bluuebunny/crossref_metadata_2025 huggingface dataset:
Effectiveness of cattle slurry as a sulphur source for grass cut for silage
Authors: LLOYD A.
Published: April 2006

Three trials were carried out in separate years during 1987–89 to investigate the effectiveness of cattle slurry as a source of sulphur (S) for grass cut four times per year for silage. They were located on different areas of the same field in Dorset, UK, in an area known to be sulphur deficient for intensive grass production. Yields of dry matter and S off takes in response to sulphur in slurry were investigated and compared with those from gypsum treatments supplying 0–100 or 0–75kg S ha−1. Slurry was applied at two times of year, November or February, and at two rates, either alone or in combination with the two lowest rates of gypsum.

Annual increases in yield from the slurry applied in February compared with the yield when no slurry was applied were significantly related (r2= 0·96) to the rate of slurry sulphur applied. For applications in November, the relationship was not significant. Sulphur in slurry increased annual dry‐matter yield with an average efficiency of 55% when compared with the sulphur in gypsum. The annual apparent recovery in the herbage of S from slurry was 21·8%, compared with 44·7% from the two lowest rates of gypsum.

Cattle slurry, in these and other trials in southwest England, contained on average 0·35 kg S m−3 and, at rates currently applied in farming practice or likely to be applied in the future, would be insufficient to satisfy annual requirements for silage in sulphur‐deficient areas.
Cell wall composition and degradability of stem tissue from lucerne divergently selected for lignin and in vitro dry‐matter disappearance
Authors: JUNG H. G. , SMITH R. R. , ENDRES C. S.
Published: April 2006

Lucerne populations that had previously been divergently selected for acid detergent lignin (ADL) concentrations of whole herbage were additionally divergently selected for in vitro dry‐matter disappearance (IVDMD) of basal stems. Parental plants of the four selected populations were intercrossed and the half‐sib progeny evaluated in a replicated field trial in 1988 over two harvests. Cell wall composition of basal stems was determined for detergent fibre components and neutral sugars, uronic acids, Klason lignin and esterified and etherified phenolic acids of the total fibre fraction. Lignin polymer composition was measured by nitrobenzene oxidation. Degradability of cell wall polysaccharide components was determined by a 48‐h in vitro ruminal fermentation. Cell wall composition was changed by both selection criteria. Klason lignin proportion of the total fibre did not differ as a result of selection, whereas the ADL concentration of neutral detergent fibre was different among selection groups. The cell wall polysaccharides of lucerne basal stems shifted towards more cellulose (glucose residues) and less hemicellulose (xylose residues) with selection for either low ADL or high IVDMD. While degradability of the cell wall polysaccharides was correlated with various measures of lignin composition and concentration, the results were variable and inconclusive. Surprisingly, Kiason lignin and ADL were positively correlated with cell wall polysaccharide degradability, and esterified ferulic acid was negatively correlated with degradation of the cell wall. Selection for herbage ADL and basal stem IVDMD of lucerne did alter cell wall degradation, but the associated changes in cell wall lignification were not consistently correlated with cell wall degradability.
Effect of nitrogen fertilization on herbage production of tall fescue swards continuously grazed by sheep. 2. Consumption and efficiency of herbage utilization
Authors: MAZZANTI A. , LEMAIRE G.
Published: April 2006

The effect of a reduced level of nitrogen fertilizer application upon the herbage consumption of a continuously grazed sward of tall fescue has been investigated during two successive years. Two contrasting cultivars were used and two levels of leaf area index were maintained on the swards in order to obtain a wide range of sward structure. The herbage growth, herbage senescence and herbage consumption were measured directly on labelled tillers. It was possible to estimate the different components of the defoliation process (frequency and intensity) at the level of individual tillers of each leaf category. The results show that the effect of reduction in N fertilizer on herbage consumption rate is proportionally more important than that on herbage growth rate. In consequence, the efficiency of herbage utilization in continuously grazed conditions is reduced when nitrogen nutrition becomes limiting for herbage growth. The data suggest that this phenomenon is not directly attributable to nitrogen deficiency but is an indirect effect owing to the reduction of the stocking density at the low N level, which leads to a lower frequency of defoliation of individual tillers.
The effects of management and plant variety on the composition, vertical structure and stock‐carrying capacity of Lolium perenne/Trifolium repens pastures
Authors: BARTHRAM G. T. , GRANT S. A.
Published: April 2006

