Pasture Variables Research Articles

APSIM model performance in simulating Piatã palisade grass growth and soil water in different positions of a silvopastoral system with eucalyptus

CONTEXTSilvopastoral systems aim to be more sustainable than conventional systems, increasing total productivity, diversifying agricultural production, and improving resource use efficiency. However, very few studies were performed to adapt crop models to simulate these systems. OBJECTIVEThis study investigates the current capacity of the APSIM Next Generation model to estimate Piatã palisadegrass growth and soil water in different positions in a silvopastoral system with eucalyptus by looking at the impact of modelling belowground and aboveground competition separately. METHODSA field experiment was conducted from December 2014 to January 2016 in a silvopastoral system with eucalyptus trees arranged in single rows, in East-West orientation, with 15 m between rows and 2 m between trees in the rows. This experiment was conducted under grazing management and rainfed conditions, during 11 growth cycles, with pasture variables, soil moisture and microclimatic conditions assessed at four distances from the eucalyptus north row (0.00 m, 3.75 m, 7.50 m and 11.25 m). APSIM testing was performed in two ways: focusing on belowground competition for soil water and nitrogen, using a multi-root-zone approach, and focusing on competition for solar radiation, using the measured data of solar radiation at each position. RESULTS AND CONCLUSIONSThe APSIM-Tropical Pasture model was effective in simulating pasture growth when only competition for solar radiation was considered (R2 from 0.75 to 0.86, Agreement index (d) from 0.88 to 0.96, and Nash-Sutcliffe efficiency (NSE) between 0.32 and 0.85). These simulations are promising taking into account the difficulties to simulate pasture growth in silvopastoral systems with grazing; however, in systems with strong belowground competition for soil water and nutrients, this approach has strong limitations. Simulations of pasture growth were not as effective when using the multi-root-zone approach (R2 between 0.57 and 0.87, d between 0.53 and 0.74, and NSE from −5.32 to −1.20), despite reasonable simulations of soil water for the positions between the tree rows (R2 between 0.70 and 0.80, d from 0.91 to 0.94, and NSE between 0.60 and 0.77). In view of these results, improvements should be performed in APSIM to better simulate silvopastoral systems, mainly for solar radiation transmission and tree roots growth and distribution. SIGNIFICANCEThis study allowed identifying the key drivers of competition within the studied environment and to inform where the main efforts should be targeted in building a more effective model for silvopastoral systems. This is important to help model development teams in organising and optimising their efforts.

Grazed rain-fed small-grain cereals as a forage option for small-scale dairy systems in central Mexico.

Small-scale dairy systems face reduced availability of water for irrigation of pastures and disruption in the amount or pattern of rains due to climate change, so research on alternative short-cycle rain-fed forages is needed. Grazing reduces feeding costs and small-grain cereals may be an option. The objective was to assess on-farm the performance of dairy cows grazing 6h/day of three small-grain cereals: rye (RYE), wheat (WHT), and triticale (TRT), and supplemented 4.5kg dry matter (DM)/cow/day of concentrate. Twelve Holstein cows were used in repeated 3 × 3 Latin squares with 14-day experimental periods. Pasture variables were analysed with a split-plot design, and economic analysis was performed with partial budgets. Sampling of forage (sward height, net herbage accumulation, botanical and chemical composition of herbage) and animal variables (milk yield and composition, live weight, and body condition score) were at the end of each period. The RYE showed a trend (P > 0.05) for higher net herbage accumulation (NHA) with highly significant differences (P < 0.001) among periods. The RYE had higher DM, a lower crude protein (CP) content (P < 0.05), and no differences for other chemical components between treatments (P > 0.05). The RYE proportion in pasture was consistently higher, whilst the lowest cereal proportion was in WHT. There were no differences (P > 0.05) for any animal variable. The RYE and TRT treatments proved useful as rain-fed forage alternatives under grazing. WHT showed lower crop and economic performance. However, given the higher cereal component in pastures, regrowth potential, and post-grazing herbage mass, as well as better economic performance, the RYE treatment was better ranked by the participating farmer.

Multi-species pastures for grazing dairy cows in small-scale dairy systems in the highlands of Mexico.

