Showing papers in "Animal Production Science in 2004"
TL;DR: This paper summarises some plausible mechanisms by which variation in efficiency of nutrient use may occur and presents several testable hypotheses for such variation.
Abstract: There is a growing body of evidence that there is genetic variation in beef cattle feed intake relative to their liveweight and weight gain Difference in feed intake, above and below that expected or predicted on the basis of size and growth, is measured as residual feed intake Variation in residual feed intake must be underpinned by measurable differences in biological processes This paper summarises some plausible mechanisms by which variation in efficiency of nutrient use may occur and presents several testable hypotheses for such variation A companion paper [Richardson and Herd (2004) Aust J Exp Ag 44, 431–441] presents results from experiments on cattle following divergent selection for residual feed intake There were at least 5 major processes identified by which variation in efficiency can arise These are associated with variation in intake of feed, digestion of feed, metabolism (anabolism and catabolism associated with and including variation in body composition), activity and thermoregulation The percentage contribution of different mechanisms, to variation in residual feed intake, was: 9% for differences in heat increment of feeding; 14% for differences in digestion; 5% for differences in body composition; and 5% for differences in activity Together, these mechanisms may be responsible for about one-third of the variation in residual feed intake The remaining two-thirds were likely to be associated with heat loss due to variation in other processes, such as protein turnover and ion transport There is no shortage of candidate mechanisms that, singularly or in combination, might contribute to genetic variation in energy utilisation in ruminants Further research in beef cattle, to better define these mechanisms and enable their incorporation into breeding programmes, may lead not only to cattle which eat less for the same performance, but are superior in other traits as well
262 citations
TL;DR: It is hypothesised that high-RFI (low-efficiency) steers have higher tissue energy requirements, are more susceptible to stress and utilise different tissue substrates to generate energy required in response to exposure to a stressful stimulus.
Abstract: Residual feed intake measures variation in feed intake independent of liveweight and liveweight gain First generation steer progeny (n = 33) of parents previously selected for low or high post-weaning residual feed intake were examined to determine metabolic processes contributing to variation in residual feed intake Blood samples were taken from the steers from weaning through to slaughter These samples were analysed for key metabolites and hormones Total urine and total faecal collections were taken from the steers in an animal-house experiment to estimate dry matter digestibility, microbial protein production and protein turnover At weaning, there were phenotypic correlations between concentrations in plasma of β-hydroxy butyrate (r = 055, P 005) Neither the ratio of 3-methyl histidine : creatinine in urine, as a measure of rate of muscle breakdown, nor the dry matter digestibility measured in the animal house were correlated with residual feed intake in the animal house (r = 004, P>005), or residual feed intake over the whole experiment (r = –022, P>005), and neither were associated with genetic variation in residual feed intake It is hypothesised that high-RFI (low-efficiency) steers have higher tissue energy requirements, are more susceptible to stress and utilise different tissue substrates (partly as a consequence of differences in body composition) to generate energy required in response to exposure to a stressful stimulus
166 citations
TL;DR: The results confirm speculation that the unfavourable structure of dense subsoils can be improved by the biological action of perennial pasture roots, although reduced wheel traffic and cultivation during the pasture phases may also play a role.
Abstract: Biopores left in the soil by perennial and annual pastures and their effects on macroporosity, water infiltration and the water use and productivity of subsequent wheat and canola crops were investigated in a field experiment on a Sodosol in southern New South Wales. Phases of both lucerne (4 years) and phalaris (10 years) improved the macroporosity and water infiltration into the dense B horizon compared with continuous annual crops and pastures. After removal of lucerne and phalaris, the subsoil (> 12 cm depth) contained similar numbers of pores > 2 mm diameter (228 and 190/m2, respectively) compared with a mean of 68/m2 after annual crops. However water infiltration rate after lucerne was greater than after phalaris, apparently because of more numerous pores > 4 mm, rather than a change in total porosity. The subsoil after phalaris on the other hand contained more pores 0.3 mm in diameter and a higher total porosity, possibly because of more roots around this diameter, and a longer period without traffic or cultivation. The number of lucerne biopores in the subsoil remained unchanged (170–180/m2) for at least 2 crops after the lucerne was removed although the average size decreased. The volume of water extracted from the subsoil by crops following lucerne was similar to that following annual crop/pasture for 10 of the 12 crop comparisons made. For 2 of the crops, more subsoil water (22 and 24 mm) was used after lucerne than after annuals, and in 1 season this was associated with higher yield of canola. During the 3-year study there was no winter waterlogging or post-anthesis water stress, so there was little opportunity for yield responses to improved subsoil structure. The results confirm speculation that the unfavourable structure of dense subsoils can be improved by the biological action of perennial pasture roots, although reduced wheel traffic and cultivation during the pasture phases may also play a role. Further studies will be necessary to demonstrate associated yield improvements.
133 citations
TL;DR: Yield and oil content penalties due to delayed sowing were similar to those found previously in other Australian environments, while the decline of grain yield with delay in sowing date could be largely explained by the decline in biomass at maturity.
Abstract: Sowing date is an important determinant of yield in canola. The arrival at an optimum sowing time will depend on trade-offs between lowered frost risk with delayed sowing and lowered yield potential. A comprehensive analysis of response to sowing date has not been conducted for northern environments, a new region for canola production. The aim of this study was to analyse the response of phenology, yield and oil content of current cultivars of canola to sowing date (April–September) in north-eastern Australia, using 17 sowings from Tamworth (31.09°S) to Lawes (27.55°S). Three cultivars were studied: an early and late flowering canola and an advanced breeding line of Indian mustard. For all 3 genotypes, a delay in sowing shortened the time to 50% flowering and to maturity, while differences among the genotypes in time to flowering for sowing dates around 15 May reflected their known differences in phenological development. For sowings at Tamworth beyond 15 May, a 1 day delay in sowing delayed flowering by 0.42, 0.42 and 0.37 days in Indian mustard, Monty and Oscar, respectively. Delay in maturity was 0.58, 0.56 and 0.54 days per day delay in sowing date. Yield and oil content penalties due to delayed sowing were similar to those found previously in other Australian environments. The decline of grain yield with delay in sowing date could be largely explained by the decline in biomass at maturity, while for oil content it could be related positively to harvest index and seed size, and negatively to temperature conditions post-anthesis. Indian mustard had a lower harvest index, grain yield and oil content than both canola cultivars. Oil content exceeded 40% in canola in half of the sowings. Information on the response of oilseed Brassicas to sowing date can be used to quantify the trade-offs between frost risk and crop productivity with sowing date for different cultivar types.