The effects of sheep grazing, with or without a 7‐week rest period before ear emergence, on species balance in four perennial ryegrass/white clover swards were assessed.

Swards of an early (Aurora) or a late (Melle) flowering ryegrass were grown with either a small‐leaved (Kent) or a medium‐leaved (Milkanova) clover.

The clover lamina, expressed as a proportion of the total lamina mass, was greater with Kent than Milkanova. This proportion was not changed by resting the Aurora (earlier rest) swards, but was increased by resting the Melle (later rest) swards. A greater proportion of the clover lamina mass was near the top of the canopy in the Milkanova than in the Kent swards, and during the summer than in spring or autumn. The densities of clover growing points were greater in the Kent than the Milkanova swards and were increased by the late rest period. This effect persisted over the winter.

Stocking density was higher on the Kent than the Milkanova swards. The effects of the two rest periods, and the variety combinations, on pasture composition are interpreted as being principally a result of the differences in temperature between the earlier and later rest periods and of the different relationships between temperature and the growth of ryegrass and clover. Varietal characteristics, such as the vertical distribution of laminae, were also shown to be important.
Rumen degradation and intestinal digestion of grass and clover at two maturity levels during the season in dairy cows
Authors: STEG A. , van STRAALEN W. M. , HINDLE V. A. , WENSINK W. A. , DOOPER F. M. H. , SCHILS R. L. M.
Published: April 2006

A comparison was made of the effect of season and maturity on the in situ ruminal breakdown and intestinal protein digestion in dairy cows between intensively N‐fertilized grass (whole sward) and moderately N‐fertilized ryegrass and clover from a mixed sward. From May to September 1990, eight consecutive cuts were made, representing alternate harvests of late and early swards. Limited effects of fertilizer‐N on chemical and ruminal degradation characteristics and intestinal digestion of grasses were observed. Clover had higher ash, crude protein (CP) and lignin and lower hemicellulose, cellulose and sugar contents than grass. Moreover, soluble fractions of organic matter (OM) and CP were higher, and rumen‐undegradable OM and CP fractions were lower. Soluble fractions of grasses and clover decreased and undegradable fractions increased during the season. More mature swards showed increased undegradable fractions. Degradation rates of OM and CP in clover were, respectively, higher than or similar to those of grass. Seasonal effects on degradation rates differed between grass and clover. Effectively rumendegradable (g kg−1 DM) carbohydrates and CP, escaped protein and intestinal digestion of escaped protein were higher in clover than in grasses. Inclusion of clover in swards may result in higher post‐rumen protein supply. Supplementation of clover‐based diets is suggested to compensate for an increased loss of N in the rumen.
The effect of grass plant size on basal frequency estimates
Authors: COOK J. W. , BRADY W. W. , ALDON E. F.
Published: April 2006

Frequency data from different‐sized plots are generally accepted as being incomparable. However, how basal frequency data are influenced by plant basal diameter is not well known. Computer simulations were used to determine the influences of grass plant basal diameter on basal frequency data. Basal frequency, basal area and density were estimated with simulated 5 × 10 cm and 20 × 50 cm rectangular plots. Simulated plants had basal diameters ranging from 1.9 to 12.7 cm.

