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1.
The main objective of this study was to determine to what extent grazing pressure and timing modulate the seasonal progression of herbage quality in hilly Mediterranean grassland systems. The study was conducted during six consecutive years between 2003 and 2008 at the Karei Deshe experimental farm, in eastern Galilee, Israel, dominated by rich hemicryptophytic grassland. Treatments included two different grazing intensities, heavy and moderate, with 1·1 and 0·55 cows ha?1, respectively, and management that included a continuous and a seasonal stocking system that was divided at both intensities into early and late grazing. Herbage samples were analysed for digestibility, crude protein, neutral detergent fibre and acid detergent fibre contents. Significant differences in herbage quality were found between seasons and years. Herbage quality was significantly higher in paddocks grazed continuously or early in the season. Herbage quality increased with increasing grazing intensity as younger herbage and continued re‐growth were maintained during the green season. The greater difference between herbage qualities was found at the peak of the growing season. The significant differences found in herbage quality emphasize the importance of the decision‐making process aimed at improving cattle grazing management in Mediterranean rangelands and its consequences for the sustainability of the system.  相似文献   

2.
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   

3.
Little is known about the long-term effects of mineral N, P and K application on the nutritional status of mown alluvial grasslands. We asked how long-term fertilizer application affected soil chemical properties, plant species composition, herbage production, nutrient concentrations in soils and plants and balance of nutrients. Six treatments (control, PK, N50PK, N100PK, N150PK and N200PK) were investigated at the Černíkovice Experiment (Czech Republic) established in 1966 on an Alopecurus pratensis meadow, using annual application rates of 50, 100, 150 and 200 kg N, 40 kg P and 100 kg K ha−1. Data were collected and analysed for 2007, 2008 and 2009. Although fertilizers had been applied over 45 years, differences in soil chemical properties between fertilization treatments were small. The legumes Lathyrus pratensis and Trifolium repens responded highly positively to PK application, and tall grasses, A. pratensis in particular, to NPK application. Herbage quality was high in terms of content of major nutrients, and its chemical properties varied considerably between treatments, cuts and years. Mean annual herbage yield ranged from 6·1 in the control to 9·7 t ha−1 in the N200PK treatment. Herbage production was N-limited in 2007 and 2009, but not in 2008. Seasonal N agronomical efficiency ranged from 4·2 to 22·9 kg of DM herbage per kg of applied N. The herbage N:P and N:K ratios did not reflect the actual response of herbage production to N application. A negative balance between N applied and N removed in harvested herbage was recorded in all treatments. We concluded that in highly productive alluvial grasslands, mineral-rich soils can respond weakly to N, P and K application, fertilizer application modifies plant species composition and herbage production is not N-limited in all years. Nutrient ratios must be interpreted with caution for the estimation of nutrient limitation.  相似文献   

4.
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   

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.
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   

7.
The effects of different levels of N fertilization (no N, 40 kg N and 80 kg N ha?1 year?1), P fertilization (no P, 21 kg P ha?1 year?1 and 21 kg P plus 53 kg K ha?1 year?1) and stocking rates (0·52 large stock units (LSU) ha?1, 0·78 LSU ha?1 and 1·56 LSU ha?1) on the chemical composition and in vitro dry matter digestibility of the herbage and the liveweight gains of steers were determined in the western variant of the Bankenveld in South Africa. The average daily liveweight gains (ADLGs) of the steers increased with increasing level of N fertilization. Fertilization with P had a positive effect on ADLG only when 53 kg of K was applied with 21 kg of P ha?1. Higher stocking rates reduced ADLGs. The liveweight gains ha?1 increased as the rates of N and P fertilization increased. The medium stocking rate (0·78 LSU ha?1) gave a higher liveweight gain ha?1 than the lowest stocking rate (0·52 LSU ha?1), but the highest stocking rate (1·56 LSU ha?1) reduced liveweight gain ha?1. In general, in terms of chemical components, a higher nutritive value of the veld herbage resulted from N fertilization. The higher crude protein (CP) content of the herbage, resulting from higher stocking rates, should be seen against the background of lower liveweight gains ha?1 at the highest stocking rate. On pasture with similar contents of CP and acid detergent fibre (ADF), higher ADLG of steers was found as a result of P and K fertilization, especially for herbage with a lower CP and a higher ADF content, implying better utilization of the nutrients in such herbage with P and K fertilization, although P was also supplemented through a lick.  相似文献   