79 citations
TL;DR: The definition of the term residual feed intake may be useful to interpret variation in production efficiency, but it does not help in obtaining a better selection response than selection on constituent traits alone.
Abstract: Residual feed intake is a linear function of feed intake, production and maintenance of liveweight, and as such is an attractive characteristic to use to represent production efficiency. The phenotypic and genetic parameters of residual feed intake can be written as a function of its constituent traits. Moreover, selection indices containing the constituent traits are equivalent with an index that includes residual feed intake. Therefore, definition of the term residual feed intake may be useful to interpret variation in production efficiency, but it does not help in obtaining a better selection response than selection on constituent traits alone. In fact, multiple trait genetic evaluation of constituent traits rather than residual feed intake is likely to be more accurate as this more appropriately accommodates different models for the constituent traits and missing data. For residual feed intake to reflect true biological efficiency in growing animals, it is important that feed intake and liveweight are accurately measured. Accounting for growth and body composition would significantly help in revealing between-animal variation in feed utilisation. Random regression models can be helpful in indicating variation in feed efficiency over the growth trajectory.
52 citations
TL;DR: A model beef cattle breeding scheme was used to evaluate the impact on genetic gain and profitability of incorporating feed intake measurements as an additional selection criterion in breeding programmes, with profit generally maximised where 10–20% of bulls were selected at weaning for measurement of intake.
Abstract: A model beef cattle breeding scheme consisting of a breeding unit and a commercial unit was used to evaluate the impact on genetic gain and profitability of incorporating feed intake measurements as an additional selection criterion in breeding programmes. Costs incurred by the breeding unit were compared with returns generated in the commercial unit, with bulls from the breeding unit being used as sires in the commercial unit. Two different market objectives were considered — a grass-fed product for the Australian domestic market, and a grain-fed product for the Japanese market. Breeding units utilising either artificial insemination or natural service were also considered. A base scenario was modelled incorporating a range of criteria available to Australian cattle breeders. A second scenario incorporated selection of sires for the breeding unit using a 2-stage selection process, with a proportion of bulls selected after weaning for measurement of (residual) feed intake. Measurement of feed intake of bulls improved accuracy of breeding unit sire selection by 14–50% over the equivalent base scenario, and genetic gain in the breeding objective was improved for all scenarios, with gains ranging from 8 to 38% over the base scenario. After accounting for the cost of measuring feed intake ($150–450), additional profit was generated from inclusion of feed intake measurement on a proportion of bulls for all breeding schemes considered. Profit was generally maximised where 10–20% of bulls were selected at weaning for measurement of intake, with improvement in profit ranging from 9 to 33% when optimal numbers of bulls were selected for intake measurement.
49 citations
TL;DR: In this article, the authors examined the potential for extended lactations on Victorian dairy farms in the context of (i) the advantages and disadvantages of existing seasonal milk production systems; (ii) projected future changes to Victorian dairy farming; (iii) the mechanics of extended lactation; and (iv) the change in costs associated with extended-lactation.
Abstract: This review examines the potential for extended lactations on Victorian dairy farms in the context of (i) the advantages and disadvantages of existing seasonal milk production systems; (ii) projected future changes to Victorian dairy farming; (iii) the mechanics of extended lactations; (iv) the change in costs associated with extended lactations; and (v) how extended lactations might be successfully implemented. Traditionally, Victorian dairying has been characterised by seasonal, low input, pasture-based milk production reliant on family labour. Successful implementation of this type of milk production system requires cows to calve in accordance with seasonal pasture supply. Recently a number of economic (static or falling milk prices), management (larger herds, increased labour expense, lower labour availability) and social pressures (animal welfare and environmental regulation) have emerged that question the viability of pasture-based dairying in a number of countries including Australia. Some of these threats to dairying may increase the attractiveness of systems that exploit the production potential of high yielding cows in larger herds, with increased supplementation of pasture-based diets over extended lactations. It is generally concluded that 12-month calving intervals are the most economic, based on the shape of the lactation curve and the perceived costs of extended lactations. However, these fundamentals have been changed by years of intensive selection for high milk production and the recent implementation of new management techniques such as Bovine somatotrophin, total mixed rations and increased milking frequency. Modern high yielding cows can maintain high daily yields for a much longer proportion of lactation than previously, but these cows are also largely unsuited to seasonal production systems due to a prolonged period of negative energy balance after calving and consequent low fertility. We have identified that calving and pregnancy incur substantial costs that are often hidden but need to be accounted for in valid economic comparisons. It is evident that seasonal pasture-based dairying requires disciplined management where certain tasks must be achieved in a timely manner if the system is to operate efficiently. Where the system does break down, often due to infertility for example, new management approaches are required. It is of concern that farmers may adopt a default position of extended lactations without realising or exploiting the potential benefits. Among the advantages of extended lactation management would be a more even spread in labour requirements, input costs and income across the year. In conclusion, extended lactations are a suitable option for some Victorian dairy enterprises. That suitability will depend on a number of factors; particularly, cow milk production potential, ability to grow pasture or feed supplements economically, management expertise, environmental constraints, herd size and labour availability.
42 citations
TL;DR: The results obtained so far show that expression profiling of bovine muscle using the microarray can reliably identify differentially expressed genes and confirm existing hypotheses and can provide new evidence on the detailed involvement of well-characterised genes.
