Uterine Tube Resection by Vaginotomy as an Alternative to Ovariectomy in Mature Cattle

The prevention of pregnancy is desirable for female cattle destined for sale in the northern Australian rangelands for both economic and welfare reasons. Controlled access to bulls is often not feasible, nor are any non-surgical methods currently available. Many females are therefore surgically spayed. This study describes a technique for uterine tube resection (UTR), which leaves the ovaries intact and is performed using a vaginal approach, and compares the outcomes from 70 Brahman cows subjected to the procedure with 60 heifers spayed using the dropped ovary technique. The animals were monitored for 10 days following the surgery. There were no mortalities, and two animals were treated for illnesses after the UTRs and recovered. The animals subjected to both surgical procedures showed signs of pelvic discomfort and mild inflammation during recovery. The cows gained an average of 9.3 kg (SD 14.5 kg) of weight over the 10 days of the study compared to the spayed heifers, which lost 3.5 kg (SD 13.3 kg), with 19 and 63% of the animals in each of the groups losing weight, respectively. Uterine tube resection can be considered as a viable alternative to surgical spaying.

High frequency of delayed milk delivery to neonates in tropical beef herds

Beef-calf mortality rates across tropical and subtropical Australia are high, with sub-optimal nutrition in pregnant cows being the primary risk. The nutritional deficiencies associated with calf mortality are the same as those associated with reduced milk yields. Although the highest mortality risk occurs during neonatal life, the role of inadequate milk delivery to beef neonates is not well established. This study investigated the frequency of low milk delivery in tropically adapted neonatal calves and the time for their dams to initiate full lactation in five management groups of Brahman and Droughtmaster calving cows in the dry tropics of northern Queensland, Australia. Change in calf weight in the days following birth was the primary measure of milk uptake. Plasma globulin concentration was used to indicate colostrum uptake. Across management groups, data were available on 250 calves for regression analysis of average daily gain vs. globulin and on 78 for plotting calf growth profiles. Calves had one of two growth profiles, either with immediate high growth from birth (day one) or with high growth delayed until day three. The frequency of delayed growth calves (with inadequate milk intake to gain at least 0.5 kg by day three after birth) was on average 30% across management groups, with management groups ranging 25%-50%. The frequency of calves growing ≤0.2 kg/day to day three was 15%-37%, depending on management group. The frequency of calves growing ≤0.2 kg/day to day five was 7%-20%, depending on management group. Calf globulin explained only 25% of the variation in calf average daily gain. Our study shows that a third of tropically adapted calves may experience a three-day delay to initiation of full lactation by their dams. Although study conditions were relatively benign, any additional risks with milk delivery, such as those that occur widely in tropical and subtropical northern Australia, would place such calves at risk of dehydration and mortality. Calf plasma globulin should not be used as a standalone measure of adequacy of neonatal milk delivery, especially when comparing across herds. This study demonstrates a fundamental problem of high frequency in northern Australia. The underlying risks for delayed milk delivery should be considered in the quest for practical solutions to reduce tropically adapted beef-calf mortalities.

Opportunities to build resilience of beef cattle properties in the mulga lands of south-western Queensland, Australia

Beef producers in the mulga lands of south-western Queensland and north-western New South Wales, Australia, face the challenges of inherently low productivity and profitability, exacerbated by widespread pasture degradation and high climate and market variability. Our objective was to use the farm-management economics framework to assess the ability of management strategies and investment options to improve profitability and build the overall resilience of beef cattle properties in the mulga lands. Options were assessed for a hypothetical, representative beef cattle property in south-western Queensland (20 000 ha; initial stocking rate 600 adult equivalents). Firstly, strategies were assessed for their ability to improve profitability when operated as a beef business. Secondly, two alternative investment options were assessed: (1) conversion to rangeland meat goat production; and (2) conversion to carbon farming through carbon sequestration. Herd and economic modelling software were used to conduct property-level, partial discounted cash-flow budgets to assess each strategy over a 30-year investment period. Results indicated very limited potential to improve the profitability and resilience of an existing beef cattle enterprise in the mulga lands. However, full or partial conversion to rangeland meat goat production or carbon farming improved property-level returns and viability.

Periconception and First Trimester Diet Modifies Appetite, Hypothalamic Gene Expression, and Carcass Traits in Bulls

Nulliparous yearling beef heifers (n=360) were used to evaluate the effects of maternal dietary protein during the periconception and first trimester periods of gestation on postnatal growth, feedlot performance, carcass characteristics, and the expression of genes associated with appetite in the arcuate nucleus of their male progeny. Heifers were individually fed a diet of 1.18g crude protein (CP)/day High protein (HPeri) or 0.62g CP/day Low protein (LPeri) beginning 60days before conception. From 24 to 98days post-conception (dpc), half of each treatment group changed to the alternative post-conception diet and were fed 1.49g CP/day (HPost) or 0.88g CP/day (LPost) yielding four treatment groups in a 2×2 factorial design. From day 98 of gestation, heifers received a common diet until parturition. Calves were weaned at 183days and developed on pasture before feedlot entry. Bulls underwent a 70-day Residual Feed Intake (RFI) feedlot test commencing at 528days of age. Feedlot entry and final body weight (BW), feedlot average daily gain (ADG) and RFI were not different (p>0.05). Progeny of dams that had a change in diet (LPeri/HPost and HPeri/LPost) had 9% higher daily dry matter intake (DMI) during the RFI test (p<0.05) than progeny of dams that received low diet throughout both the peri-conception period and first trimester (LPeri/LPost). Further, mRNA expression of the appetite-stimulating agouti-related protein (AGRP) was increased in the arcuate nucleus of High Peri/LPost bulls (p<0.05). Longissimus dorsi muscle cross sectional area, carcass dressing percentage, and estimated retail beef yield (RBY) were all higher (p<0.05), and rump (P8) fat tended to be lower (p=0.07), for bulls from HPost dams despite no difference in carcass weight (p<0.05). This study is of commercial importance to the livestock industry as specific periods of maternal dietary supplementation may increase feed intake, enhance progeny muscling, and alter fat deposition leading to improvement in efficiency of meat production in beef cattle.