8.
Results are given on the effect of sodium (Na) fertilizer applied as NaNO3 in five application sat 0 (Nil), 32 (Low) or 64 (High) kg Na ha -1yr-1 and the residual effect of sodium chloride(NaCl) fertilizer applied in the previous year on the growth rate and the chemical composition of herbage cut at fortnightly intervals over the grazing season. Na fertilizer at Low and High rates increased herbage Na contents by 20 and 40% respectively. Magnesium (Mg) content in herbage was increased at Low Na fertilizer application rate but there was no difference between the Nil and the High Na treatments. Calcium (Ca) content was increased in proportion to Na fertilizer level. Potassium (K) content of Nil Na herbage exceeded that of Low and High, but there was no effect of treatment on total harvested K yields. The contents of phosphorus (P), sulphur (S), true protein (TP) and modified acid detergent fibre (MADF) in herbage were not affected, but the dry matter digestibility (DMD) was increased with increasing Na fertilizer level. Applying Na fertilizer at the Low and High levels gave similar increases in water-soluble carbohydrates (WSC) and ash contents and decreased crude protein (CP) and non-protein nitrogen (NPN) contents. Net herbage accumulation(fresh and dry weight) was increased by 15 and 26% at the Low and High Na fertilizer application rates respectively. NaCl fertilizer residues from the previous year increased herbage Na, DM, DMD and WSC contents, reduced K contents and did not affect Ca, P, S, CP, TP and NPN contents. Residues from Na fertilizer decreased MADF and ash contents at the Low and High Na application rates. The main and residual effects of Na fertilizer were generally maximal in early season and diminished as the season progressed, with many of the effects eliminated by late season. Proportionally 0·70 of Na applied was recovered in the first two grazing seasons after application. The effects of Na fertilizer on mineral ratios are also described, together with the implications for animal health.  相似文献   

9.
Effects of timing and rate of N fertilizer application on concentrations of P, K, S, Ca, Mg, Na, Cl, Mn, Fe, Cu and Zn in herbage from perennial ryegrass/white clover pastures were studied at two sites in south-western Victoria, Australia. Nitrogen fertilizer (0, 15, 25, 30, 45 and 60 kg ha–1) was applied as urea in mid-April, early May, mid-May, early June and mid-June 1996 to pastures grazed by dairy cows. At Site 1, N fertilizer resulted in a linear increase in P, K, S, Mg and Cl concentrations in herbage and a linear decrease in Ca concentration. For all times of application, concentrations of P, K, Ca, Mg and Cl in herbage increased by 0·0048, 0·08, −0·010, 0·0013 and 0·053 g kg–1 dry matter (DM) per kg N applied respectively. For S concentration, maximum responses occurred in mid-May (0·012 g kg–1 DM per kg N applied). At Site 2, N fertilizer resulted in a linear increase in P, S and Na concentrations in herbage, a linear decrease in Ca concentration and a curvilinear increase in K and Cl concentration. The maximum responses for P, S and K concentrations in herbage occurred for the N application in mid-June and were 0·015, 0·008 and 0·47 g kg–1 DM per kg N applied respectively. For Cl concentration, the maximum response occurred for the N application in early June and was 0·225 g kg–1 DM per kg N applied. Overall, applications of N fertilizer up to 60 kg ha–1 did not alter herbage mineral concentration to levels that might affect pasture growth or animal health.  相似文献   

