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1.
A perennial ryegrass (Lolium perenne L.)‐dominated sward on a well‐drained soil (Experiment 1) and a creeping bent (Agrostis stolonifera L.)‐dominated sward on a poorly drained soil (Experiment 2) were subjected to four treading treatments: control (C, no damage), light damage (L), moderate damage (M) or severe damage (S) to quantify the effects on herbage dry‐matter (DM) production and tiller density. In Experiment 1, treading damage was imposed in spring. In Experiment 2, one‐third of the site was damaged in autumn, one‐third in spring and one‐third in both spring and autumn. Both sites were rotationally grazed after treading treatments. Pre‐grazing herbage mass was measured eight times in Experiment 1 and seven times in Experiment 2 on each plot, and tiller density was assessed four times in each experiment. In Experiment 1, pre‐grazing herbage mass was reduced by 30% in S plots at the first harvest after damage, but cumulative pre‐grazing herbage DM production was not different between treatments (12·7 t DM ha?1). In Experiment 2, annual cumulative pre‐grazing herbage mass was reduced by between 14 and 49%, depending on intensity of treading damage event and season when damage occurred. Tiller density was not affected by treatment in either experiment. A perennial ryegrass‐dominated sward on a well‐drained soil was resilient to heavy treading damage. A creeping bent‐dominated sward on poorly drained soil requires a more careful grazing management approach to avoid major losses in cumulative pre‐grazing herbage mass production during wet weather grazing events.  相似文献   

2.
Limited availability of herbage during the cool season creates a problem of a supply of nutrients for livestock producers throughout the southern Great Plains of the USA and, particularly, on small farms where resource constraints limit possible mitigating strategies. Six cool‐season grasses were individually sown into clean‐tilled ground, no‐till drilled into stubble of Korean lespedeza [Kummerowia stipulacea (Maxim) Makino] or no‐till over‐sown into dormant unimproved warm‐season pastures. The dry matter (DM) yields of mixtures of cool and warm‐season herbage species were measured to test their potential for increasing cool‐season herbage production in a low‐input pasture environment. Only mixtures containing Italian ryegrass (Lolium multiflorum Lam) produced greater year‐round DM yields than undisturbed warm‐season pasture with all establishment methods. When cool‐season grass was no‐till seeded into existing warm‐season pasture, there was on average a 0·61 kg DM increase in year‐round herbage production for each 1·0 kg DM of cool‐season grass herbage produced. Sowing into stubble of Korean lespedeza, or into clean‐tilled ground, required 700 or 1400 kg DM ha?1, respectively, of cool‐season production before the year‐round DM yield of each species equalled that of undisturbed warm‐season pasture. Productive pastures of perennial cool‐season grasses were not sustained beyond two growing seasons with tall wheatgrass [Elytrigia elongata (Host) Nevski], intermediate wheatgrass [Elytrigia intermedia (Host) Nevski] and a creeping wheatgrass (Elytrigia repens L.) × bluebunch wheatgrass [Pseudoroegneria spicata (Pursh)] hybrid. Lack of persistence and low productivity limit the usefulness of cool‐season perennial grasses for over‐seeding unimproved warm‐season pasture in the southern Great Plains.  相似文献   

3.
Extending the grazing season through the production and utilization of high‐quality forage is a key objective in grassland‐based dairy production systems. Grazing swards to a low post‐grazing sward height (PGSH) is a strategy for improving grass utilization. A grazing experiment conducted in Ireland investigated immediate and subsequent effects of PGSH on sward production, utilization and structural characteristics. Swards were grazed to 2·7 cm (severe; S1) or 3·5 cm (moderate; M1) from 10 February to 18 April 2010 (Period 1; P1). From 19 April, each P1 paddock was halved and grazed to either 3·8 cm (S2) or 4·8 cm (M2), until 30 October (Period 2; P2). The first grazing rotation was +7 d on S1 swards compared with M1 swards (45 d), due to greater herbage utilization (+0·22). Herbage production during P1 was not affected by PGSH but a severe PGSH during this period reduced subsequent herbage production: 13·9 (S1) vs. 15·5 t dry matter (DM) ha?1 (M1) by the end of the study. Leaf proportion was increased (+0·10) on S2 swards compared with M2 swards, but M2 swards produced 1·2 t DM ha?1 more herbage during P2. Despite the relatively lower level of sward utilization obtained from moderate grazing in P1 (3·5 cm) and P2 (4·5–5·0 cm), such levels of PGSH increased DM production while maintaining sward quality, compared with severe grazing (2·7 cm in P1 and 3·5–4·0 cm in P2).  相似文献   