Comparison of Gene Editing Versus Conventional Breeding to Introgress the POLLED Allele Into the Tropically Adapted Australian Beef Cattle Population

Dehorning is the process of physically removing horns to protect animals and humans from injury, but the process is costly, unpleasant, and faces increasing public scrutiny. Genetic selection for polled (hornless), which is genetically dominant to horned, is a long-term solution to eliminate the need for dehorning. However, due to the limited number of polled Australian Brahman bulls, the northern Australian beef cattle population remains predominantly horned. The potential to use gene editing to produce high-genetic-merit polled cattle was recently demonstrated. To further explore the concept, this study simulated introgression of the POLLED allele into a tropically adapted Australian beef cattle population via conventional breeding or gene editing (top 1% or 10% of seedstock bulls/year) for 3 polled mating schemes and compared results to baseline selection on genetic merit (Japan Ox selection index, $JapOx) alone, over the course of 20 years. The baseline scenario did not significantly decrease the 20-year HORNED allele frequency (80%), but resulted in one of the fastest rates of genetic gain ($8.00/year). Compared to the baseline, the conventional breeding scenarios where polled bulls were preferentially used for breeding, regardless of their genetic merit, significantly decreased the 20-year HORNED allele frequency (30%), but resulted in a significantly slower rate of genetic gain ($6.70/year, P ≤ 0.05). The mating scheme that required the exclusive use of homozygous polled bulls, resulted in the lowest 20-year HORNED allele frequency (8%), but this conventional breeding scenario resulted in the slowest rate of genetic gain ($5.50/year). The addition of gene editing the top 1% or 10% of seedstock bull calves/year to each conventional breeding scenario resulted in significantly faster rates of genetic gain (up to $8.10/year, P ≤ 0.05). Overall, our study demonstrates that, due to the limited number of polled Australian Brahman bulls, strong selection pressure on polled will be necessary to meaningfully increase the number of polled animals in this population. Moreover, these scenarios illustrate how gene editing could be a tool for accelerating the development of high-genetic-merit homozygous polled sires to mitigate the current trade-off of slower genetic gain associated with decreasing HORNED allele frequency in the Australian Brahman population.

Maternal periconceptional and first trimester protein restriction in beef heifers: effects on placental parameters and fetal and neonatal calf development

Few studies have investigated the effects of nutrition during the periconception and early gestation periods on fetal and placental development in cattle. In this study, nulliparous yearling heifers (n=360) were individually fed a diet high or low in protein (HPeri and LPeri) beginning 60 days before conception. From 24 to 98 days after conception, half of each treatment group was changed to the alternative high- or low-protein diet (HPost and LPost) yielding four groups in a 2×2 factorial design. A subset of heifers (n=46) was necropsied at 98 days after conception and fetoplacental development assessed. Placentome number and volume decreased in response to LPeri and LPost diets respectively. Absolute lung, pancreas, septum and ventricle weights decreased in LPost versus HPost fetuses, whereas the post-conception diet altered absolute and relative liver and brain weights depending on sex. Similarly, changes in fetal hepatic gene expression of factors regulating growth, glucose output and lipid metabolism were induced by protein restriction in a sex-specific manner. At term, neonatal calf and placental measures were not different. Protein restriction of heifers during the periconception and early gestation periods alters fetoplacental development and hepatic gene expression. These changes may contribute to functional consequences for progeny, but this may not be apparent from gross morphometry at birth.

An economic framework to evaluate alternative management strategies for beef enterprises in northern Australia

Context Beef producers in northern Australia are continually presented with new technologies and opportunities to enhance beef production. They need to be able to accurately and efficiently assess the potential impact of alternative strategies on profitability, risk and the period of time before benefits can be expected. Aims Our aim was to demonstrate the value of the farm-management economics framework for assessing alternative management strategies applicable to beef cattle enterprises in northern Australia. Methods Beef cattle herd models incorporated into a farm-level partial discounted cash-flow framework were used to evaluate the potential effects of alternative management strategies on the performance of enterprises. This was undertaken using constructed, representative beef enterprises developed for the following three regions in Queensland: Central, Northern Downs and Northern Gulf, and the Katherine region of the Northern Territory. The analysis considered the expected response to change in the management of the base herd. Strategies that targeted (1) overall herd or property performance, (2) breeder reproductive performance, (3) steer growth rates, (4) alternative beef cattle marketing options, or (5) enterprise expansion were assessed. All of the changes considered to the current management strategy of the base herd and property were put forward by industry participants as potentially positive. Key results The framework efficiently identified substantial differences in net benefits among strategies and allowed ranking of the alternatives at the property level. Strategies that improved profitability also generally increased management complexity and financial risk. While strategies that could substantially improve profitability were identified, many other strategies were likely to reduce profitability at the property level. Key insights were gained into the time taken to implement the strategies, the complexity of implementation, and the level of financial risk incurred. Conclusions This study (1) demonstrated the appropriate framework to compare management options and support decision making, (2) efficiently indicated the potential range of outcomes, and (3) provided insight into the risks associated with development processes and technology adoption. Implications This farm-management economics framework could be used to assess alternative strategies for individual beef enterprises and to guide appropriate adoption of technology.

The effect of molasses nitrate lick blocks on supplement intake, bodyweight, condition score, blood methaemoglobin concentration and herd scale methane emissions in Bos indicus cows grazing poor quality forage

Context The Australian government has approved a greenhouse gas (GHG) offset method that requires cattle to consume nitrate in the form of a lick block. Field studies demonstrating the effectiveness of this methodology have not been previously reported. Aims This experiment was conducted to determine the effects on productivity and health when nitrate lick blocks were provided as a supplement to grazing beef cattle. We hypothesised that beef cattle given access to nitrate lick blocks would have similar productivity compared with cattle offered urea lick blocks. Methods Bos indicus breeding cows (n = 76) grazed a 467-ha paddock near Charters Towers, Queensland, between May and November 2014. A two-way remote automatic drafting system enabled allocation of cattle to different treatments while grazing in a common paddock. Treatments were 30% urea lick blocks (30U), or molasses nitrate lick blocks (MNB). At monthly intervals liveweight (LW), body condition score (BCS), and blood methaemoglobin concentration were recorded. Estimates of individual supplement intake were made on three separate occasions using a lithium marker technique. Results Mean daily supplement intake (±s.e.m.) of 30U (122 ± 13 g) was greater (P &lt; 0.001) than MNB (67 ± 8 g). Lesser MNB intake was associated with greater variability for individual supplement intake, a greater proportion of non-consumers of supplement during July (P &lt; 0.05) and reduced voluntary supplement intake until October (P &lt; 0.001). Increasing MNB consumption during October and November was accompanied by elevated blood methaemoglobin concentration (P &lt; 0.001). It was estimated that cattle offered MNB had insufficient supplementary nitrogen intake throughout the study to resolve rumen degradable nitrogen deficiency from grazed forage. Consequently, cattle provided access to MNB demonstrated conceptus free liveweight loss and lesser BCS compared with cattle treated with 30U (P &lt; 0.001). Conclusion Nitrate lick blocks were ineffective as a dual-purpose non-protein nitrogen supplement and methane mitigant for beef cattle grazing poor quality forage. Further field experiments are required to determine if there may be situations where this GHG offset methodology is efficacious. Implications Caution is advised in implementing GHG mitigation methods that involve the use of nitrate lick blocks.

