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Context: The incidence of extreme heat events (prolonged temperatures above 35°C) is increasing in the northern Victorian dairying region in Australia. This increase is having a significant effect on the performance of perennial ryegrass, which has traditionally been the major perennial species in these pastures. Aim: During seven extreme heat events, forage sampling was conducted on commercial farms to evaluate the effects of high temperatures on the nutritive characteristics of perennial ryegrass, tall fescue and lucerne. Our hypothesis was that reductions in nutritive characteristics with an increasing external temperature would vary among species. Methods: Before, during and after heat events, replicated samples of the three forage species were collected and analysed for in vitro dry matter digestibility (IVDMD), neutral detergent fibre (NDF), acid detergent fibre (ADF), water soluble carbohydrates (WSC) and crude protein (CP). Several anti-nutritive compounds (alkaloids in perennial ryegrass, and saponins and coumestrols in lucerne) were also measured. Key results: None of the temperate forage species evaluated maintained nutritive quality under high temperatures. Linear mixed model (LMM) analyses showed that for each degree rise between 23°C and 40°C, IVDMD and WSC concentrations decreased by 0.2% while NDF and ADF concentrations increased by 0.2% and 0.15% respectively. Concentrations of the alkaloid, ergovaline, in the base of the perennial ryegrass tiller were close to, or above, the recommended threshold level for animal health and welfare in three of the six samples taken during heat events. Conclusions: These results suggest that extreme heat events have a detrimental effect on the nutritive characteristics of the evaluated forage species. Implications: Heat-induced decreases in nutritive characteristics will potentially have serious implications for milk production and farm productivity. Further research, undertaken under controlled conditions of temperature, humidity and plant growth stage, is recommended to determine the full effect of these extreme summer conditions on forage nutritive characteristics. The effects of extreme heat events on the nutritive characteristics of pastures were studied in three farms in northern Victoria, Australia. Nutritive quality decreased at high temperatures in all species, with implications for milk production. Further research is recommended. [ABSTRACT FROM AUTHOR]

Context: Metabolisable energy (ME) and crude protein (CP) concentrations of forages are key determinants of lamb performance during pasture-based finishing. However, forage species often have unbalanced proportions of ME and CP, which can lead to below-optimum performance of lambs. This may be a problem with maturing lucerne (Medicago sativa L.) swards during dry summer conditions, and is a major challenge faced by grazing industries in Mediterranean environments. Aim: We investigated whether two summer forages, lucerne and forage brassica (Brassica napus L. cv. Winfred), with differing ME and CP concentration could improve the growth of maternal-composite lambs when offered in mixtures compared with either forage fed alone. Methods: A randomised complete block experiment with five treatments and 10 replicate animals per treatment was conducted in an animal house at Hamilton, Victoria, from February to March 2014. The treatments were 100% lucerne, 75% lucerne : 25% brassica, 50% lucerne : 50% brassica, 25% lucerne : 75% brassica, and 100% brassica on a dry-matter basis and fed to lambs. The lucerne and brassica were harvested daily and chopped to ~3 cm length before mixing and feeding. The lambs were adapted for 4 weeks before the start of the experimental phase. Key results: Fasted liveweight gain of lambs increased linearly with an increasing proportion of brassica and a decreasing proportion of lucerne in the diet; no mixture performed better than brassica alone. Conclusions: Under the warm and dry conditions of this experiment, the ME of lucerne was more limiting to lamb growth than its CP concentration. Implications: The results suggest that a small increase in ME supply could improve the performance of lambs grazing a maturing lucerne sward during dry summer conditions. Further research is warranted into improving lamb growth and feed efficiency from lush lucerne and brassica forages. Different forage species often have unbalanced proportions of metabolisable energy (ME) and crude protein (CP), leading to below-optimum performance of lambs. We investigated the effects on lamb performance of two summer forages, lucerne and brassica, differing in ME and CP concentrations, during summer–early autumn in southern Australia and found that ME of lucerne was more limiting to lamb growth than its CP concentration under the warm and dry conditions. The results suggest that a small increase in ME supply could improve the performance of lambs grazing a maturing lucerne sward during dry summer conditions, a major challenge faced by grazing industries in these Mediterranean environments. [ABSTRACT FROM AUTHOR]

Context: The Australian dairy industry is characterised by pasture-based feeding systems, where grazed pasture is commonly supplemented with cereal grain to increase milk production of dairy cows. Perennial ryegrass (PRG; Lolium perenne L.) is the most commonly used pasture species, with a wide range of cultivars available. However, the nutritive characteristics and the degradation of nutrients in individual PRG cultivars grown in different environments in Australia are unknown, and significant variation between cultivars may impact on supplementary nutrient requirements. Aims: The objective of this experiment was to quantify the extent of ruminal degradation of nutrients in three contrasting PRG cultivars (Bealey NEA2, Trojan NEA2 and Victorian SE) harvested during early spring and summer from Gippsland, northern Victoria and south-west Victoria in Victoria, Australia. Methods: Degradation parameters were determined by in situ incubation in the rumens of non-lactating, rumen-fistulated Holstein–Friesian cows for 72 h using a nylon bag technique. Key results: During both seasons, Bealey NEA2 had the greatest effective degradability of crude protein and neutral detergent fibre compared with Trojan NEA2 and Victorian SE. Cultivars harvested during early spring had greater effective degradability of crude protein and neutral detergent fibre, and a greater amount of rumen degradable protein compared with cultivars harvested during summer. Cultivars harvested from Gippsland had greater crude protein and neutral detergent fibre effective degradability, as well as a greater amount of rumen degradable protein, whereas cultivars harvested from northern Victoria had a greater amount of undegraded dietary protein. Conclusions: These results demonstrate that the ruminal degradation of PRG cultivars declines with increasing maturity, and that there are differences between cultivars and regions; however, differences between seasons are of a greater magnitude and are more important to consider when formulating optimal supplementary grain rations. Implications: This research has positive implications for farmers who will be able to understand the degradation of nutrients in PRG, and the amounts of rumen degradable protein and undegraded dietary protein available from pasture during each season. Farmers will be able to use this information to formulate supplementary grain rations that complement the nutrients from pasture and optimise milk production. Dairy production in south-eastern Australia is based on pasture-based feeding systems, where perennial ryegrass is the most common pasture species grown. This research provides novel information on the degradation characteristics of perennial ryegrass cultivars grown on farms in Australia, with degradability decreasing as the pasture matures. This will help farmers to formulate supplementary grain rations to match nutrient supply from pasture. [ABSTRACT FROM AUTHOR]

Improvement in nutritive characteristics resulting from breeding perennial ryegrass (PRG) cultivars used in Australia from the 1970s to the present day was quantified in a grazed field experiment in south-western Victoria. The experiment was sown in May 2014 with measurements undertaken over 3 years. The experiment contained 36 PRG treatments (cultivar–endophyte combinations), which were replicated four times, with herbage nutritive characteristics measured at each grazing. The treatments differed in estimated metabolisable energy (ME), crude protein and neutral detergent fibre (NDF) concentrations at each harvest date. The decade of cultivar release had little effect on the ME or the NDF concentration of the cultivars released from 1970s onward. Early season diploids had a lower ME concentration than did later-maturing diploid cultivars (11.0 vs 11.4 MJ/kg DM), predominantly due to a lower ME concentration in late spring and early summer (10.3 vs 11.1 MJ/kg DM). The tetraploid cultivars had a higher ME concentration (11.8 vs 11.4 MJ/kg DM) and a lower NDF (480 vs 505 g/kg DM) concentration than did the mid- and late-season diploid cultivars. These differences are likely to be of economic importance at the farm level. The genetic gain in nutritive characteristics of perennial ryegrass cultivars has not been quantified in dairy environments in Victoria. This work aimed to quantify these improvements, but found that most cultivar differences could be attributed to cultivar maturity and ploidy factors, with little effect of the decade of release. These cultivar differences are likely to be of economic importance at the farm level. [ABSTRACT FROM AUTHOR]

There has been little research that has quantified methane (CH4) yields when dairy cows consume diets containing wheat grain. Furthermore, although rumen-fistulated animals have been used in many experiments concerned with measuring CH4 emissions, no research has examined the effect of rumen fistulation on in vivo CH4 emissions and yield. This experiment examined the effects of including either wheat or corn grain in the diet and the effects of rumen fistulation on yields of milk and milk components, CH4 emissions, yields, and intensities. Eight rumen-fistulated and six non-fistulated Holstein dairy cows in late lactation were offered a wheat-based diet (WHT) and a corn-based diet (CRN) in a crossover design. For the WHT diet, cows were offered daily, 22.4 kg DM containing 45.5% lucerne hay, 8.9% canola meal, 0.5% mineral mix, 0.5% molasses powder and 44.6% rolled wheat. The CRN diet was similar to the WHT diet except that rolled corn replaced the wheat. There was no difference between the WHT and CRN diets on mean milk yields (27.8 vs 27.9 kg/day), but the WHT diet substantially reduced milk fat concentration (2.76 vs 4.23%) and milk fat yield (0.77 vs 1.18 kg/day). Methane emissions (218 vs 424 g/day), CH4 yield (11.1 vs 19.5 g/kg dry matter intake) and CH4 intensity (7.6 vs 15.7 g/kg milk) were all reduced ~45% by the WHT diet compared with the CRN diet. Rumen fistulation did not affect dry matter intake, milk production, milk composition or CH4 emissions, but decreased CH4 yield and intensity. Including wheat in the diet of dairy cows has the potential to be an effective strategy to reduce their greenhouse gas emissions. In addition, rumen fistulation was associated with a small reduction in CH4 yield and intensity, and this should be considered when using rumen-fistulated cows in research concerned with CH4 emissions. Adding grain to the diet of dairy cows reduced methane emissions, but different grains could have different sized effects. Cows fed similar amounts of wheat or corn grain produced similar volumes of milk, but cows fed wheat had lower milk fat concentration and lower methane emissions than cows fed corn. The inclusion of wheat in the diet of dairy cows has the potential to be an effective strategy to reduce their greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