Grazing in small-scale dairy systems reduces costs and enhances sustainability. However, binary pastures (BP) have low persistency, which may be increased by including more species given their flexibility to withstand different agroecological and management situations. The objective was to assess a multi-species (MS) pasture of perennial ryegrass (RG), tall fescue (TF), bromegrass (BG), red clover (RC) and white clover (WC) in comparison to a BP of perennial ryegrass (RG) - WC grazed by six Holstein dairy cows during the dry season in an on-farm double cross-over experiment, with three 14-day each experimental periods for animal variables, and a split-plot design for pasture variables at 3 cow/ha. There were differences (P < 0.05) between pastures for sward height (MS 5.0 vs. BP 4.0 ± 0.10cm, both MS and BP) and net herbage accumulation (MS 902 vs BP 228 ± 172.4kg DM/ha, both MS and BP) and differences (P < 0.05) for chemical composition among periods. There were differences (P < 0.01) among periods for estimated DM intake, but no differences (P > 0.05) for milk yield (mean 16.8kg/cow/day), milk fat or protein content (mean 31.8 and 28.8g/kg). Multi-species pastures are a viable alternative for SSDS in the highlands of central Mexico, being more resistant to harsh environment and to weed and kikuyu grass invasion.

Persistence of perennial ryegrass, tall fescue and cocksfoot following sequential annual sowings: pasture yield, composition and density in three establishment years under cattle grazing in Waikato

Persistence is an important component of perennial pasture-grass productivity. Defining the traits that affect persistence is essential for improving pasture longevity through plant breeding and for identifying criteria that should be included in cultivar ranking indices. Compared with a conventional longitudinal study (a single study monitored over time), repeated annual sowings allow the effects on persistence of sowing year and the ensuing interactions between environment and age of pasture to be identified. An experiment commenced in 2016 in Waikato, in which eight cultivars of perennial ryegrass representing different ploidy, flowering date, and cultivar age, and one each of tall fescue and cocksfoot were sown each autumn in a randomised complete block design with four replicates in autumn 2016, spring 2017 and autumn 2018. This paper reports interim data on pasture yield, composition and density in the autumn following each sowing, and for the 2018 sowing only, in the 6 months after sowing. For the three successive autumn measurements there were significant effects due to cultivar, year of sowing and their interactions for all pasture variables. These differences in establishment may have consequences for the future resilience of these pastures under natural biotic and abiotic stressors.

Milk production and estimated enteric methane emission from cows grazing ryegrass pastures in small-scale dairy systems in Mexico.

The work assessed the productive response and estimated enteric methane (CH4) emissions of dairy cows grazing in small-scale dairy systems. Treatments were grazing annual pasture (AP) mainly of annual ryegrass and perennial pasture (PP) mainly of perennial ryegrass, complemented daily with 3.72kg DM/cow of commercial concentrate. Eight Holstein cows were used in a double cross-over design with three 14-day-each experimental periods for animal variables and CH4 emissions. Pasture variables were analysed with a split-plot design. AP showed higher sward height (P < 0.05) with no differences (P > 0.05) in net herbage accumulation or in herbage chemical composition. Cows on AP yielded 24.6% more milk (P < 0.001) than grazing PP, but there were no differences in milk fat and protein content. There were differences (P ≤ 0.05) among periods for milk yields, but no differences among periods for milk fat and protein. Milk urea nitrogen was significantly higher (P < 0.001) in PP than in AP with no differences among periods. There was higher (P < 0.001) DMI for AP than PP with a significant decline (P < 0.05) as periods progressed. There was a trend (P = 0.08) for higher daily CH4/cow in AP, but significantly lower emissions (7.2%) in AP/kg DMI, and 20.1% lower emission intensity of g CH4/kg milk. The proportion of gross energy lost as CH4 for AP was lower (P < 0.01). Higher milk yields in AP resulted in a 26% higher margin over feed costs than for PP. Results show that grazing annual pastures with moderate concentrate supplementation results in higher milk yields, higher incomes, and reduces the intensity of CH4 emissions.

