bluuebunny/crossref_metadata_2025 huggingface dataset:
The contribution of different white clover cultivars to the nitrogen yield of mixed swards
Authors: LAIDLAW A. S.
Published: April 2006

The annual contribution of clover to a mixed sward for 5 years was compared for a range of cultivars, viz. S1OO, Sabeda, Blanca and Olwen, in order of increasing leaf size. The contribution referred to as‘clover‐derived nitrogen N', was measured as the difference between N harvested in mixed swards and that in similarly treated swards devoid of clover. The swards were harvested four or five times each year and received N fertilizer, annually, at 0, 30, 60 or 90 kg N ha−1 in March.

Blanca swards had the highest clover‐derived N yield in the second year and lowest in the fourth year. By the fifth year Sabeda and S100 (medium leaved cultivars) were contributing more N than the other two cultivars. When related to the amount of clover harvested, S100 had the highest value in the second year and S100 and Sabeda in the third year. Relating the total lover‐derived N harvested over the 5 years to the amount of clover harvested, S100 had an efficiency of contribution of 54‐3 kg N t−1 dry matter (DM) compared to a mean of 49 0 kg N t−1 clover DM for the other three cultivars. Nitrogen fertilizer reduced the contribution of clover N in the first 3 years owing to a reduction in clover yield, but it did not affect clover's efficiency to contribute N.

It is concluded that although the smallest leaved type of the four (S100) made the most efficient N contribution to the sward more information is required to relate morphology of clover to its capability to contribute N directly or indirectly to the sward.
A simulation model to predict the drying time for pasture hay
Authors: GUPTA M. L. , MACMILLAN R. H. , McMAHON T. A. , BENNETT D. W.
Published: April 2006

A hay drying model (HAYDMO) which predicts the moisture content of pasture hay is described. It uses multiple regression equations based on field drying experiments with conditioned and unconditioned hay and predicts hourly changes in moisture content for both day and night and also those due to rain. The model can be used with three different combinations of weather, including hourly wet and dry bulb temperatures, radiation, wind speed and rainfall. Testing HAYDMO revealed a satisfactory agreement between predicted and observed moisture contents
Initial bacteria] numbers on lucerne prior to ensiling
Authors: MUCK R. E.
Published: April 2006

Populations of lactic acid bacteria (LAB) on lucerne before and after havesting were extensively monitored over a two‐year period and correlated with weather data, various wilting parameters and equipment used for harvest. The LAB on standing lucerne were below detectable levels (<10 colony forming units (CFU) g lucerne−1). Immediately after mowing, low levels of LAB (51 CFU g−1) were found on over half the samples. During wilting, the population of LAB generally increased. The amount of increase was affected primarily by the average air temperature during wilting, the length of wilting and the drying rate. The first two variables were positively correlated with bacterial growth whereas increased drying rate adversely affected LAB numbers. If the LAB numbers in the swath were below 100 CFU g−1 prior to chopping, the forage harvester inoculated the chopped lucerne an level of 102 to 104 CFU g−1, depending on air temperature. Considering these factors, LAB counts on chopped lucerne could be predicted within one order of magnitude approximately 95% of the time.
Criteria for breeding forages of improved feeding value: results of a Delphi survey
Authors: WHEELER J. L. , CORBETT J. L.
Published: April 2006

Progress in improving the feeding value (FV) of forage plants has been slow despite the benefits to animal production that can result from using plants of intrinsically higher FV. The slow progress is due in part to a lack of consensus on the criteria to be used in breeding or selecting forages of high FV. This paper reports the use of the Delphi technique to obtain such a consensus from an international panel of specialists in grazing animal production.

The specialists, from Europe, USA, New Zealand and Australia, ranked eleven criteria for improving the FV of grasses and legumes for liveweight gain and for wool production.

In general, the primary criteria chosen were high digestibility, easy communication, high nonstructural carbohydrate, high crude‐protein and, for sheep kept primarily for wool production, a high sulphur‐amino acid content. High relative palatability, high lipid‐content and erect growth habit were ranked as least important. It was generally considered that mineral content and anti‐quality constituents should be monitored rather than making them specific breeding objectives, although some exceptions were noted. Minor importance was attached to having ‘appropriate’ tannins in grasses; however, this was given a high priority in legumes. These criteria, and the desirability of reducing the extent of protein degradation in the rumen are discussed in relation to comments made by panel members.
Predicting the digestibility of grass grown for first‐cut silage
Authors: THOMPSON N. , KEILLER P. R. , YATES C. W.
Published: April 2006

Meteorological factors influencing the temporal changes of digestibility of grasses in spring and early summer are discussed. Annual observations in England of the digestibility of three grasses are then related to the relevant meteorological variables using two multiple regression analysis methods. The resulting regression relationships are tested on independent data, and finally sets of regression coefficients are recommended for predicting from synoptic meteorological data the weekly progress of digestibility in different areas of England: a simplified set of regression relationships for predicting digestibility values a few days ahead which require forecasts of only temperature in order to be applied operationally is also given.
Changes in stubble carbohydrate content during regrowth of defoliated perennial ryegrass (Lolium perenne L.) on two nitrogen levels
Authors: GONZALEZ B. , BOUCAUD J. , SALETTE J. , LANGLOIS J. , DUYME M.
Published: April 2006

Changes in stubble carbohydrate content during the regrowth of ryegrass (Lolium perenne L.) grown under hydroponic conditions at two nitrogen levels were studied as a function of time by high‐performance liquid chromatography. Experimental data showed that regrowth at a non‐limiting nitrogen level (1·0 mol m−3 NH4NO3) involved two different physiological periods. The first occurred during the first 6 d and was characterized by the mobilization of 60 to 90% of the soluble carbohydrates (i.e. glucose, fructose, sucrose, oligofructans and polyfructans). During the second period (6.28 d of regrowth) carbohydrate contents rose to the values observed prior to cutting (20% of dry matter at the 28th d of regrowth).

