ORCID Profile
0000-0001-6258-5014
Current Organisation
Queensland Department of Agriculture and Fisheries
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Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/AN17780
Abstract: There is widespread evidence that beef cattle land managers in Queensland are using stocking rates for perennial pastures that are substantially higher than recommended guidelines, and some indication that these decisions are motivated by perceived financial and economic benefits. Considerable effort has been, and is currently being, applied by public-sector organisations to encourage producers to reduce grazing pressure from beef cattle across Queensland’s pastoral lands. A better understanding of the relationships among stocking rate, land condition and profitability of beef-grazing enterprises is imperative to better inform cattle producers and policy makers. The present study assessed the effect of grazing pressure and land condition on the productivity and profitability of a steer-turnover enterprise utilising buffel grass (Cenchrus ciliaris) pastures in central Queensland. A property-level, regionally relevant herd model was used to determine whole-of-business productivity and profitability over a 30-year investment period. Growth paths for steers from weaning to marketing were developed for 16 scenarios encompassing a range of pasture-utilisation rates (30%, 35% and 50% of annual biomass growth), land condition (A, B and C) and market targets (feedlot entry at 474 kg or slaughter at 605 kg). The economic effect of each scenario was assessed by comparison to a base scenario of 30% pasture utilisation and turn-off of slaughter steers. Our analyses demonstrated a large economic advantage from increasing grazing pressure above 30% utilisation for buffel grass pastures, even with assumptions of declining land condition and animal performance. For instance, producing slaughter steers under a 50% pasture-utilisation regime with a continuous decline in land condition from A to C (and, hence, productivity) over Years 10–30 was AU$21 772/annum more profitable than was a 30% pasture-utilisation strategy, which is widely recommended as closer to a long-term, safe utilisation rate. The present research has provided insights into the relationship between grazing pressure and economic returns of beef producers over the medium term. However, it should be considered as a scoping study due to the paucity of data for effects of utilisation rate on the productivity of buffel grass pastures and, hence, on land-condition rating. Further research is required to better understand the effects of utilisation rate of buffel grass, and other sown pasture grass and legume species, on plant biomass production, plant-diet quality for cattle, land-condition decline and cattle productivity.
Publisher: CSIRO Publishing
Date: 14-12-2021
DOI: 10.1071/AN21422
Abstract: Context The semiarid rangelands of northern Australia have high climate variability and a history of suffering periodic severe droughts. To remain viable, livestock businesses in the rangelands need to build resilience to climatic and market variability by regularly producing a profit and increasing wealth. Aims Our aim was to use the farm-management economics framework to conduct a contemporary assessment of the profitability and resilience of alternative livestock enterprises in the semiarid rangelands of northern Australia. Methods Livestock options were examined for a constructed, hypothetical property representative of the central-western Queensland rangelands (16 200 ha long-term carrying capacity 1071 adult equivalents). First, the profitability of beef cattle, wool sheep, meat sheep and meat goat enterprises was assessed in a steady-state analysis using herd or flock budgeting models. Second, farm-level, partial discounted cash-flow budgets were applied to consider the value of integrating or fully adopting over time several of the alternative enterprises from the starting base enterprise of either a self-replacing (1) beef cattle herd or (2) wool sheep flock. Key results In the steady-state analysis of existing enterprises, meat sheep and rangeland meat goat enterprises produced the greatest rate of return on total capital (3.9 and 3.7% per annum respectively). The operating profit, of all self-replacing herds or flocks, was most sensitive to meat prices. Where full investment in a wild dog exclusion fence around the boundary of the property, and some refurbishment of existing infrastructure, was required to convert from beef to small ruminant production, the investment increased the riskiness and indebtedness of the overall enterprise. This was the case even when the long-term operating profit of the property could be substantially improved, e.g. by a change to rangeland meat goats (extra A$45 700 profit/annum). Conclusions Existing small ruminant enterprises in the semiarid rangelands of Queensland are profitable and resilient alternatives, based on contemporary prices. However, when changing from the predominant beef cattle enterprise, and incurring significant capital costs to do so, financial risk is substantially increased, which has implications for property managers. Implications The farm-management economics framework should be used by in idual grazing businesses for their specific circumstances, to support decision-making.