Endophyte-free tall fescue pastures for small-scale dairy systems in the highlands of central Mexico

The objective was to assess dairy cows in small-scale dairy systems grazing pastures of endophyte-free tall fescue (Lolium arundinaceum cv. Cajun II), or perennial ryegrass (Lolium perenne cv. Tetragrain), both associated with white clover (Trifolium repens). An on-farm double cross-over experiment was undertaken with 10 Holstein cows, continuously grazing 10 h/day of Cajun II or Tetragrain pastures, plus 4.6 kg DM of a concentrate/cow/day. Animal variables were milk yield, milk fat and protein content, live-weight, body condition score, and milk urea nitrogen. The analyses of pasture variables was with a split-plot experimental design. Pasture variables were sward height, net herbage accumulation, and chemical composition of herbage for CP, NDF, ADF, in vitro digestibility of organic matter, and estimated herbage intake from utilised metabolizable energy. There were significant differences between treatments for OM, ADF, IVDOM, and eME, with tall fescue showing higher IVDOM which resulted in a slightly higher eME value. An economic analysis compared incomes and feeding costs. There were no statistical differences in animal or pasture variables. Cajun II endophyte-free tall fescue pasture performed similarly to Tetragrain perennial ryegrass in animal, pasture, and economic variables.

Kikuyu pastures associated with tall fescue grazed in autumn in small-scale dairy systems in the highlands of Mexico

Intensive grazing increases the profitability and sustainability of small-scale dairy systems by reducing feeding costs. Kikuyu grass is a subtropical species from East Africa that has similar performance compared with temperate grasses when grazed by dairy cows in these systems during the summer rainy season but reduces growth and quality at low temperatures, when temperate species may have an advantage. The objective was to evaluate intensive grazing of kikuyu pastures (KYKY) alone or in association with two varieties of endophyte-free tall fescue, TF-33 (TF33) and Cajun II (CAJN), during the summer-autumn transition period when low temperatures set in, by lactating cows in small-scale dairy farms. Pasture variables were analysed with a split-plot design for sward height, net herbage accumulation and chemical composition, in vitro digestibility of organic matter, and estimated metabolisable energy content of herbage and concentrate. Experimental design for animal variables was a 3 × 3 Latin Square repeated three times with nine Holstein cows and 14days experimental periods. Cows received 4.65kg DM/day of a 16% CP commercial concentrate. Milk yield and composition, live weight, and body condition score were recorded. There were no significant differences (P > 0.05) for sward height and net herbage accumulation, nor for important components of chemical composition of herbages. There were no significant differences (P > 0.05) for milk yield (19kg/cow/day) and composition, although differences (P < 0.05) were detected for live weight and body condition score. The conclusion is that there is no advantage of associating tall fescue with kikuyu in summer-autumn transition period for small-scale dairy systems.

CROPGRO-Perennial Forage model parameterization for simulating Piatã palisade grass growth in monoculture and in a silvopastoral system

Silvopastoral systems are important to intensify pasture production and mitigate climate change effects. However, very few studies have been performed to adapt crop models to simulate these systems. The aim of this study was to parameterize the CROPGRO-Perennial Forage model for estimating Piatã palisade grass growth in monoculture and in a silvopastoral system with eucalyptus. To generate the dataset required for that, two field experiments were carried out. The first experiment was conducted between February 2011 and July 2012 with Piatã palisade grass under irrigated and rainfed conditions and cut-and-carry management. The second experiment was conducted from December 2014 to January 2016, in a single pasture of Piatã palisade grass and in a silvopastoral system with the same forage species and eucalypt trees. The trees were arranged in single rows, in East-West orientation, with 15 m between rows and 2 m between trees in the rows. This experiment was conducted under grazing management and rainfed conditions, during 11 growth cycles, with the pasture variables being assessed at four distances from the North row of eucalypt (0.00 m, 3.75 m, 7.50 m and 11.25 m), in the silvopastoral system, and in the single pasture. CROPGRO testing for the silvopastoral system considered only the competition for solar radiation since the model does not allow simulating belowground competition. For this, measured data of incoming solar radiation at each position were used as input for the simulations. The model was able to simulate forage live mass in the single pastures (R2 from 0.72 to up to 0.89, Agreement index from 0.88 to up to 0.95, and Nash-Sutcliffe efficiency between 0.65 and 0.85), and in the silvopastoral system (R2 from 0.76 to up to 0.89, Agreement index between 0.93 and 0.96, and Nash-Sutcliffe efficiency between 0.71 and 0.86). Despite these results, improvements should be performed in the model for simulating the effect of flowering on pasture growth, changes on pasture canopy caused by animals trampling, and competition for resources in silvopastoral systems.