Abstract: In order to gain new knowledge of the genetic control of biochemical and developmental processes that contribute to beef quality, we constructed a bovine microarray of 9600 elements comprising about 2000 expressed sequence tags (ESTs) and 7300 anonymous cDNA clones from muscle and fat-derived cDNA libraries. The microarray was used in 2 animal experiments aimed at uncovering gene expression differences associated with adipogenesis and protein turnover. The results obtained so far show that expression profiling of bovine muscle using the microarray can reliably identify differentially expressed genes and confirm existing hypotheses. Moreover, the technique can provide new evidence on the detailed involvement of well-characterised genes and can identify genes that have not previously been described as having a role in these processes.
41 citations
TL;DR: A simulation study of a grazed pasture indicated that grazing management may influence the partitioning of transpiration and evaporation from canopy, litter and bare soil, and pastures with lower evaporative losses are likely to have higher productivity and sustainability.
Abstract: Evapotranspiration is the major component of the hydrological balance of grazed pastures on the North-West Slopes of New South Wales, representing up to 93% of annual rainfall. Nearly 80% of evapotranspiration may occur as bare soil evaporation, however, representing water not available for plant growth. Few studies have reported daily values of actual evapotranspiration for pastures, particularly in northern New South Wales. The studies reported here were conducted to measure actual evapotranspiration using an evaporation dome technique, for plots with a range of pasture, litter and ground cover. Measurements were taken in each season between autumn 2000 and autumn 2001, with both wet and dry soil surface conditions, to document the range of values that might be expected. Similar measurements were conducted in areas of natural pasture, to quantify values under grazed conditions. A range of other variables were also quantified in association with each evapotranspiration measurement; these included components of net radiant energy, atmospheric conditions, pasture physical characteristics, ground cover and soil water content. These data were used to identify the most important variables, which may be influenced by or interact with grazing management, that account for variation in daily evapotranspiration values. Hourly evapotranspiration ranged from 0.02 to 0.82 mm/h and daily values ranged from 0.2 to 7.6 mm/day, in winter to summer, respectively. Linear regression models that included variables of solar radiation, herbage mass, vapour pressure deficit and soil water content accounted for up to 93% of the variation in daily evapotranspiration values. These models predicted that high litter mass (3000 kg DM/ha) may reduce evaporation by up to 1 mm/day for wet soils, making a substantial contribution to the annual hydrological balance. A simulation study of a grazed pasture, using the Sustainable Grazing Systems Pasture Model, indicated that grazing management may influence the partitioning of transpiration and evaporation from canopy, litter and bare soil. With rotational grazing, predicted soil evaporation was lower and transpiration and canopy evaporation were higher than with continuous grazing. Hence, pastures may require different management between summer and winter, so that bare soil evaporation and canopy interception losses are minimised, to maximise stored soil water available for pasture use. Pastures with lower evaporative losses are likely to have higher productivity and sustainability.
33 citations
TL;DR: It is concluded that ReTain application to 'Arctic Snow' nectarines can increase financial returns to growers through increased fruit size and quality benefits as well as maintain a higher flesh firmness following export.
Abstract: The effects ReTain Plant Growth Regulator (830 g in 1000 L water/ha) applied to a commercial block of 'Arctic Snow' nectarines 7 days before the first harvest was assessed in relation to harvest delay, fruit size, fruit quality (flesh firmness and brix), as well as the quality of the fruit following export to Taiwan. The untreated block (0.87 ha) and the ReTain-treated block (1.0 ha) were harvested according to the orchard's standard maturation criteria of background colour, size and percent blush colour. Based on picking schedules, the maturation of the ReTain block was delayed by 2.75 days (P<0.05). The fruit continued to grow during this delay and resulted in a 12.3% increase in yield and an increase of 393 packed cartons/ha. There were more (P<0.001) cartons of ReTain-treated fruit packed in grade sizes 69–78 mm diameter and less of smaller size classes (51–66 mm) compared with untreated fruit. The increase in both the number of cartons of class 1 fruit and fruit size on the ReTain block resulted in a Return on Investment (ROI) of 14.7 : 1 with an additional net return of AU$17 655/ha over the untreated block. There was a correlation between fruit size and flesh firmness with larger fruit being firmer than smaller fruit (P<0.001), however, packed ReTain-treated fruit was 3.2 N firmer on average (P<0.001) than packed untreated fruit for all size grades and from all harvests and packs. Brix levels increased (P<0.001) with fruit size but there was no difference (P = 0.568) between ReTain-treated fruit and untreated fruit. Two containers of fruit (early and late picks) were exported to Taiwan. The containers held a temperature of 0.5–2.0°C for the 14–15 day transit time from Australia to Taiwan. ReTain-treated fruit in both containers was 1.7 N firmer (P = 0.022) than untreated fruit upon arrival in Taiwan. After ambient storage (23°C) of fruit from container 1 for 45 h, fruit firmness declined (P<0.001) from an average of 65.7 to 43.2 N and there was no difference (P = 0.826) between treated or untreated fruit. It is concluded that ReTain application to 'Arctic Snow' nectarines can increase financial returns to growers through increased fruit size and quality benefits as well as maintain a higher flesh firmness following export.
31 citations
TL;DR: In this article, an economic evaluation was performed for various development options that could result in higher water use efficiency, increased profit, and meet the farm owners' objectives on an irrigated dairy farm in northern Victoria.
Abstract: A study was conducted to look at water use efficiency and profitability on an irrigated dairy farm in northern Victoria. For this case study farm, an economic evaluation was performed for various development options that could result in higher water use efficiency, increased profit, and meet the farm owners' objectives. Water use efficiency was defined as the amount of milk (kg milk fat plus protein) produced from pasture per megalitre of water (irrigation plus effective rainfall). The case study farm data indicated that between 1995–96 and 1998–99 there was no simple, direct association between water use efficiency and profitability. The development options considered included building a new dairy and increasing herd size and either increasing the area of irrigated pasture or intensifying on the existing irrigated area. The likely water use efficiency and economic efficiency were estimated for the various development options. The development budgets suggested that intensifying on the existing irrigated land was the most attractive option, if the predicted improvements in water use efficiency were achieved. This option had an internal rate of return of 64%, broke even after 5 years and was compatible with the objectives of the farm owners. Options that resulted in simultaneous increases in water use efficiency, profitability and labour efficiency appear to be more likely to be adopted than options that focus solely on increasing water use efficiency.