4.
Growth of grass herbage in Ireland is highly seasonal with little or no net growth from November to February. As a result, feed demand exceeds grass supply during late autumn, winter and early spring. At low stocking rates [≤2 livestock units (LU) ha?1], there is potential to defer some of the herbage grown in autumn to support winter grazing. This study examined the effects of four autumn‐closing dates and four winter‐grazing dates in successive years on the accumulation of herbage mass and on tiller density in winter and subsequent herbage production at two sites in Ireland, one in the south and one in the north‐east. Closing swards from grazing in early and mid‐September (north‐east and south of Ireland respectively) provided swards with >2 t DM ha?1 and a proportion of green leaf >0·65–0·70 of the herbage mass above 4 cm, with a crude protein (CP) concentration of >230 g kg?1 DM and dry matter digestibility (DMD) of >0·700. The effects of autumn‐closing date and winter‐grazing date on herbage production in the subsequent year varied between the two sites. There was no significant effect of autumn‐closing date in the north‐eastern site whereas in the south earlier autumn closing reduced the herbage mass in late March by up to 0·34 t DM ha?1 and delaying winter grazing reduced the herbage mass in late March by up to 0·85 t DM ha?1. The effects of later grazing dates in winter on herbage mass continued into the summer at the southern site, reducing the herbage mass for the period from late March to July by up to 2 t DM ha?1. The effects of imposing treatments in successive years did not follow a consistent pattern and year‐to‐year variation was most likely linked to meteorological conditions.  相似文献   

5.
Pasture herbage is a major source of minerals for livestock in pasture‐based production systems. Herbage mineral concentrations vary throughout the growing season, whereas mineral supplementation to livestock is often constant. The study objectives were to analyse the seasonal variation in herbage mineral concentrations in tall fescue [Schedonorus phoenix (Scop.) Holub]‐based pasture with regard to beef cattle mineral requirements and to create a statistical model to predict variation in herbage mineral concentrations across the growing season. Pasture herbage was analysed from 12 grazing systems in Virginia to determine its mineral concentration from April to October of 2008–2012. The pasture herbage, grown without fertilization, contained adequate macronutrient concentrations to meet the requirements of dry beef cows through the growing season and the requirements of lactating beef cows in April. Phosphorus supplementation appeared to be unnecessary for dry beef cows given adequate concentrations in pasture herbage. A model using month of harvest, soil moisture and relative humidity explained 75% of the variation in an aggregated mineral factor. The 90% prediction intervals indicated that N, P, K, S and Cu concentrations could be predicted within 1·35, 0·08, 0·80 and 0·07% and 3·83 mg kg?1 respectively. Prediction of herbage mineral concentrations could help to improve livestock health, reduce costs to producers and limit nutrient losses to the environment.  相似文献   

6.
Warm‐season pasture residue may create problems for no‐till overseeding with cool‐season grasses in the USA Southern Plains. Removal of residue to facilitate overseeding, however, represents additional cost and labour that may not be available on small livestock farms. Field experiments were undertaken to assess the effects of above‐surface residues of warm‐season pasture averaging 1·62, 2·48 or 3·36 t DM ha?1 on establishment and herbage production of Italian ryegrass (Lolium multiflorum) or tall fescue (Festuca arundinacea) overseeded by broadcasting or by no‐till drilling into dormant warm‐season pasture. On average, no‐till drilling was more effective than broadcasting in establishing both grass species, but it was no more effective than broadcasting when used with the greatest amount of residue. Cool‐season grass production was increased by 0·16 when no‐till drilled, but combined yearly total herbage production of cool‐ and warm‐season grasses was increased by 0·07 when cool‐season grasses were established by broadcasting. Amount of residue at sowing did not significantly affect herbage yield of cool‐season grass, but increased residue in autumn resulted in a 0·16 increase in total herbage production in the year following sowing. Residue amount did not affect over‐winter survival of grass seedlings, and productivity benefits of increased residue are small compared with reduced harvest arising from underutilization of warm‐season pasture residue in autumn.  相似文献   