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/AN19088
Abstract: Context Phosphorus (P) deficiency occurs in beef cattle grazing many rangeland regions with low-P soils, including in northern Australia, and may severely reduce cattle productivity in terms of growth, reproductive efficiency and mortality. However, adoption of effective P supplementation by cattle producers in northern Australia is low. This is likely to be due to lack of information and understanding of the profitability of P supplementation where cattle are P-deficient. Aims The profitability of P supplementation was evaluated for two dissimilar regions of northern Australia, namely (1) the Katherine region of the Northern Territory, and (2) the Fitzroy Natural Resource Management (NRM) region of central Queensland. Methods Property-level, regionally relevant herd models were used to determine whole-of-business productivity and profitability over 30 years. The estimated costs and benefits of P supplementation were obtained from collation of experimental data and expert opinion of persons with extensive experience of the industry. The economic consequences of P supplementation at the property level were assessed by comparison of base production without P supplementation with the expected production of P-supplemented herds, and included the implementation phase and changes over time in herd structure. In the Katherine region, it was assumed that the entire cattle herd (breeders and growing cattle) grazed acutely P-deficient land types and the consequences of (1) no P supplementation, or P supplementation during (2) the dry season, or (3) both the wet and dry seasons (i.e. 3 scenarios) were evaluated. In the Fitzroy NRM region, it was assumed that only the breeders grazed P-deficient land types with three categories of P deficiency (marginal, deficient and acutely deficient), each with either (1) no P supplementation, or P supplementation during (2) the wet season, (3) the dry season, or (4) both the wet and dry seasons (i.e. 12 scenarios). Key results In the Katherine region, year-round P supplementation of the entire cattle herd (7400 adult equivalents) grazing acutely P-deficient pasture resulted in a large increase in annual business profit (+AU$500000). Supplementing with P (and N) only in the dry season increased annual business profit by +AU$200000. In the Fitzroy NRM region, P supplementation during any season of the breeder herd grazing deficient or acutely P-deficient pastures increased profit by +AU$2400–AU$45000/annum (total cattle herd 1500 adult equivalents). Importantly, P supplementation during the wet season-only resulted in the greatest increases in profit within each category of P deficiency, comprising +AU$5600, AU$6300 and AU$45000 additional profit per annum for marginal, deficient and acutely P-deficient herds respectively. Conclusions The large economic benefits of P supplementation for northern beef enterprises estimated in the present study substantiate the current industry recommendation that effective P supplementation is highly profitable when cattle are grazing P-deficient land types. Implications The contradiction of large economic benefits of P supplementation and the generally low adoption rates by the cattle industry in northern Australia suggests a need for targeted research and extension to identify the specific constraints to adoption, including potential high initial capital costs.
Publisher: CSIRO Publishing
Date: 2021
DOI: 10.1071/AN20125
Abstract: 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 in idual beef enterprises and to guide appropriate adoption of technology.