The effect of low nitrogen conditions (0·2 mol m−3 NH4NO3) was observed only during the second phase. Plants regrown in a nitrogen‐starved medium accumulated 2·3‐fold more polyfructans than plants regrown in a non‐limiting nitrogen medium. Their fructose and glucose contents remained at 2% of dry matter from the end of the first phase of mobilization.

The experimental results are interpreted and discussed in terms of the existence of two distinct fructan synthetic pathways.
Herbage productivity of a range of grass species under a silage cutting regime with high fertilizer nitrogen application
Authors: FRAME J.
Published: April 2006

The productivity of fourteen grasses was measured under a silage cutting regime of four harvests per year for 3 years (1984‐86) with an annual fertilizer N rate of 360 kg ha−1, applied at 120, 100, 80 and 60 kg ha−1 for successive harvests. The grasses were: red fescue (Festuca rubra)cvs Reptans, Dawson and Ruby, perennial ryegrass (Lolium perenne)cvs Perma and Sprinter, Yorkshire Fog (Holcus lanatus)commercial types I and II, smooth meadow‐grass (Poa pratensis)cvs Parade and Arena, creeping bentgrass {Agrostis stolonifera)cv. Penncross, crested dogstail {Cynosurus cristatus)cv. Southlands and rough meadow‐grass (Poa trivialis)cvs Dasas, Omega Øtofte and Sabre.

Red fescue gave the highest dry‐matter (DM) production over the 3 years but because of low organic matter digestibility (OMD), its production of digestible organic matter (DOM) was lower than that of perennial ryegrass. Rough meadow‐grass was relatively low yielding in the first year and did not persist thereafter. Three‐year mean DM production ranged from 9‐22 kg ha”’(crested dogstail) to 14‐37 kg ha‐1 (red fescue cv. Reptans), while mean annual OMD values ranged from 0‐660 (smooth meadow grass cv. Arena) to 0766 (ryegrass cv. Sprinter). The mineral composition (P, K, Ca and Mg) differed among species; creeping bentgrass, crested dogstail, perennial ryegrass and Yorkshire fog had moderate to high mineral concentrations while smooth meadow‐grass had low concentrations. Mean two‐year (1985‐86) mineral composition (g kgDM−1) ranged from 3‐1 to 40 (P), 234 to 31‐0 (K), 3‐8 to 6‐0 (Ca) and 1‐6 to 2‐6 (Mg),

It was concluded that while red fescue and Yorkshire fog showed considerable potential for silage DM production, there is scope for breeding red fescue cultivars with improved digestibility and more winterhardy Yorkshire fog; characterization of their ensiling qualities would also be useful.
Estimating biomass of an improved pasture using SPOT HRV data
Authors: WILLIAMSON H. D.
Published: April 2006

SPOT high‐resolution visible (HRV) multispectral data were used to estimate the biomass of an improved pasture near Clare in South Australia. The study examined the effects of trees, senescent vegetation, surface wetness, herbage composition and management practices including the age of the pasture and stocking rate, on reflectance. This was undertaken by a comparison of spectral responses and through the use of partial correlation analyses. Changes in biomass had the greatest influence on reflectance, though the presence of trees and senescent vegetation influenced reflectance significantly in all wavebands. These areas were excluded from the model developed to estimate pasture biomass. The regression model was inverted and applied to a normalized difference SPOT HRV image. The accuracy of the biomass estimation was 43–81% at the 95% confidence level, or ±57.0 gm−2 of dry grass. This technique provides resource managers with a tool for routinely assessing pasture condition over large areas.
The effect of dry matter content on the preservation of big hale grass silages made during the autumn on commercial farms in South Wales 1983‐87
Authors: HAIGH P. M.
Published: April 2006

A total of eighty‐nine big‐bale (BB) silages made on commercial farms in South Wales during the autumn in 1983‐87 were analysed to discern the effect of dry matter (DM) content on fermentation. Silages were made predominantly in late September, during fine weather from permanent pasture or perennial ryegrass pastures, which had not been grazed for 9 weeks. On average 7·8 ha of pasture were cut; most farmers attempted to pre‐wilt grass for an average of 36 h prior to ensilage in individual plastic bags. Silage making was usually completed within 4 d of starting to cut. Silage ammonia‐N content was inversely correlated with DM content. The results indicated that a DM content of about 280 g kg−1 was needed to produce well‐preserved silage with an ammonia‐N content of 100 g (kg total N)−1. Silages were, therefore, generally poorly preserved because the DM increase from wilting was only 2·3 g kg−1 h−1.
The effect of formic acid on the rate of water loss from cut grass and lucerne
Authors: JONES L.
Published: April 2006