GrazingFutures: learnings from a contemporary collaborative extension program in rangeland communities of western Queensland, Australia

Producer reliance on drought subsidies instead of proactive planning and timely destocking in low rainfall years has prompted Queensland government investment in promoting business and drought resilience. GrazingFutures (AU$6 million budget, 2016–2022) is an extension project focussed on enhancing business management skills of extensive livestock producers in western Queensland, Australia. The region’s rangelands are in productivity decline, span 1 million km2 and are managed by graziers operating more than 2400 livestock businesses (beef, sheep and goats). The Queensland Department of Agriculture and Fisheries delivers GrazingFutures as a component of the Drought and Climate Adaptation Program, in partnership with regional natural resource management groups and other public and private organisations. Project delivery emphasised upskilling multi-agency staff and livestock producers to promote practice change within three whole of business themes: (1) grazing land management; (2) animal production; and (3) people-business. Three independent surveys (2018, 2019, 2020) indicated positive practice change was occurring in grazing businesses as a consequence of the project. Graziers instigated management changes even under major environmental challenges including extended drought (2013–2020), an extreme flood event in 2019 and the COVID-19 pandemic in 2020. This paper details the rationale, progress against the objectives, challenges and future direction of the GrazingFutures extension project.

Calf loss in northern Australia: a systematic review

Calf mortality is a key issue for the north Australian beef industry; however, the sector faces several challenges that preclude the detection and reduction of calf mortality rates. A systematic literature review methodology was employed to explore scientific literature describing the scope of calf loss in northern Australia. Online databases were used to locate articles reporting on beef calf mortality rates within the north Australian region. Articles (n=43) consisting of 668 beef cattle cohorts were retrieved that reported calf mortality between 1936 and 2014. Of these, 13 different observation periods were identified. Most cohorts (n=201) examined mortality between the pregnancy to weaning period, whereas only 20 cohorts in four studies were located that investigated calf mortality in the perinatal and postnatal periods. A broad seasonal and regional influence was identified, however, the dilution of the datasets due to the high number of timeline variations, prevented robust statistical analysis and the further examination of influential factors, such as breed. The results of the systematic literature review indicate that the resolution of the data available does not allow for producers or researchers to accurately target the occurrence or cause of calf mortality. Experimental protocols for future research pertaining to reproductive efficiency and calf loss in northern Australia should be standardised. Consistency in reporting factors and periods must first occur for robust statistical analyses to be achieved.

Effects of wet season mineral nutrition on chital deer distribution in northern Queensland

Abstract ContextTo predict the success of an invasive species, it is important to understand the habitat factors that influence its distribution and abundance. In northern Queensland, chital deer (Axis axis) is an introduced ungulate that occupies specific areas over periods of several decades. AimsThe aim was to compare mineral concentrations in the soil and food plants of areas that chital occupy in high and low densities, and to assess mineral levels in blood sera. MethodsFaecal counts were used to identify areas of high and low chital density. Samples of soil and food plants were analysed from high- and low-density areas to determine the concentrations of 10 minerals from 32 collection sites. Laboratory examination was conducted on serum collected from 46 culled chital to evaluate mineral concentrations. Key resultsChital density varied markedly, with higher mineral concentrations found in soil and food plants in areas of high chital density compared with low-density locations. Average-ranked analyses indicated soil phosphorus levels were significantly (1.5×) higher in areas of high chital density, together with levels of Na (3.4×), Mg (2.3×), Mn (2.1×) and Fe (1.3×) in grasses that comprise more than 90% of the wet season (November to March) diet. Based on minimum requirements for ruminants, the concentrations of Na and Zn in grasses were suboptimal for chital. Serum Zn concentrations suggest a marginal deficiency in most of the animals sampled. ConclusionsMineral requirements of ungulates are such that deficiencies in availability of key nutrients may be sufficient to influence density and distribution. If there are deficiencies, the principal determinants of habitat selection are likely to be P in soil, and Na and Zn in food plants. Deficiencies of both Na and Zn in the diet may limit growth and reproductive output. Implications Mineral adequacy in the diet of chital may be a determinant of their current distribution and a predictor of the habitats they may successfully colonise in the future. Recognition of mineral nutrition as a habitat predictor may aid in the management of chital as a keystone species where it is native on the Indian subcontinent, and as an invasive species where it has become naturalised.

Nitrate supplementation has marginal effects on enteric methane production from Bos indicus steers fed Flinders grass (Iseilema spp.) hay, but elevates blood methaemoglobin concentrations

This experiment has quantified the methane abatement potential of nitrate in the context of extensively managed cattle. The experimental protocol consisted of two, 4 × 4 Latin square design using eight rumen fistulated Bos indicus steers fed Flinders grass (Iseilema spp.) hay ad libitum. The treatments were Control (nil nitrogen supplement), urea (32.5 g/day urea) and two levels of calcium nitrate: CaN1 and CaN2 (to provide 4.6 g and 7.9 g NO3/kg DM equivalent to ~0.46% and 0.80% of DM, respectively). Complete supplement intake was ensured by dosing any supplement that had not been voluntarily consumed, through the rumen fistula, 1 h after feeding. Enteric methane production was measured using open circuit respiration chambers. Methane yield (g/kg DM intake) from the CaN2 treatment tended to be lower (P < 0.07) than either the Control or urea treatments. There were no significant differences in methane yield between Control, urea or CaN1 treatments. Mean blood methaemoglobin concentrations were significantly (P < 0.001) higher for CaN2 animals compared with the Control, urea or CaN1 treatments. In addition, a significant time effect after dosing (P < 0.001) and a significant interaction between treatment and time after dosing (P < 0.001) was apparent. Overall mean total volatile fatty acid concentration was 74.0 ± 1.53 mM with no significant treatment effect, but a significant effect for both time of sampling (3 h vs 6 h) within days and among 7 sampling days. The inclusion of calcium nitrate as a non-protein-N source significantly reduced the molar proportions of butyrate (P < 0.001), iso-butyrate (P < 0.05) and iso-valerate (P < 0.001) compared with the Control. The provision of nitrate supplements, providing both a NPN and an alternative sink for H that would otherwise support enteric methanogenesis, has some potential. In extensive grazing systems effective methane abatement strategies are required. The elevated concentration of MetHb using CaN2 suggests that the strategy of replacing urea with nitrate in supplements fed to extensively managed cattle in the northern rangelands may be inappropriate where supplement intake cannot be controlled on an individual animal basis and forage quality is seasonally variable.

Influence of climate variability and stocking strategies on greenhouse gas emissions (GHGE), production and profit of a northern Queensland beef cattle herd