10.
This experiment quantified the effects of: (i) heading date of perennial ryegrass, (ii) grazing frequency in spring and (iii) date of silage harvest, on the ensilability of herbages harvested for silage, and on the conservation and estimated nutritive value of the resultant silages. Replicated field plots with two perennial ryegrass mixtures (intermediate‐ and late‐heading cultivars) were subjected to three spring‐grazing regimes (no grazing, grazing in late March and grazing in both late March and late April) and were harvested on four first‐cut harvest dates between 20 May and 21 June. Herbage from each of the four replicates of these 24 treatments was precision‐chopped and ensiled unwilted and with no additive in laboratory silos. Herbage from the sward with the intermediate‐heading cultivar had a higher (P < 0·001) dry‐matter (DM) content and buffering capacity than that from the late‐heading cultivar, whereas water‐soluble carbohydrate concentrations increased (P < 0·001) with more frequent grazing in spring. Later harvesting enhanced herbage ensilability through an increased (P < 0·001) DM content and reduced (P < 0·001) buffering capacity and pH. Fermentation profiles of the silage were not markedly influenced by the cultivar mixture used but grazing in both late March and late April resulted in a more extensive fermentation with the acids produced increasingly dominated by lactic acid. The concentrations of acetic acid, and to a lesser extent, ethanol declined as silage harvest date was delayed. Overall, the relative effects of grass cultivar mixture were smaller than those of spring‐grazing treatment or silage‐harvesting date although on any given harvest date the herbage from the intermediate‐heading cultivar mixture was easier to preserve as silage than herbage from the late‐heading cultivar mixture. Delaying the harvesting of the late‐heading swards by 8 d removed the differences related to growth stage in buffering capacity, pH and DM content.  相似文献   

11.
Sloping fields on soils of shallow depth to tillage are commonly left uncultivated in many parts of the world. This study was conducted to compare the effects on morphological traits, dry‐matter (DM) yield, legume ratio (LR), crude protein content (CP), crude protein yield (CP yield) and mineral concentrations (N, P, K, S, Ca, Cu, Fe, Mg, Mn, Na, B and Zn) of Hungarian vetch (Vicia pannonica Crantz.) and barley (Hordeum vulgare L.) grown in intercropping mixtures in response to three rates of organic solid cattle manure application (M0: 0, M1: 10, M2: 20 t ha?1). Experimentation was conducted on soils of two different soil depths [shallow (8–12 cm; low‐medium erosion risk) and normal soil depth (18–22 cm; no erosion risk)] on a sloping field in the 2006–2007 and 2007–2008 growing seasons at Gumushane, Turkey. Herbage harvested on the shallow depth area had 22–73% less DM yield, 14–72% less CP yield, 6–9% greater CP content and generally higher minerals contents than herbage from the normal soil depth area. Cattle manure applications increased DM yield by about 23%, increased CP content and CP yield, and also increased the contents of most minerals in herbage of the intercropping mixtures, relative to the control, averaged over the two soil depths. It is suggested that, for areas with shallow soil depths that are prone to erosion, plant cover should be used for forage production, and that fertilization with solid cattle manure at 20 t ha?1 can support production of quality forage of acceptable DM yield.  相似文献   

12.
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   

13.
The effects of restricted access time to pasture (2, 4 or 6 h d?1; 2H, 4H or 6H) on ingestive behaviour and performance were assessed on four occasions per target grazing day (D1, initial day; D4, intermediate day; and D7, final day) in dairy ewes rotationally grazing berseem clover with a 7‐day grazing period and a 21‐day recovery period. A randomized block design with two replicates per treatment was used. All ewes were supplemented daily with 700 g per head of concentrates and 700 g per head of ryegrass‐based hay. Pasture subplot and animal group data were analysed by a factorial model including access time (AT), grazing day (D) and their interaction as fixed factors. Sward height decreased from D1 (P < 0·001) and green leaf mass from D4 (P < 0·001) onwards during the grazing period. Grazing time as a proportion of AT was higher in 2H than in 4H and 6H ewes on D1 and D4 but not on D7 (P < 0·05 for AT × D). Herbage intake rate was higher in 2H than in 4H and 6H ewes (P < 0·001). Herbage and total intakes were higher in 4H and 6H than in 2H ewes (P < 0·001), with herbage intake varying non‐linearly during the grazing period (P < 0·05). Milk yield was higher in 4H and 6H than in 2H ewes (P < 0·01). To conclude, despite the evidence of compensatory behaviour, restricting access time to 2 h d?1 constrained intake and performance of dairy ewes rotationally grazing berseem clover.  相似文献   