The drying rates of grasses and lucerne, following treatment with 1% formic acid, were compared with those of untreated crops. Material was fully exposed to a flow of air in a ventilated laboratory oven set at 23 °C. Treatment with formic acid initially enhanced the rate of drying of grass, but this was followed by retardation. This reduction in the rate of drying was caused by the rapid desiccation of laminae, which reduced their effectiveness in providing a pathway for water loss from the stem. The rate of water loss directly from the stem surface was not increased by formic acid treatment, probably because the enveloping leaf sheaths acted as a protective layer. In contrast, formic acid increased drying rate in lucerne. whose stems have no such protective layer. The results suggest that chemical desiccants. which have a contact action are unlikely to have any application in making hay from grass.
Yield and nitrogen utilization by Lolium perenne and Trifolium repens on a limed stagnohumic‐gley soil in a pot experiment
Authors: HOPKINS D. W. , SHIEL R. S. , O'DONNELL A. G.
Published: April 2006

In a pot experiment the pH of a hill peaty soil was adjusted to cover the range 3.8 to 6.8 with Ca(OH)2. Yield and N content of the harvested plant material was greatest at pH 6.8 in pots sown with only Lolium perenne, and greatest at soil pH 6.1 in pots sown with Trifolium repens and L. perenne. T. repens established only at soil pH between 4·3 and 6·1. A small reduction in sward yield and a large and highly significant decrease in total N recovered by the harvested material, which occurred with increase in soil pH from 3·8 to 4·3, was attributed to a combination of increased N immobilization in the soil microbial biomass and to the poor performance of both sown and self‐propagating indigenous species around pH 4·3.
The effect of inoculation with Lactobacillus plantarum on fermentation in laboratory silos of herbage low in water‐soluble carbohydrate
Authors: ROOKE J. A. , BORMAN ALISON J. , ARMSTRONG D. G.
Published: April 2006

In experiment 1, a mixture of perennial ryegrass and white clover (176 g DM kg−1) was ensiled with no addition, or with the application of Lactobacillus plantarum, 3 × 106(g fresh weight of herbage)−1 or enterobacteria, 3 × 106 (g fresh weight of herbage)−1 or both of these inoculants. Silos were incubated at either 18°C or 26°C for 7 d and sealing of half of the silos was delayed for 48 h. In experiment 2, cocksfoot (247 g DM kg−1) was ensiled with no additive, with the application of L. plantarum, 4 × 106 (g fresh weight of herbage)−1 enterobacteria, 4 × 106 (g fresh weight of herbage)−1 or ammonium nitrate, 5 g (kg herbage)−1. Silos were incubated at 18°C and sealing was delayed for 48 h.

In neither experiment were the untreated silages of satisfactory quality after 35 d ensilage, having pH's of 4·3 and 6·4. and ammonia‐N concentrations of 139 and 209 g N (kg total N)−1 in experiments 1 and 2 respectively. The poorer fermentation in experiment 2 reflected the lower water‐soluble carbohydrate (WSC) content of the ensiled herbage (136 and 53 g WSC (kg DM)−1 in experiments 1 and 2 respectively). Inoculation with L. plantarum significantly reduced silage pH and the concentrations of ammonia‐N (experiment 1 only) and ethanol and increased lactic acid concentrations. Inoculation with enterobacteria had only minor effects in each experiment.

In experiment 1, incubation at 26°C increased the rate of fermentation in the silos as pH was significantly lower after 7d incubation at 26°C than at 18°C, but this effect had largely disappeared after 35 d incubation. When sealing of the silos was delayed for 48 h, the resulting silages had significantly higher pH and ammonia‐N contents than silages from silos that had been sealed immediately after filling.

In experiment 2, addition of ammonium nitrate significantly reduced the concentrations of ethanol and acetic acid in silages opened after 7 d. After 35 d the concentrations of ethanol were significantly reduced and those of ammonia‐N increased by the addition of ammonium nitrate. There were marked increases in silage pH between 7 and 35 d ensilage and in the concentrations of ammonia‐N and acetic acid in the silages that had been inoculated with ammonium nitrate at ensilage.
Dry matter yield and response to nitrogen of an Agrostis stolonifera‐dominant sward
Authors: SHELDRICK R. D. , LAVENDER R. H. , MARTYN T. M.
Published: April 2006

A small‐plot cutting trial was carried out 1983‐85 at North Wyke Research Station, Devon to compare the dry matter (DM) production and response to nitrogen (N) of a naturally occurring Agrostis stolonifera‐dominant sward, developed under low fertility conditions on a poorly structured soil. and a sward of Lotium perenne cv. Melle, direct‐drilled in 1982 at the same site. All plots received standard inputs of P. and graded inputs of K, related to the four annual N treatments (0, 200, 400 and 800 kg ha−1, in seven equal applications). All plots were cut six times each year, except in 1983; DM yield, herbage digestibility, herbage N concentration, response to applied N, apparent recovery of applied N. and botanical composition of the swards were recorded.