Previous studies of greenhouse gas emissions (GHGE) from beef production systems in northern Australia have been based on models of ‘steady-state’ herd structures that do not take into account the considerable inter-annual variation in liveweight gain, reproduction and mortality rates that occurs due to seasonal conditions. Nor do they consider the implications of flexible stocking strategies designed to adapt these production systems to the highly variable climate. The aim of the present study was to quantify the variation in total GHGE (t CO2e) and GHGE intensity (t CO2e/t liveweight sold) for the beef industry in northern Australia when variability in these factors was considered. A combined GRASP–Enterprise modelling platform was used to simulate a breeding–finishing beef cattle property in the Burdekin River region of northern Queensland, using historical climate data from 1982–2011. GHGE was calculated using the method of Australian National Greenhouse Gas Inventory. Five different stocking-rate strategies were simulated with fixed stocking strategies at moderate and high rates, and three flexible stocking strategies where the stocking rate was adjusted annually by up to 5%, 10% or 20%, according to pasture available at the end of the growing season. Variation in total annual GHGE was lowest in the ‘fixed moderate’ (~9.5 ha/adult equivalent (AE)) stocking strategy, ranging from 3799 to 4471 t CO2e, and highest in the ‘fixed high’ strategy (~5.9 ha/AE), which ranged from 3771 to 7636 t CO2e. The ‘fixed moderate’ strategy had the least variation in GHGE intensity (15.7–19.4 t CO2e/t liveweight sold), while the ‘flexible 20’ strategy (up to 20% annual change in AE) had the largest range (10.5–40.8 t CO2e/t liveweight sold). Across the five stocking strategies, the ‘fixed moderate’ stocking-rate strategy had the highest simulated perennial grass percentage and pasture growth, highest average rate of liveweight gain (121 kg/steer), highest average branding percentage (74%) and lowest average breeding-cow mortality rate (3.9%), resulting in the lowest average GHGE intensity (16.9 t CO2e/t liveweight sold). The ‘fixed high’ stocking rate strategy (~5.9 ha/AE) performed the poorest in each of these measures, while the three flexible stocking strategies were intermediate. The ‘fixed moderate’ stocking strategy also yielded the highest average gross margin per AE carried and per hectare. These results highlight the importance of considering the influence of climate variability on stocking-rate management strategies and herd performance when estimating GHGE. The results also support a body of previous work that has recommended the adoption of moderate stocking strategies to enhance the profitability and ecological stability of beef production systems in northern Australia.

Peri-conception and first trimester diet modifies reproductive development in bulls

Nutritional perturbation during gestation alters male reproductive development in rodents and sheep. In cattle both the developmental trajectory of the feto–placental unit and its response to dietary perturbations is dissimilar to that of these species. This study examined the effects of dietary protein perturbation during the peri-conception and first trimester periods upon reproductive development in bulls. Nulliparous heifers (n = 360) were individually fed a high- or low-protein diet (HPeri and LPeri) from 60 days before conception. From 24 until 98 days post conception, half of each treatment group changed to the alternative post-conception high- or low-protein diet (HPost and LPost) yielding four treatment groups in a 2 × 2 factorial design. A subset of male fetuses (n = 25) was excised at 98 days post conception and fetal testis development was assessed. Reproductive development of singleton male progeny (n = 40) was assessed until slaughter at 598 days of age, when adult testicular cytology was evaluated. Low peri-conception diet delayed reproductive development: sperm quality was lowered during pubertal development with a concomitant delay in reaching puberty. These effects were subsequent to lower FSH concentrations at 330 and 438 days of age. In the fetus, the low peri-conception diet increased the proportion of seminiferous tubules and decreased blood vessel area in the testis, whereas low first trimester diet increased blood vessel number in the adult testis. We conclude that maternal dietary protein perturbation during conception and early gestation may alter male testis development and delay puberty in bulls.

Assessing and mitigating post-operative castration pain in Bos indicus cattle

Cattle on pastoral land are subject to potentially painful husbandry procedures. In northern Australia, these practices generally occur once a year after the muster and the procedures are usually performed on animals older than 6 months of age. It is seldom that any pain mitigating medications are administered at this time and there is increasing concern that this perceived impost on the animal’s welfare will become more significant at both an economic and cultural level. There is a need to investigate the possibility of using simple, cost-effective, readily available medications, administered using relatively quick and easily taught techniques to increase the chance of industry adoption. This research used castration of 6–8-month-old Bos indicus calves as the test model because it is arguably one of the most common and most painful procedures endured by the animals. Forty-eight, 6–8-month-old Brahman bulls were surgically castrated after random assignment to six different treatment groups (n = 8): no castration Control (NC); castration (C); castration with post-operative meloxicam (CMpost-op); castration with lignocaine (CL); castration with lignocaine and post-operative meloxicam (CLMpost-op); castration with pre-operative meloxicam (CMpre-op). Serial measures of weight, blood cortisol concentrations, balk score, crush score, and daily activity (steps taken, number and duration of rest bouts) were taken. Linear mixed modelling was used to compare experimental groups. Bulls that were castrated and did not receive post-operative meloxicam (C and CL) had significantly lower average weights at all time points (Days 0–13, P < 0.001) of 170.9 kg and 168.6 kg, respectively, than those that did (CMpost-op and CLMpost-op) at 174.7 kg and 173.7 kg, respectively. When lignocaine was not administered before castration, Day 1 post-operative cortisol concentrations were significantly lower when post-operative meloxicam was provided than when it was not (CMpost-op: 47.2 nmol/L vs C: 65.5 nmol/L). When post-operative meloxicam was not given, animals that were given lignocaine before castration had significantly lower cortisol concentrations than those that received no lignocaine (CL: 52.7 nmol/L vs C: 65.5 nmol/L). Animals that were given pre-operative meloxicam had, on average, significantly lower Day 1 post-operative cortisol concentrations than animals that received no lignocaine or meloxicam (CMpre-op: 44.8 nmol/L vs C: 65.5 nmol/L). Analysis of Day 1 (the day following castration) data showed that animals that were given pre-operative meloxicam (CMpre-op) were significantly more active than animals in all other treatment groups (P = 0.038). It was concluded that 6–8-month old, Bos indicus bulls benefit from the administration of both lignocaine before surgery and peri-operative meloxicam. The analgesic methods used are readily adoptable by industry with respect to cost, efficiency and degree of technical skill required.

Climate Adaptation of Tropical Cattle

There is sustained growth in the number of tropical cattle, which represent more than half of all cattle worldwide. By and large, most research in tropical areas is still focused on breeds of cattle, their particular advantages or disadvantages in tropical areas, and the tropical forages or feeds that could be usefully fed to them. A consistent issue for adaptation to climate is the heat of tropical environments. Changing the external characteristics of the animal, such as color and coat characteristics, is one way to adapt, and there are several major genes for these traits. However, further improvement in heat tolerance and other adaptation traits will need to use the entire genome and all physical and physiological systems. Apart from the response to heat, climate forcing through methane emission identifies dry season weight loss as an important if somewhat neglected trait in climate adaptation of cattle. The use of genome-estimated breeding values in tropical areas is in its infancy and will be difficult to implement, but will be essential for rapid, coordinated genetic improvement. The difficulty of implementation cannot be exaggerated and may require major improvements in methodology.

The use of walk over weigh to predict calving date in extensively managed beef herds

Beef cattle reproductive rate in northern Australia is low and substantial effort is underway to make improvements. Collection of calf birth date to inform female reproductive rate data is often not practical. Therefore, there is a need to find alternative methods for collecting birth date data. The aim of the project was to trial an automated animal weighing technology (walk over weigh) to estimate calving date for cows in a northern breeding herd grazing in an extensive pasture system. Two-hundred and thirty-two Wagyu cows from a herd of 1195 with confirmed pregnancy tests were stocked in a paddock with a walk over weigh unit at the entry point of the water yard. Each calf born in the paddock was weighed, ear-tagged and a DNA sample collected. After processing, cleaning and smoothing the data, weight profiles of the 232 cows over a 119-day period were analysed. From the weight profiles and confirmed DNA parentage, 96 out of a possible 162 (59%) cows that calved had a correct calving date prediction. It is proposed that improvements in calving date prediction could be increased through engineering changes designed to slow cow movement over the walk over weigh unit. The trial demonstrated with the proposed changes that walk over weigh could be used to estimate calving date in extensive beef herds, with the expectation that this information could be used in genetic evaluation to improve reproductive rate in northern Australia.

