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This study was conducted to determine whether circulating concentrations of blood isoprostanes can be used as an effective biomarker in lambs to predict degradation of color and/or lipid stability in meat. Lambs (n= 84) were fed diets of either lucerne pasture, annual ryegrass pasture, a commercial feedlot pellet, or a combination of annual ryegrass and feedlot pellet for 8 wk, including a 2-wk adaptation period. Blood isoprostane concentration at wk 0, 4, 6 or 8 of feeding was determined. Blood isoprostane concentration for each animal was then correlated with muscle biochemical components that impact color and/or lipid oxidative status during retail display. This included lipid oxidation levels in muscle assessed by thiobarbituric acid reactive substances and meat redness determined by a HunterLab colorimetric spectrometer. Lambs that consumed the commercial feedlot pellet had a lower muscle vitamin E level (P< 0.01) and a greater level of n-6 PUFA (P< 0.001) compared with lambs finished on annual ryegrass or lucerne. Lipid oxidation levels were greatest for lambs finished on the feedlot ration, lowest in lambs finished on the ryegrass diet, and intermediate for lambs finished on lucerne and ryegrass–feedlot combination (P< 0.01). After 8 wk of feeding, blood isoprostane concentration was positively correlated with lipid oxidation of meat displayed for 72 h in simulated retail conditions (P< 0.01). There was a negative linear relationship between isoprostane concentration and muscle vitamin E concentration (P= 0.07), lipid oxidation and muscle vitamin E concentration (P< 0.01) but a positive linear relationship between isoprostane concentration and muscle n-6 PUFA (P< 0.001) or lipid oxidation and muscle n-6 PUFA concentration (P< 0.001). Blood isoprostane concentration and lipid oxidation in meat were influenced by muscle vitamin E and n-6 PUFA but not by n-3 PUFA. There was no significant relationship observed between blood isoprostane concentration at 0, 4, 6 or 8 wk feeding vs. overall meat color (redness of meat) at 0 and 72 h of display, stored under simulated retail conditions. The results indicate that circulating blood isoprostane concentration can be a useful tool to predict the oxidative status of postmortem meat. Future work will examine the impact of this relationship on meat flavor/aroma deterioration post farm.

Microlaena stipoides (microlaena) is an important perennial grass in over 7million hectares of native pastures in southern Australia and can survive and persist despite severe soil water deficits during summer. Many other pasture species survive similar conditions by relying on summer dormancy, which raises the possibility that microlaena may behave similarly. A field experiment using rainout shelters was conducted on an existing microlaena pasture in north-east Victoria. The experiment was a split-plot design with two watering treatments (‘summer storm’ or ‘summer dry’) as main plots and three defoliation treatments (nil, intense defoliation, strategic defoliation) as subplots. The ‘summer storm’ treatment resulted in the formation of new buds and tillers and increased basal cover from 1% in February to 18% in March. A glasshouse pot experiment examined the recovery of microlaena after different periods of drought and subsequent rewatering. In the pot experiment, microlaena withstood relatively short (up to 30 days) dry periods and then recovered when rewatered. Thus, it appears that microlaena is a persistent, perennial pasture plant that, although it survives very dry summers in Mediterranean areas, is not summer dormant. Microlaena does not exhibit summer dormancy in response to moisture stress and enter a quiescent stage, because normal growth is prevented by the lack of water, but it quickly recommences growth when soil water becomes available. The ability of microlaena to withstand summer soil water deficits and to recruit from seedlings make it a valuable pasture species across drought-prone environments, and this undoubtedly partly explains its very broad adaptation across eastern Australia.

Persistence of pasture is considered an important trait by many farmers using pasture-based systems. Despite this, pasture persistence is generally poorly defined. This study includes an analysis of changes in farm operating profits (OP) when pasture persistence is improved. Persistence was defined as either a 1-year increase in years at peak dry matter (DM) production or a reduction in the rate of decline in annual pasture DM production after the year that peak production occurred (duration of pasture life), both resulting in a 1-year delay in pasture renovation. Changes in OP for these definitions of pasture persistence were modelled for two dairy farms in temperate regions of Australia (Terang in south-western Victoria and Elliott in Tasmania). An increase in duration of peak DM production on the basis of economic theory increased OP more than an increase in duration of pasture life. Increases in OP for a 1-year increase in peak DM production were AU$165ha-1 for Terang and $202ha-1 for Elliott. This compared with $21ha-1 for Terang and $15ha-1 for Elliott for a 1-year increase in the duration of pasture life. Therefore, farmers and plant breeders could place more emphasis on improving the duration of time that pasture plants achieve peak DM production than improving pasture persistence at the end of the pasture plant’s lifetime, to increase annual OP.

Relatively little is known about the weightings that breeders consciously or subconsciously place on specific traits when selecting individual plants, or the weightings agronomists and producers use when evaluating the relative merits of alternative cultivars and their potential economic value in farm systems. This is despite the many active programs for breeding improved forage plants, and in contrast to most modern animal-breeding programs where the relative merits of novel genetics are assessed against index-based breeding objectives. There are many reasons why breeding objectives based on profit indices are not used when breeding pasture plants. The nature of pasture as an intermediate input to farm output and profit poses unique difficulties in developing breeding objectives based on profit. In this paper, we review the literature about methods to value genetic gain in perennial grasses. Various methods are canvassed for assessing the value of genetic gain for different pasture species across production systems. In the context of the complexity and cost of estimating the direct economic benefits of superior characteristics of pasture plants in farm systems via bio-economic simulation methods, we outline the use, and usefulness, of discrete choice techniques in the development of weightings for specific traits in forage plant improvement. There is a clear need to estimate the value of new pasture cultivars to producers, and although the differences between individual farms mean that one value or one ‘best’ cultivar is unlikely for any farm, the estimation of potential value of traits and cultivars will allow producers to make choices that are more informed.

Persistence of pasture in grazing systems has technical and economic dimensions. Profit from investment in pasture is maximised when the profit from the pasture is maximised over cycles of investments in pasture over the life of the farm business. The economic decision-rule is that an existing pasture should be replaced when the expected extra average addition to farm profit per year over the whole of the expected life of the next cycle of pasture investment exceeds the expected addition to farm profit from one more year of the existing pasture. This profit-maximising decision-rule means that the persistence of pasture is an economic phenomenon to be accounted for over several cycles of investment—a different concept to technical views that focus on the number of years of existence (i.e. persistence) of a pasture in one investment cycle. The number of years in which a pasture performs near peak potential annual dry matter (DM) production is a useful perspective on pasture persistence. The longer a pasture persists at peak level the more profitable. An empirical example was analysed of a pasture that had declined to carrying annually 6 dry sheep equivalents/ha (DSE/ha) and reinvestment occurred. The new pasture attained a peak of 11000kg/dry matter/ha in years 4–7, carrying an extra 15DSE/ha.year, and declined to 50% of peak DM production by year 11, which was maintained until year 20. The modified internal rate of return for the base model of investing in pasture improvement was 12% real. The profit-maximising life of the pasture analysed was 8 years in repeated cycles over the life of the farm business. If this pasture produced at 65% of peak kg DM/ha for years 11–20, then the pasture was equally profitable whether the life of the pasture was any length from 8 to 20 years. If the pasture maintained production >65% of peak annual kg DM/ha, then longer pasture lives were more profitable than shorter lives.

Microlaena (Microlaena stipoides var. stipoides (Labill.) R.Br.) is a C3 perennial grass that is native to areas of south-eastern Australia. In this region, perennial grasses are important for the grazing industries because of their extended growing season and persistence over several years. This series of experiments focused on the population biology of Microlaena by studying the phenology (when seed was set), seed rain (how much seed was produced and where it fell), seed germination, germinable seedbank, seed predation and seedling recruitment in a pasture. Experiments were conducted at Chiltern, in north-eastern Victoria, on an existing native grass pasture dominated by Microlaena. Seed yields were substantial (mean 800seedsm-2), with seed rain occurring over December–May. Microlaena has two distinct periods of high seed rain, in early summer and in early autumn. Seed predation is high. Within a 24-h period during peak seed production, up to 30% of Microlaena seed was removed from a pasture, primarily by ants. Microlaena seedlings recruited throughout an open paddock; however, seedling density was low (5seedlingsm-2). Microlaena represented only low numbers in the seedbank (0.01–0.05% of total); hence, any seedlings of Microlaena that germinate from the seedbank would face immense competition from other species. Management strategies for Microlaena-dominant pastures need to focus on the maintenance of existing plants.