On average, A. stolonifera gave 69% of the DM yield of L. perenne. A. stolonifera did not out‐yield L. perenne at the low N levels (0 or 200 kg N ha−1 a−1), or in mid‐season. and yielded significantly (P<0‐001) less in drought conditions in 1984 (4‐4 t DM ha−1 and 6‐9 t DM ha−1, s.e.d.±0‐22). Average digestibility of A. stolonifera was 3 units of D‐value lower (P<0‐001) than L. perenne, but N concentrations were higher (3‐01% and 2‐53%, s.e.d. ±0‐074). However, total yields of N from A. stolonifera were lower. Responses in DM production per kg N applied were lower in A. Stolonifera than in L. perenne for all N increments, except the highest, (400‐800 kg N ha−1). Fitted response curves allowed interpolation of the values of DM yield (Y10) and N input (N10) where the response was 10 kg DM (kg N)−1. Values of Y10 for A. stolonifera and L. perenne averaged 7‐1 t DM ha−1 and 12‐9 t DM ha−1respectively. and values of Mo averaged 460 kg N ha−1 and 570 kg N ha−1, which further indicated the lower responsiveness of A. stolonifera to applied N. Apparent recovery of applied N was generally low, with significantly higher values (P<0‐001) for L. perenne in 1983 and 1984, but not in 1985. The botanical composition of L. perenne swards with no applied N showed a steady and rapid decline in ground cover by the sown species. AH L. perenne swards showed an abrupt decrease of L. perenne cover in late 1985, with invasion by A. stolonifera at all but the highest N level (800 kg N ha−1). A. stolonifera treatments receiving 400 or 800 kg N ha−1 showed initial expansion of their native L. perenne populations; however, these declined after the drought in 1984. Only low levels of L. perenne cover remained in the A. stolonifera swards at the end of the trial; these were unaffected by N level. It was concluded that under the conditions of this trial, A. stolonifera had lower DM productivity and efficiency of N use than L. perenne.
Enzymes as silage additives. 1. Silage quality, digestion, digestibility and performance in growing cattle
Authors: JACOBS J. L. , McALLAN A. B.
Published: April 2006

Four grass silages were made from perennial ryegrass ensiled after a 1h wilt in 2‐t silos without additive application, with application of formic acid or with one of two enzyme mixtures of hemicellulases and cellulases (enzyme 1 and enzyme 2). Effluent losses were monitored over the ensiling period (130 d).

Analyses of the silage showed that formic acid‐treated silage had lower concentrations of lactic acid than the other silages. Both enzyme‐treated silages had lower levels of cellulose, acid detergent fibre (ADF) and neutral‐detergent fibre (NDF) than the untreated and formic acid treated silages. Effluent production was highest with enzyme‐treated silages.

The silages were subsequently fed to growing steers equipped with rumen cannulae and T‐piece duodenal cannulae. Apparent whole‐tract digestibilities of organic matter constituents were significantly lower (P < 0·05) with both enzyme‐treated silages (untreated; 0·736, formic acid; 0·722, enzyme 1; 0·694, enzyme 2; 0·703). Both untreated and enzyme 2‐treated silages sustained higher nitrogen digestibilities (g g−1 intake) (untreated; 0·675, formic acid; 0·636, enzyme 1; 0·630, enzyme 2; 0·662) and N retentions (g d−1) untreated; 16·0, formic acid; 14·0, enzyme 1; 11·6, enzyme 2; 16·6), but none of these differences was significant. When formic acid‐treated silage was offered, there was a greater amount of organic matter apparently digested in the rumen (ADOMR). Non‐ammonia nitrogen and microbial nitrogen flows at the duodenum were similar on all diets. The efficiency of microbial protein synthesis was highest with enzyme 2‐treated silage and lowest with formic acid‐treated silage (untreated, 35·4; formic acid, 25·2; enzyme 1, 30·4; enzyme 2, 39·4), but none of these differences were significant.
The effect of a chemical hybridizing agent on the morphology and chemical composition of annual ryegrass
Authors: McGUINNESS S. F. , PEARCE G. R. , DALLING M. J. , SIMPSON R. J.
Published: April 2006

A chemical hybridizing agent (CHA: WL 84811, azetidine‐carboxylic acid. Shell Chemical) was applied to annual ryegrass (Lolium rigidum Gaud. cv. Wimmera) at four levels: 0, 1·6, 2·4 and 3·2 kg active ingredient (a.i.) ha−1, at booting and at anthesis with a view to reducing seed set and increasing the proportion of cell solubles in the senescing and dead plants. The CHA treatments reduced stem elongation by up to 40% and reduced the proportion of pollinated florets progressively according to the concentration of CHA. At 3·2 kg (a.i.) ha−1 only 14% of florets were fertilized compared with 86% on the zero (control) treatment.

The CHA treatments also resulted in progressive increases in the number of secondary tillers. Since there was no increase in the amount of neutral‐detergent solubles associated with increased CHA application, it was concluded that storage carbohydrates, which might otherwise have been directed towards seed development, were partitioned towards increased tillering. There was no effect, therefore, on the proportion of neutral‐detergent soluble material in senescing and dead plants.
The effect of stolon burial and defoliation early in the growing season on white clover performance
Authors: GRANT S. A. , TORVELL L. , SIM E. M. , SMALL J.
Published: April 2006

A factorial pot‐experiment was carried out to investigate the effect of burial of stolons (stolons unburied or buried to a depth of 0·5–1 cm at day 0), with and without defoliation (plants uncut or all unfolded laminae removed at weekly intervals) on the growth of two varieties of white clover (cv. Kent or cv. Milkanova) harvested on three dates (14 d, 28 d and 42 d after burial). The soil used was a 3:2:1 mixture of clay loam:peat:sand, and there were three replicates of each variety for each treatment at each harvest date.

Burial of stolons in the absence of defoliation had no effect on stolon extension, leaf appearance, or the concentration of water‐soluble carbohydrate in the stolons. The number of axillary buds developing (new branches plus flowers) was increased on the new surface‐growing tips of primary stolons but was reduced on branch (i.e. secondary) stolons. The proportion of branches to flowers was largely unaffected by burial.

Defoliation caused substantial reductions in the concentration of water‐soluble carbohydrates in stolons and stolon extension growth, a reduction in number of axillary buds developing, and in the proportion of buds which were floral, but had only a small effect in reducing leaf appearance.

