Perennial Ryegrass Pasture Research Articles

Fertiliser and seasonal urine effects on N2O emissions from the urine-fertiliser interface of a grazed pasture

Significant areas of ruminant-grazed pastures are simultaneously covered by excreted urine and fertiliser nitrogen (N). However, the effect of overlapping N inputs on nitrous oxide (N2O) emission factors has not been studied. Three rates of 15N-labelled urea fertiliser were applied with either no urine, an autumn-urine or a spring-urine application. These treatments were applied to perennial ryegrass pasture (Lolium perenne L.) and N2O fluxes were determined over 373 days using standard static closed chamber techniques. Cumulative N2O-N fluxes ranged from 766 to 4332 g N2O-N ha–1 (0.36%–0.74% of total N applied) and were lowest in the absence of urine; however, no fertiliser rate effect occurred regardless of urine presence or season of application. Urine-elevated N2O-N fluxes followed urine applications for up to 40 days, resulting in lower fertiliser contributions to the N2O-N fluxes at these times. Total 15N recoveries as N2O-N were ≤0.04% and did not differ with fertiliser rate.

Effects of concentrate supplementation on enteric methane emissions and milk production of grazing dairy cows

Although concentrate supplements in ruminant diets have been recognised as an effective enteric methane mitigation strategy, very few studies have examined the effects of concentrate supplementation on enteric methane emissions under grazing conditions. Twenty four multiparous Holstein Friesian cows were used in a crossover design study to investigate the effects of two concentrate feeding levels across two periods on enteric methane emissions and milk production of grazing dairy cows. Each period had a duration of four weeks (three weeks for diet adaptation and one week for measurements) and no interval in between them. Dietary treatments consisted of two concentrate feeding levels per cow (1 vs. 5kg; as-fed basis) offered daily in equal meals during milking. Enteric methane emissions from cows grazing perennial ryegrass pasture were measured during the final week of each period using the sulphur hexafluoride tracer technique. Milk yield and liveweight were determined daily during each methane measurement period, whereas milk composition and body condition score (BCS) were determined weekly. Daily herbage intake by individual cows during methane measurement weeks was estimated using an energy requirement model and animal records and diet composition. In period 1, cows receiving 5kg concentrate supplement were estimated to reduce herbage intake by 1.8kg DM/d compared to cows receiving 1kg of concentrate, whereas in period 2 cows receiving the 5kg concentrate supplementation were estimated to reduce herbage intake by 4.4kg DM/d, compared to cows receiving 1kg of concentrate. In both periods, milk yield increased with increasing concentrate level, with an average milk response to concentrate supplementation of 0.68kg milk DM/kg concentrate DM over the two periods. Concentrate feeding level had no effect on milk fat, protein or total solids contents. In period 2, lactose content increased in cows offered 5kg/d concentrate. Increasing concentrate feeding level increased liveweight and BCS in period 1, but not in period 2. Feeding 5kg of concentrate supplement increased enteric methane emission by 34g/d in period 1 (323 vs. 357g/d) and 41g/d in period 2 (349 vs. 390g/d) compared to 1kg of concentrate supplement. However, enteric methane emission per unit of estimated feed intake (dry matter or gross energy) or milk output (gross or energy corrected) was not affected by level of concentrate supplementation. It was concluded that under generous grazing conditions (high allowance of good quality herbage) a moderate increase in concentrate supplementation resulted in a simultaneous increase in milk yield and enteric methane emission, so that enteric methane emission per unit of milk yield was unaffected. Thus, a moderate level of concentrate supplementation of dairy cows grazing pastures of high digestibility would not be an effective enteric methane mitigation strategy.

Effect of climate variability on pasture-based dairy feeding systems in south-east Australia

The Australian dairy industry relies primarily on pasture for its feed supply. However, the variability in climate affects plant growth, leading to uncertainty in dryland pasture supply. This paper models the impact of climate variability on pasture production and examines the potential of two pasture-based dairy feeding systems: (1) to experience winter deficits; (2) to carry forward the conserved pasture surpluses as silage for future use; and (3) to conserve pasture surpluses as hay. The two dairy feeding systems examined were a traditional perennial ryegrass-based feeding system (ryegrass max. – RM) and a system that incorporated double cropping into the perennial ryegrass pasture base (complementary forage – CF). The conditional probability of the RM and CF systems to generate pasture deficits in winter were 94% and 96%, respectively. Both systems could carry forward the surplus silage into the following lactation almost once in every 4–5 years with the RM system performing slightly better than the CF system. The proportions of the grain-based concentrates fed in the two systems were 25% and 27% for the RM and CF systems, respectively. This study suggests that double-cropping systems have the potential to provide high-quality feed to support the feed gaps when pasture is not available due to increased variability in climatic conditions.