Pasture-based dairy farms are a complex system involving interactions between soils, pastures, forage crops, and livestock as well as the economic and social aspects of the business. Consequently, biophysical and farm systems models are becoming important tools to study pasture-based dairy systems. However, there is currently a paucity of modelling tools available for the simulation of one key component of the system—forage crops. This study evaluated the accuracy of the Agricultural Production Systems Simulator (APSIM) in simulating dry matter (DM) yield, phenology, and herbage nutritive characteristics of forage crops grown in the dairy regions of south-eastern Australia. Simulation results were compared with data for forage wheat (Triticum aestivum L.), oats (Avena sativa L.), forage rape (Brassica napus L.), forage sorghum (Sorghum bicolor (L.) Moench), and maize (Zea mays L.) collated from previous field research and demonstration activities undertaken across the dairy regions of south-eastern Australia. This study showed that APSIM adequately predicted the DM yield of forage crops, as evidenced by the range of values for the coefficient of determination (0.58–0.95), correlation coefficient (0.76–0.94), and bias correction factor (0.97–1.00). Crop phenology for maize, forage wheat, and oats was predicted with similar accuracy to forage crop DM yield, whereas the phenology of forage rape and forage sorghum was poorly predicted (R2 values 0.38 and 0.80, correlation coefficient 0.62 and –0.90, and bias correction factors 0.67 and 0.28, respectively). Herbage nutritive characteristics for all crop species were poorly predicted. While the selection of a model to explore an aspect of agricultural production will depend on the specific problem being addressed, the performance of APSIM in simulating forage crop DM yield and, in many cases, crop phenology, coupled with its ease of use, open access, and science-based mechanistic methods of simulating agricultural and crop processes, makes it an ideal model for exploring the influence of management and environment on forage crops grown on dairy farms in south-eastern Australia. Potential future model developments and improvements are discussed in the context of the results of this validation analysis.

This glasshouse study aimed to examine the performance of 7 Australian native grasses and their responses to different cutting and fertiliser regimes. The 7 native grasses comprised 2 wallaby grasses (Austrodanthonia bipartitacv. Bunderra and Austrodanthonia setacea, Woodhouse ecotype), 2 weeping grasses (Microlaena stipoidescv. Bremmer and ecotype Coleraine), 1 spear grass (Austrostipa mollis, ecotype Lexton), 1 red-leg grass (Bothriochlora macra, ecotype Hamilton), and 1 kangaroo grass (Themeda triandra, ecotype Yass). For each of the 7 grasses, 64 pots each containing 9 plants were arranged in a 4 cutting intensity×4 fertiliser level factorial design with 4 replicates. The cutting intensity treatments involved (1) cutting to 2cm at 3–5-week intervals; (2) cutting to 5cm at 3–5-week intervals; (3) cutting to 10cm at 3–5-week intervals; and (4) cutting to 2cm based on leaf stage. The fertiliser regimes included low, medium, and high fertility treatments by applying various rates of phosphorus, and the treatment with addition of compost tea. Herbage accumulation, shoot and root growth, plant survival and tiller density, nutritive characteristics, and leaf stage were monitored. All grass lines produced the lowest herbage mass when cut to 2cm above ground at 3–5-week intervals. Cutting to 5cm or to 2cm based on leaf stage favoured herbage accumulation of Lexton spear grass, Hamilton red grass, Yass kangaroo grass, and Coleraine weeping grass. Cutting to 10cm favoured herbage accumulation of Bremmer weeping grass and wallaby grass. Cutting to 10cm together with high fertiliser application considerably increased herbage accumulation in comparison with treatments with low fertiliser application or with compost tea. Shoot and root biomass were maximised when plants were cut to 10cm above ground, except Lexton spear grass which had highest root biomass when plants were managed based on leaf stage. Plant survival was dramatically affected by defoliation intensity and varied among species. Plant survival declined when plants were cut to 2cm above ground for most species. Overall, native grasses were considered to have good nutritive characteristics with crude protein ranging from 17 to 22% and neutral detergent fibre from 48 to 60%. Results from this study indicate that it may be possible to use leaf stage as a determinant for the commencement of grazing native species. Optimum leaf stages that could be used as a grazing management guide were on average 3.4 for wallaby grass, 4.2 for weeping grass, 3 for spear grass, 3.8 for red-leg grass, and 4.4 for kangaroo grass. However, further work is required to better define this for likely seasonal variation between C3and C4species.

The 2-pond system to treat and contain dairy effluent is commonplace on dry-land dairy farms in southern Australia. The first pond is a deep anaerobic treatment pond and the second a shallow aerobic pond where the liquid effluent is stored. This liquid effluent contains a range of nutrients that have the potential to influence forage dry matter (DM) yields, herbage nutritive characteristics, and mineral content of forages.The effect of applying second-pond dairy effluent to a summer turnip (Brassica rapa L.) crop over two consecutive summer periods was measured. In addition to the application of effluent, N fertiliser was also applied. Effluent was applied at three rates, 0, 30, and 60 mm ~7–8 weeks after turnips were sown each year, with fertiliser N applied at either 0, 25, 50, or 75 kg N/ha in combination with effluent rates immediately before effluent application. Turnips were assessed for DM accumulation, nutritive characteristics, and mineral and nitrate-N content.Effluent contained high concentrations of both potassium (K) (440–500 kg/ML) and sodium (Na) (637–766 kg/ML), with moderate levels of calcium (Ca) (177–180 kg/ML) and magnesium (158–213 kg/ML). Total N was higher in Year 2 (208 kg/ML) than in Year 1 (160 kg/ML), with the proportion of total N present as ammonia-N also higher in Year 2 (81%) than in Year 1 (57%).Dry matter yield responses for leaf and root were 20 and 11 kg DM/ha per effluent mm applied in Year 1 and 19 and 13 kg DM/ha.mm applied in Year 2, respectively. Total DM yield increases were 32 and 39 kg DM/ha.mm applied for Years 1 and 2, respectively. There was no effect of N application or interaction between effluent and N application in either year. For Year 1, nutritive characteristics were relatively unaffected by either effluent or N fertiliser application, while in Year 2, leaf crude protein content increased (P < 0.05) in a linear manner at 0.058% per mm effluent applied. The K and Na content of turnip leaves increased (P < 0.05) with effluent application in both Years 1 and 2, while the Ca decreased (P < 0.05) with effluent application in Year 2.Results from this study further emphasise the potential value of second-pond dairy effluent to increasing forage DM yield and improving the nutritive value of turnips. The data, however, question the value of using N fertiliser on its own or in combination with effluent to improve the same attributes. Dry matter yield responses to effluent were similar across both years despite contrasting climatic conditions, highlighting the ability of turnips to respond to limited moisture inputs.

In southern Australia, the majority of dry land dairy farms use a 2-pond system to treat and contain dairy effluent collected at the milking platform. This effluent contains a range of nutrients that have the potential to affect forage dry matter (DM) yields, nutritive characteristics, and mineral content of forages.  The effect of applying second-pond dairy effluent to the summer-active forages chicory (Chichorium intybus L. cv. Grouse), Hunter (Brassica campestris L.נBrassica napus L.), Winfred (Brassica napus L.), and Sweet Jumbo (Sorghum bicolor (L.) MoenchנSorghum sudanese (Piper) Stapf.) over two summer periods was measured. Effluent was applied at rates of 0, 40, 80, and 100mm with application split into two equal application times. The first occurred 6?10 weeks after sowing and the second immediately after the first grazing. Forages were assessed for DM yield, nutritive characteristics, and mineral content over the two growth periods in each year.  Analysis of effluent showed that on average over the 2 years, the effluent contained 146, 34, 439, and 18kg/ML of nitrogen (N), phosphorus (P), potassium (K), and sulfur (S), respectively. Furthermore, the effluent also contained 161kg/ML of calcium (Ca) and 222kg/ML of magnesium (Mg).  For the total growth period in Year 1, all crops showed a linear increase (P<0.05) in DM yield to applied effluent, with response values varying for each crop. Responses were 49, 52, 29, and 51kgDM/ha.mm applied effluent for chicory, Hunter, Sweet Jumbo, and Winfred, respectively. For Year 2, all crops also showed a linear increase (P<0.05) in DM yield (15kgDM/ha.mm applied effluent) with applied effluent. In Year 1, crude protein (CP) content of all crops increased (P<0.05) in a linear manner at rates of 0.073 and 0.047% per mm applied effluent for growth periods 1 and 2. There were also linear responses (P<0.05) in Year 2, with responses varying for each crop for each growth period. For chicory there was no effect of effluent application on CP content in either growth period, while other crops generally exhibited a linear increase with responses of up to 0.08% per mm applied effluent. The greatest changes in mineral content of herbage were those of K, Ca, and Mg. There was a linear increase (P<0.05) in K content for all growth periods in Years 1 and 2. Magnesium content of chicory (periods 1 and 2) and Winfred (period 2) showed a linear decrease (P<0.05) in response to effluent application in Year 1, whereas there was no effect in Year 2 for any crops.  The results from this study highlight the potential of second-pond dairy effluent to increase DM yields of a range of summer-active forage crops. The data also suggest that while effluent can improve DM yields when soil moisture is limiting, when additional moisture as rainfall occurs, responses from effluent are even more pronounced. In addition, the CP content of forages can be improved when effluent is applied. The combination of increased DM yield with higher CP content provides greater flexibility in dairy cattle feeding options through the dry summer period.