The combination of stolon burial and defoliation resulted in the death of secondary stolons; 42% of all secondary stolons had died by day 42, and stolon extension, leaf appearance and numbers of axillary buds developing on secondary stolons were severely reduced. The numbers of axillary buds developing on primary stolons was increased owing to more buds developing on the resurfaced stolon tips, but the increase was inadequate to compensate for the reduced growth, and death of secondary stolons.

Differences between clover varieties in response to treatments were small. In general, the smaller variety, cv. Kent, was more adversely affected by burial than the larger variety, cv. Milkanova. A variety x defoliation interaction occurred for senescence of leaves; petiole senescence of cut leaves was reduced or similar to that of intact leaves for cv. Kent, but was increased for cv. Milkanova.

The results are discussed in relation to treatment effects on carbon sources and sinks, and in relation to climate‐soil interactions.
Effect of regrowth interval on the productivity of swards defoliated by cutting and grazing
Authors: Binnie R. C. , Chestnutt D. M. B.
Published: April 2006

Over three grazing seasons (1984‐1986) a sward of perennial ryegrass, cv. Talbot, which received a total of 336 kg N ha‐1 each season, was cut or grazed with ewes at 3‐ or 4‐week intervals on a rotational basis.

Sward productivity was higher under cutting than under grazing irrespective of the interval between defoliations. Under cutting, mean herbage organic matter (OM) yields over both intervals were 8·66, 9·62 and 8·17 t ha‐1 in 1984, 1985 and 1986 respectively while under grazing the corresponding yields were 7·65, 8·63 and 7·50 t ha‐1. The mean annual yield of herbage defoliated at 3‐week intervals was 7·50, 8·64 and 7 ·20 t OM ha‐1 compared with 8·80, 9·60 and 8·46 t OM ha‐1 for swards defoliated at 4‐week intervals in the three years respectively.

The nitrogen (N) content of both the available and the residual herbage was consistently higher under grazing than under cutting. Available herbage contained 31·3 and 27·7 g N kg OM‐1 and residual herbage 26·1 and 22·7 g N kg OM‐1 under grazing and cutting respectively.

The mean yield of N under cutting was 284 kg ha‐1 compared with 304 kg ha‐1 under grazing. Defoliation interval had no effect on N yield, the overall mean yield being 294 kg ha‐1 under both 3‐ and 4‐week defoliation intervals. The effect of the treatments on tiller population was slight and inconclusive.

The process of grazing reduced yield probably as a result of damage to the sward through trampling; the positive effect of excretal N on yield was minimal on account of the short grazing periods.
Effects of cultivars of tall fescue (Festuca arundinacea Schreb.) on the botanical composition of mixed swards
Authors: SUGIYAMA S. , NAKASHIMA H.
Published: April 2006

The effect of five cultivars of Festuca arundinacea on the botanical composition of mixed swards (with Dactylis glomerata and Trifolium repens singly and combined) at two soil fertility levels (moderate fertilizer application and no application) were examined. Shoot and root morphological characteristics of seedlings in each cultivar were also examined under pot conditions.

Although there was little difference in the total biomass of the three mixed swards between cultivars, the cultivars showed significant differences in their relative contribution to total biomass. The relative order of competitive ability between cultivars was maintained over the different soil fertility levels and different species associations.

Of the two yield components of a grass sward, tiller number and tiller size, number of tillers showed a larger response to the presence of neighbour species than mean tiller size, and thus success of F. arundinacea cultivars in mixed swards depended on the extent of reduction of number of tillers caused by the neighbour species of mixtures. The least competitive cultivar had the smallest seeds and shortest roots.
Growth and water relations of simulated swards ofLolium perenneL. selection lines with contrasting leaf osmotic potentials
Authors: THOMAS H. , EVANS C.
Published: April 2006

Two selection lines ofLolium perenne, which had different leaf lamina osmotic potential (Ψs) when droughted in controlled environments, were grown as vegetative simulated swards in containers of soil 1·0 × 1·3 × 0·9 m deep in the glasshouse. Water was withheld during July, August and September.

Under irrigation the low‐ψsline had leaf lamina and leaf base ψs0·06 MPa lower than the high‐ψsline. Under drought, the two lines did not differ significantly in lamina ψsbut leaf base ψswas 0·16 MPa lower in the low line than in the high line. Upon rewatering, most of the osmotic adjustment in the leaf bases was lost within 2 d, but that in the laminae was more stable.

Herbage growth under irrigation was similar in the two lines until September, when it was greater in the highψsline. Drought reduced herbage growth, and also regrowth rates following rewatering, but the two lines did not differ in their sensitivity to drought.

Selection for low ψsalso increased leaf extension rates, and reduced tillering and leaf water conductance of irrigated plants.

The results are discussed in relation to selecting for improved drought resistance on the basis of physiological characters.
Comparison of white clover varieties under cutting and grazing
Authors: SWIFT G. , MORRISON M. W. , CLELAND A. T. , SMITH‐TAYLOR C. A. B. , DICKSON J. M.
Published: April 2006

Seven varieties of white clover (Trifolium repens L.), of varying leaf size from large to small, were sown with perennial ryegrass (Lolium perenne L.) in 1985, at an upland site, and compared over three harvest years under a cutting management (5‐6 cuts), and under continuous grazing by sheep. Fertilizer N input totalled 80 kg ha−1 in both the cutting and the grazing trial. The same varieties were included in two official National List (NL) trials sown the same year at a nearby site; these comprised a yield trial with 6‐7 cuts and a persistency trial mown very frequently (17 cuts) to simulate intensive grazing.