Milk production responses were measured in grazing cows offered mixed rations with or without canola meal. Experiments were conducted in spring (Experiment 1; early lactation) and autumn (Experiment 2; late lactation). The experiments used 140 (Experiment 1) or 96 (Experiment 2) Holstein-Friesian multiparous dairy cows that had calved in late winter/early spring. Each experiment lasted 28 days including a 14-day adjustment period and a 14-day measurement period during which intake and milk production was measured. In each experiment, there were two dietary treatments: PMR: cows grazed a restricted pasture allowance (10–15 kg DM/cow per day, measured to ground level) supplemented with a PMR comprising wheat grain (60%, DM basis), lucerne hay (21%) and maize grain (19%); and PMR+C: cows were fed the same as the PMR cows, but some wheat grain in the PMR was replaced with solvent-extracted canola meal so that it comprised wheat grain (39%, DM basis), lucerne hay (21%), maize grain (19%) and canola meal (21%). The two treatments were randomly allocated to half the cows in each experiment. Cows were then further allocated into 10 groups of 7 cows (Experiment 1) or 8 groups of 6 cows (Experiment 2). Two groups of cows were assigned to receive a different amount of each ration: 8, 10, 12, 14 or 16 kg DM total supplement/cow per day for Experiment 1 and 6, 8, 10 or 12 kg DM total supplement/cow per day for Experiment 2. In Experiment 1, yields of energy corrected milk (ECM), milk fat, and milk protein were greater for PMR+C cows than PMR cows when 12 kg/cow per day of supplement or more was offered. Milk protein concentration was greater in PMR+C cows than PMR cows but only when 16 kg DM supplement/cow per day was offered. These changes in milk yield and composition were associated with increases in the intakes of pasture, supplement and total DM intake in the PMR+C cows compared with the PMR cows. In Experiment 2 there were no differences in milk yield or composition between PMR and PMR+C cows at any amount of supplement offered, nor were there any differences in intakes of pasture, supplement or total DM intake. It is concluded that replacing some of the wheat in a well-formulated PMR with canola meal can stimulate DMI and increase per-cow production of ECM when high amounts of supplement are fed in early lactation, but not late lactation. Grazing cows were fed supplementary mixed rations with or without canola meal. In early lactation, the addition of canola meal resulted in increased yields of milk, milk fat and milk protein when high amounts of ration were offered, but this effect was not seen in late lactation. These data could be used to formulate cost-effective rations for grazing dairy cows. [ABSTRACT FROM AUTHOR]

Dairy production systems in south-eastern Australia are based primarily on grazed pasture. Perennial ryegrass (Lolium perenne L.) is the major grass species used in this region and farmers are faced with the challenge of choosing from more than 60 commercially available cultivars. This paper describes the development of a system termed as a forage value index that ranks the overall performance of perennial ryegrass cultivars relative to cultivar Victorian according to the summation of the estimated difference in the value of seasonal dry-matter (DM) yield of the cultivars. Average predicted seasonal DM yields were calculated by analysing the results of eight available perennial ryegrass plot trials across southeastern Australia, using a multi-environment, multi-harvest linear mixed model. The differences in the model-predicted DM yield of each cultivar was compared with cultivar Victorian in each of five seasonal periods (autumn, winter, early spring, late spring, summer) to generate a series of performance values (1 per period) for each cultivar. Each performance value was then multiplied by an economic value (AU$/kg extra pasture grown) relating to each of four regions (Gippsland, northern Victoria, south-western Victoria, Tasmania) and seasonal period and aggregated to generate an overall forage value index rating for each cultivar. Economic values ranged from AU$0.11 to AU$0.39 per extra kilogram of DM grown, depending on the season and region, which translated into estimated benefits on dairy farms of up to AU$183 per ha per year for farmers that use high-yielding cultivars in place of cultivar Victorian perennial ryegrass. [ABSTRACT FROM AUTHOR]

Understanding the economic trade-off between changes in the supplementary feed required and the cost of pasture renovation is important when considering investing in alternative forages. Perennial ryegrass (Lolium perenne L.) is the main pasture species used for dairy production in temperate Australia. Alternatives to perennial ryegrass are grown to complement the seasonal growth pattern of perennial ryegrass, and to potentially increase annual dry matter (DM) yield. A case study analysis of a dairy farm in Gippsland was used to explore the benefits and costs over 15 years when either 0%, 20% or 40% of the milking area was sown to chicory (Cichorium intybus L.), with the balance sown to perennial ryegrass. Chicory was part of a 3-year pasture renovation cycle; in the year of establishment, annual ryegrass was sown in the autumn, with chicory sown in spring, followed by 27 months of production. This was compared with a 5-year renovation cycle of perennial ryegrass. Stocking rates of 3.3 and 2.5 cows/ha were modelled. A whole farm budget approach with stochastic simulation was used to quantify the potential effect on profit and risk. The profitability of growing chicory depended on the balance among (1) savings in supplementary feed costs during summer and autumn, and (2) possible reductions in the overall supply of DMduring winter and early spring, and (3) increased pasture renovation costs. Stocking rate influenced the most profitable percentage of land sown to chicory. When stocking rate was 3.3 cows/ha, sowing 20% of the milking area to chicory returned a net present value (NPV) over 15 years AU$31 000 greater, on average, than did sowing 0% chicory, and AU$46 000 greater than sowing 40% chicory. With 2.5 cows/ha, sowing 40% of the milking area to chicory returned an NPV AU$39 000-AU$102 000 greater, on average, than did sowing either 20% or 0% chicory, respectively. The ratio of perennial ryegrass to chicory had little effect on the variability of NPV. For an individual farm, the most profitable percentage will fluctuate over time with variations in prices, seasonal conditions and management choices. [ABSTRACT FROM AUTHOR]

Purchased concentrates are a significant variable cost of a dairy business. Farm economic theory states that feeding supplements will enable a dairy farmer to improve profit as long as the marginal revenue received from the milk produced exceeds the marginal cost of the supplement. To do this, the quantities of milk, milk protein and milk fat produced from a unit of concentrate added to the diet are needed. Recent research has compiled results from short-term concentrate feeding experiments conducted in Victoria over a 30-year period. Using these data, relationships for the response of milk production to cereal grain supplements in dairy cows grazing temperate pastures have been developed and shown to be a better predictor than previous relationships. These response functions were used in the present study to investigate the economics of tactical (short-term; weekly, monthly or seasonally) and strategic (medium- to longer-term) supplementary feeding decisions in a pasture-based system, including, specifically, how much concentrate should be fed in a particular farm situation, given a certain feed cost and milk price. In the present paper, the relevant production economics method is explained and applied to determine the amount of supplement to feed that will maximise the margin of total extra milk income minus the total cost of supplement, thereby adding the most to farm profit. Currently, when dairy farmers make decisions about how much more supplement to feed their herd, they are making implicit judgements about the extra milk, and other potential benefits, that they expect to result as well as what the milk will be worth. More finely tuned decisions about feeding supplements based on comparing marginal cost and marginal revenue would add more to farm profit than decisions based on other common criteria, such as feeding supplement for maximum milk production. While some farmers may already be feeding supplements close to the point where marginal cost equals marginal revenue, the formal method of marginal analysis reported here makes explicit what is done implicitly at present and tests farmers' intuitive decision-making. More detailed information about the responses to supplements and the costs and benefits of feeding supplements under particular circumstances at different times through the lactation has the potential to enable better, more profitable decisions to be made about feeding cows and managing the whole farm. [ABSTRACT FROM AUTHOR]

Abstract: The determination of water‐soluble carbohydrate (WSC) concentrations in forages is important for quantifying forage feed quality as WSC is not only a major source of energy but is also associated with the grazing preferences of forages and subsequent intake by livestock. This study describes a high‐throughput ultra‐performance liquid chromatography (UPLC) method to analyse WSC concentrations of various forage samples. The application of the new method is demonstrated by investigating the WSC concentrations in (i) temperate forages at different tiller heights, and (ii) summer forage crops grown under rain‐fed and irrigated conditions. The UPLC method provided a more descriptive, specific and precise analysis of WSC concentration compared to the colorimetric method. Grass tiller height had a significant effect on total WSC concentration and individual sugar. With increasing tiller height, sucrose concentration increased and fructan and total WSC concentrations decreased. While irrigation treatment increased the dry‐matter yield of all nine summer forage crops analysed, there was no consistent effect of irrigation on WSC concentration. [ABSTRACT FROM AUTHOR]