Dairy farms in southern Australia generally use a 2-pond system to manage dairy shed effluent. This system consists of a deep anaerobic first pond and a shallow aerobic second pond. The liquid in the second pond contains a range of nutrients that may have agronomic benefits for forages.  The effect of applying second-pond dairy effluent to a summer turnip (Brassica rapa L.) crop over 3 consecutive summer periods was measured. Effluent was applied at 6 rates, 0, 15, 30, 45, 60, and 75mm, approximately 6?8 weeks after turnips were sown each year. Turnips were assessed for dry matter (DM) accumulation, nutritive characteristics, and mineral content. In addition, total annual production for years 1 and 2 was calculated by including the DM accumulation from annual ryegrass grown from autumn to spring each year.  Concentrations of nutrients within the effluent as an average over the 3 years were 31, 454, 20, and 149kg/ML for phosphorus (P), potassium (K), sulfur (S), and nitrogen (N), respectively. In addition, effluent also contained 152kg/ML of calcium (Ca), 225kg/ML of magnesium (Mg), and 529kg/ML of sodium (Na).  Soil pH was generally unaffected with effluent application, while soil EC and total soluble salt (TSS) content increased with effluent addition. In the first year, application of effluent at 15mm and higher resulted in increases in available K; however, in subsequent years, rates of 45mm and higher led to an increase in available K, while for the control and lower effluent rates there was a marked decline in K status.  In all years there was a linear increase (P<0.05) in leaf, root, and total DM yields with applied effluent. For leaf, responses were 19, 50, and 26kgDMper mm applied effluent and for roots, 10, 39, and 25kgDMper mm applied effluent for years 1, 2, and 3, respectively. In years 2 and 3, turnip leaf crude protein (CP) content increased (P<0.05) in a linear manner at rates of 0.046 and 0.044% per mm applied effluent, respectively. There was also a linear increase (P<0.05) in turnip root CP in years 2 and 3 of 0.033 and 0.021% per mm applied effluent, respectively. In all years there was a linear increase (P<0.05) in leaf K content, while for root K there was a quadratic trend (P<0.05) for year 1 and a linear increase (P<0.05) for years 2 and 3.  The results from this study indicate that the use of dairy effluent can increase DM yield and improve the nutritive value of turnips through an increase in CP content. The data also indicate that this effect can be maintained over consecutive years, which in turn may provide greater flexibility for returning effluent to farm land. While results appear to indicate that the primary responses are due to N, further work is required to determine the effects of water and other nutrients within dairy effluent.

The 2-pond effluent systems used by the majority of dairy farmers in southern Australia result in the collection of liquid effluent in an aerobic second pond. This liquid effluent contains a wide range of nutrients that have the potential to significantly affect the nutritive characteristics and mineral content of forages.  The effect of applying second pond dairy effluent to perennial ryegrass based pasture following harvesting for silage over a 3-year period was measured. Effluent was applied at 6 rates: 0, 15, 30, 45, 60, and 75mm following a spring silage harvest each year, with changes to nutritive characteristics and mineral content determined at each subsequent grazing.  Analysis of the effluent applied showed that on average, over the 3 years of application, the effluent contained 31, 454, 20, and 149kg/ML of phosphorus (P), potassium (K), sulfur, and nitrogen, respectively. In addition, the effluent contained 152kg/ML of calcium (Ca) and 225kg/ML of magnesium (Mg).  Changes in nutritive characteristics as a result of effluent application were primarily restricted to the first grazing after application. The metabolisable energy content of herbage at the first grazing in Years 1 and 2 was unaffected by effluent application; however, in Year 3 there was a linear increase of 0.0051MJ/kg dry matter (DM).mm of applied effluent. In contrast, effluent application had a positive linear effect on pasture crude protein (CP) content at the first grazing in all years. In Year 1, CP content increased by 0.083%/mm of applied effluent, while for Years 2 and 3 the increases in CP content were 0.044 and 0.029%, respectively. In all years, there was a negative linear effect on water-soluble carbohydrate content at the first grazing after effluent application. For Years 1, 2, and 3, responses were ?0.138, ?0.066, and ?0.022%/mm applied effluent, respectively.  The P content of pasture was higher at the first grazing following effluent application at rates of 60 and 75mm in each year compared with the control and the 15mm application rate. Potassium concentrations were increased with effluent application at rates of 45, 60, and 75mm in all 3 years in comparison with the control at the first and second grazing after application. In Year 1, Mg content of the pasture was lower for the control, 15, and 30mm treatments than for the 2 highest application rates at the first grazing after application.  This experiment has highlighted the potential of using second pond dairy effluent following pasture harvesting for silage to maintain the CP content of pasture in late spring. The high mineral content of effluent led to increases in the concentration of several these minerals and, while the ratio of K to (Ca + Mg) was substantially increased, it is unlikely that effluent application in late spring and the concomitant increases would lead to animal metabolic problems. Coupled with the observed increases in DM yield, the increase in CP content provides greater flexibility in feeding options to bridge feed shortfalls before summer forage crops becoming available on dryland dairy farms in southern Australia.

In southern Australia the standard treatment system for dairy shed effluent is a 2-pond system. Effluent from the dairy is first treated in a deep anaerobic pond where sedimentation and breakdown of organic matter occur. Treated liquid effluent then enters a shallow aerobic pond where it is stored. Relatively little information is available on forage agronomic responses to application of this second pond liquid.  The effect of applying this second pond dairy effluent to perennial ryegrass based pasture was measured over a 3-year period. Effluent was applied at 6 rates: 0, 15, 30, 45, 60, and 75mm following spring silage harvest each year. Changes to herbage dry matter (DM) accumulation, and botanical composition were determined at each subsequent grazing.  Over the 3 years of application, the average concentrations of phosphorus, potassium, and sulfur in the effluent were 31, 454, and 20kg/ML, respectively. In addition, the effluent contained 149kg/ML of nitrogen and 529kg/ML of sodium.  For all 3 years, the application of effluent resulted in a linear increase (P > 0.05) in annual herbage DM accumulation. Response rates for the 3 years were 27, 22, and 9kgDM/mm applied effluent, respectively. The majority of this response occurred by the first grazing after application, where effluent application gave rise to linear responses (P > 0.05) in herbage DM accumulation of 17, 18, and 7kgDM/mm for Years 1, 2, and 3, respectively. Botanical composition was not significantly affected by effluent application.  This experiment has highlighted the potential of using second pond dairy effluent following pasture harvesting for silage as a means to grow additional herbage and extend the growing season. Based on the N content of effluent, herbage DM accumulation responses (Year 1, 10.4; Year 2, 11.4; Year 3, 5.1kgDM/kgN) were similar to those expected from application of fertiliser N. It is likely that the primary response in terms of herbage accumulation is due to the N component within dairy effluent. While this study has shown positive herbage DM accumulation responses to applied effluent, further work is required to determine longer term effects of repeated effluent application, especially sodium, to soil characteristics.

A 3-year experiment (September 1999?August 2002) in south-western Victoria investigated spring grazing impacts on botanical composition, tiller densities (perennial ryegrass, other-grasses, clover growing points, and broad-leaved weeds), and perennial ryegrass plant frequencies of a pasture of perennial ryegrass (Lolium perenne L.)?white clover (Trifolium repens L.) pasture. Spring grazing treatments, applied annually from September to November were based on ryegrass leaf development stage with high (HF), medium (MF), and low (LF) grazing frequency being 2-, 3-, and 4-leaf stage, respectively, and post-grazing height as the grazing intensity with high (HI), medium (MI), and low grazing intensity being 3, 5, and 8cm, respectively. Five combinations were used: HFHI, LFHI, MFMI, HFLI, and LFLI. A sixth treatment, rapid grazing (RG), maintained pasture between 1500 and 1800kgDM/ha by grazing weekly during spring and a seventh and eighth treatment, simulating forage conservation for early-cut silage (lock-up for 6?7 weeks; SIL) and late-cut hay (lock up for 11?12 weeks; HAY), were also included.  Perennial ryegrass content remained stable in the RG and HFHI treatments, averaging 78 and 75% DM, respectively, and declined in all other treatments. For example, perennial ryegrass content in LFLI declined from 75% (September 1999) to 50% DM (August 2002). RG and HFHI resulted in a slight increase in other grass (e.g. Holcus lanatus and Poa annua) content over time. SIL, LFLI, LFHI, and MFMI resulted in a higher other-grass content than RG and HFHI. LFLI, LFHI, and HFLI resulted in a stable dead (litter) pasture content over time, while SIL, HAY, HFHI, and RG resulted in a decline in dead pasture content over time. For RG and HFHI spring treatments the decline in dead pasture content was greater than LFLI, LFHI, and HFLI spring grazing. Data for white clover and broad-leaved weeds (e.g. Rumex dumosus and Taraxacum officinale) were inconsistent and could not be statistically analysed.  While perennial ryegrass tiller density declined over time, RG and HFHI spring grazing resulted in a higher perennial ryegrass tiller density than low and medium grazing frequency treatments, and forage conservation treatments. Over time, tiller density of other grass increased, with MFMI, SIL, and HAY resulting in a greater increase than HFHI and RG treatments. During the experiment, white clover growing point density declined, while broad-leaved weed tiller data were inconsistent and not analysed.  In October 2001, perennial ryegrass plant frequencies ranged from 12 (HAY) to 27 (RG) plants/m2. RG resulted in a higher perennial ryegrass plant frequency than medium and low spring grazing frequencies, and forage conservation (HAY). At the end of the experiment (August 2002), perennial ryegrass frequencies ranged from 15 (HAY) to 45 (RG) plants/m2 with RG resulting in a higher perennial ryegrass plant density than all other treatments. HFHI grazing resulted in a higher plant frequency than LFLI, SIL, and HAY, and HFLI a higher plant frequency than SIL and HAY.  RG and HFHI spring grazing favoured perennial ryegrass persistence as it maintained botanical composition and perennial ryegrass tiller and plant frequencies relative to low and medium spring grazing frequency or high spring grazing frequency coupled with low intensity grazing and pasture locked up for forage conservation.