At the upland site the large‐leaved varieties, Milkanova and Blanca, were the highest yielding under cutting (mean 3·3 t DM ha−1), and the small‐leaved S184 and Kent the lowest yielding (mean 2·3 t DM ha−1). The rankings were reversed under grazing (corresponding yields 1·1 and 2·1 t DM ha−1). The medium‐leaved varieties Donna, Menna and Grasslands Huia behaved similarly to the large‐leaved varieties. Ranking order in the cutting trial was similar to that in the NL trial.

Ground covers after three harvest years differed significantly only under grazing, when the small‐leaved varieties had a 2‐3 times greater cover than the larger‐leaved varieties. A poor separation of the varieties in the NL persistency trial suggests that defoliation was not sufficiently severe to simulate intensive grazing.

These comparisons indicate that the performance of clover varieties under the cutting regimes used should not be extrapolated to continuous sheep grazing.
Effect of virginiamycin supplementation on the performance of young grazing cattle
Authors: FIEMS L. O. , BOUCQUÉ Ch. V. , COTTYN B. G. , MOERMANS R. J. , DE BRABANDER D. L.
Published: April 2006

Three experiments have been conducted to study the effect of virginiamycin in young grazing‐bulls (Experiment 1) and heifers (Experiments 2 and 3). Rotational grazing on permanent grassland was practised and animals were supplemented with 1 kg dried sugarbeet pulp per head daily. Control groups did not receive virginiamycin via the supplement, while it was incorporated at 120, 300 and 200 mg kg−1 for the treatment groups in Experiments 1 to 3 respectively.

Average daily liveweight gain was significantly increased from 0·59 to 0·72 kg in Experiment 1 and from 0·73 to 0·81 kg in Experiment 3, but was not affected in Experiment 2 (0·51 vs 0·55 kg). Virginiamycin also increased liveweight gain per ha by 12, 7 and 13%, respectively, for the three experiments. Grazed area per animal was not enlarged to the same extent as the calculated daily energy allowances, which may suggest an improved digestibility and/or rumen fermentation.
The effects of different protein supplements on the utilization of untreated, formic acid‐treated or enzyme‐treated silages by growing steers
Authors: JACOBS J. L. , HAINES M. J. , McALLAN A. B.
Published: April 2006

Three grass silages were made from perennial ryegrass ensiled without additive application (U) or with the application of formic acid (F) or an enzyme mixture of hemicellulases and cellulases (E).

Analysis of silages showed that both untreated and enzyme‐treated silages had higher lactic acid concentrations than formic acid‐treated silage. Enzyme‐treated silage had lower levels of ADF and NDF but higher concentrations of residual WSC than other silages.

The silages were fed to growing steers supplemented with either rapeseed meal (RSM) (60 g kg−1 silage DM) or fishmeal (FM) at a level isonitrogenous with RSM diets, so providing six diets (UR, UF, ER, EF, FR, FF). Organic matter intakes were similar, but ADF intakes were significantly (P < 0·001) lower with enzyme‐treated silage diets (UR, 1163; UF, 1160; ER, 1104; EF, 1035; FR, 1216; FF, 1213), as were intakes of NDF (P < 0·01) (UR, 1946; UF, 1955; ER, 1877; 1772; FR, 2031; FF, 2041). Apparent whole tract digestibilities of organic matter were significantly (P < 0·001) higher with enzyme‐treated silages (UR, 0·644, UF, 0·644; ER, 0·668; EF, 0·678; FR, 0·633; FF, 0·633). Liveweight gains were generally higher with treated silage diets and RSM supported a greater response than FM (UR, 0·496; UF, 0·498; ER, 0·567; EF, 0·489; FR, 0·543; FF, 0·506) with both enzyme and formic acid‐treated silages, although none of these differences were significant.
Effects of conservation method and access time on silage intake and milk production in dairy cows
Authors: MARTINSSON K.
Published: April 2006

The effects of the time of access to feed (8 h or 24 h) with silage‐based rations (unwilted or wilted silage) were studied for two years. In each year the experiment comprised 52 individually fed cows in a 2 × 2 factorial design and covered weeks 1‐20 of the lactation. The cows were offered silage ad libitum, 1 kg of hay per day, and concentrate according to the predicted energy‐corrected milk (ECM) yield.

Increasing the access time from 8 h to 24 h increased the total intake of dry matter (DM) and metabolizable energy (ME) by 6%. This resulted in increased yield of ECM by 5%. The eating rate of forage was significantly increased by restricted time of access. Wilting had no significant effect on total feed intake or milk yield. The importance of providing a sufficient length of time during which the cows have access to feed was confirmed. It was concluded that 8 h d−1 of access to silage‐based rations is not enough in early lactation.
A study of the efficacy of a bacterial inoculant and formic acid as additives for grass silage in terms of milk production
Authors: MARTINSSON K.
Published: April 2006

