Perennial Ryegrass-based Pasture Research Articles

Progress towards delivering high metabolisable energy ryegrass

A method developed at AgResearch to increase leaf fatty acids (FA) and plant growth called ‘High metabolizable energy’ (‘HME’) could elevate the nutritional quality and productivity of perennial ryegrass-based pastures. The industry strategy has been to perform HME ryegrass field trials offshore to test whether the herbage FA, gross energy (GE) and yield enhancing traits observed in containment translate into field swards. To complement the field testing programme, we have also characterised the growth and nutritional profile of HME miniswards under simulated grazing in containment. The results from one such trial are presented. The major changes measured in HME miniswards; increased FA (+0.8–1.4 %DW), increased GE (+0.3–0.5 MJ/kgDM), and generally similar herbage DW production, closely mirror data from field trials with hemizygous HME populations in the Midwest USA. Changes in other HME nutritional components were generally minor, although WSC was reduced late in the diurnal cycle. Secondary effects of HME on photosynthesis appear to be diminished in swards, suggesting that HME yield benefits may be limited to specific environment and management scenarios. The primary benefit of HME technology is thus expected to come from increasing the energy density of pasture, and animal feeding trials using homozygous HME material are now required.

Excreta emissions in progeny of low and high enteric methane yield selection line sheep fed pasture of different qualities

Selection of sheep with low enteric methane (CH4) emissions is a greenhouse gas (GHG) mitigation option suitable for pastoral systems. However, the effect of breeding sheep with low enteric CH4 emissions on excreta output and associated CH4 and nitrous oxide (N2O) emissions and therefore total GHG emissions are not known. The objective of the current experiments were to determine excreta output, and estimate associated GHG emissions, from progeny of low and high enteric CH4 per unit of dry matter intake (DMI) selection line sheep (CH4/DMI). The animals were fed two qualities of cut perennial ryegrass-based pasture (very mature vs. vegetative, 12 animals per CH4/DMI line) in Exp. 1 and cut pasture in two repeated seasons (autumn and winter; 15 animals per CH4/DMI line × 2 seasons) in Exp. 2. Total faecal and urine output was determined on individual animals, followed by enteric CH4 emission measurements in respiration chambers. GHG emissions from urine (N2O) and faeces (CH4 and N2O) were estimated based on New Zealand Agricultural GHG Inventory methodology. There was no interaction between CH4/DMI selection line and diet quality in Exp. 1 or seasons in Exp.2. Total daily faecal output of DM, organic matter (OM) and neutral detergent fibre (NDF; all g/d) and associated calculated faecal CH4 emissions were greater for low compared to high CH4/DMI sheep in Exp. 1 (P < 0.05), while being similar between CH4/DMI selection lines in Exp. 2. Nitrogen (N) excretion and N partitioning into urine, faeces and body retention, and calculated excreta N emissions, were mostly similar between CH4/DMI selection line sheep in both experiments. Except, faecal N output (g/d and per unit of N intake) and associated calculated direct faecal N2O-N emissions (g/d) were greater in low compared to high CH4/DMI sheep in Exp. 1 (P < 0.05). Enteric CH4 emissions were numerically 8% less (P = 0.15) in Exp.1 and 10% less (P = 0.004) in Exp. 2 and total animal level GHG emissions (CH4 and N2O) were numerically 7% less (P = 0.21) in Exp. 1 and 8% less (P = 0.006) in Exp.2 for progeny of the low compared to the high CH4/DMI line sheep. In conclusion, the magnitude of difference in enteric CH4 (expressed as CO2-equivalent) between low and high CH4/DMI selection line sheep were still present when CH4 from faeces and N2O emissions from urine and faeces were also accounted for. The animal genetic traits were expressed independent of environmental factors, i.e. pasture quality and season.