7.
The aims of this study were to examine the effect of three grazing treatments (year‐round stocking rates of 0·8 ewes ha?1, 0·5 ewes ha?1 and 0·5 ewes ha?1 plus grazing cattle in summer), imposed for 4 years, on the herbage mass and surface height of a Nardus stricta‐dominated grassland in western Scotland and to obtain estimates of annual productivity of this grassland. Nardus stricta‐dominated grassland comprised proportionately 0·20 of the grazing area. Stocking rate of sheep had no significant effect on the herbage mass of the grassland in the first 2 years of the experiment, although mean summer pasture heights were significantly higher under the lower stocking rate of sheep. The pasture on the treatment with cattle grazing in summer had a significantly lower herbage mass and lower surface height than the two sheep‐only grazing treatments. Year‐to‐year variation in the herbage mass and surface height of herbage in summer was greater than the effect of treatments. Despite changes in surface height, the structural diversity of the grasslands was not increased by the treatments. The annual production of vascular plant material ranged from 417 g DM m?2 in 1994 to 628 g DM m?2 in 1996.  相似文献   

8.
A mechanistic model, simulating the dynamics of production, structure and digestibility of managed permanent pastures, was developed. Its evaluation consisted of (i) studying model response to a range of grassland communities, cutting frequencies and site characteristics, and (ii) testing the model against experimental data, focusing on biomass accumulation and digestibility during three different cutting cycles, herbage production under a frequent cutting regime, and sward dynamics during the winter. The model realistically predicted the dynamics of biomass, structure and digestibility of herbage for various communities of permanent pastures, in different sites and under different management conditions for upland areas of the Auvergne region in France. The predicted responses to environmental conditions and cutting regimes were close to field observations and experimental results. Although the model successfully predicted the dynamics of average herbage production, it lacked precision in predicting the low biomass production observed in relation to the weather conditions found in a few specific years. The model was able to predict the dynamics of the sward during winter and is, therefore, fit for producing multiple‐year simulations. To improve the prediction of variability of biomass production and to predict the medium‐ to long‐term dynamics of permanent pastures, the model could be refined by adding seasonal and multiple‐year variation in nitrogen availability and in the proportion of grass functional groups in the grassland community.  相似文献   

9.
There is scope of increasing the nitrogen (N) efficiency of grazing cattle through manipulation of the energy and N concentrations in the herbage ingested. Because of asymmetric grazing by cattle between individual plant parts, it has not yet been established how this translates into the concentrations of N and water‐soluble carbohydrates (WSC) in the herbage ingested. A model is described with the objective of assessing the efficacy of individual tools in grassland management in manipulating the WSC and N concentrations of the herbage ingested by cattle under strip‐grazing management throughout the growing season. The model was calibrated and independently evaluated for early (April), mid‐ (June, regrowth phase) and late (September) parts of the growing season. There was a high correlation between predicted and observed WSC concentrations in the ingested herbage (R2 = 0·78, P < 0·001). The correlation between predicted and observed neutral‐detergent fibre (NDF) concentrations in the ingested herbage was lower (R2 = 0·49, P < 0·05) with a small absolute bias. Differences in the N concentration between laminae and sheaths, and between clean patches and fouled patches, were adequately simulated and it was concluded that the model could be used to assess the efficacy of grassland management tools for manipulating the WSC and N concentrations in the ingested herbage. Model application showed that reduced rates of application of N fertilizer and longer rotation lengths were effective tools for manipulating herbage quality in early and mid‐season. During the later part of the growing season, the large proportion of area affected by dung and urine reduced the effect of application rate of N fertilizer on herbage quality. In contrast, relative differences between high‐sugar and low‐sugar cultivars of perennial ryegrass were largest during this period. This suggests that high‐sugar cultivars may be an important tool in increasing N efficiency by cattle when risks of N losses to water bodies are largest. The model output showed that defoliation height affects the chemical composition of the ingested herbage of both the current and the subsequent grazing period.  相似文献   