Chemical and physical amelioration of subsoils has limited production benefits for perennial pastures in two contrasting soils

While broad acre grazing is the major agricultural land use in Southern Australia, there has been comparatively little research on the effect of alleviating subsoil limitations on pasture production under field conditions. The effect of modifying the physical and chemical properties of soil on perennial pasture production and root distribution was studied on 2 major soil types in two regions of Southern Victoria, Australia. Soil treatments included the deep placement of fertilisers, lime and organic matter, and soil disturbance to a range of depths. The Ellinbank field site on a Ferrasol was monitored for 2 years, while the Curdievale site on a Sodosol was monitored for 1 year. There were substantial changes in soil physical and chemical characteristics as a result of the soil treatment. Soils were softer, less acidic and had increased nutrient availability within the profile. However, these changes did not result in consistent gains in pasture productivity, over-and-above the normal practice of surface applied nutrients and lime. The deep placement of organic matter at the Ellinbank site resulted in an initial increase in pasture production, but this effect declined with time. The perennial ryegrass (Lolium perenne L.) based pasture was shallow-rooted and substantial modifications to the soil profile did not result in significant changes to root distribution. It appears that the productivity of perennial ryegrass pasture in high rainfall regions can be maintained at a productive level, with a localised nutrient and water supply.

An evaluation of contrasting C32 alkane dosing and faecal sampling regimes to estimate herbage dry matter intake by beef cattle

SUMMARYTwo experiments were carried out to evaluate different dosing and sampling regimes for estimating the dry matter intake (DMI) of vegetation by grazing beef cattle. Experiment 1 compared the DMI of a perennial ryegrass pasture by 48 grazing beef cattle dosed with C32n-alkane and faecally sampled at different time intervals. The cattle, of dairy and suckler origin, were balanced by origin and allocated to one of three alkane-dosing treatments (n=16): T1, dosed once daily (10.30 h) with two 500 mg boluses of C32 alkanes; T2, dosed twice daily (09.00 and 16.00 h) with a 500 mg bolus of C32n-alkane; and T3, dosed twice daily (07.00 and 19.00 h) with a 500 mg bolus of C32n-alkane. Faecal samples were collected concurrently with dosing in each treatment. Dosing interval had no effect on estimated DMI, when calculated using the n-alkane content of faeces sampled concurrently with dosing, suggesting that once-daily dosing with concurrent faecal sampling is adequate to estimate DMI by beef cattle. The objective of Expt 2 was to compare the accuracy of herbage DMI estimated using a once-daily C32 alkane dosing regime and n-alkane concentrations in faeces sampled at 09.00, 13.00, 17.00 and 21.00 h, against DMI measured directly. Twelve Holstein-Friesian bulls (mean body weight 265 kg) were housed individually in digestibility stalls and offered harvested perennial ryegrass or harvested semi-natural upland vegetation, both ad libitum. The DMI estimated by once-daily dosing with n-alkane and concurrent per rectum faecal sampling did not differ significantly from the directly measured DMI for either herbage type. It is concluded that a once-daily alkane dosing and concurrent faecal sampling protocol is adequate to reliably estimate the DMI of both upland and lowland pasture vegetation by beef cattle.

Influence of different systems for feeding supplements to grazing dairy cows on milk fatty acid composition

This study investigated the effects of different strategies for feeding supplements to grazing dairy cows on the proportions of fatty acids in milk. Two hundred and sixteen cows were fed supplementary grain and forage according to one of 3 different strategies; (1) CONTROL: cows grazed perennial ryegrass pasture (14kg dry matter/d) supplemented with milled barley grain fed in the milking parlour and pasture silage offered in the paddock; (2) Partial mixed ration 1 (PMR1): same pasture allotment and supplement as CONTROL strategy, but the supplements presented as a mixed ration after each milking in feedpad, and; (3) Partial mixed ration 2 (PMR2): same pasture allotment, supplemented with a mixed ration of milled barley grain, alfalfa hay, corn silage and crushed corn grain fed in a feedpad. Within each strategy, cows were assigned to receive either 6, 8, 10 or 12kg dry matter supplement/cow per d. Milk fatty acid proportions from cows fed CONTROL and PMR1 strategies were similar and different from those fed PMR2, particularly at 10 to 12kg dry matter supplement/cow per d. The reduction in milk fat yield and concentration in cows fed high amounts of supplement as CONTROL and PMR1 was coincident with 4×increase in 10t-18:1 proportion. The composition of the partial mixed ration (PMR) and the amount offered affected milk fatty acid proportions and milk fat content, however, the method of supplementation did not.