Assessment of Piatã palisadegrass forage mass in integrated livestock production systems using a proximal canopy reflectance sensor

Abstract Estimates of forage mass can help in decision making for pasture management and stocking rate adjustment in pastoral systems. This study aimed to estimate Piata palisadegrass forage mass under full sun and shaded livestock production systems using vegetation indexes obtained with a proximal canopy reflectance sensor. Pasture canopy reflectance was measured at three fractions of the radiation spectrum (670, 720, and 760 nm). Total forage mass, morphological composition, and leaf area index (LAI) were assessed at the same time as reflectance in all production systems. Reflectance data were used to calculate vegetation indexes (normalized difference vegetation index – NDVI, normalized difference red edge – NDVI_RE, simple ratio index – SRI, modified simple ratio – MSR, and chlorophyll index) for each assessment. Linear and exponential regression analyses between vegetation indexes and total forage mass, leaf + stem mass, leaf mass, and LAI were performed. The equations generated by these analyses were used to estimate such pasture variables. The best estimates of leaf + stem mass, leaf mass, and LAI were obtained using SRI (R2 between 0.55 and 0.84) for the full sun systems, MSR (R2 from 0.67 to 0.93) for the shaded systems, and NDVI (R2 between 0.65 and 0.91) when all systems were analyzed together. These pasture variables can be estimated by general equations developed for both full sun and shaded livestock production systems. However, total forage mass estimates were less efficient (R2 of 0.03–0.53), due to differences in canopy structure and senescent material content between production systems.

Effects of restricted time allocation to pasture on feeding behaviour, intake and milk production of dairy sheep rotationally grazing Italian ryegrass (Lolium multiflorum Lam) in spring

The effects of restricted time allocation (2, 4 or 6 h/day) to pasture and grazing day (Day 1, initial; Day 4, intermediate; Day 7, final) on feeding behaviour, intake and performance were assessed in Sarda dairy ewes, rotationally grazing Italian ryegrass plots for 7 days, with 21 days of regrowth. A randomised block design with two replicates per access time was used with six groups of six ewes each. The ewes were supplemented daily with 400 g/head of a commercial concentrate at milking, 300 g/head of lupin after grazing and 700 g/head of ryegrass hay overnight. Pasture variables, feeding behaviour, herbage and supplement DM intake, and milk yield and composition were measured on 12 days (4 per target grazing day). Plot average data were analysed by a bifactorial model with interaction, which was not significant. Sward height and herbage mass decreased between Day 1 and Day 4 (P &lt; 0.05). Leaf area index dropped from Day 1 to Day 7 (P &lt; 0.05). Eating time, as proportion of access time, and intake rate were higher in 2 h/day groups than in the others (P &lt; 0.05). Nevertheless, herbage and total intake were higher in 6 h/day than in 2 h/day groups, being 4 h/day groups intermediate (P &lt; 0.05). Herbage intake decreased with grazing period (P &lt; 0.05). Fat normalised milk yield was higher in 6 h/day groups than in the others (P &lt; 0.05) and in Day 1 and Day 4 than in Day 7 (P &lt; 0.05). To conclude, time restriction below 6 h/day and pasture depletion, in terms of herbage quality, constrained intake and performance of rotationally grazing dairy ewes.

The development of linear regression models using environmental variables to explain the spatial distribution of Fasciola hepatica infection in dairy herds in England and Wales

Fasciolosis caused by Fasciola hepatica is a major cause of economic loss to the agricultural community worldwide as a result of morbidity and mortality in livestock. Spatial models developed with the aid of Geographic Information Systems (GIS) can be used to develop risk maps for fasciolosis for use in the formulation of disease control programmes. Here we investigate the spatial epidemiology of F. hepatica in dairy herds in England and Wales and develop linear regression models to explain observed patterns of exposure at a small spatial unit, the postcode area. Exposure data used for the analysis were taken from an earlier study of F. hepatica infection, performed in the winter of 2006/7. Climatic, environmental, soil, livestock and pasture variables were considered as potential predictors. The performance of models that used climate variables for 5 years average data, contemporary data and a combination of both for England and Wales, and for England only, was compared. All models explained over 70% of the variation in the prevalence of exposure. The best performing models were those built using 5 year average and contemporary weather data. However, the fit of these models was only slightly better than the fit of models using weather data from one time period only. Rainfall was a consistent predictor in all models. Other model covariates included temperature, the negative predictors of soil pH and slope and the positive predictors of poor quality land, as determined by the Agricultural Land Classification, and very fine sand content of soil. Choroplethic risk maps showed a good match between the observed F. hepatica exposure values and exposure values fitted by the models. The development of these detailed spatial models is the first step towards the development of a spatially specific, temporal forecasting system for liver fluke in the United Kingdom.