This experiment compared the rumen degradability characteristics of five starch-based concentrate supplements used by Western Australia (WA) dairy producers. Six rumen-fistulated, non-lactating, Holstein-Friesian cows were used to measure the in sacco rumen degradability of maize grain, oats, wheat, sodium hydroxide-treated wheat (NaOH wheat) and Maximize® (a commercial pellet commonly used byWAdairy producers). Cows were offered a basal diet of custom-made cubes (60 : 40 lucerne hay : wheat grain) at maintenance feeding level. Rumen disappearance of dry matter (DM), starch and crude protein was determined for each concentrate at 0, 1, 2, 4, 8, 16, 24, 36, 48 and 72 h, and fitted to an exponential model to estimate degradation kinetics. Effective degradability coefficients were then calculated at three rumen solid-outflow rates (0.02, 0.05 and 0.08/h). Degradability of DM at 0.08/h was lowest (P < 0.001) in maize grain (0.64) and oats (0.68) and greatest in wheat (0.83), with that in NaOH wheat (0.80) and Maximize (0.76) being intermediate. Starch degradability at 0.08/h was also lowest (P < 0.001) in maize grain (0.70), intermediate for NaOH wheat (0.83) and Maximize (0.87), and greatest for wheat (0.96) and oats (0.98). Degradability of crude protein was lowest (P=0.001) in Maximize (0.66) andNaOH wheat (0.69), greatest in oats (0.85), with that in maize grain (0.72) and wheat (0.79) being intermediate. For producers where availability of maize grain for dairy cow rations is limited, such as in WA, these results indicated that NaOH wheat and Maximize may be considered as alternative starch sources to increase post-ruminal digestion of starch, although the magnitude of this increase will still not be as great as for maize grain. [ABSTRACT FROM AUTHOR]

Holstein-Friesian dairy cows managed in pasture-based systems are capable of lactating for considerably longer than the traditional 300 days. However, the partitioning of dietary nutrients in the second 300 days of an extended lactation has been shown to be different from that in the first 300 days. The partitioning of dietary nitrogen (N) was investigated using two groups of eight Holstein cows in four experimental periods of 6 days, at 110, 270,450 and 560 days in milk (DIM). During each period, cows were housed in individual stalls where N intake and output were measured. Cows in a control group received a forage-based diet ad libitum, whereas cows in a second group received 5 kgDMof cereal grain and the basal forage diet ad libitum. N intake was positively related to outputs of milk N, urinaryNand faecal N, and negatively to N-use efficiency (NUE). DIM was positively related to output of urinary N and negatively related to NUE and outputs of milk N and faecal N. The partitioning of N in the second year of an extended lactation was different from that in the first year, meaning that the partitioning of N reported for cows up to 300 DIM cannot be used to accurately predict the partitioning of N in cows beyond 300 DIM. Adding grain to the diet increased total nitrogen intake but decreased NUE.However, it is plausible for the addition of cereal grain to the diet of dairy cows to increase NUE, but only when the concentration of dietary crude protein decreases and any increase in dry-matter intake is small, such that total nitrogen intake is decreased. [ABSTRACT FROM AUTHOR]

There is a need to develop simple, accurate methods for predicting methane emissions, yields and intensities of dairy cows. Several studies have focussed on the relationship between the concentrations of trans-10 plus trans-11 C18:1 fatty acids in milk fat and methane yield. The aim of the present study was to perform a meta-analysis to quantify relationships between the concentrations of various trans isomers of C18:1 in milk fat and methane emissions (g/day), methane yield (g/kg dry-matter intake) and methane intensity (g/kg energy-corrected milk yield). Data were from seven experiments encompassing 23 different diets and 220 observations of milk fatty acid concentrations and methane emissions. Univariate linear mixed-effects regression models were fitted to the data with the linear term as a fixed effect and with experiment and observation within experiment as random effects. Concentrations of trans-9, trans-10, trans-11 and trans-10 plus trans-11 isomers of C18:1 were poorly related to methane emissions, yields and intensities, with the best relationships being between trans-10 C18:1 and methane emissions (R² = 0.356), trans-10 C18:1 and methane yield (R² = 0.265) and trans-10 plus trans-11 C18:1 and methane intensity (R² = 0.124). The data indicated that the relationships between trans-10 C18:1 and methane metrics were not linear, but were biphasic and better described by an exponential model. However, even exponential models poorly fitted the data. It is concluded that the concentrations of trans isomers of C18:1 have limited potential to accurately predict methane emissions, yields or intensities of dairy cows. [ABSTRACT FROM AUTHOR]

Grape marc consists of the skins, seeds and stems remaining after grapes have been pressed to make wine. Interest in grape marc for use as a dietary feed additive for ruminants has grown after recent research showed that inclusion of grape marc in the diet of dairy cows reduced their enteric methane (CH4) emissions. In the present research, in vitro fermentations were conducted on 20 diverse grape marcs to evaluate their potential as ruminant feed supplements and, in particular, mitigants of enteric CH4 emissions. The grape marcs, which were sourced from vineyards in south-eastern Australia, contained a range of red and white grape varieties with different proportions of skins, seeds and stalks, and had diverse chemical compositions. For each grape marc, four replicate samples, each of 1 g DM, were incubated in vitro with ruminal fluid. The volumes of total gas and CH4 produced after 48 h of incubation were determined. Total gas production ranged from 21.8 to 146.9 mL and CH4 production from 6.8 to 30.3 mL. White grape marcs produced more (P < 0.05) total gas (81.8 mL) than did red grape marcs (61.0 mL), but had a lower (P < 0.05) percentage of CH4 (25.3% and 30.3% of total gas). Grape marcs with a higher proportion of seeds produced less (P < 0.05) total gas than did the types composed of either skin or stalks; however, the seed types produced the greatest (P < 0.05) percentage of CH4 (49.8% of total gas). It is concluded that grape marcs differ greatly in their potential as mitigants of enteric CH4 emissions for ruminal production systems. [ABSTRACT FROM AUTHOR]

Previous research has documented nutritive characteristics of perennial ryegrass-based pastures and subsequent nutrient-selection differentials when dairy cows graze such pastures, but there has been little comparable research on alternative pasture grasses. The aim of the present study was to compare the pre-grazing nutritive characteristics of four perennial grasses, how nutrients vary with plant height, and selection differentials achieved by dairy cows grazing these grasses in late winter and late spring. The study utilised an established field experiment, with four replicates of monoculture swards of perennial ryegrass (Lolium perenne L.), tall fescue (Festuca arundinacea Schreb.), cocksfoot (Dactylis glomerata L.) and prairie grass (Bromus willdenowii Kunth.), in western Gippsland, Victoria. Eighty individual tillers per replicate were sampled to ground level immediately pre- and post-grazing in late winter (July-August, vegetative tillers only) and late spring (November-December, vegetative and reproductive tillers sampled separately), dissected into three height categories (0-5 cm, 5-10 cm and 10+ cm) and analysed for nutritive characteristics. For vegetative tillers in both seasons, perennial ryegrass had the highest estimated metabolisable energy concentration and lowest neutral detergent fibre concentration of all species. In spring, reproductive tillers had consistently lower nutritive characteristics than did vegetative tillers. Selection differentials, calculated as the ratio of nutritive characteristics selected by the herd to that available pre-grazing, showed that cows selected herbage with higher crude protein concentration but there was little evidence for selection of higher metabolisable energy concentration. The selection differentials reflected the vertical distribution of nutrients in the tillers. The present results have provided new information to assist in developing grazing guidelines for alternative perennial grasses. [ABSTRACT FROM AUTHOR]

Milk production was measured in Holstein-Friesian cows offered low, medium or high allowances of ryegrass pasture (15, 25 or 40 kg DM/cow.day to ground level) and receiving different amounts of supplement (6, 10, 12 or 14 kg DM/cow.day) as a partial mixed ration (PMR). The 27-day experiment was conducted in spring whencows were 45 ± 17.3 days in milk (mean ± s.d.). Two groups of six cows received each of the 12 combinations of pasture allowance andPMRamount. The PMRcomprised wheat grain (38%,DMbasis), maize grain (18%), lucerne hay (22%) and canola meal (22%). When 6 kgDM PMR/cow.day was offered, cows grazing the low allowance produced less milk and energy-corrected milk than did cows grazing the medium and high allowances. There was no effect of pasture allowance on production of milk or energy-corrected milk at any other amount of PMR offered. When cows were offered 14 kgDMPMR/cow.day, milk fat concentrations were lower for cows grazing the high pasture allowance than for cows grazing the medium allowance. There were no differences in milk fat concentrations between cows grazing the different pasture allowances at any other amount of PMR offered. When cows were offered 6 kg DM PMR/cow.day, cows grazing the low pasture allowance yielded less milk fat than did cows grazing the medium pasture allowance. Cows grazing the high allowance had greater concentrations and yields of milk protein than did cows grazing the low allowance at all amounts of PMR offered, while cows grazing the medium allowance yielded more milk protein at some amounts of PMR. Pasture utilisation decreased with increases in both pasture allowance and amount of PMR. These results will enable farmers to better optimise feeding systems that combine both pasture andPMR. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In southern Australia, pastures comprised of annual ryegrass may not meet the nutritional requirements of fast-growing (>250 g/day) lambs in summer-autumn (December-May). An animal house experiment was conducted from March to July 2010 to investigate the use of flaxseed and algae as two potential supplements to improve feed intake, liveweight gain and carcass traits in lambs. One hundred and twenty lambs (in two groups of 60) were fed one of four diets, pelleted annual pasture hay (subterranean clover and annual ryegrass) (T1); pelleted annual pasture hay + flaxseed flakes (T2); pelleted annual pasture hay + algae supplement (T3); pelleted annual pasture hay + flaxseed flakes + algae supplement (T4). All diets were provided on an ad libitum basis with individual feed intake measured daily and liveweight recorded weekly. Lambs offered the flaxseed flakes (T2) treatment grew faster (P < 0.05), had heavier (P < 0.05) carcass weights and greater (P < 0.05) GR fat depth (total tissue depth at 11th/12th rib, 110 mm away from midline) than lambs offered the T1 diet. Lambs offered algae supplement (T3) had lower dry matter intake but growth rate and carcass weight were not affected compared with lambs offered the T1 diet. Lambs offered both flaxseed flakes and algae supplement (T4) had greater (P < 0.05) GR fat than lambs offered the T1 diet. This experiment provides evidence that supplementing growing lambs with flaxseed flakes can increase dry matter intake, growth rate and GR fat depth. In contrast, supplementing with an algae supplement reduced dry matter intake but growth rate and carcass weight were similar to the control treatment. [ABSTRACT FROM AUTHOR]