Increasing home-grown forage consumption and profit in non-irrigated dairy systems. 4. Economic performance

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.

Hipocalcemia não puerperal em vacas leiteiras sob pastejo de aveia e azevém: estudo de fatores predisponentes

A Hipocalcemia Não Puerperal (HNP) é uma condição rara e pouco compreendida. Não há estudos que expliquem a sua relação com a ingestão de pastagens de inverno como base da alimentação volumosa. Os objetivos deste trabalho foram descrever aspectos clínicos de dois casos naturais de HNP, e estudar o balanço mineral e eletrolítico de vacas leiteiras de alta e de média produção alimentadas em pastagem de inverno em diferentes estágios de evolução. Foram acompanhados dois casos de HNP em vacas leiteiras, mantidas em pastagens de aveia ou de azevém no município de Francisco Beltrão, PR. De três propriedades localizadas no mesmo município, foram selecionadas vacas lactantes hígidas de alta produção da raça Holandesa (n=11) e de média produção das raças Holandesa (n=8) e Jersey (n=9), mantidas em pastagem mista de aveia e azevém, de junho a outubro de 2011, e complementadas com silagem de milho. Amostras de sangue, de urina e dos alimentos ingeridos foram colhidas antes do ingresso na pastagem (maio), e nos estágios inicial (junho), intermediário (julho) e final (setembro) do ciclo de maturação da forragem. Foram determinadas as concentrações séricas e urinárias de Ca, P, Mg, Na+, K+, Cl- e creatinina e calculada as excreções fracionadas. Nas amostras de alimento foram determinadas a matéria seca (MS) e as concentrações de Ca, P, Mg, Na, K, Cl e S, e calculou-se a diferença entre cátions e ânions da dieta (DCAD) nos diferentes momentos. Com base nas evidências pode-se afirmar que vacas leiteiras em lactação mantidas em pastagem de aveia e/ou de azevém nos meses de inverno podem desenvolver hipocalcemia e exibir sinais clínicos e resposta ao tratamento similares aos da hipocalcemia puerperal clássica, mesmo não sendo recém paridas. A ingestão de aveia e azevém, substituindo parcialmente a silagem de milho como volumoso da dieta, não provoca desequilíbrio eletrolítico e não interfere com a calcemia, a fosfatemia ou a magnesemia de vacas lactantes de alta e de média produção. A utilização das forrageiras de inverno como a única ou principal fonte de volumoso da dieta parece ser o fator desencadeante da doença e pode estar relacionada com o excesso de cátions ingeridos devido à elevada concentração de K, principalmente, quando a planta é jovem.

Effect of pre-grazing herbage mass on dairy cow performance, grass dry matter production and output from perennial ryegrass (Lolium perenne L.) pastures

A grazing study was undertaken to examine the effect of maintaining three levels of pre-grazing herbage mass (HM) on dairy cow performance, grass dry matter (DM) production and output from perennial ryegrass (Lolium perenne L.) pastures. Cows were randomly assigned to one of three pre-grazing HM treatments: 1150 – Low HM (L), 1400 – Medium HM (M) or 2000 kg DM/ha – High HM (H). Herbage accumulation under grazing was lowest (P<0.01) on the L treatment and cows grazing the L pastures required more grass silage supplementation during the grazing season (+73 kg DM/cow) to overcome pasture deficits due to lower pasture growth rates (P<0.05). Treatment did not affect daily milk production or pasture intake, although cows grazing the L pastures had to graze a greater daily area (P<0.01) and increase grazing time (P<0.05) to compensate for a lower pre-grazing HM (P<0.01). The results indicate that, while pre-grazing HM did not influence daily milk yield per cow, adapting the practise of grazing low HM (1150 kg DM/ha) pasture reduces pasture DM production and at a system level may increase the requirement for imported feed.