The effect of earlier mating and improving fertility on greenhouse gas emissions intensity of beef production in northern Australian herds

Approximately 5% of Australian national greenhouse gas (GHG) emissions are derived from the northern beef industry. Improving the reproductive performance of cows has been identified as a key target for increasing profitability, and this higher efficiency is also likely to reduce the GHG emissions intensity of beef production. The effects of strategies to increase the fertility of breeding herds and earlier joining of heifers as yearlings were studied on two properties at Longreach and Boulia in western Queensland. The beef production, GHG emissions, emissions intensity and profitability were investigated and compared with typical management in the two regions. Overall weaning rates achieved on the two properties were 79% and 74% compared with typical herd weaning rates of 58% in both regions. Herds with high reproductive performance had GHG emissions intensities (t CO2-e t–1 liveweight sold) 28% and 22% lower than the typical herds at Longreach and Boulia, with most of the benefit from higher weaning rates. Farm gross margin analysis showed that it was more profitable, by $62 000 at Longreach and $38 000 at Boulia, to utilise higher reproductive performance to increase the amount of liveweight sold with the same number of adult equivalents compared with reducing the number of adult equivalents to maintain the same level of liveweight sold and claiming a carbon credit for lower farm emissions. These gains achieved at two case study properties which had different rainfall, country types, and property sizes suggest similar improvements can be made on-farm across the Mitchell Grass Downs bioregion of northern Australia.

Optimising beef business performance in northern Australia: what can 30 years of commercial innovation teach us?

This paper evaluates three decades of innovation by a leading beef producer in the Barkly region of the Northern Territory. The case study represents a rare published analysis of changes in production, greenhouse gas emissions and land condition metrics for a commercial livestock business. Thirty years ago the property was under-developed and had poor livestock productivity by today’s standards. Between 1981 and 2013, the business has increased carrying capacity through water point development, and achieved a >50% increase in herd size, a 46% improvement in weaning rate, an 82% reduction in breeder mortality rate and an improvement in land condition. Annual liveweight turn-off has increased from 75 kg to 128 kg per adult equivalent (AE) carried. All of this has been achieved while using recommended stocking rates. In contrast, two additional analyses reflecting other management approaches being taken by some north Australian beef businesses resulted in poor productivity, economic, emissions and land condition outcomes. Total greenhouse gas emissions have increased on the case study property since 1981 as a result of increasing herd size. However, the intensity of emissions per tonne of liveweight sold has declined by 43% due to the improvements in livestock productivity. The potential for generating carbon revenue from this emissions intensity improvement was explored. We found that for >95% of northern beef enterprises, current project transaction costs would entirely negate carbon revenue at a carbon price of < $25 tCO2e–1. At $5 tCO2e–1, the minimum herd size needed to cover the project transaction costs would be in excess of 35 000 AE. Although substantial carbon profits appear unlikely at present, the management practices evaluated can deliver substantial economic, emissions and land condition benefits to individual businesses and the wider industry. The paper concludes that cost-effective investment to concurrently increase herd size and livestock productivity per head, in conjunction with safe stocking rate management, is a proven path to economic and environmental sustainability in the north Australian beef industry.

The structure of a cattle stud determined using a medium density single nucleotide polymorphism array

Genetic progress depends on accurate knowledge of the genetic composition of a population or herd including level of inbreeding and parentage. However, in many circumstances, such as at an individual property level, the relationships between animals may be unknown, or at best, only partly known. In this study, we used DNA from 938 animals and genotypes from ~54 000 single nucleotide polymorphisms (SNP) to determine the genetic structure of a stud from Central Queensland. Animals on the study were bred using multi-sire mating in mobs of composite tropically adapted cattle of the Senepol, Belmont and Bonsmara breeds. Following genotyping using an array of 54 000 SNP, we were able to separate animals into breed groups using principal components and show that ~400 SNP were sufficient to separate animals into stable groups if the sample was genetically diverse. However, precise principal component values were only achieved when a few thousand SNP were used. We characterised the pedigree relationships between individuals using a genome relationship matrix. At least 3000 SNP were required to calculate accurate relationship coefficients between individuals. Around 19% of paired comparisons between animals showed similarity equivalent to sharing a great-grandparent or 1/64 shared ancestry. Approximately 8% of the individuals showed more than 10% inbreeding. To demonstrate the utility of calculating the relationship coefficients, we counted the tick burden on each animal at more than one time and then calculated the heritability of tick burden of h2 = 0.46 (±0.08). There was no significant genetic difference in tick burden between Belmont and Bonsmara cattle compared with Senepol on this property once a genetic relationship matrix was included to account for co-ancestry of individuals.

Heifer nutrient intake during early- and mid-gestation programs adult offspring adiposity and mRNA expression of growth-related genes in adipose depots

Changes in maternal nutrient intake during gestation alter IGF receptor abundance and leptin (LEP) mRNA expression in fetal adipose tissue. It is not known whether such changes persist into adult life and whether they are associated with an effect on phenotype. We investigated the effect of high (240%) and low (70%) levels of recommended daily crude protein intake for beef heifers during the first and second trimesters of gestation on singleton progeny (n=68): subcutaneous (SC) adipose tissue depth at rump (P8) and rib (RF) sites from 65 until 657 days of age; plasma leptin concentrations from birth until 657 days and expression of IGF1 and IGF2, their receptors (IGF1R and IGF2R) and LEP mRNA in perirenal (PR), omental (OM) and SC adipose tissue at 680 days of age. High-protein diets during the first trimester increased LEP and IGF1 mRNA in PR of males and females, respectively, compared with low-protein diets, and decreased IGF1R mRNA in SC of all progeny but increased RF depth of males between 552 and 657 days. High-protein diets compared with low-protein diets during the second trimester increased IGF1R mRNA in PR and OM of all progeny; LEP mRNA in PR of males; and IGF2 and IGF2R mRNA in OM of all progeny. Conversely, LEP mRNA in OM and IGF2 mRNA in PR of all progeny were decreased following exposure to high- compared with low-protein diets during the second trimester. Heifer diet during gestation has permanent sex- and depot-specific effects on the expression of adipogenic and adipocytokine genes and offspring adiposity.