10.
The objective of this study, which was part of a larger grazing‐systems experiment, was to investigate the cumulative impact of three levels of grazing intensity on sward production, utilization and structural characteristics. Pastures were grazed by rotational stocking with Holstein–Friesian dairy cows from 10 February to 18 November 2009. Target post‐grazing heights were 4·5 to 5 cm (high; H), 4 to 4·5 cm (intermediate; I) and 3·5 to 4 cm (low; L). Detailed sward measurement were undertaken on 0·08 of each farmlet area. There were no significant treatment differences in herbage accumulated or in herbage harvested [mean 11·3 and 11·2 t dry matter (DM) ha?1 respectively]. Above the 3·5 cm horizon, H, I and L swards had 0·56, 0·62 and 0·67 of DM as leaf and 0·30, 0·23 and 0·21 of DM as stem respectively. As grazing severity increased, tiller density of grass species other than perennial ryegrass (PRG) decreased (from 3,350 to 2,780 and to 1771 tillers m?2 for H, I and L paddocks respectively) and the rejected area decreased (from 0·27 to 0·20 and to 0·10 for H, I and L paddocks respectively). These results indicate the importance of grazing management practice on sward structure and quality and endorse the concept of increased grazing severity as a strategy to maintain high‐quality grass throughout the grazing season. The findings are presented in the context of the need for intensive dairy production systems to provide greater quantities of high‐quality pasture over an extended grazing season, in response to policy changes with the abolition of EU milk quotas.  相似文献   

11.
The accuracy of two simple methods was compared for the prediction of crude protein (CP) content of above‐ground plant material of mixed‐species composition on abandoned cultivated land in Japan. The first method is based on standard CP values (in g kg?1 dry matter) for individual species (STV method) as listed in the literature. The second procedure (GLM method) was an application of the generalized linear model using the relative above‐ground biomass of monocots and legumes, total herbage mass, and day of year. Predictions were made at the quadrat scale, and for surveyed sites based on average of values for five or six quadrats in a single survey. A ‘leave‐site‐out’ method was adopted for model validation of the generalized linear model. The observed values of CP content ranged between 21·5 and 161·9 g kg?1 dry matter (DM). With the STV method, the values of root mean square error (RMSE indicates average estimation error) were 50·9 at the quadrat level and 53·8 at the surveyed‐site level (both g kg?1 DM). When a ‘leave‐site‐out’ validation was carried out, the RMSE‐values for the GLM method were 23·2 at the quadrat level and 13·2 at the surveyed‐site level (both g kg?1 DM). We therefore propose adoption of the GLM method for the purpose of estimating the CP content in herbage on abandoned sites.  相似文献   

12.
Poultry litter is commonly applied to pastures as an organic fertilizer. However, poultry litter also typically contains numerous heavy metals that may accumulate in soil and can pose an environmental threat when it is applied to pastures. The objective was to ascertain uptake characteristics of heavy metals by tall fescue (Festuca arundinacea Schreb.) from soil with a history of poultry litter additions as affected by subsequent applications of poultry litter. Poultry litter was applied to small plots at rates of 0, 2·2 and 4·5 t dry litter ha?1. In the 7·5 months following application of litter, cumulative dry‐matter (DM) production of herbage was higher (P < 0·05) in the plots that received poultry litter compared with the control plots where no litter was applied. However, concentrations of Al, Cu, Fe, Mg, Mn, Se and Zn in herbage were unaffected by the rate of application of poultry litter. All metal tissue concentrations, except for Fe, were affected by sampling date. While tall fescue responds to poultry litter with increased DM production, it does not appear to accumulate excessive quantities of micronutrients associated with the application of poultry litter.  相似文献   