Efeito da tosquia sobre o comportamento de ovelhas das raças Texel e Hampshire Down, ao longo do período noturno, no Noroeste do Estado do Paraná

The behavior (grazing, rumination and rest) of 16 three- and four-year old Texel and Hampshire Down sheep is provided. Experiment was conducted from April 1999 to March 2000, during three nights a month, from 18 h to 6 h, with eight sheep of each breed. Four animals of each breed were sheared. Pasture quality was evaluated, climate data were reported hourly and rainfall monthly. Conditions of pasture and climatic variables might have altered sheep’s behavior. Low yield of green leaves, crude protein and high FDA levels during the winter might have raised grazing and rumination time. Period of rest decreased during the winter and spring. Wool did not have any effect on the behavior of animals.

Effect of structure of a tropical pasture on ingestive behaviour, digestibility of diet and daily intake by grazing cattle

AbstractThe effect of the structure of a tropical pasture, based on Dichanthium spp., on the ingestive behaviour, in vivo digestibility of the diet and herbage intake by eight Creole tethered heifers was studied. Two levels of nitrogen fertilizer (0 and 50 kg ha−1) were applied to plots after each grazing cycle and there were 28 d between each of the three grazing cycles. Four heifers grazed individual subplots daily on each plot for 14 d in each of the successive grazing cycles. Simultaneous measurements of bite depth, bite mass, biting rate, short‐term intake rate and daily grazing time were made in two 4‐d periods at the end of each 14‐d period. The in vivo organic matter digestibility (OMD) and daily herbage organic matter intake (OMI, expressed on a kg LW0·75 basis) were also measured at the same times. Relationships among pasture characteristics and ingestive behaviour were similar to those reported in other short‐term studies: pasture height was highly correlated with bite depth, bite mass and biting rate (r = 0·91, r =0·79 and r = −0·68, respectively, P &lt; 0·001). Pasture variables had lower correlations with grazing time and short‐term intake rate than with bite depth, bite mass and biting rate. Pasture structure was more highly correlated with OMD than OMI: leaf mass and length and also the extended tiller length were highly correlated with OMD (r = 0·77, r = 0·76 and r = 0·72, respectively, P &lt; 0·001) whereas the crude protein concentration of the herbage was correlated with OMI and digestible OMI (r = 0·50 and r = 0·69, respectively, P &lt; 0·001). Ingestive behaviour variables, as well as OMD, were correlated more with pasture characteristics than was OMI.

Morfogênese de milheto (Pennisetum americanum (L.) Leeke) em pastejo com terneiras, recebendo ou não suplementação