Managing for rainfall variability: long-term profitability of different grazing strategies in a northern Australian tropical savanna

Several grazing strategies are recommended to manage sustainably for rainfall variability in northern Australia, but there is little objective data on their profitability relative to less sustainable management systems such as heavy stocking. In 1997, a large cattle grazing trial was initiated in northern Queensland to quantify the relative performance of a range of grazing strategies in a variable climate. These strategies were (i) moderate stocking (MSR) stocked at the calculated long-term carrying capacity (LTCC), (ii) heavy stocking (HSR) at twice LTCC, (iii) rotational wet-season spelling (R/Spell) at 1.5 LTCC, (iv) variable stocking (VAR), with stocking rates adjusted in May based on available forage and (v) a southern oscillation index (SOI)-variable strategy, with stocking rates adjusted in November based on available forage and SOI-based seasonal forecasts. Rainfall varied over the 12-year trial period, with sequences of dry and wet years. Gross margins (GM) in the HSR were initially high but collapsed in drier years due to high costs and reduced product value. GMs only recovered in later years with a reduced stocking rate and increased rainfall. The VAR and SOI were also initially very profitable, but GMs plunged as rainfall declined due to reduced animal performance and the sale of poor-condition cattle. This sharp cut in stocking rates nevertheless allowed GMs to recover well in subsequent years. In the MSR, GMs remained relatively constant across most years due to low costs and a higher product value. The R/Spell also performed relatively well despite being compromised by an ill-timed fire, drought and the subsequent sale of poor-condition cattle. Net present value (NPV) after 12 years was highest in the VAR ($11 962/100 ha), followed by the MSR ($11 873/100 ha), the SOI ($11 167/100 ha) and the R/Spell ($10 665/100 ha). NPV was by far the lowest in the HSR ($6930/100 ha). Profitability also varied the most in the HSR, with a negative GM in 6 of the 12 years. Incorporating the costs of natural resource decline would further reinforce the case against heavy stocking. These results challenge the assumption that sustainable management in a variable environment is unprofitable.

An economic case study of entire male grain-fed beef from a north-western Queensland production system

Assessing the differences in gross margins for a north-western Queensland beef-production system was undertaken using herd-budgeting software. The analysis reviewed the viability of producing beef for the domestic market from either a steer or bull production system. A hypothetical herd of 1200 breeders was created for the case study evaluation. An integrated beef production system from breeding to feedlot finishing was found to be less profitable for bull beef production than for steers at the current market prices. Although bull production was more profitable than steer production during the feedlot phase, the production of bulls in this phase failed to compensate for the earlier economic losses in the weaning phase of –AU$24.04 per adult equivalent for bulls. During the feedlot phase, bull production systems had lower break-even sale prices than did steer production systems. In reviewing two pricing scenarios for bulls, it was found that marketing bulls at the same price as steers was the most profitable production system. We conclude that the production of bull beef from a north-western Queensland production system can be profitable only if bulls can be sold without discount relative to steers.

A review of factors that impact on the capacity of beef cattle females to conceive, maintain a pregnancy and wean a calf-Implications for reproductive efficiency in northern Australia

A review of factors that may impact on the capacity of beef cattle females, grazing semi-extensive to extensive pastures in northern Australia, to conceive, maintain a pregnancy and wean a calf was conducted. Pregnancy and weaning rates have generally been used to measure the reproductive performance of herds. However, this review recognises that reproductive efficiency and the general measures associated with it more effectively describe the economic performance of beef cattle enterprises. More specifically, reproductive efficiency is influenced by (1) pregnancy rate which is influenced by (i) age at puberty; (ii) duration of post-partum anoestrus; (iii) fertilisation failure and (iv) embryo survival; while (2) weight by number of calves per breeding female retained for mating is influenced by (i) cow survival; (ii) foetal survival; and (iii) calf survival; and (3) overall lifetime calf weight weaned per mating. These measures of reproductive efficiency are discussed in depth. Further, a range of infectious and non-infectious factors, namely, environmental, physiological, breed and genetic factors and their impact on these stages of the reproductive cycle are investigated and implications for the northern Australian beef industry are discussed. Finally, conclusions and recommendations to minimise reproductive inefficiencies based on current knowledge are presented.

Dietary manipulation of Bos indicus x heifers during gestation affects the reproductive development of their heifer calves

The effect of nutrition during the first and second trimesters of pregnancy in composite beef heifers on reproductive parameters of their female calves was determined in the present study. At artificial insemination, heifers were assigned to one of four treatment groups (i.e. HH, HL, LowH and LL) depending on the level of crude protein intake (H = high; L = low) for first and second trimesters of pregnancy. Gonadotrophin concentrations and ovarian parameters were measured in their female calves at 5 and 23 months of age. Crude protein intake was positively associated with dam plasma urea (P < 0.001). The density of healthy follicles in heifers at the time of death was negatively correlated with dam plasma urea at Day 179 (P = 0.009). Heifers from LowH dams had a smaller-sized prepubertal largest ovarian follicle (P = 0.03) and lower densities of primordial and primary follicles (P = 0.02) and healthy antral follicles (P = 0.009) when they were killed. There was a positive correlation between plasma FSH concentrations at 5 and 23 months of age (P = 0.02), as well as between the sizes of the largest ovarian follicles at 6 and 23 months of age (P = 0.01). In conclusion, the reproductive development of heifers may be affected by prenatal nutrition during early and mid-gestation.

Dietary protein during gestation affects circulating indicators of placental function and fetal development in heifers

The influences of nutritional protein during the first and second trimesters of pregnancy on placental hormones and fetal growth were determined in composite beef heifers. At artificial insemination, heifers were stratified by weight within each composite genotype into 4 treatment groups: High High (HH=1.4kg crude protein (CP)/day for first and second trimesters of gestation; n=16), High Low (HL=1.4kg CP/day for first trimester and 0.4kg CP/day for second trimester; n=19), Low High (LH=0.4kg CP/day for first trimester and 1.4kg CP/day for second trimester; n=17) or Low Low (LL=0.4kg CP/day for first and second trimesters; n=19). Maternal plasma bovine pregnancy associated glycoprotein (bPAG) and progesterone (P4) were determined at gestation day (gd) 28, 82, 179 and 271 (mean gestation length 286 days) in addition to P4 at term. Estrone sulphate (ES) and bovine placental lactogen (bPL) concentrations were measured at gd 124, 179, 236 and 271 and at term in addition to ES at gd 82. Low dietary protein increased placental function as indicated by increased bPAG (P<0.001) and ES (P=0.02) concentrations in first trimester and increased bPL concentrations (P=0.01) in the second trimester of gestation. In the third trimester, when dietary treatment had ceased, placental function was no longer associated with previous dietary treatments. Dam genotype affected placental function as measured by bPL (P<0.001) and ES concentrations (P=0.02). Calf gender, heifer age and maternal insulin-like growth factor (IGF)-I, -II and leptin did not affect hormonal indicators or circulating markers of placental function. Enhanced placental function during the third trimester, as measured by ES, was associated with increased calf birth weight (P=0.003).