Agronomic advantages conferred by endophyte infection of perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) in Australia

Perennial ryegrass and tall fescue are key grasses of sown pastures in the high-rainfall zone of south-eastern Australia. Ryegrass in naturalised pastures, and in sown seed, is widely infected with Neotyphodium fungal endophytes, with toxic endophyte strains occasionally causing toxicosis in livestock. Endophyte infection is also beneficial in sown grasslands, assisting ryegrass hosts to overcome biotic stresses, and tall fescue hosts to overcome biotic and abiotic stresses. We review the literature for Australia and present new data, to examine the agronomic effects of endophyte. Frequency of endophyte infection in old, perennial ryegrass pastures and ecotype-based cultivars is high and, in all pastures, increases with time, providing evidence for endophyte-infected plants having an agronomic advantage over endophyte-free plants. Within a cultivar, agronomic field experiments have compared endophyte-infected with endophyte-free swards. Endophyte significantly improved ryegrass establishment in seven of 19 measurements taken from 12 trials. In mature ryegrass pastures, over half of the experiments found advantages to endophyte infection. Tall fescues infected with a selected endophyte (‘AR542’) had improved agronomic performance relative to endophyte-free in a majority of experiments, and on occasions, the endophyte was essential for tall fescue persistence. Cultivar × endophyte interactions occurred but were inconsistent. In high-stress environments, endophyte was more important for agronomic performance than difference between cultivars. The relative importance of cultivar and endophyte is discussed, with elite cultivars that are adapted to the region and are infected with elite endophytes being the best avenue to capture the benefits and minimise detrimental endophyte effects on livestock. The major drivers are likely to be insect pests and drought, but evidence is limited.

Increasing home-grown forage consumption and profit in non-irrigated dairy systems. 2. Forage harvested

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.

Feeding a partial mixed ration once a day did not increase milk production compared with feeding grain in the dairy and forage in the paddock

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.

Increasing home-grown forage consumption and profit in non-irrigated dairy systems. 1. Rationale, systems design and management

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.

Replacing wheat with canola meal in a partial mixed ration increases the milk production of cows grazing at a restricted pasture allowance in spring

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.

Nutritive value, in vitro fermentation and methane production of perennial pastures as affected by botanical composition over a growing season in the south of Chile

Permanent pastures have been shown to produce similar herbage masses and nutrient contents to perennial ryegrass pastures. To the best of our knowledge, little research has been conducted on the ruminal fermentation of permanent pastures. Our objective was to evaluate the effect of botanical composition of four perennial pastures during a growing season in the south of Chile [winter, September 2010 ‘S1’; spring, November 2010 ‘S2’; and summer, January 2011 ‘S3’]: on in vitro fermentation products using a batch culture system. The perennial pastures studied included: permanent (PP), permanent fertilised (PFP) and renovated pastures (Lolium perenne and Trifolium repens pasture ‘RGWC’; Bromus valdivianus, Dactylis glomerata, Holcus lanatus, L. perenne and T. repens ‘MIXED’). There were strong interactions between pasture type and regrowth period for true organic matter, nitrogen (N) and neutral detergent fibre digestibility; total gas and volatile fatty acid (VFA) production; ammonia and microbial N. In general, all pasture treatments showed a high true organic matter digestibility (&gt;800 g/kg), and tended to decrease in S3. In vitro fermentation of PFP and RGWC produced the highest total VFA concentration during S1 and S2, and no differences among pastures were observed in summer. Propionate proportion of total VFA was affected by pasture type and regrowth period, being higher for RGWC and S1, respectively. In vitro microbial N was higher for MIXED in S1, and PFP in S2 and S3. No pasture and regrowth period effects were observed for methane production and its proportion of total gas production. These results indicate that the in vitro fermentation products of a permanent fertilised pasture reach similar levels to those obtained from a sown pasture, and thus may be considered as a sustainable alternative for grazing livestock systems.

