving early in the production year, being in at least moderate body condition and having access to more digestible pastures that address the nutritional requirements for both protein and phosphorus. This indicates focus for management, especially in the Northern Forest where the likelihood of non-pregnancy was highest. A large epidemiological study of annual pregnancy rate was conducted in commercial beef cattle breeding herds in northern Australia. The effect on non-pregnancy of the major herd management, nutritional and environmental risk factors and individual cow factors was determined and quantified. This paper presents the findings of the study designed to determine the major predictors of cows not achieving pregnancy. [ABSTRACT FROM AUTHOR]

Context: Sound reproductive efficiency is a key determinant for the overall productivity of a beef breeding business. For beef breeding herds to obtain high levels of reproductive productivity, breeding females need to efficiently become pregnant while lactating. Aims: This study aimed to determine and quantify the major factors associated with lactating cows becoming pregnant within 4 months of calving (P4M) in commercial beef breeding herds of northern Australia. Methods: A prospective epidemiological study was conducted using 78 commercial northern Australian beef breeding herds and involved 78 000 cattle that were monitored for 3–4 years. A multivariable model-building process was employed to scrutinise the resulting dataset to identify what herd-management practices, and nutritional, environmental and individual cow factors were major determinants of lactating cows becoming pregnant within 4 months of calving (P4M) and to estimate their magnitudes of effect. Key results: Overall, 41.6% of cows per production year were successful for P4M. Country type was strongly associated with 65.4%, 57.5%, 61.8% and 16.4% P4M for the Southern Forest, Central Forest, Northern Downs, and Northern Forest respectively. Between-year variability ranged between 3.3 and 11.7 percentage points. Cows calving in December–January (61%) had a substantially higher occurrence of P4M than did cows calving between July and September (15%). The difference in P4M when comparing availability of wet-season pasture protein and phosphorus was 12.7 and 20.3 percentage points respectively. Modelling of the impact of group seroprevalence and management group prevalence of recent infection with several infectious diseases was estimated, with a large negative association between group bovine viral diarrhoea seroprevalence and P4M suggested. Conclusions: This study further demonstrated the substantial impact that environment, herd management practices, nutrition and disease factors can have on the reproductive performance of females. Implications: To optimise the performance of females (through increasing the occurrence of cows contributing calves in consecutive years) under commercial conditions in northern Australia, herd managers should focus on maximising the proportion of cows within a herd calving at the desired time of the year, ensuring that any nutritional deficiencies and herd health issues are managed, and that cows are managed such that they are of good body condition score at the time of calving. An observational study was conducted in commercial beef breeding herds in northern Australia to determine and quantify the major associations between herd management, and nutritional, environmental and individual cow factors and measures of reproductive performance. This paper presents the findings of the study designed to determine the major predictors of lactating cows becoming pregnant within 4 months of calving. [ABSTRACT FROM AUTHOR]

Context: Dual-purpose wheat (Triticum aestivum L.) and canola (Brassica napus L.) crops have been extensively researched for grazing in Australian farming systems, with a focus on grazing by sheep. In some regions, dual-purpose crops have been grazed by cattle, but there have been reports of animal health problems. Aims: This paper sought to collate all known experiments conducted throughout Australia of cattle grazing dual-purpose crops, in order to evaluate grazing management options for cattle on dual-purpose crops that result in high growth rates and good animal health outcomes. Methods: There were six experiments. In Expts 1–3, cattle were grazed on wheat crops with and without available mineral supplementation of NaCl and MgO in a 1:1 ratio. In Expt 3, lime was also added to the mineral mix. In Expts 4 and 5, dual-purpose crops were grazed in combination with annual pastures to determine whether strategic use of dual-purpose crops could increase whole farm livestock productivity. In Expt 6, cattle were introduced to dual-purpose canola with different periods of adaptation (0, 4 and 7 days). Liveweight gain was monitored regularly to assess differences between adaptation treatments. Key results: Liveweight gain was increased by 0–27% when cattle grazing high quality, dual-purpose wheat were provided with mineral supplement. Cattle had an initial lag in growth rate when introduced to dual-purpose canola for grazing and this was not affected by the adaptation strategy used. Cattle that experienced a shorter adaptation period achieved higher weight gains more quickly. After the lag phase, average daily gain (ADG) was ≥2 kg/head.day, with an ADG over the entire grazing period for all treatments of 1.75 kg/head.day. The effect on the farm system was determined by extending the length of the grazing period on the dual-purpose crops. Grazing periods of shorter duration did not increase overall liveweight gains compared with grazing only pasture, whereas extending the period of dual-purpose crop grazing resulted in increased cattle weights. Conclusions: Cattle benefit from the addition of mineral supplements when grazing a dual-purpose wheat crop, with a response similar to that previously demonstrated in sheep. Cattle can safely graze dual-purpose canola and achieve high ADG. Inclusion of dual-purpose crops can improve overall cattle performance in the farming system. Implications: The potential area for production of dual-purpose crops within the Australian mixed farming zone is large and there may be insufficient livestock numbers within the zone to utilise the potential forage production. Cattle from other regions could be introduced during autumn and winter to realise this large forage potential during a period that is commonly a feed deficit on grazing-only properties. Estimates suggest that up to two million young cattle could be supported for 60 days, increasing liveweight by 90 kg/head. Beef cattle grazing dual-purpose crops on mixed farms can achieve high liveweight gains during periods of pasture deficit. Use of dual-purpose crops for beef production offers significant opportunity for the southern Australian beef industry. Growth rates of young cattle can be improved by appropriate mineral supplementation and livestock management. [ABSTRACT FROM AUTHOR]