13.
This study examined the quantity of mineral N in soil and nitrate‐N losses to groundwater from grassland‐based dairy production in 2001 and 2002. There were four treatments with different inputs of N, through fertilizers, concentrates and biological fixation, and four associated stocking densities. Nitrogen inputs were 205, 230, 300 and 400 kg ha?1, respectively, and annual stocking densities were 1·75, 2·10, 2·50 and 2·50 cows ha?1. There were 18 cows per treatment. Grazed herbage accounted for 0·64, grass‐silage for 0·26 and concentrates 0·10 of annual DM consumed by the cows. Quantities of mineral N (nitrate‐N and ammonium‐N) in soil were measured, following extraction in 2 M KCl (1:2 w/v) shaken continuously for 2 h, on three occasions between late September and early February each winter. Concentrations of nitrate‐N in groundwater from wells inserted vertically to a depth of 1 m were determined throughout both winters. Quantities of mineral N in the soil increased (P < 0·001) with higher N inputs and declined (P < 0·001) with later sampling date. There were no relationships between nitrate‐N concentrations in groundwater and N inputs, N surpluses, deposition of excreta‐N at the soil surface and soil mineral N during both winters. Low losses of nitrate‐N to groundwater were primarily attributed to high rates of denitrification associated with a heavy soil texture, wet anaerobic soil conditions, relatively high organic carbon contents throughout the soil profile and mild soil temperatures throughout the year. Uptake of N by herbage made an important contribution to low N losses over the winter.  相似文献   

14.
The benefits of white clover (Trifolium repens L.) in pastures are widely recognized. However, white clover is perceived as being unreliable due to its typically low content and spatial and temporal variability in mixed (grass‐legume) pastures. One solution to increase the clover proportion and quality of herbage available to grazing animals may be to spatially separate clover from grass within the same field. In a field experiment, perennial ryegrass (Lolium perenne L.) and white clover were sown as a mixture and compared with alternating strips of ryegrass and clover (at 1·5 and 3 m widths), or in adjacent monocultures (strips of 18 m width within a 36‐m‐wide field). Pastures were stocked by ewes and lambs for three 10‐month grazing periods. Over the 3 years of the experiment, spatial separation of grass and clover, compared with a grass–clover mixture, increased clover herbage production, although its proportion in the sward declined through time (0·49–0·54 vs 0·34 in the mixture in the first year, 0·28–0·33 vs 0·15 in the second year and 0·03–0·18 vs 0·01 in the third year). Total herbage production in the growing season in the spatially separated treatments decreased from 11384 kg DM ha?1 in the first year to 8150 kg DM ha?1 in the third year. Crude protein concentration of clover and grass components in the 18‐m adjacent monoculture treatment was greater than the mixture treatment for both clover (310 vs 280 g kg?1 DM) and grass (200 vs 180 g kg?1 DM). There was no clear benefit in liveweight gain beyond the first year in response to spatially separating grass and clover into monocultures within the same field.  相似文献   

15.
The rates of drying of herbage, cut from perennial ryegrass (Lolium perenne L.) – dominant swards and subjected to different treatments, were investigated under field conditions by changes in weight of herbage in wire mesh trays in 1995 and 1996. A series of replicated factorial experiments studied the effects, in different combinations, of intensity of conditioning achieved by passing the cut herbage through a laboratory‐scale macerator zero (0C), once (1C), three (3C) or six (6C) times; weight of herbage per unit area equivalent to 450, 675 and 900 g dry matter (DM) m?2. In one experiment, pressing the herbage to form a mat was incorporated into the experimental design. A further experiment investigated the effect of varying the proportion of conditioned herbage in the herbage mass from 0·00, 0·25, 0·50, 0·75 and 1·00 on drying rate. On each occasion the trays plus herbage were weighed at hourly intervals over an ≈6‐h period and the DM content of the herbage estimated from the change in weight. On all occasions, conditioning and weight of herbage per unit area significantly (P < 0·001) influenced herbage drying rate. Lowering the weight per unit area of both unconditioned and conditioned herbage increased the rate of moisture loss. Unconditioned herbage at the equivalent of a herbage mass of 450 g DM m?2 had a total moisture loss that was on average 1·5–1·8 times greater than unconditioned herbage at the equivalent of a herbage mass of 900 g DM m?2. Similarly, conditioned herbage at the equivalent of a herbage mass of 450 g DM m?2 had a total moisture loss that was 1·8–2·3 times greater than unconditioned herbage at the equivalent of a herbage mass of 900 g DM m?2. Increasing the level of conditioning produced a non‐linear response in rate of moisture loss, consequently 3 passes through the macerator produced >0·95 of the total moisture loss that was produced by 6 passes through the macerator. Increasing the proportion of conditioned herbage in the herbage mass increased rate of moisture loss and consequently final DM content (P < 0·001) although there was little effect from increasing the proportion of conditioned herbage above 0·75. The effects of conditioning and weight of herbage per unit area treatments on total nitrogen , water‐soluble carbohydrate and acid‐detergent fibre concentration of the herbage were small.  相似文献   