Publisher: CSIRO Publishing
Date: 2021
DOI: 10.1071/AN19691
Abstract: Context The large inter-annual and decadal rainfall variability that occurs in northern Australian rangelands poses major challenges for the profitable and sustainable management of grazing businesses. Aims An integrated bio-economic modelling framework (GRASP integrated with Breedcow and Dynama (BCD)) was developed to assess the effect of alternative grazing-management options on the profitability and sustainability of a beef cattle enterprise in the central-western Mitchell grasslands of Queensland over a multi-decadal time period. Methods Four grazing-management strategies were simulated over a 36-year period (1982–2017) in the GRASP pasture-growth model, using historic climate records for Longreach in central-western Queensland. Simulated annual stocking rates and steer liveweight-gain predictions from GRASP were integrated with published functions for mortality and conception rates in beef-breeding cattle in northern Australia, and then used to develop dynamic BCD cattle-herd models and discounted cash-flow budgets over the last 30 years of the period (1988–2017), following a 6-year model-equilibration period. The grazing-management strategies differed in the extent to which stocking rates were adjusted each year, from a common starting point in Year 1, in response to changes in the amount of forage available at the end of the summer growing season (May). They ranged from a low flexibility of ‘Safe stocking rate’ (SSR) and ‘Retain core herd’ (RCH) strategies, to a moderate flexibility of ‘Drought responsive’ (DR), to a ‘Fully flexible’ (FF) strategy. The RCH strategy included the following two herd-management scenarios: (1) ‘Retain herd structure’, where a mix of cattle were sold in response to low pasture availability, and (2) ‘Retain core breeders’, where steers were sold before reducing the breeder herd. Herd-management scenarios within the DR and FF strategies examined five and four options respectively, to rebuild cattle numbers and utilise available pasture following herd reductions made in response to drought. Key results Property-level investment returns expressed as the internal rate of return (IRR) were poor for SSR (–0.09%) and the three other strategies when the herd was rebuilt following drought through natural increase alone (RCH, –0.27% DR, –1.57% and FF, –4.44%). However, positive IRR were achieved when the DR herd was rebuilt through purchasing a mix of cattle (1.70%), purchasing pregnant cows (1.45%), trading steers (0.50%) or accepting cattle on agistment (0.19%). A positive IRR of 0.70% was also achieved for the FF property when purchasing a mix of cattle to rebuild numbers. However, negative returns were obtained when either trading steers (–2.60%) or agistment (–0.11%) scenarios were applied to the FF property. Strategies that were either inflexible or highly flexible increased the risk of financial losses and business failure. Property-level pasture condition (expressed as the percentage of perennial grasses %P) was initially 69%P and was maintained under the DR strategy (68%P average of final 5 years). The SSR strategy increased pasture condition by 25% to 86%P, while the RCH and FF strategies decreased pasture condition by 29% (49%P) and 65% (24%P) respectively. Conclusions In a highly variable and unpredictable climate, managing stocking rates with a moderate degree of flexibility in response to pasture availability (DR) was the most profitable approach and also maintained pasture condition. However, it was essential to economic viability that the property was re-stocked as soon as possible, in line with pasture availability, once good seasonal conditions returned. Implications This bio-economic modelling analysis refines current grazing-management recommendations by providing insights into both the economic and sustainability consequences of stocking-rate flexibility in response to fluctuating pasture supply. Caution should be exercised in recommending either overly conservative safe stocking strategies that are inflexible, or overly flexible stocking strategies, due to the increased risk of very poor outcomes.
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/AN16180
Abstract: This study measured forage biomass production, diet quality, cattle liveweight gain, and economic performance of six forage types at 21 sites across 12 commercial beef cattle properties in the Fitzroy River catchment of Queensland during 2011–2014 (28 annual datasets in total). The forages were annual forage crops (oats (Avena sativa), sorghum (Sorghum spp.) and lablab (Lablab purpureus)), sown perennial legume-grass pastures (leucaena-grass (Leucaena leucocephala spp. glabrata + perennial, tropical grass (C4) species) and butterfly pea-grass (Clitoria ternatea + perennial, C4, grass species)), and perennial, C4, grass pastures. The sown forages resulted in 1.2–2.6 times the annual cattle liveweight gain per ha than perennial grass pastures. Annual cattle liveweight gain per ha, forage establishment and management costs, and cattle price margin (sale price less purchase price, $/kg liveweight) all influenced gross margin, however, none was an overriding factor. The average gross margins ($/ha.annum) calculated using contractor rates, ranked from highest to lowest, were: leucaena-grass pastures, 181 butterfly pea-grass pastures, 140 oats, 102 perennial grass, 96 sorghum, 24 and lablab, 18. It was concluded that the tendency towards greater average gross margins for perennial legume-grass pastures than for annual forage crops or perennial grass pastures was the result of the combined effects of lower average forage costs and high cattle productivity.