Feeding a marine-based rumen buffer increases milk production and decreases time of low reticulo-rumen pH in grazing dairy cows offered perennial ryegrass-based pasture

Dairy cows grazing highly digestible perennial ryegrass-based pastures are reportedly susceptible to low rumen pH. This experiment investigates the effect of feeding a novel marine-based rumen buffering product on milk production, milk composition and reticulo-rumen pH in dairy cows grazing perennial ryegrass-based pasture supplemented with concentrates. Three primiparous and twenty-one multiparous spring calving dairy cows (58 ± 12.6 days in milk) were blocked by parity (3.2 ± 1.56) and pre-experimental milk yield (36.0 ± 6.55 kg) and randomly assigned to three experimental treatments in a three-period crossover-design experiment. Dietary treatments consisted of Control; 8 kg of a commercial cereal-based compound, BUF1; control diet +70 g of a novel marine-based buffer (a mix containing only calcified seaweed and a marine source of magnesium oxide: see detailed analysis provided) and BUF2; control +140 g of the same marine-based buffer in a changeover design experiment. Experimental periods lasted for 35 d with 21 d for diet adaptation and a 14 d measurement period. In-dwelling reticulo-rumen pH probes recorded reticulo-rumen pH and temperature during d 58–63 (Period 2) and d 93–98 (Period 3) of this experiment. Cows fed BUF1 and BUF2 showed an increased milk yield of 1.20 kg/d and 1.07 kg/d respectively when compared to the Control diet (P = 0.004 and P = 0.012). There were increases in energy corrected milk yield (ECM) of 1.53 kg/d (P = 0.02) and 3.5% and 4% fat corrected milk (FCM) of 1.87 kg/d and 1.76 kg/d, respectively (P = 0.012), when cows were fed BUF2 compared to cows fed the Control. Number of minutes per treatment per day at reticulo-rumen pH < 5.8 and < 6.0 was significantly greater for cows fed Control compared to cows fed BUF2 (P<0.001). Results of this experiment suggest that supplementation with a novel marine-based rumen buffering product increased milk production and reduced the amount of time the reticulo-rumen was below pH 5.8 and 6.0 in grazing dairy cows supplemented with a cereal-based concentrate.

The effect of by-product inclusion and concentrate feeding rate on milk production and composition, pasture dry matter intake, and nitrogen excretion of mid-late lactation spring-calving cows grazing a perennial ryegrass-based pasture

Interest is growing in the use of by-products as economical sources of nutrients that complement grazed grass, particularly at times when grass supply is insufficient to meet the nutritional demands of lactating dairy cattle. The objective of this research was to assess the effect of the amount of by-product inclusion and concentrate feeding rate on pasture dry matter intake, milk production and composition, and N excretion from spring-calving cows grazing summer pasture during mid-late lactation. Forty-eight Holstein Friesian dairy cows were randomly assigned to 1 of 4 dietary treatments in a 2 × 2 factorial design. Cows were grazed in one group on a perennial ryegrass-based sward, with pelleted concentrates offered twice daily during milking over a 63-d experimental period. The dietary treatments were 3 kg of concentrate containing 35% by-products; 6 kg of concentrate containing 35% by-products; 3 kg of concentrate containing 95% by-products; and 6 kg of concentrate containing 95% by-products on a fresh matter basis. The by-products used were soybean hulls, palm kernel expeller, and maize dried distillers grains with solubles, included in equal proportions on a dry matter basis. Pasture dry matter intake (14.5 kg/d) was not affected by the amount of by-product inclusion or feeding rate. By-product inclusion had no effect on milk yield (27.1 kg/d) or milk solids (MS) yield (2.0 kg/d). Cows offered 6 kg of concentrate had a greater milk (+1.6 kg/d) and MS (+0.13 kg/d) yield, consumed more N (+0.08 kg/d), and excreted a lower proportion of N in the milk (0.25 vs. 0.27) and feces (0.39 vs. 0.41) and a higher proportion in the urine (0.39 vs. 0.32) compared with cows offered 3 kg of by-product-based concentrate. In conclusion, by-products can be included at up to 95% of the concentrate fed to cows grazing pasture without affecting pasture dry matter intake, milk production or composition, or N excretion. Cows offered 6 kg of concentrates produced more milk and MS than cows offered 3 kg but had higher urinary N excretion. Economics of this yield response will depend on milk and concentrate prices.