Basal diameter had a significant effect on the relationship between frequency and both basal area and density. As differences in plant size increase, the effect on basal frequency becomes larger and the likelihood of an ecologically important influence also increases. Thus, frequency data should not be used to compare relative abundance of species, unless corrections are made for differences in plant basal diameter among species. Additionally, frequency data should not be used to monitor change in abundance of a species through time, unless mean plant basal diameter can be assumed to remain relatively constant.

Basal frequency data could be used to ‘signal’ when change has occurred. Then, other sampling methods must be used to determine the nature and direction of change or relative species abundance. For frequency data, the simplicity of collection may be offset by difficulty in interpretation.
Aerobic deterioration of grass silage: the need to couple models and experiments
Authors: RUXTON G. D. , GIBSON G. J.
Published: April 2006

A mathematical model of the aerobic stability of grass silage is presented. The model is shown to predict as well as more complex models previously published. Sensitivity analysis performed on model parameters suggests that current understanding of the temperature dependence of yeast growth needs to be advanced in order to produce more accurate models of deterioration. Inhibition of yeast growth by organic acids is identified as a critical process worthy of further investigation. We discuss how model validation experiments must identify different yeast species and track their growth separately. Such experiments should also attempt to minimize or measure heat losses.
A note on the behavioural strategies used by grazing animals to alter their intake rates
Authors: NEWMAN J. A. , PARSONS A. J. , PENNING P. D.
Published: April 2006

A large, and often neglected, component of grazing intake is behavioural. Grazing animals may employ two strategies to increase their intake rates during grazing: increasing bite mass and decreasing handling time. These strategies are discussed in the context of fasted and non‐fasted sheep grazing white clover (Trifolium repens L. cv. Kent wild white) and perennial ryegrass (Lolium perenne L. cv. Parcour). It is concluded that within a forage species sheep have little flexibility for increasing their intake rates by altering their handling times but have some latitude for altering bite masses. Between forage species, differences in intake rates may be more strongly affected by the ‘species‐specific’ requirement for mastication than by differences in bite masses per se. Comparisons are also made with grazing strategies of cattle.
The effect of blending white clover varieties and their contribution to a mixed grass/clover sward under continuous sheep stocking
Authors: EVANS D. R. , WILLIAMS T. A. , JONES S. , EVANS S. A.
Published: April 2006

The effect of blending small‐ and medium‐leaved white clovers together in a mixture of varieties was examined under continuous sheep stocking over a period of three years. Four varieties were used, S184 and Gwenda, small‐leaved varieties suitable for intensive sheep grazing, together with medium leaved varieties Menna and Donna, which are mainly used in general purpose seed mixtures for medium term leys. The small‐leaved varieties were blended with Menna or Donna, sown with a commercial grass mixture and managed as near as possible to farm practice. Although the leaf size of Gwenda is only slightly greater than that of S184, blends based on these two small‐leaved varieties behaved differently. In spring of the first harvest year the yield of Gwenda and of the clover in mixtures containing Gwenda was 27% greater than the yield of the same mixtures which contained S184. As the season progressed this difference decreased. In terms of total annual yields and saving in fertilizer N, the benefits of including white clover in a seed mixture were more pronounced when Menna was mixed with S184 and Gwenda, rather than when Donna was used, although both varieties are in the medium‐leaf category. It was concluded that the slower establishment and the lower clover yield of S184, when compared with larger leaved varieties, can be overcome by blending with a variety that is slightly larger in leaf size, such as Menna, although the choice of variety may depend on sward management and its persistency under grazing.
Herbage intake and N excretion by sheep grazing monocultures or a mixture of grass and white clover
Authors: ORR R. J. , PENNING P. D. , PARSONS A. J. , CHAMPION R. A.
Published: April 2006