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/AN15535
Abstract: The efficiency of microbial protein synthesis (EMPS) in cattle grazing a range of tropical pasture types was examined using a new method of intra-jugular infusion of chromium–EDTA to estimate urinary excretion of purine derivatives. Seven pasture types were studied in south-eastern Queensland, Australia, over a 13-month period. These included native tropical grass (C4) pasture (major species Heteropogon contortus and Bothriochloa bladhii) studied in the early wet, the wet–dry transition and the dry season introduced tropical grass (C4) pasture (Bothriochloa insculpta) in the mid-wet season two introduced tropical legume species (C3 Lablab purpureus and Clitoria ternatea) and the temperate-grass (C3) pasture, ryegrass (Lolium multiflorum). There was a large range in EMPS across pasture types, with a range of 26–209 g microbial crude protein per kilogram digestible organic matter intake (DOMI). Estimated rumen-degradable protein (RDP) supply (42–525 g/kg DOMI) was the major factor associated with EMPS across the range of pasture types studied. EMPS in steers grazing all tropical grass pastures was low (& g/kg DOMI) and limited by RDP supply. Negative linear relationships (P & 0.05) between EMPS and concentrations of both neutral detergent fibre and acid detergent fibre in extrusa were evident. However, non-fibre carbohydrate in extrusa, total non-structural carbohydrate concentration in plucked pasture leaf, rumen fluid and particle dilution rate, protozoal concentration in rumen fluid and rumen fluid pH were not correlated with EMPS. It was concluded that EMPS was well below 130 g microbial crude protein per kilogram DOMI when cattle grazed unfertilised, tropical grass pastures in south-eastern Queensland and that RDP was the primary limiting nutrient. High EMPS was associated with a very high RDP, vastly in excess of RDP requirements by microbes.
Publisher: Centro Internacional de Agricultura Tropical
Date: 31-05-2019
Abstract: Keynote paper presented at the International Leucaena Conference, 1‒3 November 2018, Brisbane, Queensland, Australia.In Australia’s central and southern Queensland regions, Leucaena leucocephala-grass pastures produce substantially more beef and higher profits than grass-only pastures and annual forage crops. Near infrared reflectance spectroscopy (NIRS) provides a rapid and cost-effective approach to assessing quality of available forage as well as the quality of the diet selected by cattle, but existing calibrations have not been comprehensively validated for leucaena-grass pastures. This study examined the reliability of existing northern Australian calibrations for NIRS to predict the crude protein (CP) concentration of the edible fraction of the leucaena plant, and the proportion of leucaena in the diet of grazing cattle. S les of edible leucaena and cattle faeces were analyzed by NIRS and the predictions plotted in a linear regression and fitted to a 1:1 line with Dumas analysis of CP for leucaena forage, and mass spectrometry of δ13C for cattle faeces. Results demonstrated that prediction of the CP concentration of leucaena forage and the proportion of leucaena in the diet of grazing cattle using current broad northern Australian NIRS forage calibrations were associated with substantial error. However, it is likely that these errors can be reduced with the inclusion in the calibration data set of more s les representing leucaena forage and faeces of cattle grazing leucaena from varying locations, seasonal conditions and management strategies.