Milk yield and urinary-nitrogen excretion of dairy cows grazing forb pasture mixtures designed to reduce nitrogen leaching

The effect of including a mixture of forbs in a standard perennial ryegrass-white clover pasture, with or without Italian ryegrass was investigated in a two-period grazing study comparing urinary nitrogen (N) excretion and milk yield of dairy cows in late lactation. Forty-eight mixed age, Holstein Friesian x Jersey cows were assigned to replicated, balanced, groups of six and offered one of four pasture treatments. Pasture types were either a perennial ryegrass-based pasture (PRG) with white clover or a forb-containing mixed pasture (MIX) including perennial ryegrass, white clover, chicory, plantain and lucerne. A second factor was the inclusion of Italian ryegrass (PRG+I and MIX + I). During Period I, ten cows in each of the MIX and PRG treatments were fitted with urine sensors to measure urine N parameters (urination frequency, volume and N concentration). During Period II, milk yield was measured from cows on all four pasture types. In both the ryegrass and forb pasture types, legume content exceeded 30% of the DM and in forb pastures chicory and plantain accounted for over 30% of the DM. Italian ryegrass in the MIX + I and PRG+I was respectively 5% and 15% of the DM. Digestibility and crude protein was similar for all pasture types, but fibre content was lower for forb pastures. During Period I, there was no effect of pasture type on the amount of N per urination event (averaged 13gN/event) and daily urine-N excreted (190gN/cow/day). However, pasture type affected the diurnal pattern in urine-N excretion with MIX pastures having a lower urine N loading per event during the day and higher urine N loading at night compared with PRG pastures. During Period II, milk yield was greater for forb compared with ryegrass pasture types (1.66 vs 1.50kg MS/cow/d). There was no effect of Italian ryegrass on milk yield due to low botanical content. This study demonstrated that forb containing pastures altered the diurnal pattern in urine-N excretion and offers opportunities to mitigate N leaching from grazed pastures whilst supporting high milk production in late lactation.

Changes in nutritive characteristics associated with plant height, and nutrient selection by dairy cows grazing four perennial pasture grasses

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.

The effect of by-product inclusion level on milk production, nutrient digestibility and excretion, and rumen fermentation parameters in lactating dairy cows offered a pasture-based diet

The objective of this study was to investigate the effects of replacing barley and soybean meal with increasing levels of by-products on production, digestive, and metabolic parameters in early-mid lactation dairy cows offered perennial ryegrass-based pasture. Forty-eight (32 multiparous and 16 primiparous) dairy cows that were 64 ± 24 d in milk were assigned to 1 of 4 pasture-based dietary treatments (n = 12) in a randomized block design experiment that ran for 70 d. Treatments consisted of a perennial ryegrass-based pasture and 1 of 4 supplementary concentrates: BP35, BP55, BP75, and BP95 containing 35, 55, 75, and 95% by-products, respectively, in the concentrate on a dry matter basis. The by-products used were soyhulls, dried distillers grains, and palm kernel extract in equal proportions. Barley and soybean meal were replaced as by-product inclusion level increased. In this study, intakes of pasture dry matter (15.7 kg) and total dry matter (21.1 kg) were not affected by treatment. Similarly, milk production parameters (milk yield, milk composition, somatic cell count, and urea) were not different between treatments. Unsaturated fatty acids were lower in the milk of cows offered BP35 and BP55 compared with those offered BP75 and BP95. Concentrations of β-hydroxybutyrate, nonesterified fatty acids, and other blood metabolites were within normal range and did not differ between treatments, and cow body condition score and body weight were also not different. Equally, N was unaffected by diet. Blood urea N was lower in the BP75 group compared with BP35. This study demonstrated that barley and soybean meal can be replaced with soyhulls, dried distillers grains, and palm kernel extract without affecting milk production, digestive, or metabolic parameters in dairy cows offered a pasture-based diet.

Sustainable perennial pastures in Northland

In the northern half of Northland, perennial ryegrassbased pastures have exhibited poor persistence. Nineteen tall fescue and ryegrass pastures in the region infected with either MaxP or AR37 fungal endophytes, respectively, had high levels of endophyte-infected tillers and low levels of contamination from wild endophytes. On surveyed farms, MaxP-infected tall fescue pastures had good contents of sown grass, which were higher than sown grass contents in AR37-infected ryegrass pastures, but on two far-north monitor farms these temperate grasses failed to compete with summer active C4 grasses such as kikuyu and carpet grass. For tall fescue and perennial ryegrass to form productive pastures in this region, sown seed should have high levels of viable endophyte, soil fertility should be adequate for good grass and legume growth, and pastures should be well managed. Summer droughts may still be too severe in some years for these temperate grasses to persist in the face of C4 grass competition. Keywords: Endophyte, Epichloë, Neotyphodium, Lolium perenne, Festuca arundinacea, soil fertility