16.
High dietary cation–anion difference (DCAD) of grass herbage increases the occurrence of hypocalcaemia of dairy cows. Application of chloride fertilizer reduces DCAD of herbage but it could increase cadmium concentration in herbage. This study includes an experiment conducted in Australia and in Canada. A glasshouse experiment in Australia evaluated the effect of four rates of chloride application (0–240 kg ha?1) on values of herbage DCAD and cadmium concentration of above‐ground plant material of timothy (Phleum pratense L.) and phalaris (Phalaris aquatica L.), harvested 6 weeks after sowing and grown on two soils that had received cadmium either as a contaminant in superphosphate (soil + Super) or in sewage biosolids (soil + Bio) along with respective control soils (soil 0 Super and soil 0 Bio). Application of chloride fertilizer decreased values of herbage DCAD by 349 mmolc kg?1 dry matter (DM). Herbage DCAD values were highest on the 0 Bio soil (739 mmolc kg?1 DM) and were not different among the three other soils. Species did not differ in herbage DCAD values. Cadmium concentration in the above‐ground plant material was highest on the +Bio soil treatment (1·67 mg kg?1 DM) and was lower for the three other soil treatments. Above‐ground plant material of phalaris had a higher cadmium concentration than that of timothy. Application of chloride fertilizer did not affect cadmium concentration in above‐ground plant material, despite the high cadmium content of the soil on the +Bio treatment. The field experiment in Canada evaluated the effect of four rates of chloride application (0–144 kg ha?1) on cadmium concentration of a timothy‐based grass sward grown on four sites with soils of different potassium content. Application of chloride fertilizer increased cadmium concentration of herbage at two of the four sites but the maximum increase in cadmium concentration was only 0·025 mg kg?1 DM. Chloride fertilizer can be applied to decrease forage DCAD with minimal risk of increasing Cd in the food chain.  相似文献   

17.
The effects of one severe winter‐grazing of lucerne were studied over 3 years in an experiment in the Ebro Valley, Spain. In this region the crop is harvested six to seven times per season and winter grazing is a traditional practice. On average, winter‐grazing reduced the yield at the first harvest in spring by 200 kg dry matter (DM) ha?1. This limited yield reduction of 0·06 was accompanied by an increase in the proportion of lucerne in the herbage DM from 0·54 to 0·62, a reduction in the proportion of weeds from 0·39 to 0·36, and a reduction in the proportion of dead material from 0·06 to 0·02. The crude protein concentration and the in vitro DM digestibility increased by 20 g kg?1 DM and 0·03, respectively. The traditional practice, i.e. of grazing lucerne with sheep once in the winter season, results in only a limited reduction in yield in the spring. In addition, the spring crop has a higher nutritive value.  相似文献   

18.
Potassium fertilization in intensive grassland systems is particularly important on sandy soils with limited K storage capacity. A 3‐year plot experiment was conducted in south‐western Australia to determine the critical K concentration in herbage dry matter (DM) of annual and Italian ryegrass required to achieve 0.95 of the maximum yield, under best‐practice grassland management. A factorial design was employed with eight fertilizer K rates (range 0–360 kg ha?1 year?1) and two ryegrass species replicated four times, on a sandy soil site managed over 7 years to deplete mean soil Colwell K concentration to 42 mg/kg. Herbage was defoliated six times per year at the 3‐leaf stage of regrowth. Herbage DM yield, macronutrient and micronutrient concentrations were measured at each defoliation. Dry‐matter yield increased significantly (p < .001) with increasing levels of K fertilizer in all 3 years and the effect was curvilinear, while 0.95 of the maximum herbage DM yield was achieved at an annual K fertilizer application rate of 96, 96 and 79 kg/ha respectively. At these K fertilizer application levels, the mean K concentration of herbage DM over the 3 years was derived to be 11.4, 12.7 and 11.2 g/kg respectively. Sodium, magnesium and calcium concentrations of herbage DM all declined significantly (p < .001) as the K concentration increased. Grassland producers on sandy soils should target a K concentration in herbage DM of 16 g/kg for annual ryegrass and Italian ryegrass‐dominant swards to ensure K availability is not limiting herbage production.  相似文献   