O experimento foi conduzido em área pertencente ao Departamento de Zootecnia da Universidade Federal de Santa Maria, região Central do Rio Grande do Sul, Brasil, para avaliar o efeito da freqüência de desfolhação nas características morfogênicas de Pennisetum americanum quando utilizada ou não suplementação aos animais em pastejo, no período de 20/02 - 08/03/01 e 11/03 - 01/04/01. Foram utilizadas terneiras de corte em pastejo contínuo com lotação variável de forma a manter uma oferta de 12kg de MS/100kg de peso vivo. Para acompanhar a dinâmica de crescimento da pastagem, foi utilizada a técnica dos perfilhos marcados. O delineamento utilizado foi o completamente casualizado com 36 repetições. Os tratamentos adotados foram: pastagem de milheto sem suplemento; pastagem de milheto + 1% do peso vivo de polpa cítrica moída e pastagem de milheto + 1% do peso vivo de milho moído. As variáveis da pastagem avaliadas foram taxa de surgimento de folhas (folha.dia-1.perfilho-1), taxa de elongação de folhas (mm.dia-1.perfilho-1), duração de vida das folhas (graus-dia) e freqüência de desfolhação (% desfolha.dia-1.perfilho-1). Na média dos períodos, a freqüência de desfolhação não diferiu entre tratamentos, tendo em média, 23% de desfolha.dia-1.perfilho-1. Os tratamentos com suplementação apresentaram taxa de surgimento de folhas e de elongação de folhas em torno de 0,187 folhas.dia-1.perfilho-1 e 24mm.dia-1.perfilho-1, respectivamente. Esses resultados foram superiores (P&lt;0,05) ao tratamento em que não era fornecido aos animais suplemento energético. A duração de vida das folhas dos tratamentos com uso de suplementos foi em média igual a 295,8 graus-dia, enquanto no tratamento sem suplemento este valor foi de 339 graus-dia. O uso da suplementação com milho ou polpa cítrica para terneiras de corte não afetou a freqüência de desfolhação, condicionando a respostas positivas nas características morfogênicas. A seleção de forragem de melhor qualidade pode fazer com que ocorra a redução de folhas jovens, prejudicando o crescimento da planta.

Pastures and forages for deer growth

Pasture is the primary feed source for NZ deer production with the greatest proportion grazed in situ. The quantity and quality of the pastures available to grazing deer varies markedly as a result of environmental factors and feed planning decisions by deer farmers. The grazing behaviour of deer responds to changes in pasture height and mass and the effect of pasture variables (height, pre -and post-grazing pasture mass and pasture allowance) on deer productivity are presented. These show that maximum levels of deer production from pasture will be achieved at a pasture height of around 8 cm (continuously stocked or post-grazing) although there is some evidence that for large genotypes, higher pasture availability is required. The relationship of liveweight gain of young deer with pasture availability shows marked seasonal effects. At the same level of pasture availability liveweight gain in spring is about twice that in winter, with autumn and summer intermediate. Increasing pasture availability cannot compensate for seasonal differences in liveweight gain. Furthermore, liveweight gain increases at a greater rate in spring than winter to increasing pasture availability, thus it is more important that appropriate pasture allowances are provided in spring than in winter. There is more variability in liveweight gain at a similar pasture availability in summer than in other seasons because of the greater variation in pasture quality in summer with the potential accumulation of seedheads and dead material. Alternative forage species are used in deer production for times of the year when quantity and quality of perennial ryegrass-based pastures limit productivity. Relative to weaner red deer grazed on perennial ryegrass/ white clover pasture, grazing on pure swards of red clover or chicory increased growth during autumn by 26-47% and during spring by 10-14%. The proportion of stags attaining target slaughter liveweight at 12 months of age increased from 75 to 94%. Pre-weaning growth during lactation was increased by approximately 20%. Red clover and chicory produce a greater proportion of their total DM during late summer and autumn than does perennial ryegrass/white clover pasture, and are therefore better aligned with deer feed requirements, particularly those of lactating hinds. Grazing on sulla in autumn and spring increased the growth of weaner deer by 33 and 10%, relative to pasture fed deer. Indoor studies showed that relative to perennial ryegrass, chicory was of higher organic matter digestibility, disintegrated more rapidly in the rumen with a low rumination time and had shorter mean retention time of material in the rumen. This explains differences in voluntary feed intake which were 56, 26 and 15% higher for deer grazing chicory than perennial ryegrass/white clover pastures during summer, autumn and spring respectively. Similar r esults have been found for the digestion of red clover versus perennial ryegrass by red deer. Plant density in stands of both chicory and red clover declines with time, with their lifetime under deer grazing being approximately 4 years. A mixture of both plants offers a food option as specialist forage for increasing deer growth and also fixing nitrogen. To ensure good persistence such forages should not be grazed in periods of prolonged wet weather. Best persistence is obtained when these are managed as specialist forages for increasing deer growth on a small area of the farm, (10- 20% total area), rather than being sown as a mixture with grasses over large areas of the farm. There is no specific comparison of deer production under different stocking systems and both continuous grazing and rotational grazing are used. Based on evidence and practices with other species, choice of stocking system has more to do with pasture/forage species, feed budgeting, pasture management and animal behaviour than with productivity. At high stocking densities (150 deer/ha), the grazing time of subordinate animals is reduced. Where possible, without inducing undue stress (e.g. at weaning), young deer should be grouped for grazing by liveweight. Deer production systems have a seasonal pattern of energy demand that does not match that of pasture growth in most NZ environments. This calls for manipulation of the feed demand by integration of livestock systems and/ or modification of the feed supply through conservation and supplementation. The most commonly used supplements are pasture and lucerne silage/baleage and grain. The quality (ME/kg DM) has a significant impact on the resulting liveweight gain.