14.
The effects of levels of application of potassium (K) fertilizer, and its interactions with both nitrogen (N) fertilizer and the growth interval between fertilizer application and harvesting on ryegrass herbage yield and chemical composition, and the fermentation, predicted feeding value, effluent production and dry-matter (DM) recovery of silage were evaluated in a randomized block design experiment. Twenty plots in each of four replicate blocks received either 0, 60, 120, 180 or 240 kg K ha?1, each at either 120 or 168 kg N ha?1. Herbage from the plots was harvested on either 24 May or 8 June and ensiled (6 kg) unwilted, without additive treatment, in laboratory silos. Immediately after harvesting, all plots received 95 kg N ha?1 and were harvested again after a 49-day regrowth interval. From the primary growth, herbage DM yields were 6·31, 6·57, 6·74, 6·93 and 6·93 (s.e. 0·091) t ha?1, herbage K concentrations were 15·5, 16·2, 19·1, 22·4 and 26·1 (s.e. 1·06) g kg?1 DM and herbage ash concentrations were 57, 63, 71, 73 and 76 (s.e. 0·9) g kg?1 DM, and for the primary regrowth herbage DM yields were 2·56, 2·73, 2·83, 2·94 and 2·99 (s.e. 0·056) t ha?1 for the 0, 60, 120, 180 and 240 g K ha?1 treatments respectively. Otherwise, the level of K fertilizer did not alter the chemical composition of the herbage at ensiling. After a 120-day fermentation period the silos were opened and sampled. The level of K fertilization had little effect on silage fermentation and had no effect on estimated intake potential, in vitro DM digestibility (DMD), DM recovery or effluent production. Increasing N fertilizer application increased silage buffering capacity (P < 0·05) and the concentrations of crude protein (P < 0·001), ammonia N (P < 0·01) and effluent volume (P < 0·01), and decreased ethanol concentration (P < 0·05) and intake potential (P < 0·05). Except for the concentrations of lactate and butyrate, delaying the harvesting date deleteriously changed the chemical composition (P < 0·001) and decreased intake potential (P < 0·001) and DMD (P < 0·001) of the silages. It is concluded that, other than for K and ash concentration, increasing the level of K fertilizer application did not alter the chemical composition of herbage from the primary growth or the resultant silage. Also, the level of K fertilizer application did not affect predicted feeding value, DM recovery or effluent production. Herbage yield increased linearly with increased fertilizer K application. Except for acetate and ethanol concentrations, there were no level of K fertilizer application by level of N fertilizer application interactions or level of K fertilizer application by harvest date interactions on silage fermentation or predicted feeding value. Increasing N fertilizer application from 120 to 168 kg ha?1 had a more deleterious effect on silage composition and feeding value than increasing K fertilizer application from 0 to 240 kg ha?1. Delaying harvesting was the most important factor affecting herbage yield and composition, and silage composition and had the most deleterious effect on silage feeding value.  相似文献   