TL;DR: In this paper, the effects of nutrition, seasonal and climatic variation on marbling appearance and fat hardness are reviewed and linked to the visual appearance of marbling in cattle and cattle.
Abstract: Marbling refers to the appearance of white flecks of fatty tissue between muscle fibre bundles. The whiteness and opacity of the fat is important for visual assessment of marbling and depends on the crystallisation of the triacylglycerols within the fat cells. In the living animal, fat is in a liquid state. With chilling, the triacylglycerols undergo phase changes (solidify) and become opaque. The temperature at which this occurs is largely dependent upon the melting points of the individual fatty acids. Marbling fat can comprise a diverse range of fatty acids and each has an individual melting point (e.g. palmitoleic melts at 0°C; stearic melts at 70°C). The visual appearance of marbling will thus depend on the melting points of the constituent fatty acids at chiller temperature. The high melting point stearic acid can vary significantly in content across groups of cattle and has a major influence on the physical properties and visual appearance of marbling fat. The effects of nutrition, seasonal and climatic variation are reviewed and linked to marbling appearance and fat hardness.
TL;DR: Evidence in livestock suggests that graded production of pro-inflammatory cytokines during challenge with pathogens or subclinical infection can induce an incremental reduction in nutrient accretion in products of commercial value from livestock, highlighting the value of good hygiene and reduced stress to improved feed utilisation for growth.
Abstract: The pro-inflammatory cytokines, IL-1, IL-6, TNFα and IFN α/β, produced during immune activation and tissue injury, override control of nutrient utilisation by the hypothalamic-somatotropic axis. The many effects of these cytokines include induction of fever and sickness behaviour, reduced fatty acid uptake by adipose tissue, reduced protein synthesis and enhanced protein breakdown in skeletal muscle, and gluconeogenesis, increased fatty acid synthesis and synthesis of acute phase proteins in the liver. Resistance to the effects of insulin, GH and IGF-1 is induced in adipose tissues, liver and muscle, at least in part through induction by pro-inflammatory cytokines of SOCS proteins which inhibit signal transduction and activation of gene transcription via the JAK/STAT pathway. These homeorhetic changes mobilise nutrients to fuel host defence responses. While an understanding of the mechanisms contributing to the catabolic state have arisen largely from studies of sepsis, trauma and acute challenge with biological mediators of the acute phase response, recent evidence in livestock suggests that graded production of pro-inflammatory cytokines during challenge with pathogens or subclinical infection can induce an incremental reduction in nutrient accretion in products of commercial value from livestock. This relationship highlights the value of good hygiene and reduced stress to improved feed utilisation for growth.
TL;DR: In this paper, runoff plots were established on grazed pastures at three sites as part of the Sustainable Grazing Systems National Experiment (SGS NE), where a range of grazing management treatments were imposed to manipulate pasture herbage mass, litter mass and ground cover.
Abstract: Surface runoff can represent a significant part of the hydrological balance of grazed pastures on the north-west slopes of New South Wales, and is influenced by a range of rainfall characteristic, soil property, and pasture conditions. Runoff plots were established on grazed pastures at 3 sites as part of the Sustainable Grazing Systems National Experiment (SGS NE). Pastures were either native (redgrass, wallaby grass and wire grass) or sown species (phalaris, subterranean clover and lucerne) and a range of grazing management treatments were imposed to manipulate pasture herbage mass, litter mass and ground cover. Rainfall and runoff events were recorded using automatic data loggers between January 1998 and September 2001. Stored soil water in the surface layer (0-22.5 cm) was monitored continuously using electrical resistance sensors and automatic loggers. Pasture herbage mass, litter mass and ground cover were estimated regularly to provide information useful in interpreting runoff generation processes. Total runoff ranged from 6.6 mm at Manilla (0.3% of rainfall) to 185 mm at Nundle (5.7% of rainfall) for different grazing treatments, with the largest runoff event being recorded at Nundle (46.7 mm). Combined site linear regression analyses showed that soil depth, rainfall depth and rainfall duration explained up to 30.3% of the variation in runoff depth. For individual sites, these same variables were also important, accounting for 13.3-33.6% of the variation in runoff depth. Continuous monitoring of stored soil water in relation to these runoff events indicated that the majority of these events were generated by saturation excess, with major events in winter contributing substantially to regional flooding. Long-term simulation modelling (1957-2001) using the SGS Pasture Model indicated that most runoff events were generated in summer, which concurred with the number of flood events recorded at Gunnedah, New South Wales, downstream of the SGS sites. However, floods also occurred frequently in winter, but the simulations generated few runoff events at that time of the year. These results have important implications for sustainability of grazed pastures and long-term simulation modelling of the hydrological balance of such systems, since runoff generation processes are likely to vary both spatially and temporally for different rainfall events.
TL;DR: The results indicate that early life nutritional restriction has some influence on FCR in the feedlot, but little effect on those feed efficiency measures, such as RFI, that account for energy required for both maintenance of liveweight and growth.