The feeding of cereal-based supplements is common in the Australian dairy industry, as it allows cows to increase intakes of total dry matter (DM) and metabolisable energy (ME), while achieving greater stocking rates, greater pasture utilisation and greater milk production per hectare than occurs when cows are fed pasture-only diets. However, for this practice to be profitable, it is important to know how much extra milk, milk protein and milk fat are produced for each kilogramDMconsumed. This is difficult to determine in such a complex biological system. We combined information from 24 concentrate-feeding experiments using meta-analysis techniques, so as to develop improved prediction models of the milk, milk protein and milk fat produced when cereal-based concentrates are fed to grazing, lactating dairy cows. Model terms, consistent with biological processes, linear, quadratic and factorial, were selected according to statistical significance. The models were then tested in two ways, namely, their goodness of fit to the data, and their ability to predict novel production data from a further six, unrelated, experiments. A sensitivity analysis was also undertaken to determine how sensitive these predictions are to changes in key inputs. The predictive model for milk yield was shown to very closely reflect milk yield (kg/cow.day) measured under the experimental conditions in unrelated experiments (r = 0.96), with very little bias (Lin's bias correction factor = 0.98) and high concordance (Lin's concordance coefficient = 0.95). Predictions generated by multiplying predicted milk protein concentration by predicted milk yield closely matched observed milk protein yield (kg/cow.day) (r = 0.96, Lin's bias correction factor = 0.98, Lin's concordance coefficient = 0.95), and predictions found by multiplying predicted milk fat concentration by predicted milk yield closely matched observed milk fat yield (kg/cow.day) (r = 0.94, Lin's bias correction factor = 0.99, Lin's concordance coefficient = 0.93). Factors included in the new models for milk, milk protein and milk fat yield reported here have been identified previously as elements that can influence milk production. The value to the dairy industry from being able to predict profitable amounts of concentrates to feed at various stages throughout lactation is considerable. For farmers and their advisers, being able to apply these models to estimate the immediate marginal milk protein and milk fat responses to supplementary feeds should lead to more robust, efficient and profitable milk production systems. [ABSTRACT FROM AUTHOR]

Dry matter production and nutritive characteristics of the pasture feedbase during autumn are key drivers of profitability in Australia's prime lamb systems. An experiment was conducted to test the hypothesis that offering lambs dietary choice through spatially separated combinations of perennial ryegrass (Lolium perenne L.), plantain (Plantago lanceolata L.) and/or lucerne (Medicago sativa L.) improves the post-weaning liveweight gain, condition score (CS), pre- and post-slaughter carcass characteristics and reduces the internal parasite burdens of weather lambs finished to a slaughter weight over autumn, relative to lambs offered no dietary choice. The experiment tested seven treatments, replicated four times in a randomised complete block design with plot sizes of 10.1 ha. The treatments were: 100% perennial ryegrass (PR), 100% plantain (PL), 100% lucerne (LU), 50 : 50 perennial ryegrass/plantain (PR + PL), 50 : 50 perennial ryegrass/lucerne (PR + LU), 50 : 50 plantain/lucerne (PL + LU) and 33 : 33 : 33 perennial ryegrass/plantain/ lucerne (PR + PL + LU). Plots were grazed by weaned lambs between March and June 2011. The lambs had been born between 3 August and 7 September 2010 and were derived from either Coopworth composite dams joined to Coopworth maternal sires or from Merino dams (Toland or Centreplus bloodlines) joined to Border Leicester sires. Backgrounding the lambs on a pasture system that contained lucerne during the lactation to weaning period increased (P < 0.05) liveweight at slaughter by 8% and hot carcass weight by 10%, relative to lambs backgrounded on perennial ryegrass. Finishing lambs on the LU treatment between weaning and slaughter increased (P < 0.05) liveweight at slaughter by 11%, CS at slaughter by 0.3 units, hot carcass weight by 16%, carcass CFAT (measured over the loin) by 2.5 mm, carcass eye muscle depth by 1.1 mm and carcass GRFAT (total tissue depth at 11/12th rib, 11 cm from mid line) by 3.8 mm, relative to lambs finished on the PR treatment. Finishing lambs on LU + PR, LU + PL or LU + PR + PL did not (P > 0.05) improve any of the measured parameters, relative to finishing lambs on the LU treatment. The PL and PR treatments did not differ (P > 0.05) in liveweight at slaughter, CS at slaughter or carcass characteristics, but the PL treatment had lower (P < 0.05) liveweight gain than the PR treatment during the first 2 weeks of the experiment (39 g/day vs 330 g/day), which was later partially compensated for. Our hypothesis has not been supported given that the use of spatially arranged mixes resulted in no improvement in liveweight gain, CS, carcass characteristics or internal parasite burdens relative to the comparable single species sward. [ABSTRACT FROM AUTHOR]

Offering livestock dietary choice through access to different pasture species enables livestock to regulate their own feed intake, select for nutrients and minerals, balance rumen health and display natural grazing and foraging behaviours, which could in turn result in increased livestock productivity. An experiment was conducted at Hamilton, Victoria, Australia, to test the hypothesis that offering lambs dietary choice through spatially separated combinations of pasture species would improve lamb performance, relative to lambs with no dietary choice. The experiment tested seven treatments, replicated four times in a randomised complete block design with plot sizes of 1 ± 0.1 ha. The treatments were: 100% perennial ryegrass (Lolium perenne L.) (PR), 100% plantain (Plantago lanceolata L.) (PL), 100% lucerne (Medicago sativa L.) (LU), 50 : 50 perennial ryegrass/plantain (PR + PL), 50 : 50 perennial ryegrass/lucerne (PR + LU), 50 : 50 plantain/lucerne (PL + LU) and 33 : 33 : 33 perennial ryegrass/plantain/lucerne (PR + PL + LU). In the multiple species swards, the pasture species were separated spatially (by area). Plots were grazed by weaned lambs between March and June 2011. Pre-grazing herbage mass during March and April were highest (P < 0.05) from the lucerne and lowest (P < 0.05) from the plantain, with lucerne producing 4.5-5.5 t DM/ha during this time, whereas the perennial ryegrass and plantain produced 3.5-3.9 t DM/ha and 2.3-3.0 t DM/ha, respectively. Herbage disappearance (calculated estimate of feed intake) was highest (P < 0.05) from the lucerne and lowest (P < 0.05) from the plantain during March and April. Leaf crude protein between the perennial ryegrass and plantain did not differ (P > 0.05) and were lower (P < 0.05) than the lucerne, but the perennial ryegrass and plantain had higher (P< 0.05) leaf on offer (kg DM/ha). Plantain leaf had higher (P< 0.05) Fe, Zn, Co, Ca and S than the perennial ryegrass leaf and higher (P < 0.05) Se, Cu, Mg, Na and Cl than the perennial ryegrass and lucerne leaf and a more negative (P < 0.05) dietary cation : anion difference. The agronomic data presented in this paper provides support for the hypothesis, with lambs showing dietary preferences between pasture species and morphological components, and forms to basis for why these preferences exist. The two subsequent papers show how offering lambs dietary choice affected the performance of male lambs to slaughter and female lambs to first joining. [ABSTRACT FROM AUTHOR]

Forage brassica and chicory crops provide an alternative to perennial grass pastures as a forage supply for grazing dairy cows during summer, but there is little information about their effects on milk production and methane (CH4) emissions. Thirty-two Holstein-Friesian cows were fed for 10 days on a diet of lucerne cubes (750 g/kg DM) and grain (250 g/kg DM) (CON) or diets in which forage brassica (410 g/kg DM, FBR) or reproductive-stage chicory (410 g/kg DM, RCH) were offered with lucerne cubes (340 g/kg DM) and grain (250 g/kg DM). Cows offered the FBR diet produced more energy-corrected milk (25.4 kg/day) than did cows offered the CON diet (22.7 kg/day, P = 0.001), even though DM intake was not different for cows between the two groups (20.6 kg/day on average). In contrast, cows offered the RCH diet produced less energy-corrected milk (19.3 kg/day) than did cows in the other two groups (P = 0.001), reflecting the lower DM intake by cows offered the RCH diet (17.7 kg/day, P < 0.01). Methane yield (g CH4/kg DMI) was lower (P < 0.01) on the CON (21.0) and FBR (20.5) diets than on the RCH diet (26.1). Methane intensity (g/kg energy-corrected milk) was different (P < 0.01) for all diets, with CON (19.4) being intermediate, FBR (17.3) lowest and RCH (23.8) the greatest. Diet type was associated with differences in the proportions of only a small number of specific milk fatty acids, and differences in proportions of specific fatty acids were not related to CH4 emissions. [ABSTRACT FROM AUTHOR]

A widely used method for the in vitro measurement of fermentation parameters, total gas and methane (CH4) production (mL/g) from feed samples employs AnkomRF Technology with vented bottles, initially flushed with carbon dioxide (CO2). The volumes of gas accumulated between ventings, and the volumes vented, are calculated from the headspace pressure data. By using these data, it is possible to infer mathematically the quantity of CH4 produced, given just a single measurement of the CH4 mixing ratio measured in the headspace at the termination of fermentation. However, this calculation requires an additional assumption. Two possibilities for this are considered. We present mathematical formulae arising from each, and describe their sensitivity to violations of their respective assumptions. Also considered is a formula based on using N2 instead of CO2 as the flushing gas. It appears that, in practice, all three formulae are suitable for estimating CH4 production, with errors less than 3%. [ABSTRACT FROM AUTHOR]