15.
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   

16.
The provision of grass for early spring grazing in Ireland is critical for spring calving grass‐based milk production systems. This experiment investigated the effect of a range of autumn closing dates (CD), on herbage mass (kg DM ha?1), leaf area index (LAI) and tiller density (m?2) during winter and early spring. Thirty‐six grazing paddocks, closed from 23 September to 1 December 2007, were grouped to create five mean CD treatments – 29 September, 13 October, 27 October, 10 November, 24 November. Herbage mass, tiller density and LAI were measured every 3 weeks from 28 November 2007 to 20 February 2008; additionally, herbage mass was measured prior to initial spring grazing and tiller density was measured intermittently until September 2008. Delaying CD until November significantly (P < 0·05) reduced herbage mass (by approximately 500 kg DM ha?1) and LAI (by approximately 0·86 units) in mid‐February. On average, 35% of herbage mass present on swards on 20 February was grown between 28 November and 30 January. LAI was positively correlated with herbage mass (R2 = 0·78). Herbage mass increased by approximately 1000 kg DM ha?1 as spring grazing was delayed from February to April. Tiller density increased from November to February, although it did fluctuate, and it was greatest in April (9930 m?2). This experiment concludes that in the south of Ireland adequate herbage mass for grazing in early spring can be achieved by delaying closing to early mid‐October; swards required for grazing after mid‐March can be closed during November.  相似文献   

17.
Groups of mature, non-lactating sheep and cattle grazed a Nardus stricta community during the growing season for six consecutive years from 1984 to 1989. Three unreplicated treatments were applied by continuous variable stocking to maintain between-tussock sward height at (a) 4·5 cm by cattle grazing and (b) 4·5 cm or (c) 3·5 cm by sheep grazing. Diet composition and herbage intake were measured from 1984 to 1987 on three occasions in the growing season, and live weight and stock density were recorded from 1984 to 1988. The diet of cattle usually contained more dead herbage, Nardus, sedges and rushes but less forbs and other fine-leaved grasses than the diet of sheep. Principal coordinate analysis showed different trends across years in diet composition, especially between the sheep and cattle treatments at 4·5 cm. Diet digestibility was usually higher for sheep treatments than for the cattle treatment. Diet digestibility and herbage intake increased between 1984 and 1985, and 1986; they also declined from spring to late summer. Regression of diet digestibility on independent principal components — which were derived from diet composition measurements — showed that the two most important principal components accounted for 72% of the variation in digestibility. Stock-carrying capacity (kg LW × d ha?1, calculated from live weight, grazing days and stock density) was greater on the cattle treatment than on either sheep treatment. Stock-carrying capacity also increased more in successive years on the cattle than on either sheep treatment, and it was greater on the sward maintained at 3·5 cm than at 4·5 cm by sheep. These increases in stock-carrying capacity were generally positively associated with the increase in the percentage specific frequency both of live material and of the more productive grasses in the swards. These data indicate that sheep-only stocking tends to Nardus dominance and suggest that further study using productive cattle — either alone or mixed with sheep — is needed, preferably in association with measurements of floristic change both within and between tussocks.  相似文献   

18.
Herbage intake is usually depressed when beef cattle grazing abundant pastures are supplemented with energy-rich feedstuffs but relatively little is known about the effects of supplementation on the components of ingestive behaviour. An experiment was conducted to establish the effect of ground corn (Zea mays L.) on the ingestive behaviour of yearling Angus and Angus × Hereford steers (Bos taurus) (mean live weight (LW) of 323 kg) grazing autumn stockpiled Boone cocksfoot (Dactylis glomerata L.) using a tethered grazing system in which the experimental unit was the tethered steer and its grazing area (45 m2) for one grazing session. Herbage dry matter (DM) mass was 1662 kg ha?1 and herbage DM allowance was 7–5 kg steer?1 for each grazing session. Herbage DM intake was measured as the difference between herbage DM mass offered and refused. Grazing took place during two daily sessions each of about 2 h duration commencing at 08.00 and 14.00 h for 9 days. Ground corn (0, 1·5, 3·0 and 4·5 kg steer?1) was fed each day at 12.00 h and had no significant (P < 0·05) effect on rate of DM intake, rate of biting or DM intake per bite. Mean DM intake was 6 2 kg steer?1 d?1 (87 mg (kg LW)?1 min?1). Steers averaged 4832 bites per grazing session, with a mean DM intake per bite of 644 mg (2·0 mg (kg LW)?1) and a mean rate of 44 bites min?1. Data obtained at the beginning and end of each grazing period on ingestive behaviour of one group of four steers (mean LW of 306 kg) fitted with oesophageal fistulae supported data for the two groups of normal steers and showed no response to supplementation. Mean values for rate of DM intake, DM intake per bite and rate of biting established for the fistulated cattle were 73 mg (kg LW)?1 min?1, 521 mg bite?1 (1·7 mg (kg LW)?1) and 39 bites min?1, respectively.  相似文献   