Managing for rainfall variability: effect of grazing strategy on cattle production in a dry tropical savanna

Rainfall variability is a challenge to sustainable and profitable cattle production in northern Australia. Strategies recommended to manage for rainfall variability, like light or variable stocking, are not widely adopted. This is due partly to the perception that sustainability and profitability are incompatible. A large, long-term grazing trial was initiated in 1997 in north Queensland, Australia, to test the effect of different grazing strategies on cattle production. These strategies are: (i) constant light stocking (LSR) at long-term carrying capacity (LTCC); (ii) constant heavy stocking (HSR) at twice LTCC; (iii) rotational wet-season spelling (R/Spell) at 1.5 LTCC; (iv) variable stocking (VAR), with stocking rates adjusted in May based on available pasture; and (v) a Southern Oscillation Index (SOI) variable strategy, with stocking rates adjusted in November, based on available pasture and SOI seasonal forecasts. Animal performance varied markedly over the 10 years for which data is presented, due to pronounced differences in rainfall and pasture availability. Nonetheless, lighter stocking at or about LTCC consistently gave the best individual liveweight gain (LWG), condition score and skeletal growth; mean LWG per annum was thus highest in the LSR (113 kg), intermediate in the R/Spell (104 kg) and lowest in the HSR (86 kg). Mean LWG was 106 kg in the VAR and 103 kg in the SOI but, in all years, the relative performance of these strategies was dependent upon the stocking rate applied. After 2 years on the trial, steers from lightly stocked strategies were 60–100 kg heavier and received appreciable carcass price premiums at the meatworks compared to those under heavy stocking. In contrast, LWG per unit area was greatest at stocking rates of about twice LTCC; mean LWG/ha was thus greatest in the HSR (21 kg/ha), but this strategy required drought feeding in four of the 10 years and was unsustainable. Although LWG/ha was lower in the LSR (mean 14 kg/ha), or in strategies that reduced stocking rates in dry years like the VAR (mean 18 kg/ha) and SOI (mean 17 kg/ha), these strategies did not require drought feeding and appeared sustainable. The R/Spell strategy (mean 104 kg/ha) was compromised by an ill-timed fire, but also performed satisfactorily. The present results provide important evidence challenging the assumption that sustainable management in a variable environment is unprofitable. Further research is required to fully quantify the long-term effects of these strategies on land condition and profitability and to extrapolate the results to breeder performance at the property level.

A systems evaluation of high-input management using fortified molasses for beef production in Australia's dry tropics

The potential of beef producers to profitably produce 500-kg steers at 2.5 years of age in northern Australia’s dry tropics to meet specifications of high-value markets, using a high-input management (HIM) system was examined. HIM included targeted high levels of fortified molasses supplementation, short seasonal mating and the use of growth promotants. Using herds of 300–400 females plus steer progeny at three sites, HIM was compared at a business level to prevailing best-practice, strategic low-input management (SLIM) in which there is a relatively low usage of energy concentrates to supplement pasture intake. The data presented for each breeding-age cohort within management system at each site includes: annual pregnancy rates (range: 14–99%), time of conception, mortalities (range: 0–10%), progeny losses between confirmed pregnancy and weaning (range: 0–29%), and weaning rates (range: 14–92%) over the 2-year observation. Annual changes in weight and relative net worth were calculated for all breeding and non-breeding cohorts. Reasons for outcomes are discussed. Compared with SLIM herds, both weaning weights and annual growth were ≥30 kg higher, enabling 86–100% of HIM steers to exceed 500 kg at 2.5 years of age. Very few contemporary SLIM steers reached this target. HIM was most profitably applied to steers. Where HIM was able to achieve high pregnancy rates in yearlings, its application was recommended in females. Well managed, appropriate HIM systems increased profits by around $15/adult equivalent at prevailing beef and supplement prices. However, a 20% supplement price rise without a commensurate increase in values for young slaughter steers would generally eliminate this advantage. This study demonstrated the complexity of profitable application of research outcomes to commercial business, even when component research suggests that specific strategies may increase growth and reproductive efficiency and/or be more profitable. Because of the higher level of management required, higher costs and returns, and higher susceptibility to market changes and disease, HIM systems should only be applied after SLIM systems are well developed. To increase profitability, any strategy must ultimately either increase steer growth and sale values and/or enable a shift to high pregnancy rates in yearling heifers.

Evaluation of carcass characteristics of Bos indicus and tropically adapted Bos taurus breeds selected for postweaning weight

Data from 9 studies were compiled to evaluate the effects of 20 yr of selection for postweaning weight (PWW) on carcass characteristics and meat quality in experimental herds of control Nellore (NeC) and selected Nellore (NeS), Caracu (CaS), Guzerah (GuS), and Gir (GiS) breeds. These studies were conducted with animals from a genetic selection program at the Experimental Station of Sertãozinho, São Paulo State, Brazil. After the performance test (168 d postweaning), bulls (n = 490) from the calf crops born between 1992 and 2000 were finished and slaughtered to evaluate carcass traits and meat quality. Treatments were different across studies. A meta-analysis was conducted with a random coefficients model in which herd was considered a fixed effect and treatments within year and year were considered as random effects. Either calculated maturity degree or initial BW was used interchangeably as the covariate, and least squares means were used in the multiple-comparison analysis. The CaS and NeS had heavier (P = 0.002) carcasses than the NeC and GiS; GuS were intermediate. The CaS had the longest carcass (P < 0.001) and heaviest spare ribs (P < 0.001), striploin (P < 0.001), and beef plate (P = 0.013). Although the body, carcass, and quarter weights of NeS were similar to those of CaS, NeS had more edible meat in the leg region than did CaS bulls. Selection for PWW increased rib-eye area in Nellore bulls. Selected Caracu had the lowest (most favorable) shear force values compared with the NeS (P = 0.003), NeC (P = 0.005), GuS (P = 0.003), and GiS (P = 0.008). Selection for PWW increased body, carcass, and meat retail weights in the Nellore without altering dressing percentage and body fat percentage.

Heifer fertility on commercial cattle properties in the Northern Territory

The performance of heifers at their first (maiden heifers) and second matings (first lactation heifers) was recorded between 2003 and 2008 to establish current heifer fertility levels on 14 commercial cattle properties in the Northern Territory (NT). Pregnancy rates in maiden heifers (joined first at ~2 years of age) were generally adequate (>75%) to produce enough pregnant replacement breeders. Pregnancy rates in first lactation heifers were often very low (<20%) due to the low liveweight of heifers between calving and weaning. However on properties where first lactation heifers were in good condition at this time, pregnancy rates were high (>70%). Calf loss between pregnancy diagnosis and weaning in first lactation heifers was often high (>30%). The average of the calf loss figures from all the herds studied was 22%.

Genetic options to replace dehorning in beef cattle—a review

Breeding polled cattle is a long-term solution to problems commonly associated with horned cattle. The current practice of dehorning does not eradicate the problem and is an animal-welfare concern. The present study reviews the current state of knowledge on the genetic basis of polled inheritance in cattle. The poll/horn condition is presumed to be under a relatively complex mode of inheritance whereby poll, scur, and African horn genes segregate independently, but interact with each other to produce polled, scurred, and horned animals. Molecular genetic studies have mapped the polled gene to a specific region on bovine chromosome 1 in Bos taurus animals, but the actual gene is still to be located. Scur and African horn genes have not been studied extensively at a molecular genetic level. With the current advances in molecular genetics and statistical methods, there is large scope to undertake new research programs to develop DNA tests that identify homozygous/heterozygous animals for poll, scur, and African horn genes. This would assist faster introgression of the polled condition into beef cattle populations. Existing scientific evidence to counter or support industry perceptions about the production-related issues of the polled condition are presented.