19.
The objective of this study was to investigate the effects of an early (February; F) or delayed (April; A) primary spring grazing date and two stocking rates, high (H) and medium (M), on the grazing management, dry matter (DM) intake of grass herbage and milk production of spring‐calving dairy cows grazing a perennial ryegrass sward in the subsequent summer. Sixty‐four Holstein‐Friesian dairy cows (mean of 58 d in milk) were assigned to one of four grazing treatments (n = 16) which were imposed from 12 April to 3 July 2004. Cows on the early spring‐grazing treatment were grazed at 5·5 cows ha?1 (treatment FH) and 4·5 cows ha?1 (treatment FM) while cows on the late‐grazing treatment were grazed at 6·4 cows ha?1 (treatment AH) and 5·5 cows ha?1 (treatment AM). The organic matter digestibility and crude protein concentration of the grass herbage were higher on the early‐grazing treatment than on the late‐grazing treatment. The cows on the FM treatment had significantly (P < 0·001) higher milk (24·5 kg), solids‐corrected milk (22·5 kg), fat (P < 0·01, 918 g) and protein (831 g) yields than the other three treatments. Cows on the FM treatment had a higher (P < 0·001) DM intake of grass herbage by 2·3 kg DM per cow per day than cows on the AH treatment, which had a DM intake significantly lower than all other treatments (15·2 kg DM per cow per day). The results of the present study showed that grazing in early spring has a positive effect on herbage quality in subsequent grazing rotations. The study also concluded that early spring‐grazed swards stocked at a medium stocking rate (4·5 cows ha?1; FM) resulted in the highest DM intake of grass herbage and milk production.  相似文献   

20.
Eighty winter‐calving dairy cows of mixed parity were managed in four grassland‐based systems of milk production (F‐F, F‐C, C‐F and C‐C) over a full lactation (year 1) and during the winter period of the subsequent lactation (year 2). During the winter periods cows on systems F‐F and F‐C were offered silages of high feeding value, supplemented with 6·0 kg d?1 of concentrate [crude protein (CP), 307 g kg?1 dry matter (DM)] through an out‐of‐parlour feeding system, while cows on systems C‐F and C‐C were offered silages of medium feeding value, supplemented with c. 12·8 kg d?1 of concentrate (CP, 204 g kg?1 DM), in the form of a complete diet. After 25 February in year 1, cows on systems F‐F and C‐F were given access to grazing for periods of increasing duration, achieving full turnout on 17 April. Thereafter, until 21 October, these cows were offered a high daily allowance of herbage within a flexible grazing system (23·0 kg DM per cow, measured above a height of 4·0 cm), supplemented with 0·5 kg d?1 of a ‘high magnesium’ concentrate. Cows on systems F‐C and C‐C (year 1) commenced grazing on 1 April, achieving full turnout on 17 April. Thereafter, until 20 October, these cows were managed on a restricted allowance of herbage in a rotational paddock grazing system, with concentrates (average allocation, 3·9 kg d?1) being offered according to yield. In year 2, cows on systems F‐F and C‐F were given access to grazing for periods of increasing duration, from 11 March to 8 April, at which point the study was terminated. With systems F‐F, F‐C, C‐F and C‐C, mean feed inputs and milk outputs (per animal) during year 1 of the study were as follows: total concentrate DM intakes [881, 1272, 1729 and 2171 kg (s.e.m. 96·1)]; total silage DM intakes [1722, 1713, 1047 and 1154 kg (s.e.m. 70·7)], total grass DM intakes (3245, 2479, 3057 and 2481 kg) and total milk outputs [7541, 7527, 7459 and 7825 kg (s.e.m. 305·8)] respectively. Stocking rates associated with each of the four systems were 2·2, 2·5, 2·6 and 2·9 cows per hectare respectively. Performance of dairy cows on the systems during the winter of year 2 was similar to that recorded during year 1. The results of this study indicate that similar levels of milk output, DM intakes, tissue changes and plasma metabolite profiles can be achieved from grassland‐based systems involving very different combinations of grass silage, grazed grass and concentrate feeds.  相似文献   

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