Abstract: Records on 78 steers and heifers were used to determine relationships among different measures of growth, feed efficiency and carcass traits, and to evaluate the effects of 2 preweaning growth rates on growth and efficiency in a feedlot. The preweaning growth rates (g/day; 871 (high) or 466 (low)) were imposed on the steers and heifers for 115 days before they were weaned at a mean age of 220 days. They were 'backgrounded' for 7 months on high quality pastures before finishing on grain-based diets in a feedlot for 85 days. The cattle were then slaughtered and carcass measurements recorded. Estimates were made on 10 growth and feed efficiency indices during the feedlot, and 5 carcass traits were assessed at slaughter. Of the indices, the Kleiber ratio which does not require measurement of feed intake ( r = 0.98), was highly correlated with relative growth rate (RGR), as was feed conversion ratio (FCR, r = -0.82), which includes feed intake in the calculation. Residual feed intake, calculated using the expected feed intake estimated from the dataset (RFI REG ), was correlated ( r = 0.62) with RFI calculated from Australian feeding standards (RFI SCA ), and with FCR ( r = 0.45). FCR was not correlated with either carcass rib or hot P8 fat depths but was significantly correlated with carcass weight (0.39), dressing percentage (0.41) and eye muscle area (0.33). RFI REG was not correlated with any of the 5 carcass traits. Whilst the average daily gain in the feedlot was similar between the 2 preweaning groups (1.544 kg/day), the low group was significantly ( P <0.05) lighter at feedlot entry (323 v . 376 kg). Daily feed intake was lower ( P <0.01) in the low group (10.9 v . 11.8 kg) such that the FCR tended to be lower ( P <0.10) relative to the high group. Differences between the preweaning treatment groups were not significant for the other measures of feed efficiency. The results indicate that early life nutritional restriction has some influence on FCR in the feedlot, but little effect on those feed efficiency measures, such as RFI, that account for energy required for both maintenance of liveweight and growth.
TL;DR: The importance of the irrigated dairy industry to Australia, the production system, industry trends and some of the main challenges facing the industry are overviewed.
Abstract: The irrigated dairy industry is an important rural industry and confers significant social and economic benefits to Australia. The future prosperity of irrigated dairying will depend on the efficient use of water resources to overcome: (i) limited irrigation water availability, (ii) rising farm production costs, and (iii) the potential negative impacts of irrigation on the environment. This paper overviews the importance of the irrigated dairy industry to Australia, the production system, industry trends and some of the main challenges facing the industry.
TL;DR: AVG has major benefits as a harvest management tool, as it allows growers to regulate fruit ripening and differential delays for starch pattern index and fruit softening did not adversely affect the fruit quality of either apple variety.
Abstract: Aminoethoxyvinylglycine (AVG) was applied to Gala and Pink Lady apple trees on commercial orchards at label rates (830 g/ha ReTain with 0.1% v/v organosilicone surfactant) 21–28 days before anticipated first harvest. Fruit from treated and untreated trees in each orchard were sampled weekly during the commercial harvest period (2–6 times) and assessed for starch pattern index, background colour, soluble solids and flesh firmness. Ripening of AVG-treated Gala apples was delayed by 9–12 days based on starch pattern index and background colour whereas fruit softening was delayed by 5 days. Ripening of AVG-treated Pink Lady apples was delayed by 5 days based on SPI and fruit softening was delayed by 7 days. These differential delays for starch pattern index and fruit softening did not adversely affect the fruit quality of either apple variety, as there was no difference between the flesh firmness of treated and untreated fruit when fruit of the same starch pattern index were compared. Regardless of treatment, Gala apples grew an average 1.16 g per day during the harvest period whereas Pink Lady apples grew an average 0.22 g per day. These results suggest AVG has major benefits as a harvest management tool, as it allows growers to regulate fruit ripening.
TL;DR: This paper conducted an evaluation study with 100 graziers in Western Queensland to explore levels of knowledge and use of climate information, practices and information needs, and found that 36% of respondents apply the Southern Oscillation Index to property decisions but 92% were unaware that the predictive signal in the region is greater for pasture growth than rainfall, suggesting they may not recognise the potential of pasture growth forecasts.
Abstract: Researchers developing climate-based forecasts, workshops, software tools and information to aid grazier decisions undertook an evaluation study to enhance planning and benchmark impact. One hundred graziers in Western Queensland were randomly selected from 7 shires and surveyed by mail and telephone (43 respondents) to explore levels of knowledge and use of climate information, practices and information needs. We found 36% of respondents apply the Southern Oscillation Index to property decisions but 92% were unaware El Nino Southern Oscillation’s predictive signal in the region is greater for pasture growth than rainfall, suggesting they may not recognise the potential of pasture growth forecasts. Almost 75% of graziers consider they are conservative or risk averse in their attitude to managing their enterprise. Mail respondents (n= 20) if given a 68%, on average, probability of exceeding median rainfall forecast may change a decision; almost two-thirds vary stocking rate based on forage available, last year’s pasture growth or the Southern Oscillation Index; the balance maintain a constant stocking rate strategy; 90% have access to a computer; 75% to the internet and 95% have a fax. This paper presents findings of the study and draws comparisons with a similar study of 174 irrigators in the Northern Murray-Darling Basin (Aust. J. Exp. Ag. 44, 247-257). New insights and information gained are helping the team better understand client needs and plan, design and extend tools and information tailored to grazier knowledge, practice, information needs and preferences. Results have also provided a benchmark against which to measure project impact and have influenced the team to make important changes to their project planning, activities and methods for transferring technology tailored to grazier preferences.
TL;DR: Heritability estimates confirm that genetic progress will be faster when selection is based on IMF% rather than marble score, and there is a trend for marbling to become more important as a consumer issue in 5-star products where higher order sensory attributes of beef come into play.