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/AN18311
Abstract: Beef producers have to determine the best allocation of a limited resource of high-quality forage. This analysis assessed the most profitable way of incorporating high-quality forages into the whole-of-life steer growth path on forage systems in central Queensland, using property-level, regionally relevant herd models that determine whole-of-business productivity and profitability over a 30-year investment period. Twenty-two growth paths (liveweight change over time) from weaning to marketing were investigated for steers grazing buffel grass (Cenchrus ciliaris) pastures with and without access to leucaena–grass pastures (Leucaena leucocephala spp. glabrata + perennial, tropical grass (C4) species) or forage oats (Avena sativa) for varying intervals throughout their growth path. The production, economic and financial effect of each growth path was assessed by comparison to a base scenario that produced finished, slaughter steers (605 kg) from buffel grass pastures. The relative profitability of marketing steers at feedlot entry (feed-on) weight (474 kg) instead of slaughter weights was also assessed. The growth paths were applied within two beef enterprises, namely (1) steer turnover and (2) breeding and finishing. For both enterprises, grazing steers on leucaena-grass pastures from weaning until they achieved feedlot entry weight (474 kg) was substantially more profitable than any other growth path. Compared with the base scenario, this optimal growth path improved profitability by 121% and 37% for the steer turnover and the breeding and finishing enterprises respectively. The purchase of additional breeders for the latter enterprise was required to optimise utilisation of the leucaena–grass pastures immediately. Incorporating leucaena–grass pastures at any steer age improved the profitability of the steer turnover enterprise (AU$7368–AU$106508 extra profit/annum), and similarly for the breeding and finishing enterprise (AU$1754–AU$31383 extra profit/annum) except for two scenarios where leucaena–grass pastures were provided to older steers targeted at the feed-on market (AU$4816 and AU$23886 less profit/annum). However, incorporation of leucaena–grass into steer growth paths also resulted in increased peak deficit levels and financial risk to the business compared with buffel grass-only production systems, with payback periods for the most profitable growth path of 8 and 14 years for the steer turnover and the breeding and finishing enterprise respectively. All growth paths that incorporated forage oats and leucaena–grass resulted in lower economic and financial performance than did comparable growth paths that incorporated leucaena–grass only. Furthermore, incorporating oats into buffel grass-only growth paths always reduced the enterprise profitability. There was no relationship, across scenarios within an enterprise, between change in profit and the number of extra weaners produced or the amount of extra beef produced per hectare.
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/EA08161
Abstract: Remote drafting technology now available for sheep makes possible targeted supplementation of in iduals within a grazing flock. This system was evaluated by using 68 Merino wethers grazing dry-season, native Mitchell grass pasture (predominantly Astrebla spp.) as a group and receiving access to lupin grain through a remote drafter 0, 1, 2, 4 or 7 days/week for 8 weeks. The sole paddock watering point was separately fenced and access was via a one-way flow gate. Sheep exited the watering point through a remote drafter operated by solar power and were drafted by radio frequency identification (RFID) tag, according to treatment, either back into the paddock or into a common supplement yard where lupins were provided ad libitum in a self-feeder. Sheep were drafted into the supplement yard on only their first time through the drafter during the prescribed 24-h period and exited the supplement yard via one-way flow gates in their own time. The remote drafter operated with a high accuracy, with only 2.1% incorrect drafts recorded during the experimental period out of a total of 7027 sheep passes through the remote drafter. The actual number of accesses to supplement for each treatment group, in order, were generally less than that intended, i.e. 0.02, 0.69, 1.98, 3.35 and 6.04 days/week. Deviations from the intended number of accesses to supplement were mainly due to sheep not coming through to water on their allocated day of treatment access, although some instances were due to incorrect drafts. There was a non-linear response in growth rate to increased frequency of access to lupins with the growth rate response plateauing at ~3 actual accesses per week, corresponding to a growth rate of 72.5 g/head.day. This experiment has demonstrated the application of the remote drafting supplementation system for the first time under grazing conditions and with the drafter operated completely from solar power. The experiment demonstrates a growth response to increasing frequency of access to supplement and provides a starting point with which to begin to develop feeding strategies to achieve sheep weight-change targets.