A 3-year experiment (September 1999?August 2002) was conducted in south-western Victoria to determine the impact of spring grazing on pasture accumulation rates, dry matter (DM) consumed yield (estimate of DM yield), and pasture nutritive characteristics [metabolisable energy (ME), crude protein (CP), neutral detergent fibre (NDF), and water-soluble carbohydrates (WSC)] of a perennial ryegrass (Lolium perenne L.)?white clover (Trifolium repens L.) pasture. Spring grazing treatments, applied annually from September to November, were based on ryegrass leaf development stage with high (HF), medium (MF), and low (LF) grazing frequency being 2-, 3-, and 4-leaf stage, respectively, and post-grazing height as the grazing intensity with high (HI), medium (MI), and low (LI) grazing intensity being 3, 5, and 8cm, respectively. Five combinations were used: HFHI, LFHI, MFMI, HFLI, and LFLI. A sixth treatment, rapid grazing (RG), maintained pasture between 1500 and 1800kgDM/ha by grazing weekly during spring, and a seventh and eighth treatment, simulating forage conservation for early-cut silage (lock-up for 6?7 weeks; SIL) and late-cut hay (lock-up for 11?12 weeks; HAY), were also included. For the remainder of the year, all plots were grazed at the perennial ryegrass 3-leaf stage of growth, or when pasture mass had reached 2800kgDM/ha, and grazed to a residual height of 5cm.  On average, pasture accumulation rates ranged from <5 (February?March) to 100?110kgDM/ha.day (September?October). Overall, SIL resulted in a lower accumulation rate than all other treatments. High spring grazing frequency (including RG) treatments led to more grazing events than medium and low spring grazing frequency treatments. In Years 1, 2, and 3, DM consumed ranged from 9.7 (HAY) to 16.3 (RG), 4.2 (HAY) to 10.1 (HFHI), and 7.3 (SIL) to 10.9tDM/ha.year (HAY), respectively.  HAY resulted in a lower pasture ME content than SIL, HFHI, and LFHI spring grazing, and LFLI spring grazing resulted in a lower pasture ME content than all other treatments except HAY. HFHI grazing resulted in an increase in ME content over time, whereas the rate of increase in ME content over time was higher for LFLI spring grazing than for HAY, RG, and HFLI spring grazing. For all treatments, average pasture ME content ranged from 9.4 (January?February) to 11.4MJ/kgDM (September). HAY resulted in a lower CP content than all treatments except LFLI grazing. RG resulted in no change in CP content over time. For all treatments, average pasture CP content ranged from a low of 11?14 (January?February) to a high of 24?28% DM (August?September). LFLI grazing resulted in a higher NDF content than HFHI, LFHI, MFMI, and HFLI grazing, while RG resulted in a lower NDF content than LFHI, MFMI, and HFLI. For all treatments, average pasture NDF content ranged from a low of 48?55 (August?September) to a high of 58?62% DM (January?February). All treatments resulted in an increase in pasture WSC content over time.  The results demonstrate that frequent and intense grazing management (e.g. HFHI and RG) during spring is important in maintaining high pasture DM yields. Results also indicate positive pasture nutritive characteristic (ME, CP, and NDF) gains with more frequent spring grazing than with infrequent spring grazing. No treatment effect was observed for WSC content.

Summer forage crops form an integral component of feed rations to meet the dietary requirements of dairy cows in south-west Victoria. Irrigation of such crops has the potential to increase the availability of feed of high nutritive value. The effect of irrigation strategies and nitrogen (N) fertiliser on forage crop accumulation rates, dry matter yield, water use efficiency and nutritive characteristics was determined at each harvest over 2 summers. The crops used were Hunter (Brassica campestris L. Brassica napus L.), Graza (a complex hybrid of Raphanus sativus L. with introgression from Raphanus maritimus L. and Brassica oleracea L.) and Shirohie millet (Echinochloa utilis Ohwi & Yabuno). Irrigation treatments were dryland control, weekly irrigation to 100% of estimated requirements, weekly irrigation to 50% of estimated requirements and 25% of estimated requirements every second week. Following sowing and after each harvest, N was applied at either 50 or 100 kg N/ha (brassica crops, 3 applications; millet, 2 applications). In both years, fully irrigated crops produced higher dry matter yields than the dryland crops for all species. For Hunter and Graza, full irrigation also resulted in higher dry matter yields than irrigating every second week. Nitrogen at the higher application rate led to higher dry matter yields for Graza in both years and for millet in year 1. Irrigation had inconsistent effects on the nutritive characteristics of all species. Metabolisable energy content ranged from 10.1 to 13.6, 9.8 to 13.3 and 8.2 to 11.3 MJ/kg dry matter for Hunter, Graza and millet, respectively. Nitrogen application at 100 kg N/ha resulted in higher crude protein content for Hunter and Graza at the second and third harvests and for millet at the second harvest at 50 kg N/ha in both years. Water use efficiencies (irrigation plus effective rainfall) varied according to species with all dryland crops having higher water use efficiencies than the irrigated crops. Total water use efficiencies ranged from 21 to 55, 17 to 39 and 28 to 86 kg dry matter/ha.mm for Hunter, Graza and millet, respectively. In contrast, water use efficiencies from applied irrigation water ranged from 0 to 18 kg dry matter/ha.mm for Hunter, 5 to 18 kg dry matter/ha.mm for Graza and 3 to 33 kg dry matter/ha.mm for millet. Economic assessments indicated average costs for dryland Hunter, Graza and millet to be AU$94, $124 and $76/t dry matter and average costs for fully irrigated crops to be $57, $67 and $51/t dry matter, respectively. This study indicates there is potential to economically irrigate these species to provide additional dry matter of medium to high nutritional value to feed lactating dairy cows through late spring and summer. The data also indicate that for the irrigation of summer forage crops in this environment, the most efficient use of limited water supplies is likely to be a weekly application of water at 50% of the estimated perennial pasture requirements.

A 3-year grazing experiment undertaken on a commercial dairy farm in south-west Victoria ascertained the effects of multiple applications of different rates of nitrogen (N) fertiliser over autumn and winter on pasture growth rates, dry matter (DM) consumed, and N fertiliser response efficiencies. Four treatments, replicated 3 times in a randomised block design, comprised: zero N (A); 3 applications of 25 kg N/ha (B); 3 applications of 50 kg N/ha (C); and 3 applications of 75 kg N/ha (D), with N applied as urea (46% N).Treatments B, C, and D increased pasture growth rates relative to Treatment A, with Treatments C and D having the greatest affect. Treatments B, C, and D also increased pasture DM yield, with Treatment D having the greatest effect. Total pasture DM consumed in 1997 was 7.1, 7.9, 8.2, and 8.9 t DM/ha for A, B, C, and D, respectively. For 1998, the values were 5.4, 6.5, 7.2, and 8.7; and in 1999 5.7, 6.6, 6.9, and 7.7 t DM/ha. During 1997, N response efficiencies were 11, 7, and 8 kg DM/kg N for treatments B, C, and D, respectively. Based on a cost of AU$400/t urea (including freight, handling, and spreading), Treatment B was the most economical, costing 8 cents/kg additional pasture DM produced. Nitrogen application resulted in response efficiencies of 14, 12, and 15 kg DM/kgN in 1998 and 13, 8, and 9 kg DM/kg N in 1999 for Treatments B, C, and D, respectively. In 1998 the most economical application was Treatment D, costing 6 cents/kg additional pasture DM produced, whilst in 1999 Treatment B was most economical costing 7 cents/kg DM for additional pasture. The apparent recovery of applied N fertiliser by the pasture was calculated and found to fall within the range reported in the literature. Apparent recoveries estimated during 1997, 1998, and 1999, respectively, were Treatment B: 62, 78, and 70%; Treatment C: 50, 69, and 45%; and for Treatment D: 45, 82, and 51%.It is concluded that, for the range of N fertiliser rates tested, N fertiliser is a cost-effective option for the production of extra pasture DM during autumn and winter on grazed perennial ryegrass dairy pastures in south-west Victoria.

A grazing experiment was undertaken on a commercial dairy farm in south-west Victoria over a 3-year period to study the effects of multiple applications of different rates of nitrogen (N) fertiliser over autumn and winter on dairy pasture species composition, nutrient characteristics, mineral content, and nutrient selection. Four treatments, replicated 3 times in a randomised block design, comprised: zero N (A); 3 applications of 25 kg N/ha (B); 3 applications of 50 kg N/ha (C); and 3 applications of 75 kg N/ha (D).Increasing rates of N fertiliser generally elevated whole sward metabolisable energy (ME) content. The effect of N fertiliser on whole sward ME content was evident through to the end of sampling each year (2–3 months after the last N application). Increasing rates of N fertiliser consistently elevated whole sward crude protein (CP) content. The effect of N fertiliser on whole sward CP content was evident through to the end of sampling each year (2–3 months after the last N application). For each year there was a slight decrease in CP, with Treatments C and D decreasing at a greater rate than treatments A and B. Increasing rates of N fertiliser generally depressed whole sward neutral detergent fibre (NDF) content. The effect of N fertiliser on whole sward NDF content was evident through to the end of sampling each year (2–3 months after the last N application). For each year there was a slight increase in NDF, with Treatments C and D having a lower increase in NDF over time than Treatment A. Nitrogen fertiliser had no effect on whole sward water soluble carbohydrate content.There was no consistent effect of N fertiliser on whole sward pasture mineral content during the growth season (June–December), with mean annual levels of P, K, S, Na, Ca, and Mg satisfying the nutritional requirements of high producing dairy cows and the growth requirements of both perennial ryegrass and white clover.Although N fertiliser had no influence on the concentration of nutrients consumed by grazing dairy cows, the mean annual range in selection differentials for the 3 years for ME (1.06–1.11) and CP (1.18–1.32) concentrations consumed was higher and the NDF (0.85–0.91) lower than those of the pasture.Each year there was an increase in perennial ryegrass, with Treatments B and C having a higher overall ryegrass presence compared with Treatment A. Nitrogen fertiliser had no effect on white clover, other grasses, weeds, or dead fractions.