Abstract: The biology of marbling is a considerable issue for the Australian beef industry. Measurement of the trait is still a concern: subjective assessment based on the degree of visual fat deposition and its distribution is the 'industry standard' and the basis for payment of marbling grades. Yet this measurement may be subject to operator error and is influenced by chiller temperature. Chemical extraction gives an unequivocal measure of all fat in the muscle (intramuscular fat percentage: IMF%) and has higher heritability and genetic variation than marble score; but does this mirror exactly what the trade regards as 'marbling'? Progeny test results from the Cooperative Research Centre (CRC) for Cattle and Beef Quality breeding projects provide improved understanding of breed and genetic effects on IMF% and marble score. Estimated breeding values (EBVs) for IMF% have been released to the industry for 7 breeds. Heritability estimates confirm that genetic progress will be faster when selection is based on IMF% rather than marble score. Genetic correlations of IMF% with growth, retail beef yield (RBY%), P8 fat, residual feed intake (RFI) and tenderness are now available to underpin selection indices. A favourable allele for marbling (TG5) on chromosome 14 has been identified by CSIRO/MLA as a direct gene marker for the trait. This is now being marketed as GeneSTAR marbling. Other favourable chromosomal regions are under investigation by the CRC. Nutritional manipulation of marbling remains problematic. It is accepted that high-energy grain diets achieve higher marbling than pasture diets. Within grain-based feedlot diets higher marbling is achieved with maize than barley, while barley diets in turn are better than sorghum. Steam flaking produces higher marbling than dry rolled grain and this effect is more marked with sorghum than maize. Beyond these establishments there are many uncertainties: experiments have examined the effects of diets with high protein; low protein; protected lipid; protected protein; added oil with and without calcium; vitamin A deficiency. None of these manipulations gave consistent improvement in marble score or IMF%. Commercial feedlots supplying Japanese B3/B4 markets may have successful dietary manipulations to enhance marbling but because of its proprietary nature the information is not normally available for scientific scrutiny. Japan is the only market for Australian beef where marbling is an important component of the market specification. There can be no doubt that marbling meets a special consumer preference in that niche market. In other markets scientific evidence for a link between marbling and beef tenderness or eating quality has been difficult to define (marbling is a key component of the USA grading scheme for primal cuts but Australia is not a big supplier to that market). In the domestic Meat Standards Australia market there is a trend for marbling to become more important as a consumer issue in 5-star products where higher order sensory attributes of beef come into play. Early meat science investigations concluded that beef flavour elements were water-soluble. This would exclude marbling fat as having a notable influence on flavour. Marbling remains the major determinant of carcass value in Australia's most valuable beef market. Research should continue to assist Australian producers to meet the specifications of that market with increased precision and reduced costs.
TL;DR: Both sheep and goats removed stem and flowering points preventing seed production within browse reach and also removed the new broom shoots over summer, whereas sheep preferred pasture once it became more abundant.
Abstract: Sheep and goats were allocated to 1.6 ha paddocks containing populations of scotch broom with 4-10% ground cover and grazed by either 4 sheep or 6 goats. Subjective scoring of defoliation and persistence was conducted at 4-8-weekly intervals over almost 2 years. While the sheep had minimal impact on the vigour of the broom plants, goats had a major impact when broom density was low (4% ground cover) but no impact when broom density was at 10% ground cover. This same pattern was evident for defoliation. Goats also stripped bark from broom stems during winter increasing broom ill thrift in goat paddocks. While sheep browsed up to 90 cm height, goats browsed up to 120 cm at low broom density. Both sheep and goats removed stem and flowering points preventing seed production within browse reach and also removed the new broom shoots over summer, whereas sheep preferred pasture once it became more abundant. Pasture availability was greater in goat-grazed paddocks over the flowering period and when new shoots were produced by broom. When broom seeds were fed to goats, 8% of the seeds remained viable following ingestion.
TL;DR: In this article, the authors used the Agricultural Production Systems Simulator (APSIM) to simulate the measured changes in soil water and mineral nitrogen, which was found to be useful in stimulating the learning of both farmers and researchers.
Abstract: Collaboration of researchers and service providers with farmers in addressing crop and soil management, using on-farm experiments and cropping system simulation, was negotiated in 2 districts in Central Queensland, Australia. The 2 most influential variables affecting crop productivity in this region (soil water and mineral nitrogen contents) and the growth of sown crops, were monitored and simulated for 3 years beginning in December 1992. Periodic soil sampling of large experimental strips on 3 farms, from paddocks that differed in cropping history and soil properties, provided robust datasets of change, over time, of soil water and mineral nitrogen status. Farmers participated in twice-yearly discussions with researchers, informed by the accumulating data, which influenced thinking about soil behaviour and possible new management strategies. As the study period coincided with a prolonged drought, so that cropping opportunities were few, the objectives of the work were modified to concentrate almost exclusively on the soil variables. The contribution of the Agricultural Production Systems Simulator, which was used to simulate the measured changes in soil water and mineral nitrogen, was found by all participants to be useful. The APSIM output generally demonstrated close correspondence with field observations, which raised confidence in its applicability to local cropping systems. Exploration of hypothetical situations of interest to farmer participants, in the form of what-if scenarios, provided insights into the behaviour of the production system for a range of soil and seasonal conditions. The informed speculation of the simulator became a substitute for the farmers' own, more tentative, efforts. The regular participative review sessions proved to be highly effective in stimulating the learning of both farmers and researchers. The farmers were able to feel comfortable as owners of the collaborative experiments and custodians of the learning environment. Clear evidence for the ongoing learning of these farmers appeared in post-collaboration practices and experiences.
TL;DR: Grazing of the purple capitula of nodding thistle by goats in lieu of pasture indicates the potential for mixed animal species grazing of weed-infested pastures.
Abstract: Goats and sheep grazed replicate plots of perennial pasture infested with nodding thistle (Carduus nutans). Neither goats nor sheep ate the vegetative thistle until it reached ~30 cm in diameter at which time goats consumed outer leaves on some plants. Active goat grazing commenced at flowering as the capitula matured from green to purple, with subsequent preferential grazing of the purple capitula in the presence of abundant pasture (2500 kg green DM/ha). The stage of maturation of the thistle influenced the proportion of purple capitula eaten by goats. Over the extended (5 month) 1991–92 flowering period induced by above average summer rain, dispersal of viable seeds was prevented in goat-grazed plots as goats ate 100% of the flowering stems. In the short 1992–93 flowering season (1.5 months) dry conditions resulted in seedheads rapidly maturing from green to brown. Goat numbers were insufficient to eat 100% of capitula as they reached the palatable stage. Consequently viable seeds were dispersed. Sheep consumed the thistle capitula only when pasture became limiting, allowing viable seeds to be dispersed in both flowering seasons. Spraying with non-lethal doses of herbicide increased the proportion of vegetative thistles consumed by both sheep and goats. Goats selectively removed maturing capitula then grazed the stems of the nodding thistle. As goats consumed thistle capitula throughout the flowering period, the quantity of pasture in goat plots exceeded that in sheep plots, principally due to an increase in the proportion of clover. The stocking density of goats required to control nodding thistle is proportionate to the level of weed infestation and must be modified as a response to prevailing seasonal conditions and rate of removal of purple capitula. Grazing of the purple capitula of nodding thistle by goats in lieu of pasture indicates the potential for mixed animal species grazing of weed-infested pastures.