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/AN15739
Abstract: Low values for the efficiency of microbial protein synthesis (EMPS) in cattle consuming tropical forages are related to low rumen degradable crude protein (RDP) intakes. This study examined the effect on the EMPS of the quantity and source of nitrogen (N) supplied to the rumen of eight entire and four rumen-fistulated Brahman steers consuming mature tropical grass hay (57.3 g crude protein/kg DM). Four treatment diets were fed in a Latin square design and included a basal diet of mature pangola grass (Digitaria eriantha) hay (control) and hay plus supplements estimated to provide 150 g RDP/kg digestible organic matter intake (DOMI), as urea or casein, or 300 g RDP/kg DOMI as casein. The EMPS was only increased (P 0.05) above that for the control diet (167 vs 123 g microbial crude protein (MCP)/kg DOMI) when RDP was provided at the highest rate of 293 g/kg DOMI. This increase was also associated with an ~4-fold increase in the concentration of NH3-N (277 vs 73 mg/L) and of branched-chain volatile fatty acids (44 vs 10 mmol/mol of total volatile fatty acids) in rumen fluid of the steers. However, the source of rumen degradable N (urea or casein) had no effect on the EMPS (109–115 g MCP/kg DOMI) when supplied at ~150 g RDP/kg DOMI. There was no effect of treatment on in vivo neutral detergent fibre digestibility (599 g/kg DM) or the rate (0.037/h) or extent (potential degradable fraction: 636 g/kg OM) of in sacco disappearance of pangola grass hay. In addition, rumen particle dilution rate was unaffected by treatment (0.022/h) and rumen fluid dilution rate, although showing some treatment differences (0.048–0.062/h), was poorly correlated with EMPS. It was concluded that only high amounts of RDP supply to the rumen, in the form of true protein, resulted in increased EMPS whereas at the lower intakes of RDP formulated to achieve EMPS in the range suggested in the feeding standards (130–170 g MCP/kg DOMI) there was no difference in providing the RDP as non-protein N or degradable-protein.
Publisher: Elsevier BV
Date: 2009
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/AR05182
Abstract: Estimates of microbial crude protein (MCP) production by ruminants, using a method based on the excretion of purine derivatives in urine, require an estimate of the excretion of endogenous purine derivatives (PD) by the animal. Current methods allocate a single value to all cattle. An experiment was carried out to compare the endogenous PD excretion in Bos taurus and high-content B. indicus (hereafter, B. indicus) cattle. Five Holstein–Friesian (B. taurus) and 5 Brahman ( 75% B. indicus) steers (mean liveweight 326 ± 3.0 kg) were used in a fasting study. Steers were fed a low-quality buffel grass (Cenchrus ciliaris 59.4 g crude protein/kg dry matter) hay at estimated maintenance requirements for 19 days, after which hay intake was incrementally reduced for 2 days and the steers were fasted for 7 days. The excretion of PD in urine was measured daily for the last 6 days of the fasting period and the mean represented the daily endogenous PD excretion. Excretion of endogenous PD in the urine of B. indicus steers was less than half that of the B. taurus steers (190 µmol/kg W0.75.day v. 414 µmol/kg W0.75.day combined s.e. 37.2 µmol/kg W0.75.day P 0.001). It was concluded that the use of a single value for endogenous PD excretion is inappropriate for use in MCP estimations and that subspecies-specific values would improve precision.