A study was conducted to examine in vitro ruminal fermentation profiles and methane production of some alternative forage species (n = 10) in Australia. Extent of fermentation was assessed using an in vitro batch fermentation system, where total gas production, methane production, and concentrations in ruminal fluid of volatile fatty acids (VFA) and ammonia were measured. Forages varied in their fermentability, with highest total gas, methane, VFA and ammonia production recorded from selected samples of Brassica napus L. cv. Winfred. Lowest methane production (i.e.30%less than that formed by the highest-producing one) was observed in Plantago lanceolata L. cv. Tonic and Cichorium intybus L. cv. Choice. Selected plants, including P. lanceolata L. cv. Tonic, Brassica rapa L. cv. Marco, Brassica napus L. cv. Hunter had reduced acetate : propionate ratio and/or ammonia concentration, along with relatively low methane production compared with other species tested, while overall fermentation was not affected. It was concluded that selected novel forages have some advantageous fermentability profiles in the rumen and, in particular, inhibit methane production. However, before these can be recommended as valuable supplementary feedstuffs for ruminants in Australia, further studies are needed to confirm these effects over a range of samples, conditions and in vivo. [ABSTRACT FROM AUTHOR]

Traditional measures of the nutrient concentration of herbage before grazing may not accurately depict the nutrient intake of grazing animals. An experiment was conducted to investigate differences in DM and nutrient intake, and milk production of lactating cows offered chicory- or perennial ryegrass-based diets during spring on a commercial dairy farm in south-west Victoria. This experiment was conducted in mid-lactation (spring), with chicory (Cichorium intybus L.), perennial ryegrass (Lolium perenne L.) and a mixed sward of chicory and perennial ryegrass offered at two daily allowances (nominally 20 and 30 kg DM/cow to ground level). Selection differentials for estimated metabolisable energy (MJ/kg DM), neutral detergent fibre (NDF; g/kg DM) and acid detergent fibre (g/kg DM) varied (P < 0.05) with forage type, while allowance affected selection for estimated metabolisable energy, crude protein, acid detergent fibre and NDF (P < 0.01). However, the differences in selection differentials observed between the chicory, mixed sward and perennial ryegrass under the same conditions indicated that preferential grazing for leaf rather than stem in chicory may affect nutrient selection in a way that differs from perennial grass species, resulting in much lower intakes of NDF than indicated by traditional measurements of feed characteristics. Chicory, a summer-active forage crop, is an alternative herbage source to perennial ryegrass for dairy cows in southern Australia. However, there is limited understanding of nutrient selection from chicory by grazing dairy cows. Nutrient selection, the difference between nutrients in herbage offered and consumed, was measured in chicory during spring 2012. Preferential grazing for leaf rather than stem from chicory may affect nutrient selection in a way that differs from perennial grass species. [ABSTRACT FROM AUTHOR]

The profitability of temperate dairy systems in southern Australia and New Zealand is underpinned by the efficient use of the home-grown feed-base and purchased supplements. While there are well established principles on which to devise nutritionally balanced rations for ruminants, it is evident that in grazing systems the variable supply of nutrients from forage often results in suboptimal performance compared with predicted responses. This review discusses the key factors likely to directly affect responses to supplementation in grazing systems, namely pasture supply, nutritive characteristics and intake, feeding systems, substitution, associative effects and nutrient synchrony. Intake is the primary driver for metabolisable energy (ME) and nutrient supply and uncertainties on the actual ME and nutrients supplied by pasture will remain due to variability within and between pasture types and within paddocks. It is suggested that improvements in ration formulation will require a better understanding of the kinetics of intake and digestion within the rumen and of nutrients supplied to the tissues from grazed pasture with and without supplements. Research which clearly elucidates which mechanism or mechanisms determine substitution rates with concentrate and forage supplements would be valuable. Such knowledge could also be used to develop feeding strategies that result in a reduction in the degree of substitution and, in turn, lead to higher DM and ME intake compared with existing feeding practices. This in turn would lead to a better understanding of associative effects and nutrient synchrony with benefits in better design of rations and feed-use efficiency. Temperate dairy systems in southern Australia and New Zealand are underpinned by the efficient use of the home-grown feed-base and purchased supplements. While established principles exist to nutritionally balance such rations, the variable supply of nutrients under grazing often results in suboptimal performance. This review discusses the key factors that affect responses to supplementation in grazing systems, and considers where future research may be directed to improve animal performance from pasture-based systems. [ABSTRACT FROM AUTHOR]

This experiment measured milk production responses of grazing cows offered supplements in different ways. Holstein-Friesian cows averaging 89 days in milk, were allocated into six groups of 36 (each group including three rumen-fistulated cows). Two groups were randomly assigned to each of three dietary treatments: (1) cows were offered milled barley grain twice daily at milking and pasture silage in the paddock (Control); (2) the same amounts of milled barley grain and pasture silage were fed as a partial mixed ration (PMR) once a day following morning milking (PMR1); and (3) cows were supplemented with a PMR containing milled barley grain, lucerne hay, maize silage and crushed maize grain fed once a day following morning milking (PMR2). All dietary treatments were formulated to provide the same metabolisable energy and cows were offered a restricted allowance of ~14 kg DM/cow.day (to ground level) of perennial ryegrass pasture in addition to their supplement. Each group of 36 cows was further divided into four groups of nine, each of which were offered supplements at either 6, 8, 10 and 12 kg DM/cow.day. The experiment consisted of a 14-day adaptation period and an 11-day measurement period. Cows fed PMR1 and PMR2 once a day did not show an increase in milk production compared with the traditional feeding system (Control). Presumably this was a result of asynchronous supply of nutrients to the rumen (in isoenergetic diets) compromising conditions for digestion and milk production. Milk production responses of dairy cows in early lactation grazing perennial ryegrass and offered supplements in different ways were investigated. Feeding supplements as a partial mixed ration (PMR) once a day did not result in any production advantages over the more traditional twice daily bail feeding system under the conditions imposed in this experiment. This information will be important for farmers feeding supplements as a PMR. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to compare ruminal pH and whole-tract digestibility in cows consuming fresh cut herbage plus concentrates and silage or hay fed either separately or as a partial mixed ration (PMR). Fourteen rumen-fistulated Holstein-Friesian cows that had calved in late winter were housed in metabolism stalls for 9-day experiments in spring (97 days in milk (DIM)) and autumn (237 DIM). All cows were offered 8 kg dry matter (DM)/day of fresh cut perennial ryegrass (Lolium perenne L.) herbage, provided in two equal portions after each milking. Seven cows were assigned to each of two diets: (i) Control: 8.8 kg DM/cow.day milled wheat grain in two equal portions at milking, plus 3.2 kg DM/cow.day perennial ryegrass silage, with all cows receiving the silage portion of their diet after their grain but before their fresh herbage at the afternoon milking; and (ii) PMR: 12 kg DM/cow.day of a PMR containing similar ME as the Control supplements, but comprising maize grain, maize silage, wheat grain, lucerne hay (spring) and pasture silage (autumn). Intake and faecal output was measured on 5 days during each experiment, and ruminal pH was measured every 2 h for a 24-h period. Degradability of wheat and maize grain was measured using standard in sacco techniques. In both experiments, cows fed PMR had higher ruminal fluid pH than Control cows for at least part of the day. Apparent whole-tract digestibilities of DM, organic matter, nitrogen, neutral detergent fibre and starch were greater for Control than PMR cows in spring and not different in autumn (except starch). Ruminal pH was increased by feeding a maize-based PMR but this was not associated with increased whole-tract digestibility. We conclude that the ruminal pH in the Control cows was not low enough for long enough to compromise digestion, or that there was compensatory post-ruminal digestion. Feeding high amounts of supplements to grazing dairy cows as a mixed ration containing maize grain can increase milk production responses compared to traditional systems of feeding supplements. An experiment showed that cows fed PMR had higher ruminal pH than cows fed grain and silage separately, but that this did not result in any changes to whole tract digestibility. Benefits of PMR systems are presumably related to increased intake of both supplement and pasture rather than improvements in digestibility. [ABSTRACT FROM AUTHOR]

Milk production responses were measured in grazing cows offered supplements in different ways. Holstein-Friesian cows averaging 70 days in milk were allocated into 20 groups of eight, each including one rumen-fistulated cow. One of three dietary treatments was then randomly assigned to each of the 20 groups. Treatments were (1) Control (8 groups), where cows were supplemented with rolled wheat grain fed twice daily in the dairy and pasture silage provided in the paddock; (2) partial mixed ration (PMR; 8 groups), where cows were offered a PMR comprising rolled wheat grain, maize grain, maize silage and lucerne hay, which was presented on a feedpad immediately after each milking; the PMR was formulated to provide the same estimated metabolisable energy intake as the Control supplements; and (3) PMR+Canola (4 groups), where cows were fed in the same way as the PMR cows, except that a proportion of the wheat in the PMR was replaced with solvent-extracted canola meal. This ration was formulated to provide the same metabolisable energy as the Control and PMR treatments, but had greater amounts of crude protein. For Control and PMR treatments, supplements were offered at 8, 10, 12 or 14 kg DM/cow.day (2 groups per amount) while for the PMR+Canola treatment supplement was offered at 12 or 14 kg DM/cow.day (2 groups per amount). In addition to their supplements, all groups grazed an allowance of ~14 kg DM/cow.day (measured to ground level) of perennial ryegrass pasture. Yields of energy-corrected milk increased linearly with increasing supplement intake, but there was no difference between Control and PMR cows. When canola meal was added to the PMR, there was an increase in energy-corrected milk at a predicted supplement intake of 13.0 kg DM/cow.day. This was associated with a greater concentration and yield of milk fat in the PMR+Canola cows. Ruminal fluid pH and DM intake from pasture were also greater in PMR+Canola cows. It is concluded that farmers feeding high amounts of supplements to grazing cows could increase milk production by carefully considering the composition and form of the supplement mix, including the inclusion of canola meal. Different systems for feeding high amounts of supplements to grazing dairy cows were compared. Feeding supplements on a feedpad as a mixed ration containing canola meal can have milk-production advantages over feeding grain in the dairy at milking times. This information will be important for farmers needing to feed high amounts of supplements because of climate variability. [ABSTRACT FROM AUTHOR]