A survey on the effect of management techniques and pasture composition and quality at harvesting on silage quality on dairy farms in western Victoria

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

Pasture status in a semi-arid grassland

Abstract Landsat-MSS data were used to estimate pasture biomass, cover and greenness of semi-arid grassland in central western New South Wales, Australia. The green pasture dominated the reflectance and while green cover, green biomass and percentage green were estimated to acceptable levels (±9-7 per cent, ± 0-35t ha-1 and ±M11 6 per cent respectively); it was not possible to estimate total pasture or brown pasture variables. Variability within relatively homogenous pastures is so large that the regression models between reflectance and pasture variables were not significantly different for the three pasture types analysed. Information on green biomass, cover and curing are useful for monitoring changes in pasture condition and in bushfire prediction models. †Currenl address: ESYS Limited, Berkeley House, London Square, Cross Lane, Guildford, Surrey GUI 1UE, England.

Influence of some sward characteristics on the consumption of irrigated pastures grazed by lactating dairy cattle

AbstractPasture variables measured in eight experiments at Kyabram, Victoria were used to quantify factors influencing the consumption of irrigated pastures grazed by dairy cows. In addition, whether intake prediction equations based on sward characteristics could be developed and applied in the field was also considered.Herbage intake (DMI) was positively related to herbage allowance (HA) in all cases; however, the increase in daily DMI achieved for every additional kg herbage offered to a cow ranged from 015 to 0·35 kg. Herbage intake was also consistently related to residual herbage (RH). For every additional tonne herbage dry matter (DM) ha−1 remaining after grazing, each cow consumed increased daily amounts of herbage ranging from 3·2 to 5·1 kg DM. However, of the other pasture variables, herbage mass (HM), pasture type (PT) and digestibility of the herbage DM on offer (DMD) influenced herbage intake less consistently.When the data from all experiments were included together, DMI was influenced by sward characteristics in the following manner: image where LW = live weight of the cow (kg) and DE = duration of experiment (d).When RH was considered instead of HA, only 61% of the variability in intake was accounted for compared to 80% when HA was considered: image In both of these equations, two variables other than the sward characteristics were significant; these were LW and DE. The significance of these variables in these relationships are discussed together with the possibility of using them for predicting DMI in other environments. However, it is concluded that they do not have general applicability and it is suggested that they may be useful only in the environment in which they were generated.

Summer-growing components of a pasture system in a subtropical environment. 2. Relations between pasture and animal production

SummaryRelations were developed between the carrying capacity or production of fat-corrected milk (FCM)/ha and various measures of pasture growth for six pasture treatments grown in a subtropical environment. The pasture and animal production variables were obtained from pastures grazed on a weekly rotation using stocking densities which were varied so that a target weight of leaf material remained on the pasture at the conclusion of each grazing.Within a treatment, there was a curvilinear relation between the rate of leaf growth and carrying capacity, with the greatest efficiency of conversion at the lowest leaf growth rates. This relation generally varied between pasture treatments because of differences in grazing intensity. There was little variation in the production of FCM per cow between grazing periods within a treatment, reflecting the experimental technique of matching the stocking density to the amount of forage. Consequently FCM/ha largely mirrored the stocking density with some adjustment for differences in production per cow caused by differences in grazing intensity between treatments. Production of FCM/ha was affected more by a unit change in residue leaf yield than by a unit change in leaf yield before grazing.Using the rate of leaf removal (intake plus grazing losses) per cow as an inverse index of grazing intensity, it was apparent that the use of variable stocking densities to obtain specified residue yields after grazing did not necessarily equalize the grazing intensity because the rate of leaf removal per cow varied according to the before-grazing leaf yield. Also soiling by dung caused differences in the acceptability of forage for grazing, resulting in differences in grazing intensity between pastures with the same yield and stocking density.