In a two‐year experiment, three silages were prepared from herbage treated either with an inoculant at 1·25 × 105 organisms (g fresh material (FM))−1. formic acid (850 g kg−1) at 4 1 (t FM)−1, or no additive (untreated). In Experiment 1, unwilted and in Experiment 2, wilted silages were investigated and had mean dry matter (DM) and water soluble carbohydrate (WSC) concentrations at ensiling of 171 g kg−1 and 17·6 g (kg FM)−1 and 263 g kg−1 and 25·1 g (kg FM)−1, respectively. In Experiment 1, 45 and in Experiment 2, 54 individually fed cows were used to evaluate the silages in three‐treatment, randomized‐block design experiments. During weeks 4‐12 of lactation the cows were offered silages ad libitum and during weeks 15‐26 a constant amount of silage was fed. There were few major differences in chemical composition of the resulting silages. Formic acid had no effect on silage digestibility. Inoculant treatment increased digestibility when the grass had been wilted. The use of formic acid resulted in increased silage DM intake of 9% during weeks 4‐12 of lactation in Experiment 1 but not in Experiment 2. The inoculant gave no increase in silage DM intake over the control in Experiment 1 but increased silage DM intake by 7% in Experiment 2. There was no significant response in milk yield to formic acid. In Experiment 2 the response in milk yield to inoculant treatment was significant both in weeks 4‐12 of lactation (4%) and in weeks 15‐26 of lactation (5%). It is concluded that the response in milk yield to the use of a specific inoculant appears to be mediated through increased intake of metabolizable energy (ME).
The effect of time of sowing and sowing method on production of white clover in mixed swards
Authors: LAIDLAW A. S. , McBRIDE JAN
Published: April 2006

Two field trials were carried out in successive years in which (1) perennial ryegrass and white clover seeds were drilled together, or (2) clover was broadcast and grass drilled, or (3) both clover and grass were broadcast. The last two treatments were followed by harrowing or not of the seed bed. Sowing took place in early May or August. Four harvests were taken in each full harvest year.

In establishment years, sowing in May resulted in a total dry matter (DM) production at least ten times higher than that resulting from sowing in August. No sowing method treatment effects on total DM or clover yield were significant in the establishment year (measured only in spring‐sown plots). In the first harvest year the August‐sown treatments produced 15% less DM than those sown in May and clover yield was, on average, 40% lower than the earlier sown treatments; clover proportion followed a similar pattern to yield.

Drilling of both grass and clover without harrowing produced swards with a significantly lower proportion of clover in the first harvest year in the first trial than in treatments in which clover was broadcast but not harrowed. In the second trial at harvest 1, clover proportion just failed to be significantly lower in the treatment in which grass and clover were drilled than in the treatment when clover was broadcast and the seed bed harrowed.

In the second harvest year (first trial only), annual clover yield and proportion were not affected but drilled grass and clover had lower DM yield than when grass was drilled and clover broadcast without harrowing and when both were broadcast, without harrowing. At one harvest, the yield of clover in treatments sown in May was actually lower than that in the later‐sown plots.

In a subsidiary controlled environment experiment to investigate the effect of stage of clover development on cold hardiness (a factor in autumn‐sown swards), plants which were about to initiate stolons (58 days old) had an LD50 of −5·1° compared with −9·3°C for plants 60 days older.

It is concluded that autumn sowing delays the time at which optimum clover production is achieved (late in the first full harvest year) and method of sowing does not compensate for this. However, sowing in August under Northern Ireland conditions does not seem to jeopardize the chances of a successful establishment of white clover, and plants should be sufficiently winter hardy to withstand relatively hard freezing conditions.
Assessment of contrasting perennial ryegrasses, with and without clover, under continuous sheep stocking in the uplands. 4. Animal performance in years 4–6
Authors: DAVIES D. A. , FOTHERGILL M. , MORGAN C. T.
Published: April 2006

Relative sheep production from Aurora (very early flowering), Mellra (late‐flowering tetraploid) and Aberystwyth S23 (late flowering) perennial ryegrass (Lolium perenne L.) varieties was compared during harvest years 4‐6 (1988‐90) as grass only (200 kg N ha−1) and grass/clover (75 kg N ha −1 in 1988, 0 kg N ha−1 in 1989 and 1990) at Bronydd Mawr Research Centre (310‐363 m) in mid‐Wales. The pastures were continuously stocked with Beulah Speckled Face ewes and their Suffolk cross lambs from spring to mid‐July. From late July to early November only the weaned lambs grazed the swards.

Mean (1988‐90) total annual lamb production per hectare from Aurora and Meltra was 70% and 16% more than that from S23. However, the difference between both varieties and S23 was much greater as grass/clover (Aberystwyth S184 small‐leaved type) than as grass‐only swards. Differences between the grasses in individual lamb growth rates were most pronounced during the post‐weaning period, when that on Meltra was 38% and 23% more than on Aurora and S23 respectively.

Mean annual lamb output from grass/clover swards was only 70% of that from grass‐only swards during the 2 years when the former swards received no fertilizer N. Averaged over the 3 years (1988‐90) individual lamb liveweight gain post weaning was 38% higher on grass/clover than on grass‐only swards.

The results are discussed in relation to those for the first 3 harvest years (1985‐87). It is concluded that, although Aurora was less persistent than both late‐flowering varieties, its superiority in providing an average of 29% more lamb output than S23 during the critical spring period (up to early June) would be of considerable practical significance in upland sheep systems, as would be the overall superiority of the tetraploid Meltra over S23.
Observations on the incidence of plant parasitic nematodes in grassland in England and Wales
Authors: COOK R. , MIZEN K. A. , PLOWRIGHT R. A. , YORK P. A.
Published: April 2006

Soil samples taken from one‐ to four‐year‐old swards of white clover and perennial ryegrass at 34 sites, and from older clover/grass swards at 56 sites in England and Wales, were examined for plant parasitic nematodes. Stolons of white clover from 46 of these sites were examined for nematodes. Clover cyst nematode (Heterodera trifolii) and white clover stem nematode (Ditylenchus dipsaci) were found in 62% and 41% of sites respectively. The grass cyst nematode (Punctodera punctata) was present in 56% of 71 sites examined, and other grass cyst nematodes (H. bifenestra and species of the H. avenae group) occurred in 13% and 17% of sites. Two root‐knot nematodes were found, Meloidogyne naasi and M. hapla, in 15% and 4% of the samples examined. Migratory nematodes were extracted from 63 samples, and spiral, pin and lesion nematodes were found in more than 90%. Stunt nematodes were less frequent (65%) and criconematids (19%) were found relatively infrequently. The significance of these observations to grassland productivity is discussed.
Effects of field drainage on the growth of herbage and the liveweight gain of grazing beef cattle
Authors: TYSON K. C. , GARWOOD E. A. , ARMSTRONG A. C. , SCHOLEFIELD D.
Published: April 2006