The profitability of dairy farm systems in southern Australia is closely related to the amount of pasture grown and consumed on-farm by dairy cows. However, there are doubts regarding the extent to which gains in feed supply from perennial ryegrass pasture can continue to support productivity growth in the industry. A farmlet experiment was conducted in south-western Victoria for 4 years (June 2005-May 2009), comparing a production system based on the use of forage species that complement perennial ryegrass in their seasonal growth pattern ('Complementary Forages', or CF) with a well managed system solely based on perennial ryegrass pasture ('Ryegrass Max', or RM). The forage base in CF included perennial ryegrass with a double-cropping rotation of winter cereal grown for whole-crop silage, followed by a summer brassica for grazing on 15% of farmlet area, a summer-active pasture based on tall fescue (on average 20% of farmlet area), perennial ryegrass oversown with short-rotation ryegrasses (average 16% of farmlet area) and summer brassica crops used in the process of pasture renovation (average 5% of farmlet area). The stocking rate was 2.2 and 2.8 cows/ha on RM and CF, respectively. Both systems were profitable over the 4 years of the experiment, with the modified internal rate of return over 4 years being 14.4% and 14.7% for the RM and CF farmlets, respectively. The coefficient of variation (%) of annual operating profit over 4 years was higher for the CF farmlet (56% and 63% for RM and CF, respectively). A severe drought in one of the 4 years exposed the more highly stocked CF system to greater supplementary feed costs and business risk. By comparison, the RM system performed consistently well across different seasons and in the face of a range of milk prices. The very small gain in profit from CF, plus the associated higher risk, makes it difficult to endorse a substantial change away from the traditional RM feed supply to greater reliance on summer-grown forages on non-irrigated dairy farms in southern Australia, as implemented in this experiment. [ABSTRACT FROM AUTHOR]

A dairy farmlet experiment was conducted at Terang in south-west Victoria, Australia, over 4 years to test the hypothesis that a 30% increase in forage harvested per ha could be achieved in a production system that incorporated a range of Complementary Forages with perennial ryegrass (CF) compared with a well managed perennial ryegrass-only farmlet ('Ryegrass Max', RM). The CF farmlet included perennial ryegrass pasture (44% of the farmlet area on average over 4 years), but also incorporated oversowing perennial ryegrass with short-term ryegrasses (average 16% of farmlet area) to increase winter growth, tall fescue-based pasture (average 20% of farmlet area) to increase production in the late spring-summer period, a double cropping rotation (15% of farmlet area) based on winter cereal for silage production followed by summer brassica crops for grazing, and summer crops used in the pasture renovation process (average 5% of farmlet area). The RM and CF farmlets were stocked at 2.2 and 2.82 June-calving cows/ha, respectively and average annual nitrogen (N) fertiliser application rates (pasture only) were 141 and 153 kg N/ha, respectively. The total amount of forage harvested per year was generally less than predicted from pre-experimental modelling of both farmlets. However, the proposed target of a 30% increase in home-grown forage harvest per ha in the CF system compared with RM was exceeded in 2005-06 (+33%), with 21, 16 and 11% higher forage harvest achieved in CF in 2006-07, 2007-08 and 2008-09, respectively (average for all 4 years = 20%). Annual forage harvested in RM ranged between 6.5 and 8.9 t DM/ha compared with 7.9-10.3 t DM/ha in CF. Approximately two-thirds of the increased forage harvest in CF came from higher rates of pasture consumption per ha and one-third from the double cropping component of the system, although the performance of the double crop (mean annual production of 11.5 t DM/ha) was well below the expected 20 t DM/ha based on pre-experimental modelling. The higher per-hectare pasture harvest rates in CF were primarily due to increased perennial ryegrass pasture consumption achieved through higher stocking rates and efficient responses to higher N inputs from both higher fertiliser rates and additional supplementary feeding. In CF, the DM harvested from pastures oversown with short-term ryegrasses was lower than perennial ryegrass, while tall fescue-based pastures were similar to perennial ryegrass. Poor spring rainfall in 2006-07 and 2008-09 likely contributed to the lower than expected DM yields of tall fescue-based pasture and the summer crops within the double cropping component. Home-grown forage harvest rates can be increased by 11-33% above what is currently achieved by best industry practice with perennial ryegrass-only pastures using complementary forages but perennial ryegrass will remain a key component of the forage base for dairy production in southern Australia. In pasture-based dairy systems increasing forage harvested per hectare supports productivity gains. A 20% increase in forage harvested was achieved on a farmlet consisting of perennial ryegrass plus complementary forages compared to a farmlet with perennial ryegrass only. There are opportunities to increase forage harvest using complementary species but perennial ryegrass remains a key component of the forage base in southern Australia. [ABSTRACT FROM AUTHOR]

This paper reports the performance [intake, milk production, bodyweight and body condition score (BCS)] of cows managed under two feeding systems over 4 years (June 2005-May 2009) in south-west Victoria, Australia. The feeding systems were 'Ryegrass Max' (RM) a well managed perennial ryegrass pasture-based system stocked at 2.2 cows/ha, and a 'Complementary Forage' (CF) system based on perennial ryegrass, tall fescue and a double crop of winter-sown cereal and summer-sown brassica crops stocked at 2.82 cows/ha. There were no significant differences in milk production per lactation between feeding systems, with an average of 543 and 553 kg milk solids per cow (1246 and 1642 kg milk solids per ha) produced in the RM and CF systems, respectively. These production levels were 20.9 and 10.8% above pre-experimental model targets, respectively. The bodyweight and BCS of multiparous cows were not significantly different between the two feeding systems; however, bodyweight of heifers in early lactation declined more rapidly in the CF compared with RM feeding system. Over the 4-year study in the RM system pasture comprised 60% of total DM consumed (grazed + conserved), with 26% of the ration being concentrate and the balance being purchased hay supplements. In the CF system, home-grown forage contributed 57.9% of total DM consumed of which 46.6% was pasture (grazed + conserved) and 11.3% was from the double cropping system. These levels of home-grown forage consumption were lower than those predicted by the pre-experimental modelling, leading to higher than predicted levels of purchased concentrates and conserved forages being fed. The lower than expected levels of consumption of the forages produced in the double cropping system reflected both the low intake potential and moderate nutritive value of cereal silage, and the failure of establishment and subsequent low DM yields from the summer brassica crop. Further work is required to determine the risk of implementing CF in rain-fed dairy systems reflecting uncertainties in forage management planning and nutrient delivery to support high levels of milk production. [ABSTRACT FROM AUTHOR]

The profitability of dairy businesses in southern Australia is closely related to the amount of feed consumed from perennial ryegrass-dominant pasture. Historically, the dairy industry has relied on improvements in pasture productivity and utilisation to support profitable increases in stocking rate and milk production per hectare. However, doubts surround the extent to which the industry can continue to rely on perennial ryegrass technology to provide the necessary productivity improvements required into the future. This paper describes the design and management of a dairy systems experiment at Terang in south-west Victoria (780-mm average annual rainfall) conducted over four lactations (June 2005-March 2009) to compare the production and profitability of two forage base options for non-irrigated dairy farms. These options were represented by two self-contained farmlets each milking 36 mixed-age, autumn-calving Holstein-Friesian cows at peak: (1) well managed perennial ryegrass pasture ('Ryegrass Max', or 'RM'); and (2) perennial ryegrass plus complementary forages ('CF') including 15% of farmlet area under double cropping with annual species (winter cereal grown for silage followed by summer brassica for grazing on the same land) and an average of 25% of farmlet area in perennial pasture based on tall fescue for improved late spring-early summer feed supply. The design of these systems was informed by farming systems models (DairyMod, UDDER and Redsky), which were used to estimate the effects of introducing different forage options on farm profitability. The design of the CF system was selected based on modelled profitability increases assuming that all forage components could be managed to optimise forage production and be effectively integrated to optimise milk production per cow. Using the historical 'average' pasture growth curve for the Terang district and a mean milk price of $3.71 per kg milk solids, the models estimated that the return on assets of the RM and CF systems would be 9.4 and 15.0%, respectively. The objectives of the experiment described here were to test whether or not such differences in profitability could be achieved in practice, and to determine the risks associated with including complementary forages on a substantial proportion of the effective farm area. Key results of the experiment are presented in subsequent papers. [ABSTRACT FROM AUTHOR]