A 3-year experiment determined the impact of multiple applications of different rates of nitrogen (N) fertiliser, applied over autumn and winter in 1997, 1998, and 1999, on N2 fixation in grazed dryland perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) dairy pastures. Four treatments replicated 3 times in a randomised block design comprised: 0 N (A); 3 applications of 25 kg N/ha (B); 3 applications of 50 kg N/ha (C); and 3 applications of 75 kg N/ha (D). Urea (46% N) was the N source and applications were from autumn to late winter. 15N abundance methods, based on herbage samples, were used to estimate N2 fixation. Percentage N derived from the atmosphere (%Ndfa) through white clover N2 fixation decreased as the rate of N fertiliser application increased during 1997, but remained unaffected by treatment during 1998 and 1999. Slight decreases in %Ndfa, associated with an increase in soil nitrate, were offset by the positive association between clover dry matter (DM) and soil ammonium. The amount of N2 fixed by white clover decreased from 43 kg N/ha.year (A) to 23 kg N/ha.year (C) during 1997. The amount of N2 fixed by white clover during 1998 and 1999, however, was unaffected by increasing rates of N fertiliser application and averaged 17 and 12 kg N/ha.year in 1998 and 1999, respectively. White clover sward composition (percentage of DM) was unaffected by the rate of N fertiliser application. The average white clover composition across treatments declined from 23% DM in 1997 to 12% DM in 1999. It is concluded that the DM yield production of dryland perennial ryegrass/white clover dairy pastures is likely to be restricted by available soil N, as the amount of N2 fixed annually by clover is low (approx. 20 kg N/ha.year). There is, therefore, scope to supplement pasture N nutritional requirements with fertiliser N. Further, application of N fertiliser may restrict the ability of white clover to fix N2; however, under the grazing management adopted, N fertiliser had no effect on the percentage of white clover.

A 3-year grazing experiment determined the impact of multiple applications of different rates of nitrogen (N) fertiliser, applied over autumn and winter in 1997, 1998, and 1999, on perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) tiller and growing point densities (stolon apices with at least 2 nodes). Annual pasture dry matter (DM) yields were also monitored. Four treatments were replicated 3 times in a randomised block design and included: 0 N (A); 3 applications of 25 kg N/ha (B); 3 applications of 50 kg N/ha (C); and 3 applications of 75 kg N/ha (D). Urea (46% N) was the N source. Grazing of treatment plots occurred at a pre-grazing herbage mass of 2200–2500 kg DM/ha.Over 3 years, N applications consistently increased annual pasture DM yields by 0.9–3.3 t/ha when a total of 75–225 kg N/ha was applied annually.Generally, treatments B, C, and D resulted in higher perennial ryegrass tiller densities than treatment A. An exception occurred from July 1998 in Year 2 to July 1999 in Year 3, when all perennial ryegrass densities were similar. Nitrogen fertiliser generally produced no consistent effect on white clover growing point density, with the exception of July–December in Year 2 when treatments B, C, and D resulted in lower growing point densities than treatment A. Clover growing point density decreased over the trial period irrespective of treatment. There were no N fertiliser effects on 'other' grasses and broadleaved weeds. 'Other' grasses (mainly winter grass, Poa annua) did, however, peak in density (up to 2500 tillers/m2) from July to September each year.Seasonally, the peak perennial ryegrass tiller density was similar each year and occurred during late winter–early spring (5450 tillers/m2 in July 1997; 6200 tillers/m2 in August 1998; 5400 tillers/m2 in July 1999). This was followed by a trough over midsummer (800 tillers/m2 in January 1998; 725 tillers/m2 in January 1999). White clover growing point density declined over 3 years. During this decline there were peaks in June 1997 (2650 growing points/m2), November 1997 (1600 growing points/m2), June 1998 (1250 growing points/m2), April 1999 (1050 growing points/m2), and November 1999 (850 growing points/m2). Troughs occurred in January 1998 (530 growing points/m2) and February 1999 (380 growing points/m2).It is concluded that although increasing applications of N increased annual pasture DM yields and generally increased perennial ryegrass tiller densities, with little effect on clover growing point densities, there is little to suggest that N fertiliser alone would enhance the persistence of these pasture species. Persistence is likely to be influenced by a combination of factors including grazing management and climatic effects, rather than N fertiliser alone.

Factors associated with turnip dry matter yield, metabolisable energy and crude protein were investigated in 266 turnip forage crops on 142 dairy farms in south-western Victoria during spring 1999 and summer 2000. Factors measured were primary cultivation method, secondary cultivation method, soil texture, soil temperature and moisture at sowing, seedbed preparation, turnip variety, sowing method, sowing rate, rolling post-sowing, harrowing post-sowing, seedling establishment, insect damage, water received, phosphorus and nitrogen application. The average date for the commencement of seedbed preparation was early October, although the range was from mid-March until mid-December. Sowing dates ranged from mid-September to mid-December, with an average of mid-October. The most common turnip variety sown was Barkant, followed by Mammoth Purple Top, Vollenda and Rondo. Growing periods ranged from 8 to 23 weeks, with the majority of crops grazed from 8 to 15 weeks. The average dry matter yield was about 5 t DM/ha, with values ranging from 0.4 to 19.2 t DM/ha. The average metabolisable energy content of turnips was 13.7 MJ/kg DM with values ranging from 11.3 to 14.6 MJ/kg DM. The metabolisable energy of roots was on average higher than the leaf component of the plants (14 v. 13.5 MJ/kg DM). Conversely, crude protein content of leaves (15.4&percnt;) was higher than in the root fraction (13.9&percnt;). The average neutral detergent fibre content of turnips was 22.5&percnt; with values ranging from 16.9 to 30.5&percnt;. The water-soluble carbohydrate content of the leaf component ranged from 1.1 to 26.8&percnt; with an average of 14.7&percnt;, while starch content of the root component ranged from 0.3 to 38.8&percnt; with an average content of 16.9&percnt;. The average cost of growing a turnip crop was &dollar;485/ha or &dollar;133 t DM. Total, leaf and root dry matter yield as well as metabolisable energy and crude protein were analysed by a mixed effects model (with factors fixed and farms and paddocks random). Factors that were associated with total dry matter yield were total water received, soil temperature and moisture at sowing, seedling density, method of secondary cultivation, soil type and insect damage. The application of nitrogen fertiliser had the greatest association with turnip crude protein content. In conclusion the findings of this study indicate potential ways to increase the dry matter yield of turnips grown in south-western Victoria. Given the current average dry matter yields and cost of growing turnips, purchasing cereal grain may be a viable alternative. An increase in average dry matter yield would make the choice of growing turnips as a feed for lactating dairy cows a more profitable option.

A study in south-western Victoria determined effects of 3 perennial ryegrass (Lolium perenne L.) cultivars (Vedette, Impact and Nevis) with differing maturities, duration of lock up and nitrogen (N) application on the dry matter yield and nutritive characteristics of pasture for silage. Treatments were cultivar (3), N (0 and 50 kg N/ha) and duration of lock up (5–10 weeks) arranged in a completely randomised design in 3 by 5 m plots replicated 3 times. Plots were mown to a uniform height (5 cm) on 14 September 1998 (first day of lock up) and 1 week later N was applied as urea (46% N) at either 0 or 50 kg N/ha to the respective plots. Weekly sampling commenced on 19 October (week 5 of lock up), and continued until 23 November. For each treatment and harvest date, dry matter yield and botanical composition were determined, and samples of total pasture and the ryegrass fraction were collected and chemically analysed for dry matter digestibility, concentrations of crude protein, neutral detergent fibre, water-soluble carbohydrates and minerals. Metabolisable energy was derived from dry matter digestibility. All pasture types were predominantly ryegrass (>90%) with no differences in the nutritive characteristics of total pasture swards or the respective ryegrass fraction. Nitrogen at 50 kg N/ha significantly (P&lt;0.05) increased dry matter yield for all cultivars. Metabolisable energy (MJ/kg DM) of the pasture declined with time for all treatments, with Vedette having a significantly (P&lt;0.05) greater rate of decline than the other cultivars. Vedette reached early ear emergence about 3 weeks earlier (week 7) than the other cultivars. The harvestable metabolisable energy yield (MJ/ha) at ear emergence was highest for Impact, followed by Nevis and Vedette. In conclusion, there is potential to use later-maturing cultivars of ryegrass in south-eastern Australia to allow for later harvesting of forage for silage, while maintaining metabolisable energy and maximising dry matter yields. Furthermore, the use of N fertiliser can also increase dry matter yields without impinging on pasture quality provided the time between N application and harvest date does not exceed 5–6 weeks.