A long‐term field grazing experiment was begun in 1982 to examine the impact of efficient field drainage on herbage and animal production from swards on an impermeable clay loam in the south‐west of England. Drained and undrained lysimeter plots (each of 1 ha) were established on the existing permanent sward and received annual applications of fertilizer N of 200 or 400 kg ha−1. Similar plots were initially ploughed and reseeded with Lolium perenne (cv. Melle), and received fertilizer N at an annual rate of 400 kg ha−1. All plots were continuously stocked by beef cattle and stock numbers were adjusted to maintain a constant sward height and to avoid poaching damage. Results for the first 5 years show that the benefits from drainage were modest and, for beef production, unlikely to pay for its costs over the shorter term. The main benefit was in spring when herbage dry matter yield was 11% greater on the drained plots, but with no significant interaction with fertilizer N level or sward type. This benefit was reduced to 3% on an annual basis, due to the effect of the larger soil water deficits sustained by the drained swards in mid‐season. Drainage increased the annual liveweight gain per ha by the grazing cattle by 11%. Possible mechanisms accounting for these effects are discussed in relation to the influences of seasonal patterns of weather.
The effect of an acid salt‐type additive on the fermentation of grass silages made in bunker silos on commercial dairy farms in Wales
Authors: HAIGH P. M.
Published: April 2006

The fermentation characteristics and chemical composition of 57 first‐cut and 30 second‐cut samples of grass silages, made in bunker silos on commercial dairy farms in Wales in 1990, and treated with a nominal 61 t−1 of an acid salt‐type additive at ensilage, is described. Typical chemical composition of grass cut for ensilage was 156 g kg−1 dry matter (DM) and 28 g kg−1 water soluble carbohydrate (WSC), with 181 g (kg DM) −1 crude protein (CP) and 232 g (kg DM) −1 modified acid detergent fibre (MADF). The effect of additive use was to produce silages with DM 230 g kg−1 pH 3·93, ammonia N 70 g kg−1 total N, with residual WSC 35 g (kg DM) −1, lactic acid 83 g (kg DM) −1, total acids 118 g (kg DM) −1 and butyric acid 0·7 g (kg DM) −1. No significant differences were found between first‐ and second‐cut silages. Silage fermentation was restricted (i.e. lactic acid less than 60 g kg DM−1) in only 20% of the samples.

It is suggested that on commercial farms the application rate achieved may be insufficient to produce a restricted fermentation.
Nutrient efficiency and cellular contents of phosphorus and nitrogen in Trifolium repens and a diploid and tetraploid Lotus uliginosus
Authors: HART A. L. , COLLIER W. A.
Published: April 2006

Two cultivars of white clover (Ladino and Kent Wild White) and two cultivars of lotus (Grasslands Maku and G4703) were grown in pots of soil at low to moderate levels of phosphorus (P) supply. Nitrogen supply was by fixation. Cell size and nitrogen, phosphorus and chlorophyll content per cell were estimated from samples of leaf tissue. Maku lotus had larger cells and higher cellular contents of metabolites than the clovers. These measurements support earlier suggestions that, compared with white clover, the higher P‐efficiency (dry matter per unit of internal P) of Maku lotus may be explained by cytological factors without recourse to explanations based on differences in nutrient metabolism. The relatively large cells and high metabolite levels per cell of Maku lotus appear to arise from its creation as an artificial tetraploid.
Proteolysis and amino acid degradation during ensilage of untreated or formic acid‐treated lucerne and maize
Authors: FAIRBAIRN R. L. , ALLI I. , PHILLIP L. E.
Published: April 2006

Lucerne (Medicago sativa), field wilted to 330 g dry matter (DM) kg−1, and whole‐plant maize (Zea mays), 383 g DM kg−1, were treated with formic acid (FA) at the rate of 4‐5 1 t−1 fresh forage. The effects of FA treatment on proteolysis and amino acid degradation was investigated at several intervals over a 90‐d period of ensilage in laboratory silos. Formic acid treatment produced different patterns of pH decline during ensilage of the two forages, suggesting some degree of crop specificity in response to FA treatment. After 7 d of ensilage of lucerne there were increases of 81% in nonprotein nitrogen (NPN), and 104% in free amino acid nitrogen (FAA‐N), but with FA‐treated lucerne the increases were 39% and 31%, respectively. FA treatment resulted in a reduction in the concentration of most free amino acids in lucerne silage, with the exception of glutamic acid and serine; the branched chain amino acids as well as glycine, tyrosine and proline were significantly (P<0·05) reduced after 3 d of ensilage. By contrast, FA treatment of maize did not significantly (p<0·05) affect the NPN content nor was there a consistent pattern in the changes in FAA‐N. Formic acid treatment of maize did produce a significant reduction (P<0·05) in the concentration of most individual free amino acids at 90 d of ensilage. Overall, FA treatment had a more predictable effect on proteolysis and amino acid degradation in ensiled lucerne than in ensiled whole‐plant maize.