There is a growing diversity and complexity of dairy farming systems in Australia. Feeding systems based on the provision of mixed rations to dairy cows grazing perennial pastures (termed partial mixed rations or PMR systems) have emerged and present the dairy industry with opportunities for improved production and feed efficiency, but also with significant challenges. Early research results are beginning to define the situations in which PMR systems are profitable and the mechanisms responsible for the improved milk responses. This review focuses on the role of PMR feeding systems in temperate dairying regions of Australia, highlights initial research findings, and identifies some of the gaps in current knowledge that warrant further research. The key findings were that, when very low allowances of pasture are offered to cows, milk production responses were driven mostly by increases in dry matter (DM) intake, and there appeared to be a minimal contribution to increased energy supply from improved whole tract DM digestibility. Differences in milk responses became apparent when >10 kg of total supplement DM was consumed (0.75:0.25 concentrate to forage) as PMR. There was a consistent maintenance of milk fat concentration when increasing amounts of concentrates were consumed as PMR, in contrast with supplements consumed in the dairy. There was also a consistent finding that replacing some wheat in the PMR with canola meal resulted in cows consuming more grazed pasture despite the limitations of very low pasture allowances (10-15 kg DM/cow.day, expressed to ground level). This was accompanied by further increases in energy-corrected milk yield. The potential to improve DM intake was further highlighted when pasture allowance was increased, with intake increasing from 3.6% to 4.5% of liveweight (from 20 to 25 kg DM/day for a 550-kg cow). There was also an indication that ~50% of the milk production benefit from PMR can be captured by providing the concentrate supplement as a grain mix in the dairy. There did not appear to be negative impacts of PMR systems on the social and grazing behaviour or health of cows. Feeding systems based on the provision of partial mixed rations (PMR) to grazing dairy cows present the dairy industry with opportunities for improved production and feed efficiency, but also with significant challenges. Early research results are beginning to define the situations in which PMR systems are profitable and the mechanisms responsible for the improved milk responses. This review focuses on the role of PMR in temperate dairying regions of Australia, highlights initial research findings, and identifies some of the gaps in knowledge that warrant further research. [ABSTRACT FROM AUTHOR]

A high proportion of the Australian and New Zealand dairy industry is based on a relatively simple, low input and low cost pasture feedbase. These factors enable this type of production system to remain internationally competitive. However, a key limitation of pasture-based dairy systems is periodic imbalances between herd intake requirements and pasture DM production, caused by strong seasonality and high inter-annual variation in feed supply. This disparity can be moderated to a certain degree through the strategic management of the herd through altering calving dates and stocking rates, and the feedbase by conserving excess forage and irrigating to flatten seasonal forage availability. Australasian dairy systems are experiencing emerging market and environmental challenges, which includes increased competition for land and water resources, decreasing terms of trade, a changing and variable climate, an increasing environmental focus that requires improved nutrient and water-use efficiency and lower greenhouse gas emissions. The integration of complementary forages has long been viewed as a means to manipulate the home-grown feed supply, to improve the nutritive value and DM intake of the diet, and to increase the efficiency of inputs utilised. Only recently has integrating complementary forages at the whole-farm system level received the significant attention and investment required to examine their potential benefit. Recent whole-of-farm research undertaken in both Australia and New Zealand has highlighted the importance of understanding the challenges of the current feedbase and the level of complementarity between forage types required to improve profit, manage risk and/or alleviate/mitigate against adverse outcomes. This paper reviews the most recent systems-level research into complementary forages, discusses approaches to modelling their integration at the whole-farm level and highlights the potential of complementary forages to address the major challenges currently facing pasture-based dairy systems. This paper reviews the most recent dairy systems research into complementary forages. In environments which are most favourable to perennial ryegrass pasture production there is little evidence for major improvements in farm profits when moving away from this pasture based dairy system. However, complementary forages do have the potential to advance the dairy industry particularly in dairy regions with limited land and water availability. [ABSTRACT FROM AUTHOR]

The efficient production and utilisation of home-grown feed is considered one of the key factors that underpins the profitability of dairy systems in southern Australia. The use of winter forage cereals for grazing and silage provides an opportunity to achieve high dry matter yields over the winter and spring period. However, questions remain on the nutritive value of whole-crop cereal silage and its subsequent use as a production feed in livestock systems. This experiment examined the nutritive characteristics of winter wheat, triticale, forage peas and bi-crops of cereals and peas sown at different proportions, cut for silage at the soft dough growth stage of the cereals and their subsequent silage nutritive characteristics and fermentation patterns when ensiled with and without bacterial inoculant additives over 2 consecutive years. The estimated metabolisable energy (ME) (Year 1) and crude protein (CP) (Years 1 and 2) concentrations of the forage pea before and after ensiling were higher (P < 0.05) than all other forages in both years. The cereal-pea mixes had similar estimated ME values to the cereal monocultures both before harvesting and as silage, although there were significant improvements in CP concentration at the higher rates of pea inclusion. All resultant silages were well fermented as indicated by low pH, low proportions of total N as ammonia-N and high lactic acid concentrations. There were marked differences in the proportions of lactic acid and acetic acid in the pea silages between years and this is likely a result of dry matter content differences at ensiling. There was no effect of silage additives on resultant silage nutritive characteristics or fermentation parameters indicating that well fermented silage can be achieved without the additional cost of using a silage additive. This study has indicated that forage peas can be ensiled with winter cereals and produce silages that have higher CP concentrations than cereal silage but with similar fermentation parameters. Furthermore, this experiment has highlighted the potential of growing a monoculture of forage peas for ensiling with the resulting silage having higher estimated ME and CP concentrations. Winter forage cereals grown for grazing and silage can achieve high dry matter yields over the winter and spring period but often nutritive characteristics of resultant silages are low. This experiment evaluated silage nutritive and fermentation characteristics of winter wheat, triticale, forage peas and bi-crops of cereals and peas cut for silage at the soft dough growth stage of the cereals and ensiled with and without bacterial inoculant additives. Results indicated that forage peas can be ensiled with winter cereals to produce silages with higher CP concentrations than cereal silage and there is potential to use monocultures of forage peas to produce silages with higher estimated ME and CP concentrations than cereal or cereal-pea combinations. [ABSTRACT FROM AUTHOR]

The use of summer brassica forage crops in dryland dairy systems in southern Victoria is considered a key component of the feed base as they provide home-grown forage with high nutritive characteristics during a period where perennial ryegrass growth is limited due to high summer temperatures and low soil water content. Current knowledge on the use of single-grazing brassica crops such as turnips (Brassica rapa L.) is well defined; however, information on the management of regrowth brassica species that can provide multiple grazings is more limited. The present experiment determined the effect of different grazing regimes (high, medium and low defoliation intensity) at the first grazing on subsequent regrowth capability and nutritive characteristics of Winfred (Brassica napus L.) over the summer growing period across 2 years. We hypothesised that intensive defoliation of a summer regrowth brassica at the first grazing will result in lower total DM yields and harvested estimated metabolisable energy (ME) and crude protein per hectare for the growing season than do more lax grazing options that results in less DM removal at the first grazing. Total DM and estimated ME consumed over the growing period varied between years. In Year 1, more (P < 0.05) DM was consumed at the first grazing and less (P < 0.05) at the subsequent grazing for the high-intensity treatment. However, both total DM and estimated ME consumed were higher (P < 0.05) for the high-intensity treatment than for the low-intensity treatment, while in Year 2, there were no differences between the treatments. Nutritive characteristics and mineral concentrations were relatively unaffected by grazing regimes. The results of the present experiment indicated that the optimum grazing management to maximise total DM yields and consumption of spring-sown Winfred will vary depending on the seasonal growing conditions. In years where moisture stress will be limiting crop growth, a high defoliation-intensity first grazing that consumes a high proportion of DM on offer, including some of the main stem, will maximise the total DM grown and consumed from the crop. Care, however, should be taken not to remove all axillary buds from the remaining stems. In summers where moisture stress is not likely to seriously restrict crop growth, a medium defoliation-intensity grazing where the leaf and petiole, but little of the stem, are removed will maximise DM regrowth, leading to maximum total DM grown for the season. A high defoliation-intensity first grazing that removes at least half the stem is, under these conditions, likely to remove too many axillary buds and reduce water-soluble carbohydrate reserves required for DM regrowth, while a lax first grazing will result in a lower DM regrowth. Regrowth summer forage crops are becoming a popular option in southern Australia; however, little is understood about grazing strategies at the first grazing to optimise subsequent regrowth. An experiment was conducted to determine the effect of different grazing regimes (high, medium and low defoliation intensity) at the first grazing on subsequent regrowth capability and nutritive characteristics of Winfred (Brassica napus L.). Results indicated that the optimum grazing management will vary depending on the seasonal growing conditions with high grazing intensity a better option under moisture stress conditions and more lax grazing when moisture stress is not limiting growth. [ABSTRACT FROM AUTHOR]

The potential net benefits of pasture species with enhanced genetic potential can be estimated using the acquisition value technique. This method values potential extra production of pasture dry matter (DM) as being equivalent to the market value of alternative sources of equivalent metabolisable energy (ME) and crude protein (CP). The market price of equivalent alternative sources of ME and CP gives an estimate of the maximum potential value of extra pasture DM produced on farm. In the work reported in this paper the improvement of two traits in white clover (Trifolium repens L.) are valued using the acquisition value technique. The traits are 1) alfalfa mosaic virus resistance (AMV Res.), and, 2) summer survival through delayed leaf senescence (SS). One hectare of pasture from two different environments in southern Australia was considered. Discounted cash flow budgeting was used to estimate the extra potential annual benefits minus the extra potential annual costs from growing a novel white clover compared to an existing common white clover cultivar over a 10 year period. Net present value (NPV) of the additional ME and CP was estimated using a real discount rate of 10% p.a. Probability distributions were developed and stochastic simulation was used to incorporate the effects of uncertain variables on the value of extra DM produced. Sensitivity testing of key parameters was conducted. The analysis presented here indicates there are potential net benefits from the genetic innovations, and these net benefits would be shared between suppliers and users. For the 'what if' scenarios explored, combining individual plant traits into a trait stack showed greater annual net benefit than individual trait improvements in white clover. For example, the 'AMV Res.' as a single trait improvement returned a mean annuity value of approximately $170/ha/yr for the 10 year period, with 68% of annuities calculated falling within approximately $80 of this mean, for the single hectare analysis of the high rainfall (1000 mm) using the market value of ME and CP. Comparatively, the trait stack option returned a mean annuity value of additional annual ME and CP of approximately $540/ha/yr for the 10 year period with a standard deviation of $275. Economic models applied to molecular breeding programs can produce information to help inform decisions on prioritisation of research and investment in new traits, and assists in determining the magnitude of improvements in trait efficiencies that is required to justify such investment. The approach presented here, based on the acquisition value technique to value extra annual DM from a hectare of pasture, represents an initial look at the question; such partial estimates are not the potential net benefits from trait improvements in pasture species that would occur at whole farm level, within years and over time. For this information, analysis at the whole farm scale is required to capture the impact on the complexity of the farm system from changes to the pasture base, as the next phase of this research will explore. [ABSTRACT FROM AUTHOR]