Botanical survey of perennial ryegrass-based dairy pastures in three regions of New Zealand: implications for ryegrass persistence

A botanical survey of 24 commercial dairy pastures ranging in post-sowing age and perennial ryegrass type (mid-season diploid, late-season diploid, tetraploid) was undertaken in each of Waikato-Bay of Plenty (BoP), Taranaki and Canterbury during autumn/winter. The mean perennial ryegrass proportion (85% of total DM) and tiller density (3252 m−2) was greatest in Canterbury and the broadleaved weed proportion lowest (2%). Conversely, Waikato–BoP had the lowest ryegrass proportion (59%), tiller density (1817 m−2) and greatest proportion of broadleaved weeds (15%), with Taranaki intermediate. Tiller density was greater in pastures sown with diploid rather than tetraploids (averaging 3033 vs. 1784 m−2). Grass grub (Costelytra zealandica, 11 m−2) populations were lowest in the youngest age category pastures where nematode populations were highest (80 g−1 dry soil). The soil seedbank was dominated by unsown species (with total species emergence averaging 4594 seeds m−2), with negligible ryegrass emergence.

Effect of supplemental concentrate type on milk production and metabolic status in early-lactation dairy cows grazing perennial ryegrass-based pasture

Forty-four early-lactation dairy cows of mixed parity were used to examine the effect of 4 supplemental concentrate types (n=11) on milk production and metabolic status. Animals were blocked by parity and calving date, and blocks were balanced for previous milk yield and milk protein yield. Cows received grazed pasture plus 5.17kg of DM/d of 1 of the following isoenergetic (1.1 units of energy for lactation) concentrates: 1) high crude protein (CP) with rolled barley (HP, 19% CP); b) low CP with rolled barley (LP, 15% CP); c) low CP with barley and a supplemental methionine hydroxy analog (HMBi; LP + HMBi, 15% CP); and d) low CP with ground corn (LP-corn, 15% CP). Milk yield was recorded from d 1 to 100 postpartum, with weekly milk sampling, body weight, and body condition score (BCS) measurements. Blood and rumen sampling were conducted weekly from wk 2 to 6 postpartum. Milk yield was lower for cows in the LP treatment compared with those offered other concentrate types (25.2 vs. 27.5±0.39kg/d). Animals in the HP group had a higher milk yield than those in the LP + HMBi group (28.2 vs. 26.8±0.39kg/d). Milk fat yield was lower from animals in the LP-corn group compared with those in the LP + HMBi group (0.94 vs. 1.03±0.03kg/d). Milk protein yield was lower in the LP group compared with those in the HP group (0.88 vs. 0.97±0.02kg/d). Animal body weight, BCS, and BCS loss were not affected by concentrate type. However, nonesterified fatty acids were higher from animals in the HP group than for those in the LP + HMBi group (0.41 vs. 0.33±0.03mmol/L), and β-hydroxy butyric acid was higher from animals in the HP group than for those in the other treatments (0.71 vs. 0.59±0.03mmol/L). Glucose was higher from animals in the LP-corn group than for those in the HP and LP groups (3.3 vs. 3.2±0.05mmol/L). Blood urea-N was higher from animals offered HP compared with those offered the other treatments (5.49.6 vs. 4.21±0.44mmol/L). However, rumen NH3-N and volatile fatty acid concentration in the rumen were not affected by supplemental concentrate type. Reducing supplemental concentrate CP reduced milk yield. However, milk fat production and energy-corrected milk were not different, reducing the likelihood of an improved energy balance or a more favorable blood metabolic profile in early-lactation dairy cows grazing perennial ryegrass. Offering HMBi with low-CP concentrates or replacing rolled barley with ground maize improves milk production relative to low-CP concentrates and metabolic status relative to high-CP concentrates.