Experiments were conducted at three sites to study effects of different nitrogen (N) fertilisers (e.g. urea, ammonium nitrate, di-ammonium phosphate and ammonium sulphate), applied at 45 kg N ha-1, with and without phosphorus (P), potassium (K) and sulphur (S), on pasture dry matter (DM) yield and botanical composition. Autumn and spring applied N increased DM yield at all sites. Different N fertilisers generally produced similar DM yield increases. Where different N fertiliser types were balanced with respect to P, K and S there was a similar marginal, but usually nonsignificant (P≥0.05) increase in DM yield over unbalanced N fertiliser types. Average autumn N response efficiencies (excluding P, K and S) at Sites 1, 2 and 3 (after 47, 34 and 37 days, respectively) were 10:1 (10 kg DM per kg N), 16:1 and 13:1, respectively. Including P, K and S, N response efficiencies were 12:1, 17:1 and 15:1, respectively. Residual N response efficiencies without P, K and S (after 50, 41 and 29 days at Sites 1, 2 and 3, respectively), were 5:1, 5:1 and 3:1, respectively. When P, K and S were included, N residual response efficiencies were 6:1, 6:1 and 4:1, respectively. Average spring N response efficiencies at Sites 1, 2 and 3 (without P, K and S) after 29, 30 and 26 days, respectively were 9:1, 6:1 and 16:1, respectively. Including P, K and S, N response efficiencies were 12:1, 7:1 and 17:1, respectively. Residual N response efficiencies (excluding P, K and S) were 6:1, 6:1 and 7:1 at Sites 1, 2 and 3 after 21, 20 and 21 days, respectively. Including P, K and S, average N residual response efficiencies were 5:1, 7:1 and 8:1, respectively. The botanical composition of the pasture was unaffected by the application of N.

Experiments were conducted at three sites to examine effects of applying different nitrogen (N) fertilisers at 45 kg N ha-1, with and without phosphorus (P), potassium (K) and sulphur (S) on dairy pasture nutritive value and mineral content in autumn and spring. Pasture nutritive value was assessed by measures of crude protein (CP), metabolisable energy (ME), water-soluble carbohydrates (WSC) and neutral detergent fibre (NDF). Pasture mineral content was assessed by estimates of the major minerals phosphorus (P), potassium (K), sulphur (S), sodium (Na), calcium (Ca), and magnesium (Mg), and trace minerals manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn). Apart from some exceptions, applications of N, with and without additional P, K and S generally increased pasture CP and ME content in autumn and CP content in spring. Again with some exceptions, pasture WSC content was unaffected by fertiliser application in autumn, but was decreased by some treatments (containing N and N with P, K and S) in spring. Fertiliser treatments generally had no effect on pasture NDF content at Sites 1 and 3 during autumn and spring. At Site 2, some treatments (containing N and N with P, K and S) reduced pasture NDF content in autumn while during spring some treatments (containing N and N with P, K and S) increased pasture NDF content. Different N fertilisers applied at the same rate, with and without additional P, K and S, generally produced the same effect on pasture nutritive value. The application of P, K and S in the absence of N generally had no effect on pasture nutritive value. Apart from some exceptions, pasture P content was increased by fertiliser treatments including P, K and S, but N on its own did not influence pasture P content. Pasture K content was generally not influenced by treatment. At Site 1 during autumn and spring, and at Site 3 during spring, treatments containing P, K and S increased pasture S content while applications of N had no effect. At Site 2 during autumn, P, K and S increased pasture S content relative N only, while during spring pasture S content was generally increased by all treatments. At Site 3 during autumn, applications of N decreased pasture S content while P, K and S increased pasture S content relative to no fertiliser. Pasture Na and Ca content were generally not influenced by treatment. Pasture Mg content was not influenced by treatment at Sites 2 and 3. At Site 1 during autumn and spring, however, some treatments (containing N and N with P, K and S) increased pasture Mg content. Fertiliser treatments produced no consistent patterns or differences with respect to trace minerals (Mn, Fe, Cu and Zn).

Effects of nitrogen (N) (0, 15, 30, 45 and 60 kg N ha-1) applied at five different times during autumn and early winter on the N fixation of Trifolium repens L. (white clover) in Lolium perenne L. (perennial ryegrass) / white clover pastures were examined (Experiment 1). Effects of applying different N fertilisers (e.g. urea and ammonium nitrate) at 45 kg N ha-1 in autumn, with and without phosphorus (P), potassium (K) and sulphur (S) on N fixation were also tested (Experiment 2). In Experiment 1, percentage N derived from the atmosphere (percent Ndfa) by white clover varied between 87% and 91% in the period after (24 to 36 days) N application. Increasing rates of N and time of application did not influence percent Ndfa. The amount of N fixed by white clover ranged from 0.8 to 3.7 kg N ha-1 in the period after N application. Increasing rates of applied N produced a significant (P<0.05) linear increase in the amount of N fixed. In Experiment 2, percent Ndfa and amount of N fixed (1.9 to 4.1 kg N ha-1) were unaffected by different N fertilisers, with and without P, K and S, in the period after (37 days) fertiliser application. For both experiments, fertiliser N increased dry matter yield while having no effect on white clover composition. It is concluded that single applications of N during the autumn and early winter benefit pasture growth without adversely affecting white clover N fixation or clover composition. This finding, however, will require further investigation.

Polysialic acid-containing glycoproteins consisting of extended chains of at least 55 sialyl residues (DP55, where DP represents degree of polymerization) are expressed on human neuroblastoma cells, CHP-134. The strategy used for detecting these unique carbohydrate structures was based on the use of two highly specific prokaryotic-derived enzyme systems and an anti-polysialosyl antibody (H.46). These probes were developed for the detection of polysialic acid on neural cell adhesion molecules (Troy, F. A., Hallenbeck, P. C., McCoy, R. D., and Vimr, E. R. (1987) Methods Enzymol. 138, 169-185). Proof for the presence of long chain multimers of sialic acid was based on two types of experiments which utilized: 1) a glycopeptide fraction of CHP-134 cells, labeled metabolically with D-[3H]GlcN and 2) a membrane fraction from CHP-134 cells which served as an exogenous acceptor of [14C] NeuNAc residues in an Escherichia coli K1 sialyltransferase assay. In vitro, this enzyme CMP-NeuNAc:poly-alpha-2,8-sialosyl sialyltransferase catalyzes the transfer of [14C]NeuNAc from CMP-[14C]NeuNAc to exogenous acceptors containing at least 3 sialyl residues. In the first series of experiments, endo-N-acetylneuraminidase (Endo-N), a bacteriophage-derived enzyme specific for hydrolyzing poly-alpha-2,8-sialosyl chains containing a minimum of 5 sialyl residues was used. Limit Endo-N digestion of the 3H-glycopeptides from the [3H] GlcN-labeled cells released short [3H]sialyl oligomers [(3H]DP1-6) which were degraded to [3H]NeuNAc by exosialidase. Partial Endo-N digestion released a series of [3H]sialyl oligomers extending up to DP55. The longer (DP20-55) and intermediate sized (DP10-20) oligomers were isolated and converted to short oligomers ((3H]DP1-6) by retreating with Endo-N, thus confirming their identity as homo-oligomers of alpha-2,8-linked [3H]NeuNAc residues. In the second series of experiments, a membrane fraction of CHP-134 cells was radiolabeled in vitro with [14C]NeuNAc by E. coli K1 sialyltransferase. The membrane fraction had a major portion of radioactivity that was high Mr and polydisperse (Mr 100,000-250,000) as demonstrated in sodium dodecyl sulfate-polyacrylamide gels. Using Western blotting, pre-existing material of similar size was shown to react with antibody H.46.(ABSTRACT TRUNCATED AT 400 WORDS)

A type of immediate wheal-and-erythema reaction, similar to that observed in human atopic hypersensitiveness, was induced in guinea pigs that had been sensitized and tested with chemical compounds of the anhydride group.

Sensitization to allyl isothiocyanate was accomplished in a small percentage of unselected guinea pigs. By selective breeding a strain was obtained practically all the members of which could be readily and strongly sensitized with this substance. A strain resistant to sensitization is being further bred out.

Immediate generalized skin-reactions following contact with or ingestion of allergens have been observed in humans but not hitherto in animals, although Dienes and Simon1reported a generalized delayed reaction in guinea pigs treated with human serum. No observations of generalized skin-reactions in animals, due to simple chemical substances, have been noted in the literature. It seemed of interest, therefore, to report recent observations of such effects in a number of guinea pigs sensitized to citraconic anhydride, together with the sensitization of guinea pigs to new anhydrides having similar properties.The animals were rendered hypersensitive to citraconic anhydride by a method previously described2and were tested by scratching the skin through a 25% dioxane solution of the same substance, usually at intervals of 2 weeks.It was regularly observed that the more hypersensitive the guinea pig the quicker the onset of the reaction. Animals developing generalized reactions showed within a very few minutes a large local wheal and erythema surrounding the scratch, often several centimeters in diameter. At the same time in both contiguous and remote parts of the skin some pigs showed a diffuse pinkishness apparently accompanied by slight thickening, while others exhibited discrete, urticaria-like wheals with distinct elevation and pinkness. Often some of the old injection-sites on the back flared up at the same time, with marked wheal-formation. The erythema reached a maximum 20 to 30 minutes after the test, following which it gradually faded. Edema associated with reactivated sites and other lesions distant from the original scratch increased for about 2 hours and then also diminished. By the next day all such subsidiary reactions had completely disappeared. In striking, possibly significant contrast to this, the reaction in the vicinity of the scratch after receding to a minimal color and edema in 4 to 5 hours, gradually increased in pinkishness and induration to a second maximum reached about 24 hours after the test.