19.
The concentration of mineral elements in herbage from permanent swards of mixed species composition (predominantly Agrostis spp., Holcus lanatus, Festuca rubra, Lolium perenne, Poa spp., etc.) was compared with that from sown perennial ryegrass ( Lolium perenne ) at two fertilizer rates (0 and 300kg N ha−1 year−1, both with P and K) and with L. perennel Trifolium repens (at 0 N with P and K). The investigation was conducted over four years at sixteen contrasting sites in England and Wales. Herbage samples for mineral analysis were taken at first and fourth harvests (May and August) each year from plots under 4-weekly cutting. There was a wide degree of variation between sites, particularly for concentrations of Ca, Mg, Na and all trace elements analysed. Herbage from L. perenne reseeds had significantly higher concentrations of Ca, Mg, Na, Co and S, but K, Mo, Zn, Cu and P were generally lower than in the permanent swards. L. perennel T. repens swards had the highest concentration of major cations, but trace element levels were generally intermediate between those for 0 N permanent and L. perenne swards. Fertilizer N reduced concentrations of Ca, Mn, Mo and S, and increased Mg, Na and Zn, with no consistent effects on K, Co and Cu. Herbage at harvest 4, compared with harvest 1, had higher Ca, Mg, Na, Mn, Zn and S. Permanent and L. perenne swards responded similarly to fertilizer N and between harvest dates. Results are discussed in relation to previous reports of botanical and fertilizer effects on mineral concentrations, and the mineral requirements of livestock. Changes in mineral concentration resulting from reseeding permanent swards are considered unlikely to increase mineral-related livestock disorders, and in many cases could be beneficial, though problems might arise on sites where some elements, e.g. Cu and Mg, are low.  相似文献   

20.
The effects of continuous stocking by sheep at sward surface heights (SSH) of 3, 5, 7 and 9 cm in grass/clover (GC) and nitrogen-fertilized grass (GN) swards were examined in relation to herbage mass and quality, clover content, tiller density and rates of herbage production and senescence in two periods in each of three grazing seasons (1987-89). The GN swards received a total of 300 kg N ha?1 each year in six equal dressings from March; GC swards received a single dressing of 50 kg N ha?1 in March each year. Herbage mass measured from ground level increased linearly with SSH with overall mean herbage masses of 0·89, 1·38, 1·78 and 2·12 t OM ha?1 (s.e.m.0·024, P < 0·001) at SSH of 3, 5, 7 and 9 cm respectively. GN and GC swards had mean herbage masses of 1·58 and 1·51 t OM ha?1 (s.e.m. 0·051, NS) respectively. Mean N content of herbage on GN swards was greater than that on GC swards and declined with increasing SSH. Crude, fibre (CF) content of herbage was similar for both sward types and increased with increasing SSH. Clover content of GC swards remained low throughout the experiment, ranging from 0·002 to 0·074 of herbage mass. However, from tissue turnover rates it was estimated that its contribution to herbage production was in the range of 0·049–0·219 of net herbage growth. Total growth increased with increasing SSH in both sward types, with maximum growth rates in GN swards of 143 and 130 kg DM ha?1 d?1 and in GC swards of 88·2 and 85·4 kg DM ha?1 d?1 in Periods 1 (up to early July) and 2 (after July) respectively. Senescence rates ranged between 13·3 and 50·1 kg DM ha?1 d?1 and tended to be higher in Period 2 than in Period 1. Net production increased with increasing SSH in Period 1, while in Period 2 net production declined at SSH above 6·5 cm. The increased net herbage production in taller swards was not associated with greater utilized metabolizable energy production at sward heights above 5 cm.  相似文献   

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