Herbage production from five grazable forages

Maintaining an adequate feed supply throughout the year is an important consideration in dairy systems. Systems based on perennial ryegrass pastures are often limited by poor growth and feed quality when soil moisture is low and temperatures are high. Alternative forage species better adapted to these conditions may provide options for maintaining feed supply. Annual and seasonal dry matter (DM) production, and nutritive value of five grazable forages with and without irrigation were compared under cutting in the Waikato over two successive years. Perennial ryegrass produced the greatest annual DM yield in both years under both irrigation regimes, largely through superior cool season production and mild temperatures with above average rainfall during the experiment. Plantain tended to provide more DM than perennial ryegrass under irrigation in summer and autumn, a time when additional DM is important for maintaining milk production. With the exception of sudan grass, nutritive value of all forages exceeded values expected to limit milk production. Keywords: dry matter yield, nutritive value, chicory, plantain, perennial ryegrass, sudan grass, sulla

Can summer-active perennial species improve pasture nutritive value and sward stability?

Although generally well adapted and productive, the summer-dormant perennial pastures of southern Australia do not provide a year-round, high nutritive value feed base, they fail to respond to summer rainfall, and they are inefficient in using stored soil water, which can contribute to dryland salinity. An experiment was conducted to test the hypothesis that deep-rooted, summer-active perennial pasture species, matched to soil type, can be grown successfully in southern Australia to increase pasture and animal productivity and to provide high quality feed in summer–autumn. Specifically, the experiment compared a traditional perennial ryegrass (Lolium perenne L.) pasture system with two systems based on summer-active species: the triple system with lucerne (Medicago sativa L.) and tall fescue (Lolium arundinaceum (Schreb) Darbysh), and the novel system with chicory (Cichorium intybus L.) and kikuyu (Pennisetum clandestinum Hochst. ex Chiov). The experiment incorporated three livestock systems (two sheep and one cattle) and took into account the three main soil types occurring on the DPI Hamilton research farm. After 4 years the perennial ryegrass, lucerne, and tall fescue components were all persisting well and providing feed with high nutritive value (all with frequency scores &gt;70% in the last year of the experiment). The chicory and kikuyu pastures declined over the life of the experiment and were contributing little at the end (frequency scores &lt;15% in the final year). Lucerne, tall fescue, and perennial ryegrass cv. Banquet were able to respond to summer rainfall events to provide valuable, high-quality feed at a time when the quality of perennial ryegrass pasture is normally at its lowest; April 2007 crude protein per cent dry matter values were Avalon perennial ryegrass 16.6, Fitzroy perennial ryegrass 15.6, kikuyu 24.2, lucerne 25.8, and tall fescue 20.3 following a 98 mm rainfall event in late January 2007. This study has shown that the triple and ryegrass systems were persistent and of high nutritive value, with the sown perennial species contributing the majority of the sward dry matter during the growing season.

Summer-active perennials in pasture systems improve seasonal pasture distribution without compromising winter-spring production

Improved dryland pastures for sheep and beef cattle production in south-western Victoria are typically based on summer-dormant cultivars of perennial ryegrass (Lolium perenne L.) or phalaris (Phalaris aquatica L.). These are highly productive in spring but exhibit low accumulation rates over summer–autumn. Summer-active perennial pasture species could potentially alleviate this summer–autumn feed gap. Three pasture systems that used different pastures on each of the three landscape classes (crest, slope, and valley floor) were compared over 4 years. The perennial ryegrass system (henceforth Ryegrass) had a different ryegrass cultivar on each landscape class. The Triple system used lucerne (Medicago sativa L.) (crest), perennial ryegrass (slope), and summer-active tall fescue (Lolium arundinaceum (Schreb) Darbysh.) (valley floor). The Novel system used chicory (Cichorium intybus L.) (crest), Italian ryegrass (Lolium multiflorum Lam.) or hybrid ryegrass (L. × boucheanum Kunth.) (slope), and kikuyu (Pennisetum clandestinum Hochst. ex Chiov.) (valley floor). The pastures were grazed by either one (in the case of the Novel system) or three (in the case of the Ryegrass and Triple systems) animal systems that varied over the life of the experiment. Total annual herbage accumulation of the Ryegrass and Triple systems did not differ. The Novel system consistently had lower total annual dry matter accumulation than the other two systems. Lucerne pastures generally had the highest accumulation rates over summer, followed by the chicory pastures. The kikuyu pastures responded well to summer rainfall but otherwise had similar accumulation rates to the perennial ryegrass and tall fescue pastures over summer. Tall fescue pastures grew well in autumn following wet summers. In spring the perennial ryegrass pastures based on Fitzroy or Avalon were highly productive but seldom grew faster than other pastures. The results support the hypothesis that incorporating deep-rooted, summer-active perennial species will increase pasture production over summer–autumn compared with conventional pasture systems but not at the expense of winter–spring production.