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/EA06145
Abstract: Grain feeding low bodyweight, cast-for-age (CFA) sheep from pastoral areas of eastern Australia at the end of the growing season can enable critical carcass weight grades to be achieved and thus yield better economic returns. The aim of this work was to compare growth and carcass characteristics for CFA Merino ewes consuming either simple diets based on whole sorghum grain or commercial feed pellets. The experiment also compared various sources of additional nitrogen (N) for inclusion in sorghum diets and evaluated several introductory regimes. Seventeen ewes were killed initially to provide baseline carcass data and the remaining 301 ewes were gradually introduced to the concentrate diets over 14 days before being fed concentrates and wheaten hay ad libitum for 33 or 68 days. Concentrate treatments were: (i) commercial feed pellets, (ii) sorghum mix (SM whole sorghum grain, limestone, salt and molasses) + urea and ammonium sulfate (SMU), (iii) SMU + whole cottonseed at 286 g/kg of concentrate dry matter (DM), (iv) SM + cottonseed meal at 139 g/kg of concentrate DM, (v) SMU + virginiamycin (20 mg/kg of concentrate) for the first 21 days of feeding, and (vi) whole cottonseed gradually replaced by SMU over the first 14 days of feeding. The target carcass weight of 18 kg was achieved after only 33 days on feed for the pellets and the SM + cottonseed meal diet. All other whole grain sorghum diets required between 33 and 68 days on feed to achieve the target carcass weight. Concentrates based on whole sorghum grain generally produced significantly (P 0.05) lower carcass weight and fat score than pellets and this may have been linked to the significantly (P 0.05) higher faecal starch concentrations for ewes consuming sorghum-based diets (270 v. 72 g/kg DM on day 51 of feeding for sorghum-based diets and pellets, respectively). Source of N in whole grain sorghum rations and special introductory regimes had no significant (P 0.05) effects on carcass weight or fat score of ewes with the exception of carcass weight for SMU + whole cottonseed being significantly lower than SM + cottonseed meal at day 33. Ewes finished on all diets produced acceptable carcasses although muscle pH was high in all ewe carcasses (average 5.8 and 5.7 at 33 and 68 days, respectively). There were no significant (P 0.05) differences between diets in concentrate DM intake, rumen fluid pH, meat colour score, fat colour score, eye muscle area, meat pH or meat temperature.
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/EA06189
Abstract: In parts of Australia, sorghum grain is a cheaper alternative to other cereal grains but its use and nutritive value in sheep feeding systems is not well understood. The aim of this work was to compare growth and carcass characteristics for crossbred lambs consuming several simple, sorghum-based diets. The treatments were: (1) whole sorghum grain, (2) whole sorghum grain + urea and ammonium sulfate, (3) cracked sorghum grain + urea and ammonium sulfate, (4) expanded sorghum grain + urea and ammonium sulfate, (5) whole sorghum grain + cottonseed meal, and (6) whole sorghum grain + whole cottonseed. Nine lambs were slaughtered initially to provide baseline carcass data and the remaining 339 lambs were gradually introduced to the concentrate diets over 14 days before being fed concentrates and wheaten hay ad libitum for 41, 56 or 76 days. Neither cracking nor expanding whole sorghum grain with added non-protein nitrogen (N) resulted in significantly (P 0.05) increased final liveweight, growth rates or carcass weights for lambs, or in decreased days on feed to reach 18-kg carcass weight, although carcass fat depth was significantly (P 0.05) increased compared with the whole sorghum plus non-protein N diet. However, expanding sorghum grain significantly (P 0.05) reduced faecal starch concentrations compared with whole or cracked sorghum diets with added non-protein N (79 v. 189 g/kg DM after 59 days on feed). Lambs fed whole sorghum grain without an additional N source had significantly (P 0.05) lower concentrate intake and required significantly (P 0.05) more days on feed to reach a carcass weight of 18 kg than for all diets containing added N. These lambs also had significantly (P 0.05) lower carcass weight and fat depth than for lambs consuming whole sorghum plus true protein diets. Substituting sources of true protein (cottonseed meal and whole cottonseed) for non-protein N (urea and ammonium sulfate) did not significantly (P 0.05) affect concentrate intakes or carcass weights of lambs although carcass fat depth was significantly (P 0.05) increased and the days to reach 18-kg carcass weight were significantly (P 0.05) decreased for the whole sorghum plus cottonseed meal diet. In conclusion, processing sorghum grain by cracking or expanding did not significantly improve lamb performance. While providing an additional N source with sorghum grain significantly increased lamb performance, there was no benefit in final carcass weight of lambs from substituting sources of true protein for non-protein N.