TL;DR: The results indicate that a deficiency of metabolisable amino acids contributes to the low milk protein concentrations recorded during summer–autumn in south-west Australia.
Abstract: Low concentrations of protein in milk occur during the summer–autumn in south-west Australia. This is the period, on dryland farms, when the diet of lactating cows typically consists of grass silage and a mixture of crushed lupins and cereal grain. This experiment was conducted to test the hypothesis that supplying protected canola meal would increase the protein concentration of milk and, possibly, milk yield in cows fed grass silage and a lupin–cereal concentrate. Sixty Holstein cows in mid lactation were allocated to 2 equal-sized dietary treatment groups: control (lupin) or protected canola meal. The control diet consisted of 14.5 kg DM grass silage (annual ryegrasses–subterranean clover) and 5.4 kg DM of crushed lupins and barley (4:1) per head per day. For the protected canola meal diet, 2.15 kg DM protected canola meal replaced 2.15 kg lupins. The protected canola meal was produced by treating solvent-extracted canola meal with formaldehyde, to produce a product with an in sacco fractional degradability of 0.29 at a rumen fractional outflow rate of 0.08/h. The equivalent degradability of untreated canola meal was 0.80 and of lupin was 0.83. Cows were individually fed the concentrate ration twice daily, after each milking, then were managed as a single herd in dry lots and fed grass silage. By the end of 8 weeks, cows fed the protected canola meal diet had higher milk protein concentrations (30.7 v. 29.2 g/L; P 0.10). Fat concentration was unaffected by diet (P>0.05). Since the only difference in treatment was the replacement of a portion of lupins with protected canola meal, the results indicate that a deficiency of metabolisable amino acids contributes to the low milk protein concentrations recorded during summer–autumn in south-west Australia. Whether this was acting primarily through a stimulus of appetite, or directly on milk components, could not be determined because silage intakes were not recorded.
TL;DR: In this paper, the authors investigate the growth of high density maize for fodder production through thinning and subsequent grain yield, and show that with particular maize densities and thinning regimes, production of both fodder and grain is possible.
Abstract: Maize (Zea mays L.) plant density is an important management practice for successful grain and forage production. The objective of this study was to determine the most suitable maize seeding and time of thinning maize as fodder in grain maize crops. Previously the focus in this area has been on grain and silage production, and consequently information on the production of fodder in grain maize crops is limited. This study therefore aims to investigate the growth of high density maize for fodder production through thinning and subsequent grain yield. A plant density experiment in randomised complete block design was carried out at Egerton University, Njoro, using a Kenyan hybrid (H511) where 4 densities (44 444, 88 888, 177 777 and 355 555 plants/ha) and 4 thinning regimes (V4, V6, V10 and VT phenological stages) were used. The densities vary through number of seed per hill (i.e. 1, 2, 4 and 8 seeds/hill, not row or plant spacing) and spacing of 30 cm between the hills within the row and 75 cm between the rows was used. Maize plants were thinned following the appropriate thinning regime to leave 1 plant per hill, giving a plant density of 44 444 plants/ha in all treatments after thinning. Their biomass was then determined. The single plants per hill left, as a normal farmers practice, were used to determine grain yield at harvest. Plant density of 355 552 plants/ha, with a treatment structure of 4 seeds/hill and thinned at the VT phenological stage gave the highest thinning biomass per hectare, while 44 444 plants/ha, with a treatment structure of 1 seed/hill and no thinning, gave the highest grain yield. The thinning regime of the V10 phenological stage and 2 seeds/hill thinned at the VT phenological stage gave appreciable amount of fodder and grain yields. This study has shown that with particular seeding densities and thinning regimes, production of both fodder and grain is possible.
TL;DR: Dam/litter units converged completely for daily feed intake immediately in the postnatal stage, during a period of negative energy balance when feed intake and rate of gain were both maximised.
Abstract: Females from lines of mice divergently selected for post-weaning net feed intake maintained significant line differences in daily feed intake (0.8 g/day difference, 22%) and net feed intake (± 0.35 g/day respectively) both before and during pregnancy. Dam/litter units converged completely for daily feed intake immediately in the postnatal stage, during a period of negative energy balance when feed intake and rate of gain were both maximised. Feed intake net of that required for growth and maintenance of liveweight was effectively zero for both lines during this 2-week period. The lines re-diverged in late-lactation. Variance for all traits increased substantially over the 11 weeks of the experiment. In an extensive production environment, where peak lactation generally coincides with abundant pasture supply, this short convergence would have little impact on overall production efficiency. Consequently, selection for post-weaning net feed intake based on growth/weight components remains a potential means to improve production efficiency.
TL;DR: In this paper, a long-term management of soil acidity should aim to eliminate the exchangeable aluminium from the soil profile by maintaining a high pHCa (5.5 or above) in the 0-10 cm soil depth.