The impact of innovation on beef production in far northern Australia

In this paper we examine the forces that have shaped Australia’s far northern (north of 20° south) beef industry over the past 35 years. This is done for the purpose of tracing its transformation from a state of relative isolation to an integral part of the national beef industry. We note that integration is being accompanied by a greater focus, particularly by corporate producers, on specialised breeding in the far north and this is being assisted by innovations that increase herd fertility and raise the meat quality of the progeny, while retaining adaptation of the breeding herd to the local environment. Among a range of technologies, genetic improvement has significant potential to bring about rapid improvement in the meat quality of tropically adapted cattle. With respect to gene-based technology, however, independent producers will have to be convinced about the rigour of the technology and the prospects of economic gains before they make significant management changes. To this end, innovative marketing systems are needed that will reveal the link between expected meat returns and the offer prices applying to groups of growing cattle in any location. Accordingly, there is an urgent need to develop and introduce a descriptive and informative trading language for growing cattle that incorporates inherent qualities including those that influence meat quality. Innovations that will complement those applying to enhancement of meat quality are more general but will significantly raise herd productivity. We also compare the operating systems of both corporate and independent producers in the region.

The northern Australian beef industry, a snapshot. 5. Land and pasture development practices

The land and pasture development practices of 375 northern Australian beef properties in 8 regions were surveyed during 1996–97. These properties represented a broad cross-section of the beef industry in terms of geographical location, enterprise and herd size, and ownership structures. Both tree clearing and killing were more common in Queensland than in the Northern Territory or northern Western Australia. In all regions where trees were poisoned, native pasture was more widely used than sowing introduced grass and/or legume species. In contrast, tree clearing was most often accompanied by sowing pastures (either an introduced grass only or introduced grass and legume species together), rather than using native pastures. Central coastal Queensland had the highest use of poisoning trees for pasture development. Tree clearing and using native pasture was most important in central Queensland regions and the Maranoa South West. Sowing introduced pasture species under live trees was more commonly practiced in northern Queensland, the Northern Territory and northern Western Australia than in other regions. A considerable number of introduced grass and legume species were sown by producers. Most of the sown species were grasses. Many of the sown grass and legume species were spreading naturally. Buffel grass was spreading in all areas with < 1000 mm average annual rainfall, but most sown species were spreading only in wetter regions. Stylosanthes spp. were the most commonly spreading legume species in regions with > 500 mm average annual rainfall. The results are discussed in relation to contemporary natural resource management issues and how this may affect land and pasture development activities in the future.

The northern Australian beef industry, a snapshot. 1. Regional enterprise activity and structure

During 1996 and 1997, a survey examined the business activities of 375 selected northern Australian beef producers during the 1991 and 1992 to 1995 and 1996 financial years. The producers represented a broad cross-section of the northern beef industry in terms of geographical location, size of enterprise and herd, and ownership structures. The survey examined the enterprise structures and herd productivity of the participating properties. A diverse range of production activities were carried out with breeding and finishing, of which breeding stores and live cattle export being the most common activities. About 50% of the survey properties were run in conjunction with another property, both of which tended to be located in the same survey region. The additional properties served various purposes, depending on their location. There was evidence of specialist roles for the additional properties. The purchase of store cattle tended to be an opportunistic activity with younger cattle (<2 years old) being most preferred. Survey properties tended to target a range of markets; Northern Territory and northern Western Australian properties being the most likely to target a single market (live export). Aspiring to supply the slaughter markets was of greatest interest to Queensland beef producers. Aspiring to supply the USA manufacturing beef market was lowest where interest in live export was greatest. During the survey period, the USA manufacturing beef market, store and live cattle export markets were important outlets for cattle. Many herd and pasture-related improvements were planned to boost profitability in the 5 years post-survey (1997–2002). Increasing turn-off weight and branding rate, and decreasing turn-off age were of greatest interest to surveyed beef producers. Pasture improvement and improving pasture management also rated highly. The survey data indicated that the female genotype of the northern Australian herd had changed significantly over a 10- and 30-year period, with Bos indicus, Bos indicus cross and Taurindicus breeds being the most commonly reported breeds. The bull breeds present in regional herds suggest crossbreeding is occurring in conjunction with pure breeding. Most herds had more than 1 bull and female breed. Regional patterns were also found to exist for female and bull breeds with Bos indicus being common in herds in the northern parts of the survey area and Taurindicus breeds popular in southern herds. The results of this survey are discussed in relation to future developments in the northern Australian beef industry.

The northern Australian beef industry, a snapshot. 4. Condition and management of natural resources

Natural resource management practices were surveyed on 375 northern Australian beef properties in 8 regions during 1996–97. These producers represented a broad cross section of the beef industry in terms of geographical location, size of enterprise, and herd and ownership structures. More than 48% of producers reported land degradation (erosion, salinity, weeds, etc.) and >68% reported woody weeds on their properties. Eucalypt (Eucalyptus and Corymbia spp.) and wattle (Acacia spp.) regrowth were universally common native woody weeds. Parkinsonia (Parkinsonia aculeata) was widespread across all survey regions occurring with the greatest frequency in northern regions. A range of native and exotic woody weed species were regionally significant. Brigalow (Acacia harpophylla) regrowth was mainly reported in the central Queensland and Maranoa South West regions. Prickly acacia (Acacia nilotica) was mainly reported in central and north-west Queensland. Rubber vine (Cryptostegia grandiflora) was mainly reported in northern Queensland with a significant presence in central coastal and north-west Queensland. Infestations with multiple weed species were common. Although many producers reported the presence of problem woody weeds, only 3–29% indicated that weed management was practised. Most producers (67–100%) used fire. The intended purpose of fire varied across survey regions but fire was commonly used to reduce rank material, reduce fire risk, control woody weeds and for grazing management. Seasonal conditions and variability restricted fire use. Assessment by visual observation was a commonly used practice for determining stocking rate. Between 4–20% of producers were using visual observation combined with some form of calculation of stocking rate at the end of the growing season to determine stocking rate. A majority (>67%) of producers used some form of paddock spelling or regeneration practice. Many producers (47–89%) considered that they used conservative stocking rates. Carrying sufficient stock to meet income requirements was significantly (P<0.05) correlated with the percentage of producers reporting woody weeds as a problem on their property. In the 5 years preceding the survey, >66% of producers had increased the number of stock watering points, and more than 85% of producers had erected fencing. Most fencing was for new paddocks and laneways, or to replace old fences, and was not associated with new stock watering points. However, the installation of new stock watering points was associated with the creation of new paddocks. Planned future fencing focused on creating new paddocks or laneways or replacing old fences. The results are discussed in relation to contemporary natural resource management issues and the future approaches to and challenges of implementing sustainable rangeland management.