The benefits, costs and risk from introducing aluminium-tolerant lucerne (alfalfa) into a sheep grazing enterprise, consisting of a perennial ryegrass-based pasture, located in the high rainfall zone of Victoria, Australia, were estimated using a discounted cash flow analysis. Two 'what if' scenarios were compared for a modelled representative case study farm; 1) where aluminium toxicity occurred in the top-soil, and 2) where aluminium toxicity occurred in the sub-soil. Discrete seasonal pasture growth scenarios were examined, and price variability was captured using Monte Carlo simulation. Growing aluminium-tolerant lucerne on 10% of the farm area was consistently more profitable than continuing to graze the perennial ryegrass pasture, returning an extra $7-28/ha/year of profit for the 9 year analysis period. However, if the use of conventional lucerne with liming was a viable option for incorporating lucerne into the grazing system, the advantage of the aluminium tolerance ( 'Al Tol') technology was minimal. The results of this analysis suggest that aluminium-tolerant lucerne could be a profitable option for livestock graziers in the high rainfall zone, and is likely to be more beneficial when aluminium toxicity occurs in the sub-soil compared to the top-soil. [ABSTRACT FROM AUTHOR]

An experiment was undertaken over 2 years (2007-09) to determine the effect of intercropping forage peas with either forage winter wheat or triticale for whole-crop silage. Monocultures of triticale (T100), wheat (W100) and forage peas (P100) and plus cereal-pea combinations of 75% triticale : 25% pea (T75), 50% triticale : 50% pea (T50), 25% triticale : 75% pea (T25), 75% wheat : 25% pea (W75), 50% wheat : 50% pea (W50), 25% wheat : 75% pea (W25), with ratios based on sowing rate, were evaluated for DM yield and nutritional characteristics at a range of growth stages. It was hypothesised that an increase in the ratio of peas to cereal would not adversely affect DM yield and would have a positive impact on nutritive characteristics across a range of harvest times based on growth stages of the cereal component of mixes. In Year 1, at the boot stage of growth of cereals, P100 had a lower DM yield than W100 and all triticale-based treatments, while in Year 2 P100 had a lower DM yield than all other treatments. By the soft dough growth stage in Year 1, all triticale treatments except T25 had higher DM yields than P100 and in Year 2 P100 had a lower DM yield than all triticale treatments and W100. The crude protein (CP) concentration of P100 at the boot stage of growth was higher than T100, T75, T50, W100 and W50 in Year 1 and all treatments in Year 2. At soft dough, P100 had a higher CP concentration than all other treatments in both years, while T25 and W25 had higher CP concentrations than their respective monocultures. In Year 1 at soft dough, W100 had a lower estimated ME concentration than other wheat treatments and P100, while in Year 2, T50 and W50 had higher values than T100 and W100, respectively. Bi-cropping forage peas with winter cereal forage crops did not adversely affect DM yields at a range of different harvest times, but did not consistently and significantly improve nutritive characteristics. Despite relatively high sowing rates of forage peas, their total contribution in mixes with cereals to DM yield was low, indicating that their ability to compete with winter cereals under the high fertility conditions of the experiment was low. When grown as a monoculture peas tended to produce lower DM yields but had higher CP concentrations and a higher harvested CP/ha at the soft dough stage of growth. The timing of harvesting will affect DM yields and nutritive characteristics and can be manipulated depending upon the end use of the feed grown and also to allow greater flexibility in the sowing of subsequent forages. Consideration should also be given to the growing of monocultures of winter cereals and forage peas and developing systems to mix during ensiling to capture both DM yield potential and optimum nutritive characteristics. The use of cereal crops in association with forage peas offers the opportunity to produce high yields of forage with high nutritive characteristics for ensiling in spring. This experiment investigated different combinations of cereals and peas and found that despite sowing high proportions of mixes as peas, the cereals constituted the majority of dry matter produced, with only minimal improvements in nutritive characteristics. There are opportunities, however, to manipulate nutritive characteristics through earlier harvesting and this may provide greater flexibility for the use of silage produced. [ABSTRACT FROM AUTHOR]

The article discusses the cohort survey conducted by Jacobs and colleagues on the widespread use of personal digital assistants (PDAs) and practice patterns of Japanese resident physicians. It indicates that 30.7 percent or only 297 respondents have reported using PDAs. It implies that the use of PDAs is remarkably low among Japanese resident physicians.

Gemcitabine is the first-line chemotherapeutic agent for advanced adenocarcinoma of the pancreas; however, chemoresistance to gemcitabine remains a major cause of failure for the clinical treatment of this disease. Polo-like kinase 1 (Plk-1) is highly expressed in pancreatic cancer cell lines and pancreatic tumour tissues, and is involved in a wide variety of cell cycle processes. Nevertheless, its biological role and implication for gemcitabine resistance are not clearly defined. In this study, we used RNA-interference (RNAi)-mediated depletion of Plk-1 to determine its potential for sensitizing pancreatic tumour cells to gemcitabine. We showed that the level of Plk-1 protein was correlated significantly with gemcitabine resistance in human pancreatic adenocarcinoma cells and that overexpression of Plk-1 reduced sensitivity to gemcitabine in these cells. In addition, small interfering RNA (siRNA)-mediated knockdown of Plk-1 caused cell cycle arrest at G2/M and the reduction of cellular proliferation. More importantly, the treatment of pancreatic cancer cells with Plk-1 siRNA followed by exposure to gemcitabine dramatically decreased cell viability and increased cellular apoptosis, as compared with treatment with either agent alone. These observations indicate that down-regulation of Plk-1 expression by RNAi enhances gemcitabine sensitivity and increases gemcitabine cytotoxicity in pancreatic tumour cells. This is the first demonstration that the combination of Plk-1 gene therapy and gemcitabine chemotherapy has synergistic anti-tumour activity against pancreatic carcinoma in vitro. This combination treatment warrants further investigation as an effective therapeutic regimen for patients with resistant pancreatic cancer and other tumours. [ABSTRACT FROM AUTHOR]

Phenotypic mechanisms that enhance bacterial UVR survival typically include pigmentation and DNA repair mechanisms which provide protection from UVA and UVR wavelengths, respectively. In this study, we examined the contribution of pigmentation to field survival in Clavibacter michiganensis and evaluated differences in population dynamics and leaf colonization strategies. Two C. michiganensis pigment-deficient mutants were significantly reduced in UVA radiation survival in vitro; one of these mutants also exhibited reduced field populations on peanut when compared to the wild-type strain over the course of replicate 25-day experiments. The UVR-tolerant C. michiganensis strains G7.1 and G11.1 maintained larger epiphytic field populations on peanut compared to the UVR-sensitive C. michiganensis T5.1. Epiphytic field populations of C. michiganensis utilized the strategy of solar UVR avoidance during leaf colonization resulting in increased strain survival on leaves after UVC irradiation. These results further demonstrate the importance of UVR tolerance in the ability of bacterial strains to maintain population size in the phyllosphere. However, an examination of several bacterial species from the peanut phyllosphere and a collection of environmental Pseudomonas spp. revealed that sensitivity to UVA and UVC radiation was correlated in some but not all of these bacteria. These results underscore a need to further understand the biological effects of different solar wavelength groups on microbial ecology. [ABSTRACT FROM AUTHOR]

Effects of timing and rate of N fertilizer application on concentrations of P, K, S, Ca, Mg, Na, Cl, Mn, Fe, Cu and Zn in herbage from perennial ryegrass/white clover pastures were studied at two sites in south-western Victoria, Australia. Nitrogen fertilizer (0, 15, 25, 30, 45 and 60 kg ha–1 ) was applied as urea in mid-April, early May, mid-May, early June and mid-June 1996 to pastures grazed by dairy cows. At Site 1, N fertilizer resulted in a linear increase in P, K, S, Mg and Cl concentrations in herbage and a linear decrease in Ca concentration. For all times of application, concentrations of P, K, Ca, Mg and Cl in herbage increased by 0·0048, 0·08, -0·010, 0·0013 and 0·053 g kg–1 dry matter (DM) per kg N applied respectively. For S concentration, maximum responses occurred in mid-May (0·012 g kg–1 DM per kg N applied). At Site 2, N fertilizer resulted in a linear increase in P, S and Na concentrations in herbage, a linear decrease in Ca concentration and a curvilinear increase in K and Cl concentration. The maximum responses for P, S and K concentrations in herbage occurred for the N application in mid-June and were 0·015, 0·008 and 0·47 g kg–1 DM per kg N applied respectively. For Cl concentration, the maximum response occurred for the N application in early June and was 0·225 g kg–1 DM per kg N applied. Overall, applications of N fertilizer up to 60 kg ha–1 did not alter herbage mineral concentration to levels that might affect pasture growth or animal health. [ABSTRACT FROM AUTHOR]