Effect of supplementary concentrate type on nitrogen partitioning in early lactation dairy cows offered perennial ryegrass-based pasture

Forty-four early lactation (64±20 d in milk) dairy cows of mixed parity were used to assess the effect of 4 supplementary concentrate types (n=11) on N partitioning. Animals were blocked on parity and calving date, and blocks were balanced for previous milk yield and milk protein yield. Cows received grazed pasture plus 5.17kg of dry matter (DM)/d of one of the following isoenergetic concentrates: high crude protein (CP) with rolled barley (HP, 19% CP); low CP with rolled barley (LP, 15% CP); low CP with barley and supplementary 2-hydroxy-4-methylthio butanoic acid (HMBi; LP+HMBi, 15% CP); and low CP with ground corn (LP Corn, 15% CP). Nitrogen partitioning studies were conducted at wk 6 and 10 postpartum by using the n-alkane technique to determine pasture dry matter intake (DMI). Pasture DMI (13.3kg of DM/d) and dietary digestibility of DM were not affected by concentrate type. Milk yield was lower for LP compared with other concentrate types (25.4 vs. 28.3kg/d). Yields of milk protein and milk casein were not affected by concentrate type. However, milk solid yield and milk fat yield were higher for LP+HMBi (1.97 and 0.92kg/d) compared with LP (1.72 and 0.87kg/d). Concentrations of fat, protein, lactose, and casein were not affected by concentrate type. Dietary N intake was higher for HP compared with other treatments (0.545 vs. 0.482kg/d, HP vs. average of the 3 LP treatments). Dietary N intakes were not different among low CP concentrates. Fecal N excretion was not affected by concentrate type. However, urinary N excretion was related to N intake and was higher for HP compared with other treatments (0.261 vs. 0.195kg/d, HP vs. average of the 3 LP treatments). Urinary N excretion was not different among low CP concentrates. Milk N output was higher for HP (0.139kg/d) compared with LP (0.12kg/d) but not LP+HMBi (0.137kg/d) or LP Corn (0.138kg/d). The portion of feed N excreted as feces N was lower for HP compared with other treatments (0.272 vs. 0.327, HP vs. average of the 3 LP treatmentsHowever, the portion of feed N excreted as urine N was higher for HP (0.466) compared with LP+HMBi (0.408) and LP Corn (0.366) but not compared with LP. The portion of feed N excreted as milk N was higher for LP Corn (0.282) compared with HP (0.257) but not LP+HMBi or LP. Dietary reformulation to reduce N excretion in pasture-based dairy production systems is possible. However, maintenance of milk yield and milk N when concentrate CP was reduced (19 vs. 15%) required the use of either protected AA (HMBi) or ground corn.

Non-ryegrass pastures - the science and farmer practice

A review of recently published science demonstrates that relatively simple non-perennial ryegrass mixtures have performed well in environments as diverse as under deer grazing in Dunedin and the Manawatu, under sheep grazing in dryland mid-Canterbury, and under both irrigated and dryland dairy cow grazing in the Waikato and Northland. Animal productivity has been lifted by up to 30% in milk solids and 50% in deer liveweight gain in non-perennial ryegrass mixtures compared to perennial ryegrass-based pastures. In some cases, the ryegrass pasture has produced similar or more dry matter, yet animal performance has been greater on the non-perennial ryegrass pastures. In other cases, dry matter productivity from complex nonryegrass mixtures has been around 30% higher than from perennial ryegrass pastures. Interviews with farmers from South Canterbury to Northland have all reported positive experiences with non-ryegrass pastures and most have said they will not be planting perennial ryegrass-based pastures again.

Mixed herb and legume pasture improves the growth of lambs post-weaning

The potential of mixed herb and legume pastures to increase post-weaning growth rates of lambs in comparison to ryegrass-based pastures was evaluated. Unrestricted allowances of pasture treatments were offered to weaned, Romney lambs in consecutive autumns of 2007 and 2008. In Experiment 1 (2007), 300 ewe lambs were allocated for 64 days to one of four permanent sward mix treatments; chicory, plantain, red clover and white clover [herb/clover (n = 75)]; plantain, perennial ryegrass and white clover [plantain/pasture (n = 75)]; tetraploid perennial ryegrass and white clover [new pasture (n = 75)]; or diploid perennial ryegrass, other grass species and white clover [old pasture (n = 75)]. In Experiment 2 (2008), the first three pasture treatments from Experiment 1 were re-used (‘old pasture’ not used) with 168 wether lambs allocated for 35 days; herb/clover (n = 56); plantain/pasture (n = 56); and new pasture (n = 56). Unfasted liveweights of all lambs were recorded at weekly intervals and before slaughter. A sub-sample of 78 lambs from Experiment 2 was slaughtered to obtain the carcass weights, tissue depth (11 cm from the spine over the 12th rib) and commercial meat percentages. At the conclusion of Experiment 1 the herb/clover treatment lambs were heavier than the new pasture and plantain/pasture treatment lambs, which were heavier than the old pasture treatment lambs (47.4 vs 41.5 vs 41.5 vs 39.6 ± 0.4 kg, respectively) (P &lt; 0.05). At the conclusion of Experiment 2 the herb/clover treatment lambs were heavier than the new pasture treatment lambs, which were heavier than the plantain/pasture treatment lambs (35.6 vs 32.8 vs 28.8 kg ± 0.4, respectively) (P &lt; 0.05). In Experiment 1 a higher percent of herb/clover treatment lambs grew faster than 200 g/day (P &lt; 0.001) than of the pasture/plantain, new pasture and old pasture treatment lambs (87 vs 4 vs 3 vs 0 percent, respectively). In Experiment 2 only the herb/clover lambs (71%) grew faster than 200 g/day (P &lt; 0.05). In Experiment 2 herb/clover treatment lambs had heavier (P &lt; 0.05) final carcass weight (15.7 ± 0.20 vs 14.8 ± 0.38 vs 14.6 ± 0.27 kg) compared with the plantain/pasture and new pasture lambs, respectively. It was demonstrated that a herb/clover mixed sward can increase post-weaning lamb liveweight gains during unrestricted feeding conditions compared with traditional perennial ryegrass-based pastures.