The recent paper by Cheever1on complement fixing antibodies in rabbits bearing Brown-Pearce tumors, observed by Kidd,2prompts the publication of a similar study carried out in the Spring of 1939 in which similarly positive results were obtained at first, but appeared questionable after the introduction of more rigid controls.The tumor strain was provided by Dr. J. B. Murphy and Mr. Ernest Sturm. Rabbits were inoculated by intratesticular injection. Antigens were prepared and the complement fixation tests carried out as described by Kidd.2aTwenty-five rabbits in all were tested after inoculation with tumor. In the early tests on some 14 rabbits, sera of 3 out of 6 rabbits in which tumors were rapidly developing with many metastases showed definite complement fixation, as compared with 10 negative normal sera used for control. Two other sera were doubtful and one negative. Of 5 animals with small tumors all were negative; and of 3 animals in which tumors indubitably grew and then regressed, all were negative. It may be of interest to note that in 2 of these latter animals kidney metastases appeared to have attained a size of from 3 to 6 mm or larger and subsequently regressed.However, difficulties were encountered in attempts to repeat this experiment. A considerable capacity of some normal sera to fix complement was observed under these conditions, and it was noted that the tumor extracts used as antigen also varied markedly in their complement fixing properties. Prolonged centrifugation, filtration through a Mandler filter, or simply passage of time reduced this tendency to fix complement. Attempts to distinguish more clearly between the sera of the normal and tumor-bearing rabbits by altering the strength of the antigen by dilution were unsuccessful, since a dilution of antigen which eliminated all reactions with normal sera usually also obliterated reactions with the sera of tumor-bearing rabbits.

Sensitization of guinea pigs to Rhus toxicodendronwas reported by Rackemann and Simon,1and has been repeated by a number of workers.2For testing it has been customary to apply an acetone solution of the substance to the skin and to note differences in speed of appearance and intensity of reactions in treated animals and controls. While treated animals react more strongly to these extracts than untreated, the latter also give reactions which develop within 48 hours and make it difficult to interpret results. Recently, hypersensitiveness in guinea pigs was again studied by Ginsberg, Becker, and Becker3who, attempting to overcome this difficulty, applied several dilutions of acetone extract in the tests. Straus,4on the other hand, deeming the guinea pig unsatisfactory, used the Rhesusmonkey which shows less irritation of normal skin; this finding has been utilized by Straus and Coca5in further experiments.It seemed desirable to obtain a method of testing guinea pigs that would bring out more clearly differences between sensitized animals and controls. An experiment typical of results obtained is given below.Six guinea pigs were sensitized, after clipping the hair with an electric clipper, by applying 5 drops of a 2% acetone solution of poison-ivy extract†on the back, spread with a glass rod. Ten days later the animals were tested on an untreated, clipped site (Table I) by applying gently with a glass rod 2 drops of a 2% solution of poison-ivy extract in acetone. This was washed off in 5 hours with an aqueous solution of potassium permanganate (2.5 %) containing 1 cc of N/1 sodium hydroxide per 100 cc. The site was then washed with water and dried with cotton, and wadings were made the next day not less than one hour after application of a depilatory. A preliminary test before the sensitizing treatment was negative in all animals, and an incidental test 2 days after the sensitizing treatment showed that none of the animals had acquired hypersensitiveness at this stage, as would be expected.

Changes in pasture metabolisable energy (ME), crude protein (CP), neutral detergent fibre (NDF), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), sodium (Na) and chlorine (Cl) were measured at each grazing, in 4 paddocks on 2 farms (farm A and farm B) in western Victoria from May 1995 to March 1997. Selection differentials were calculated from quality parameters using measures of pre- and post-grazing masses. Changes in botanical composition and pasture allowance were also measured. The nutritive characteristics of pasture on both farms followed similar trends. Metabolisable energy and CP were highest in winter and early spring with values of over 11 MJ/kg DM and 250 g/kg DM respectively. The lowest concentrations of ME and CP in pasture on farm A (9.4 MJ/kg DM; 128 g/kg DM) were observed in April and February respectively. On farm B the corresponding lowest values (8.4 MJ/kg DM; 100 g/kg DM) were in March. In contrast, NDF values on farm A were lowest in June (466 g/kg DM) and on farm B (436 g/kg DM) in May, with highest values in February (648 g/kg DM) and March (692 g/kg DM) respectively. Concentrations of P, K, S and Cl in pasture followed a similar pattern to that of ME with highest values in winter and lowest in summer, while changes in Ca concentrations related more closely to changes in NDF. The concentrations of Mg and Na were highest in autumn and spring, respectively, with lowest values in late spring and summer. Selection differentials indicated that the ME of pasture consumed was 4–22% higher than the pasture on offer. For CP the range of selection differentials was always greater than 1, but varied widely (1.08–1.83). The selection differentials for NDF were always negative, with an average value of 0.84. Selection differentials for minerals varied little over the year, with values generally indicating a positive selection differential (P 1.12, 1.15; Ca 1.16, 1.16; Mg 1.15, 1.18; K 1.23, 1.27; Na 1.05, 1.07; Cl 1.16, 1.14; S 1.27, 1.28) for farms A and B. Pasture allowances ranged from 10–60 kg DM/cow.day and there was no relationship between selection differentials for all nutritive characteristics and pasture allowance. The results obtained in this study indicated that although the ME of pasture consumed throughout the year should be adequate to meet production of 30 L/cow.day in early lactation with minimal liveweight loss, it was associated with high levels of CP and potentially low concentrations of NDF in relation to cow requirements. Results therefore indicate a possible need for supplementing pasture diets in winter and spring to balance the diet for CP and NDF. In addition, it is likely that both Ca and Mg intake from pasture may be limiting in early lactation and therefore additional supplements of both minerals may be required during this period.

Field experiments were carried out at 2 sites to study the effects of time and rate of nitrogen (N) application from autumn to midwinter on perennial ryegrass–white clover pasture dry matter (DM) yield and species composition. Nitrogen (0, 15, 25, 30, 45, and 60 kg/ha) was applied in mid-April, early May, mid-May, early June, and mid-June 1996 onto a grazed pasture. Dry matter yield was estimated when perennial ryegrass in the 45 kg N/ha treatment reached the 3-leaf stage of development. Species composition estimates were made on all plots in autumn, late winter, and late spring (November). Asecond DM yield estimate was taken one regrowth cycle after the primary DM yield estimate to determine residual N impact on pasture growth, and then the pastures were returned to the grazing routine of the farm. Increasing levels of N fertiliser resulted in a linear (Site 1) and curvilinear (Site 2) primary DM yield response. Residual DM yield responses were linear at both sites. The highest primary DM yield response at Site 1 was 9.1 kg DM/kg N (mid-April application), whereas the highest residual N response was 9.4 kg DM/kg N (mid-May application). The time taken for the 45 kg N/ha treatment to reach the 3-leaf stage of development ranged from 38 (early June application) to 47 (mid-April application) days for the primary harvest, and from 46 (early May application) to 72 (early June application) days for the residual harvest. At Site 2, the highest primary DM yield response to N was 15.8 kg DM/kg N at 45 kg N/ha (mid-April application), whereas the highest residual N response was 8.3 kg DM/kg N (mid-June application). The time taken for the 45 kg N/ha treatment to reach the 3- leaf stage of development ranged from 24 (early June application) to 36 (mid-April and early May applications) days for the primary harvest, and from 30 (mid-April) to 57 (early June application) days for the residual harvest. Based on the current cost of urea, the study concluded that N fertiliser use during autumn to midwinter is economically viable for dairy farmers. Botanical composition was unaffected by N application. There were no treatment effects on botanical composition of the sward at either site the following spring (November). It is concluded that a ‘once-off’ strategic N application up to 60 kg N/ha during autumn to midwinter is not likely to influence dairy pasture composition in western Victoria. dry matter yield, nitrogen responses, Lolium perenne, Trifolium repens.