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/EA07412
Abstract: Remote drafting technology now available for sheep allows targeted supplementation of in iduals within a grazing flock. This paper reports results of three experiments. Experiment 1 examined the weight change of Merino wethers allowed access to either lupin grain or whole cottonseed 0, 1, 2 or 7 days/week for 6 weeks. Experiment 2 examined the weight change of Merino wethers allowed access to either lupins or a sorghum + cottonseed meal (CSM) supplement 0, 2, 4 or 7 days/week for 8 weeks. Experiment 3 investigated the relationship between five allocations of trough space at the supplement self-feeders (5–50 cm/sheep) and the weight change of Merino wethers allowed access to lupins 1 day/week for 8 weeks. In all experiments, the Merino wethers had free access as a single group to drinking water and low quality hay in a large group pen and were allowed access to supplement once per day on their scheduled days of access. No water was available in the areas containing supplement, but one-way flow gates allowed animals to return to the group pen in their own time. There was a linear response in growth rate to increased frequency of access to lupins in Experiments 1 and 2, with each additional day of access increasing liveweight gain by 26 and 21 g/day, respectively. Similarly, the response to the sorghum + CSM supplement was linear, although significantly lower (P 0.05), at 12 g/day. Providing access to whole cottonseed resulted in no significant change in growth rate compared with the control animals. In Experiment 3, decreasing trough space from 50 to 5 cm/sheep had no effect on sheep liveweight change. It was concluded that the relationships developed here, for growth response to increased frequency of access to lupins or a sorghum + CSM supplement, could be used to indicate the most appropriate frequency of access to supplement, through a remote drafting unit, to achieve sheep weight change targets. Also, that a trough space of 5 cm/sheep appears adequate in this supplementation system.
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/EA07414
Abstract: The rumen degradability parameters of the diet selected by two to four oesophageal-fistulated Brahman steers grazing a range of tropical pastures were determined by incubation of extrusa in nylon bags suspended in the rumen of rumen-fistulated (RF) Brahman steers. The effective protein degradability (Edg) was determined by measuring the rate of disappearance of neutral detergent insoluble nitrogen (NDIN) less acid detergent insoluble nitrogen (ADIN) in the incubated extrusa. Six to eight RF steers also grazed each of the pastures along with the oesophageal-fistulated steers, to allow determination of key rumen parameters and rumen particulate matter fractional outflow rates (FOR). The seven pastures studied included: native tropical grass (C4) pasture (major species Heteropogon contortus and Bothriochloa bladhii), studied in the early wet (NPEW), the wet/dry transition (NPT) and the dry (NPD) seasons introduced tropical grass (C4) pasture (Bothriochloa insculpta), studied in the mid wet season (BB) the introduced tropical legumes (C3), Lablab purpureus (LL) and Clitoria ternatea (BP) and the temperate grass (C3) pasture, ryegrass (Lolium multiflorum, RG). Using the measured particle FOR values in calculations, the Edg estimates were very high for both C4 and C3 species: 0.82–0.91 and 0.95–0.98 g/g crude protein (CP), respectively. Substitution of an assumed FOR (kp = 0.02/h) for the measured values for each pasture type did not markedly affect estimates of Edg. However, C4 tropical grasses had much lower effective rumen degradable protein (ERDP) fractions (23–66 g/kg DM) than the C3 pasture species RG and LL (356 and 243 g/kg DM, respectively). This was associated with a lower potential degradability and degradation rate of organic matter (OM) in sacco, lower in vitro organic matter digestibility (IVOMD) and CP concentrations in the extrusa, and lower ammonia-N and branched-chain fatty acid concentrations in rumen fluid for the tropical grasses. As tropical grass pastures senesced, there was a decline in Edg, the ERDP and rumen undegradable protein (UDP) fractions, the potential degradability and degradation rate of OM and the IVOMD. These results provide useful data for estimating protein supply to cattle grazing tropical pastures.
Location: Australia
No related grants have been discovered for Maree Bowen.