Companion cropping chicory with winter forage cereals for grazing and forage conservation. Dry matter yields, nutritive characteristics and mineral content

Limitations to the current perennial ryegrass-based pasture system on dryland dairy farms in southern Australia has led to research into alternatives that can produce either additional DM, out of season feed or can improve nutritive characteristics. The use of winter annual crops followed by a summer crop have the potential to achieve these goals but often result in considerable periods where new crops are establishing and feed is not available for consumption. Companion cropping offers an option to overcome these limitations. The experiment reported in this paper examines the DM yields, nutritive characteristics and mineral content of companion cropping wheat or triticale at different sowing rates into an existing chicory monoculture over a 2-year period. We hypothesised that oversowing cereal crops in autumn into an existing stand of chicory would result in improvements in nutritive characteristics at ensiling, without adversely affecting DM yield or subsequent chicory DM yields following harvesting, thus negating the need to sow a new summer forage crop each year. Total DM yields for the chicory and cereal monocultures were similar over the experimental period, while DM yields for all triticale mixtures were higher than the chicory only treatment. Chicory produced lower DM yields for silage but higher DM yields at most grazing events. The crude protein and estimated metabolisable energy content of the chicory only treatment was higher than the cereal monocultures and all triticale/chicory mixtures at both silage harvests with wheat/chicory mixes being intermediate. The proportion of chicory in the mixed swards declined over the course of the experiment. The use of chicory with cereals resulted in no adverse effects on total DM yields, some improvements in nutritive characteristics and mineral content and a more continuous supply of DM compared with double cropping with annual species in winter and summer. This experiment has highlighted the potential of oversowing cereal forages into an existing chicory sward to contribute to DM production on dairy farms in southern Australia. Such forage mixes can provide flexibility into forage systems through the provision of forage for grazing in early winter, the production of high DM yield silage harvests and then subsequent feed supply over summer and early autumn.

Interannual variation in pasture growth rate in Australian and New Zealand dairy regions and its consequences for system management