Field experiments were carried out at 2 sites to study the effects of time and rate of nitrogen (N) application from autumn to midwinter on the nutritive value of perennial ryegrass–white clover dairy pastures in western Victoria. Nitrogen (0, 15, 25, 30, 45, and 60 kg/ha) was applied in mid-April, early May, mid-May, early June, and mid-June during 1996 onto a pasture which had been grazed and topped to a uniform height of 5 cm prior to imposition of treatments. Pasture samples to a height of 5 cm were collected when perennial ryegrass in the 45 kg N/ha treatment reached the 3-leaf stage of development. Samples were analysed for metabolisable energy (ME), crude protein (CP), neutral detergent fibre (NDF), and water-soluble carbohydrates (WSC). Increasing rates of N gave rise to a curvilinear (Site 1) and linear (Site 2) increase in pasture ME and CPcontent. The actual response of 0.007 MJ/kg DM. kg N at 45 kg N/ha was the same at both sites, regardless of N application time, and corresponded to an increase of 0.32 MJ/kg DM. At Site 1 the actual increase in CPcontent at 45 kg N/ha (0.067% per kg N applied) was the same for all application times and corresponded to an increase in CPcontent of 3%. For Site 2, the increase ranged from 0.040% (mid-April) to 0.098% (mid-May) per kg N, corresponding to a pasture CPcontent increase of 1.8 to 4.4% at 45 kg N/ha, respectively. The application of N gave rise to a curvilinear (Site 1) and linear (Site 2) decrease in pasture NDF. For Site 1 at 45 kg N/ha, the actual decrease ranged from –0.04% (early May) to –0.10% (mid-May) per kg N, corresponding to a pasture NDF content decrease of 1.69 to 4.61%, respectively. At Site 2, the actual decrease in NDF content (–0.04% per kg N applied) was the same for all application times and corresponded to a decrease of 1.58% at 45 kg N/ha. Apart from some exceptions, increasing rates of applied N gave rise to a linear (Sites 1 and 2) decrease in pasture WSC content. For Site 1, the change in pasture WSC content ranged from 0.007% (early May) to –0.032% (mid-June application) per kg N, corresponding to a change in pasture WSC content of 0.32 to –1.44% at 45 kg N/ha, respectively. At Site 2, the change in WSC content ranged from 0.0004% (mid-April) to –0.076% (mid-May) per kg N, corresponding to a change in pasture WSC content of 0.02 to –3.42% at 45 kg N/ha, respectively. In this study, N application had a positive effect on the nutritive value of dairy pastures in the autumn to midwinter, in western Victoria. This is particularly important for the provision of quality feed during this period as the majority of dairy herds in the region are calving at this time. Thus, the provision of an increased quantity of higher quality feed may lead to a reduction in the requirement for purchased feeds. Additional keywords: crude protein, metabolisable energy, neutral detergent fibre, water-soluble carbohydrates, Lolium perenne, Trifolium repens.

Summary. This study aimed to define the effect of differing rates of nitrogen application and lock up length on harvested material for silage in south-western Victoria. At 2 sites in south-western Victoria, 140, 3 by 2 m plots of predominantly perennial ryegrass pasture were randomly allocated, within 4 replicate blocks. Five nitrogen fertiliser rates (0, 25, 50, 75, 100 kg N/ha) in combination with 7 lock up lengths were randomly allocated to the 35 plots within each replicate. Nitrogen was applied 1 week after initial lock up (September 10, site 1; September 12, site 2) and harvesting commenced 3 weeks after initial lock up. For each treatment and harvest date, dry matter yield and botanical composition were determined and samples of total pasture and the ryegrass fraction were collected and chemically analysed for dry matter digestibility, crude protein, neutral detergent fibre, water-soluble carbohydrates and mineral content. Metabolisable energy was derived from dry matter digestibility. Increasing rates of nitrogen increased herbage dry matter yield regardless of length of lock up. The yield response was greatest 8 weeks after initial lock up at both sites (site 1, 26 kg DM/kg N; site 2, 14.9 kg DM/kg N). Subsequent regrowth of pasture was increased by nitrogen application over shorter lock up lengths (weeks 3 and 4). Botanical composition was unaffected by treatment during the harvesting period or in the subsequent autumn. Application of nitrogen gave rise to a linear increase in pasture metabolisable energy and crude protein content at both sites until week 5. Thereafter, this response diminished and by week 8 there was a decrease in metabolisable energy and crude protein content. Neutral detergent fibre content was relatively unaffected by nitrogen application until week 8 of the study, at which point there was a linear increase. Application of nitrogen reduced the water-soluble carbohydrate content of pastures throughout the sampling period. It is concluded that application of nitrogen to a mixed sward locked up for silage can increase dry matter yield and, provided pasture is harvested before ryegrass ear emergence, can also have a positive effect on metabolisable energy and crude protein. Given that the decision for removing paddocks from the grazing rotation is based upon pasture growth and stocking rates, the use of nitrogen fertilisers on higher stocked farms could lead to increased dry matter yield over shorter lock up periods. On farms with lower stocking rates shorter lock up periods may allow for pastures to be returned to the grazing rotation earlier, or provide the opportunity for a second harvest of pasture for silage.

Summary. Factors associated with silage quality were investigated on 140 dairy farms in western Victoria. The management factors measured were date of lock up, date cut, length of lock up, duration of wilting, raking and tedding during wilting period, rainfall during wilting period and the type of silage made. Pasture variables measured at harvesting included percentage composition (ryegrass, legume, other grasses and weeds), dry matter of pasture, metabolisable energy, crude protein, neutral detergent fibre and water-soluble carbohydrate of the pasture, and dry matter yield of the pasture. The average lock up time of pasture for silage was mid September, although the range was from late July to early November. The length of lock up varied from 16 to 91 days with a mean value of 49 days and pastures were on average harvested in early November. Ryegrass on average accounted for 61%, legumes and other grasses accounting for a further 15% each and weeds about 5%. The range in quality of pasture at harvesting was highlighted by the range in metabolisable energy (8.9–11.3 MJ/kg DM) and crude protein (10.2–20.4%) values. Wilting times varied from 0.5 to 15 days with the biggest range being observed in pastures used for baled silage. All factors were regressed against final silage metabolisable energy and crude protein. Factors which had the greatest effect on final silage metabolisable energy were date of cutting, length of lock up, type of silage, the interaction between type of silage and length of lock up, length of wilting and mechanical treatment during the wilting period. Final silage crude protein was most strongly associated with date of cutting, crude protein content of the pasture and mechanical treatment during the wilting period. Mechanical treatment during the wilting period had the greatest influence on silage quality. Other options to improve silage quality such as cutting earlier or reducing wilting periods may not be possible or economically viable.

Summary. At 2 sites in south-western Victoria, 132 plots of predominantly perennial ryegrass pasture were randomly allocated, within 4 replicate blocks, to each of 3 lock up dates (L1, L2, L3) by 12, 12 or 9 harvest times. Harvesting commenced 2 weeks after initial treatment lock up with L1 and L2 being harvested 12 times (weekly intervals) and L3, 9 times. Lock up dates were 15 August (L1), 5 September (L2) and 26 September (L3) at site 1 and 17 August (L1), 7 September (L2) and 28 September (L3) at site 2. For each treatment and harvest date, dry matter yield and botanical composition were determined and samples of total pasture and the ryegrass fraction were collected and assessed for dry matter digestibility, crude protein and neutral detergent fibre. Dry matter yield was measured from the start of L1 (site 1, 15 August; site 2, 17 August) until the final harvest date of L3 (site 1, 12 December; site 2, 14 December). At site 1, L3 produced higher dry matter yields than L1 and L2 at comparable lengths of lock up time, whilst there were no differences at site 2. Over the total experimental period (site 1, 15 August–12 December; site 2, 17 August–14 December) there were no differences in total dry matter yield (t/ha) between treatments at either site (site 1—L1 5.79, L2 6.43, L3 5.94; site 2—L1 6.68, L2 5.07, L3 5.73). Treatments had little effect on botanical composition at either site when compared at the same time after lock up, both during the harvesting period or in the subsequent autumn. Pasture metabolisable energy and crude protein all declined with increasing length of lock up whilst neutral detergent fibre content increased, changes which were similar for both the total pasture and the ryegrass fraction. The metabolisable energy of pasture in L1 and L2 was higher than that of L3 at least until week 8 at both sites. Initial crude protein values were higher for L1 and L2 than for L3 at site 1, whilst at site 2, L1 had higher values than either L2 or L3. Although longer lock up periods produced more herbage, if conserving forage is to be an integral component of managing surplus spring pasture, then dairy farmers should aim to produce high quality pasture for forage conservation. This will be achieved through shorter lock up periods and harvesting pasture no later than early ear emergence in the ryegrass fraction of the sward. This management will reduce dry matter yields, but allow more flexibility for maintaining intensive grazing practices through the spring period. The decision about when to lock up pasture will depend on both plant growth rates and animal feed requirements.

The ability of different Haemophilus influenzae type b conjugate vaccines to induce immunologic memory was compared in 381 infants who were vaccinated with one of three conjugate vaccines beginning at 2 months of age. All infants were vaccinated with unconjugated type b capsular polysaccharide, polyribosylribitol phosphate (PRP), at 12 months. In each group, high antibody responses were detected by 6–9 days after vaccination. One month after receiving PRP, infants primed with PRP conjugated to the outer membrane protein of Neisseria meningitidis or PRP oligomers conjugated to the cross-reactive mutant diphtheria protein, CRM197, had twofold higher total anti-PRP antibody concentrations than did infants primed with PRP conjugated to tetanus toxoid (P < .005). After the conjugate and the PRP boost, notable differences were present among vaccine groups with respect to the magnitude of the IgG anti-PRP antibody concentrations and light chain variable region usage as determined by idiotypic analysis. Thus, each of the conjugate vaccines primed infants for the ability to evoke memory antibody responses to PRP, but qualitative and quantitative differences in priming induced by different vaccines may affect their ability to confer protection against disease.