Abstract: Phalaris (Phalaris aquatica L.)-based pastures were established with and without lime in 1992 as a part of a long-term pasture–crop rotation experiment (Managing Acid Soils Through Efficient Rotations). Pre- and post-grazing pasture dry matter, phalaris basal cover and proportion of phalaris in sward were measured since 1992. In general, phalaris persisted well and its productivity was high on the highly acidic soil studied in the current experiment, and this was improved on the limed treatment. After establishment in 1992, the average proportion of phalaris in spring 2001 was 32.1% in the limed treatment and 15.6% in the unlimed treatment. Basal cover at the end of summer 2002 was 4.5% and 2.0% for the limed and unlimed treatments, respectively. The results from the current experiment showed that subsurface acidity (low pHCa and high exchangeable aluminium percentage in the 10–30 cm soil depth) had significant impacts on phalaris persistence. It is concluded that subsurface pH was one of the major constraints for the persistence of phalaris. The long-term management of soil acidity should aim to eliminate the exchangeable aluminium from the soil profile by maintaining a high pHCa (5.5 or above) in the 0–10 cm soil depth. Rainfall during growing season had no direct effect on phalaris persistence. Nevertheless, feed scarcity in dry years due to moisture stress often exacerbated grazing pressure on phalaris, which may affect the phalaris persistence indirectly. It is the grazing management in autumn and summer that had significant effects on phalaris persistence. It is suggested that rotational grazing plus strategic rest if possible in autumn could prolong the life of phalaris-based pastures. Repeated heavy grazing should be avoided during summer, particularly after light to moderate summer rainfall events have stimulated sprouting.
TL;DR: Both the USDA and JMGA systems are compared with the potential performance of the MSA system applied on a cut by grade by cooking method basis.
Abstract: Over the past 30 years there has been increasing pressure for the establishment of a beef, quality grading system in Australia. During this time, many and varied options have been proposed and comparisons have often been made with the United States Department of Agriculture (USDA) and the Japanese Meat Grading Association (JMGA) systems. Australia has now developed a grading system that is driven by the consumer — Meat Standards Australia (MSA). Although some years (70+) behind the USDA, the Australian model has been scientifically proven to identify product that can achieve a guaranteed level of satisfaction to the consumer. While this paper evaluates the 3 systems and their specific operations, both the USDA and JMGA systems are compared with the potential performance of the MSA system applied on a cut by grade by cooking method basis.
TL;DR: The effect of missing feed intake records on the estimate of feed intake in cattle over a 70-day test period was studied in this paper, where a first-, second-and third-order polynomial and a non-linear function were fitted to the intake data.
Abstract: The effect of missing feed intake records on the estimate of feed intake in cattle over a 70-day test period was studied. Two datasets, containing several cattle breeds at different ages, were analysed. The first dataset comprised 300-day-old Angus cattle, while the second dataset consisted of 900-day-old Limousin and Jersey crossbred cattle. A first-, second- and third-order polynomial and a non-linear function were fitted to the intake data. The 3 polynomial functions showed minimal differences in their goodness of fit to the data, with the non-linear function explaining the least variation in intake. Both datasets were analysed over a 70-day test period and shortened tests were compared to the full 70-day test. Tests were shortened by randomly deleting intake records or periodically deleting data on a daily or weekly basis. The effect of missing data on feed intake estimates was evaluated using Pearsons correlation and t-tests. The results suggest that a greater proportion of data can be removed randomly and daily, compared with missing data in weekly blocks. However, when data are removed in weekly blocks, removal in the middle of the test period gives a more accurate estimate of feed intake. It appears that in young growing animals, estimation of daily feed intake is more sensitive to missing feed intake records than for older cattle.
TL;DR: A survey of 29 sheep producers was conducted to benchmark current sheep production practices and producer attitudes to sheep and pasture management in the Victorian Mallee as discussed by the authors, and it was concluded that further research is needed to collect data and benchmark pasture and livestock enterprises to allow quantification of the potential impact on farm profit of changes to pasture and sheep management in this region.
Abstract: A survey of 29 sheep producers was conducted to benchmark current sheep production practices and producer attitudes to sheep and pasture management in the Victorian Mallee. This report describes the farming systems, defines current sheep management practices and identifies management issues that are limiting production. It also highlights limitations of adoption, suggests potential adoption rates of specific practices by producers, and estimates increases in productivity achievable. Sheep producers could achieve small gains in farm productivity (an estimated average 0.3% annually) by adopting sheep management practices including using superior genetics, reducing ram numbers and introducing supplementary feeding. Possible reasons why recommended practices have not been adopted are discussed. The difficulty of integrating sheep into current short cropping systems was considered to be a key limitation to the adoption of management that could substantially increase productivity, such as higher stocking rates and winter–spring lambing. Important benefits to both productivity and environmental sustainability may be achieved through the replacement of fallowed land with improved pastures. However, a lack of data on the feed base and sheep production in relation to a changing feed base made it impossible to estimate the size of these benefits. It was concluded that further research is needed to collect data and benchmark pasture and livestock enterprises to allow quantification of the potential impact on farm profit of changes to pasture and sheep management in this region.
TL;DR: Results suggest that there is scope for management of this plant disease by reducing immigration of leafhopper vectors into lucerne from non-crop vegetation.
Abstract: Three newly-sown lucerne stands in the mid Lachlan Valley region of New South Wales, Australia, were sampled, over 50 weeks, for Australian lucerne yellows disease symptom distribution and severity. Leafhopper populations were also monitored. Symptoms developed in all 3 stands within 32 weeks of sowing. There were statistically significant spatial differences in the density of symptomatic plants for 2 dates at this and another site. Two possible insect vectors, Austroagallia torrida and Batracomorphus angustatus were more numerous in some sections of crop margins at 2 sites. These 2 species and a third possible insect vector Orosius argentatus each had a statistically significant spatial and temporal correlation with symptomatic plant numbers for at least 1 site date. Two subsequent border treatment experiments evaluated the effect of crop-margin treatments on leafhopper movement into and from the stand. The second border treatment experiment examined also the treatment effect on Australian lucerne yellows disease symptomatic plant numbers. Treatment with insecticide or herbicide significantly reduced the overall movement of leafhoppers. In addition, the insecticide treatment lowered the incidence of disease expression in adjacent lucerne. Results suggest that there is scope for management of this plant disease by reducing immigration of leafhopper vectors into lucerne from non-crop vegetation.