The profitability of dairy farms in Australia and New Zealand is closely related to the amount of pasture dry matter consumed per hectare per year. There is variability in the pasture growth curve within years (seasonal variation) and between years (interannual variation) in all dairy regions in both countries. Therefore, the biological efficiency of production systems depends on the accuracy and timeliness of the many strategic and tactical decisions that influence the balance between feed supply and demand over an annual cycle. In the case of interannual variation, decisions are made with only limited quantitative information on the range of possible pasture growth outcomes. To address this limitation, we used the biophysical simulation model ‘DairyMod’ to estimate mean monthly herbage accumulation rates of annual or perennial ryegrass-based pastures in 100 years (1907–2006) for five Australian sites (Kyabram in northern Victoria, Terang in south-west Victoria, Ellinbank in Gippsland, Elliott in north-west Tasmania and Vasse in south-west Western Australia) and in 35 years (1972–2006) for three sites in New Zealand (Hamilton in the Waikato, Palmerston North in the Manawatu and Winchmore in Canterbury). The aim was to evaluate whether or not a probabilistic approach to the analysis of pasture growth could provide useful information to support decision making. For the one site where annual ryegrass was simulated, Vasse, the difference between the 25th and 75th percentile years was 20 kg DM/ha.day or less in all months when pasture growth occurred. Irrigation at Kyabram and Winchmore also resulted in a narrow range of growth rates in most months. For non-irrigated sites, the 25th–75th percentile range was narrow (10–15 kg DM/ha.day) from May or June through to September or October, because plant available soil water was adequate to support perennial ryegrass growth, and the main source of interannual variability was variation in temperature. Outside of these months, however, variability in growth was large. There was a positive relationship between total annual herbage accumulation rate and mean stocking for four southern Australian regions (northern Victoria, south-west Victoria, Gippsland and Tasmania), but there was evidence of a negative relationship between the co-efficient of variation in pasture growth and stocking rate. The latter suggests that farmers do account for risk in pasture supply in their stocking rate decisions. However, for the one New Zealand region included in this analysis, Waikato, stocking rate was much higher than would be expected based on the variability in pasture growth, indicating that farmers in this region have well defined decision rules for coping with feed deficits or surpluses. Model predictions such as those presented here are one source of information that can support farm management decision making, but should always be coupled with published data, direct experience, and other relevant information to analyse risk for individual farm businesses.

The effects of high stocking rates on milk production from dryland and irrigated Mediterranean pastures

An experiment using herds of ~20 cows (farmlets) assessed the effects of high stocking rates on production and profitability of feeding systems based on dryland and irrigated perennial ryegrass-based pastures in a Mediterranean environment in South Australia over 4 years. A target level of milk production of 7000 L/cow.year was set, based on predicted intakes of 2.7 t DM/cow.year as concentrates, pasture intakes from 1.5 to 2.7 t/cow.year and purchased fodder. In years 1 and 2, up to 1.5 t DM/cow.year of purchased fodder was used and in years 3 and 4 the amounts were increased if necessary to enable levels of milk production per cow to be maintained at target levels. Cows in dryland farmlets calved in March to May inclusive and were stocked at 2.5, 2.9, 3.3, 3.6 and 4.1 cows/ha, while those in irrigated farmlets calved in August to October inclusive and were stocked at 4.1, 5.2, 6.3 and 7.4 cows/ha. In the first 2 years, when inputs of purchased fodder were limited, milk production per cow was reduced with higher stocking rates (P &lt; 0.01), but in years 3 and 4 there were no differences. Mean production was 7149 kg/cow.year in years 1 and 2, and 8162 kg/cow.year in years 3 and 4. Production per hectare was very closely related to stocking rate in all years (P &lt; 0.01), increasing from 18 to 34 t milk/ha.year for dryland farmlets (1300 to 2200 kg milk solids/ha) and from 30 to 60 t milk/ha.year for irrigated farmlets (2200 to 4100 kg milk solids/ha). Almost all of these increases were attributed to the increases in grain and purchased fodder inputs associated with the increases in stocking rate. Net pasture accumulation rates and pasture harvest were generally not altered with stocking rate, though as stocking rate increased there was a change to more of the pasture being grazed and less conserved in both dryland and irrigated farmlets. Total pasture harvest averaged ~8 and 14 t DM/ha.year for dryland and irrigated pastures, respectively. An exception was at the highest stocking rate under irrigation, where pugging during winter was associated with a 14% reduction in annual pasture growth. There were several indications that these high stocking rates may not be sustainable without substantial changes in management practice. There were large and positive nutrient balances and associated increases in soil mineral content (P &lt; 0.01), especially for phosphorus and nitrate nitrogen, with both stocking rate and succeeding years. Levels under irrigation were considerably higher (up to 90 and 240 mg/kg of soil for nitrate nitrogen and phosphorus, respectively) than under dryland pastures (60 and 140 mg/kg, respectively). Soil organic carbon levels did not change with stocking rate, indicating a high level of utilisation of forage grown. Weed ingress was also high (to 22% DM) in all treatments and especially in heavily stocked irrigated pastures during winter. It was concluded the higher stocking rates used exceeded those that are feasible for Mediterranean pastures in this environment and upper levels of stocking are suggested to be 2.5 cows/ha for dryland pastures and 5.2 cows/ha for irrigated pastures. To sustain these suggested stocking rates will require further development of management practices to avoid large increases in soil minerals and weed invasion of pastures.