Effects of different strategies for feeding supplements on milk production responses in cows grazing a restricted pasture allowance

Milk production responses of grazing cows offered supplements in different ways were measured. Holstein-Friesian cows, averaging 227d in milk, were allocated into 6 groups of 36, with 2 groups randomly assigned to each of 3 feeding strategies: (1) cows grazed perennial ryegrass pasture supplemented with milled barley grain fed in the milking parlor and pasture silage offered in the paddock (control); (2) same pasture and allotment supplemented with the same amounts of milled barley grain and pasture silage, but presented as a mixed ration after each milking (PMR 1); and (3) same pasture and allotment, supplemented with a mixed ration of milled barley grain, alfalfa hay, corn silage, and crushed corn grain (PMR 2). For all strategies, supplements provided the same metabolizable energy and grain:forage ratio. [75:25, dry matter (DM) basis]. Each group of 36 cows was further allocated into 4 groups of 9, which were assigned to receive 6, 8, 10, or 12kg of supplement DM/cow per day. Thus, there were 2 replicated groups per supplement amount per dietary strategy. The experiment had a 14-d adaptation period and an 11-d measurement period. Pasture allotment was approximately 14kg of DM/d for all cows and was offered in addition to the supplement. Positive quadratic responses to increasing amounts of supplement were observed for yield of milk, energy-corrected milk (ECM), and fat and protein, and positive linear responses for concentrations of fat and protein for cows on all 3 supplement feeding strategies. No difference existed between feeding strategy groups in yield of milk, ECM, or protein at any amount of supplement offered, but yield and concentration of fat was higher in PMR 2 cows compared with control and PMR 1 cows at the highest amounts of supplementation. Responses in marginal ECM production per additional kilogram of supplement were also greater for PMR 2 than control and PMR 1 cows when large amounts of supplement were consumed. For all diets, marked daily variation occurred in ruminal fluid volatile fatty acids and pH, especially in cows fed the largest amounts of supplement. It was concluded that when supplements are fed to grazing dairy cows, a simple mix of grain and pasture silage has no benefit over traditional strategies of feeding grain in the parlor and forage in the paddock. However, yield of milk fat and marginal milk production responses can be greater if the strategy uses an isoenergetic ration that also contains alfalfa hay, corn silage, and corn grain.

The influence of herbage mass and supplementary feeding on nutrient flows and animal performance in grazing, lactating ewes

SUMMARYThe present paper examines the effect of the type of supplement given to grazing ewes in early lactation on the performance of ewes and lambs on temperate sown pastures. Lactating ewes grazed perennial ryegrass pastures at either low- or high-herbage masses, between days 8 and 96 of lactation. On the low-herbage mass treatments, ewes were either unsupplemented or received either an energy supplement (sugarbeet pulp) or a protein supplement (1:1 sugarbeet pulp:formaldehyde-treated soyabean meal) between days 8 and 50 of lactation. The provision of supplements or the higher herbage mass led to increases in live weight (LW) and body condition score of ewes during days 8–50 of lactation, while unsupplemented ewes on the low-herbage mass treatment lost LW and had lower body condition scores. After supplementation finished, previously supplemented ewes or those grazing the higher herbage mass lost LW and condition, while unsupplemented ewes grazing the low-herbage mass gained both LW and condition. Non-treatment factors such as ewe dentition score significantly affected ewe and lamb LW gains. Regression analyses indicated that lamb LW gains between days 8 and 50 of lactation were 40–60 g/d greater in lambs from supplemented ewes or ewes grazing the higher herbage mass cf. unsupplemented ewes. Overall, there was no difference in the response of ewes or lambs to the type of supplement. Milk yields were estimated in a subset of ewes (replicate 4). Ewes on the high-herbage mass treatment or those supplemented with protein had higher milk yields than those on the low-herbage mass treatment or those given the energy supplement. Supplemented ewes in this replicate had higher metabolizable energy intakes (MEIs). Measurements of digesta flow in a further subset of ewes indicated that both supplements resulted in greater ruminal and post-ruminal supplies of energy and protein than in the unsupplemented ewes at the lower herbage mass, but differences in ruminal and post-ruminal nutrient provision between the supplements were less than had been intended. It is suggested that this is the reason for there being no statistical difference in the performance of ewes and lambs in response to the type of supplement.