The performance of pasture mixes containing 'Ceres Tonic' plantain (Plantago lanceolata) in Northland

Over the last 10-15 years 'Ceres Tonic' plantain (Plantago lanceolata) has been added to many ryegrass/ white clover pastures in Northland. From 2001 to 2009, measurements were undertaken monthly in six locations throughout Northland to record the dry matter contribution of 'Tonic' plantain in mixes relative to perennial ryegrass-based pasture, using pasture cages in paired paddocks. Keywords: pasture mixes, dry matter production, seasonal distribution of dry matter, persistence

Subacute ruminal acidosis (SARA) in grazing Irish dairy cows

Subacute ruminal acidosis (SARA) is a significant production disease of dairy cattle. Previous concerns have been raised over the occurrence of SARA in pasture-fed dairy cattle and the potential consequences of laminitis and lameness. Highly digestible perennial rye grass contains high concentrations of rapidly fermentable carbohydrate and low concentrations of physical effective fibre that may result in SARA. This study conducted a point prevalence survey of rumen health status in grazing Irish dairy cattle fed predominantly perennial rye grass-based pasture. The survey assessed rumen fluid, animal health status, milk production data and pasture composition. A total of 144 cows between 80 and 150 days in milk were sampled on 12 farms. Eleven percent of cows were classified as affected with SARA (pH⩽5.5), 42% were marginal (pH 5.6–5.8) and 47% were normal (pH>5.8). The study showed that low rumen pH is prevalent in grazing Irish dairy cattle consuming perennial rye grass-based pasture and raises concerns regarding effective pasture utilisation and possible consequences for animal health.

Effect of age on methane emissions of red deer stags from weaning until one year of age grazing pasture

The aim of this study was to determine if methane emissions from young farmed deer increase with age. Methane emissions of 20 red deer stags grazing permanent perennial rye grass-based pasture were measured four times post-weaning, at 4.5, 6.5, 9 and 11.5 months of age, using the sulphur hexafluoride technique. Methane production and methane yield increased with age (P＜0.05) and appeared lower (26％) than previous measurements from adult deer on similar pasture. These results imply that total methane emissions from young deer recorded in the New Zealand Greenhouse Gas Inventory are likely to be overestimated if values are based on adult methane emissions only.

Responses to the renovation of an irrigated perennial pasture in northern Victoria. 2. Botanical composition, and plant and tiller densities

A field experiment was established in northern Victoria in the autumn of 1999 to quantify the effects of renovating a 15-year-old, irrigated perennial pasture with a high paspalum content. The treatments were: (i) control, the existing pasture; (ii) oversown, the existing pasture grazed, topped and direct drilled; and (iii) resown, the existing pasture sprayed, cultivated and a new pasture sown. The grass species used in both renovation treatments were perennial ryegrass, Italian ryegrass and tall fescue. The treatments were grazed by dairy cows. The botanical composition, tiller density and plant frequency are reported in this paper. Oversowing with either perennial or Italian ryegrass increased the sown grass content by an average of 4–8% DM, and by up to 20% DM during winter and spring, but did not affect the average white clover, volunteer species or dead contents. Oversowing did not affect the sown grass or paspalum tiller densities but annual oversowing with either perennial or Italian ryegrass increased the ryegrass plant frequency and, in 2 of the 4 years, reduced the white clover growing point density. Resowing increased (P &lt; 0.05) the content of sown grasses (by 12% DM for perennial ryegrass and by 20% DM for tall fescue) and white clover (by 8% DM) and decreased (P &lt; 0.05) the content of volunteer species (by 18% DM) and, in years 1 and 2, dead material. The plant frequency of tall fescue increased over time (from 75 to 83% of quadrats), whereas that of perennial ryegrass declined (from 87 to 72% of quadrats). This resulted in the resown tall fescue having a lower (P &lt; 0.05) white clover content and growing point density in years 3 and 4, and a tendency for a lower volunteer species content and tiller density in year 4, than the resown perennial ryegrass. Tall fescue is thus better able to resist the invasion of summer-active species and is less likely to require either oversowing or resowing than perennial ryegrass-based pastures. These results suggest that tall fescue should be considered as an alternative to perennial ryegrass when sowing pastures. The use of nitrogen did not improve the sown grass content, tiller density or plant frequency and will not therefore overcome problems resulting from a low ryegrass content.