In 1988 and 1989, swards of grass (G0), while clover (C0) and grass/white clover (GC0) receiving no N fertilizer, and a grass sward supplied with 420 kg N ha−1 (G420), were grazed by non‐lactating sheep to maintain a sward surface height of 6 cm. Herbage organic matter (OM) intakes averaged between 1200 and 1700 g OM ewe−1 d−1. For treatments G0, C0, GC0 and G420 respectively, the ewes' live weight gain was 102, 112, 100 and 110 g d−1 and changes in body condition scores were +0·28, +0·52, +0·36 and +0·44 units season−1. However, the effect of treatment was not significant for either variable. There were similar levels of output of faecal N ewe−1 but significantly more urinary N ewe−1 was excreted on treatments C0 and G420, where the concentrations of N in herbage laminae were also higher. For example, in 1989, total daily N excreted was 39·7, 64·4, 44·0 and 63·3 g N ewe−1 for G0, C0, GC0 and G420 respectively. Taking into account the mean daily stocking rates, which were 19·4, 26·6, 27·2 and 36·5 ewe ha−1, the total faeces and urine returns over the season were 161, 358, 249 and 484 kg N ha−1 for each treatment respectively. The herbage OM intakes ewes−1 d−1 measured in September and October were similar for C0 and G420, and so the intake of herbage OM ha−1 d−1 was related to stocking rate, i. e. the estimated herbage intake ha−1 over the growing season for the white clover monoculture was 73% of that for N‐fertilized grass. Excretal nitrogen returns to the pasture from grazed mono‐cultures of clover were high, and similar to those from a grass sward receiving 420 kg fertilizer N ha−1. Consequently potential losses of N to the environment are high under these management systems.
Interactions between variety and the timing of conservation cuts on species balance in Lolium perenne‐Trifolium repens swards
Authors: BARTHRAM G. T. , GRANT S. A.
Published: April 2006

The effects of two periods of rest from grazing by sheep (either April‐May or May‐June) on the composition of swards of both an early‐flowering (Aurora) and a late‐flowering (Melle) perennial ryegrass variety grown with cither a small‐leaved (Kent) or a medium‐leaved (Milkanova) white clover variety are described. Compared with a continuously stocked treatment, the early rest period did not affect the mass of clover in the swards (expressed as a proportion of the total) but resulted in a subsequent decrease in its population density. The late rest period doubled clover mass in the swards at the time of cutting but did not affect the subsequent population density of clover. The magnitude of the change in mass during the late rest period depended on ryegrass variety, but not on clover variety. The adverse effect of the early rest period on the subsequent population density of clover was associated with the degree of shading experienced by clover laminae at the end of the rest period. Temperature may also have had an effect here as mean temperatures were cooler during the early rest period than during the late rest period. It is concluded that the effects of the two rest periods on the clover content of the swards were primarily due to timing, and less to inherent differences between ryegrass varieties.
Negative effects of winter‐ and spring‐applied cattle slurry on the yield of herbage at simulated early grazing and first‐cut silage
Authors: SMITH K. A. , JACKSON D. R. , UNWIN R. J. , BAILEY G. , HODGSON I.
Published: April 2006

Experiments were earned out on seven UK sites during 1985–1988 to evaluate the importance of negative effects (smoethering and scorch) of winter and spring‐applied cattle slurry on grass yield, assessed at the time of early grazing or first‐cut silage. Slurry application has both positive and negative effects on herbage growth. Positive effects, usually associated with herbage yield increases, derive from the nutrient value of the slurry. Negative effects, often resulting in herbage yield decreases, are caused by smothering and/or scorch. The net effect on herbage depends on the balance between these positive and negative effects. These experiments were designed to isolate the negative effects of slurry whilst attempting to minimize the positive effects. Yield reductions of up to 20% for early grazing and 5% for first‐cut silage were recorded, following applications of cattle slurry in February and March. Earlier applications smaller yield reductions. The threshold for the occurrence of yield reduction was estimated at 3–4 t ha−1 of slurry solids applied, at 6% solids content. In practice this would mean an application of 50–65 m3 ha−1 at 6% dry matter, which would supply 150–200 kg ha−1 total nitrogen, based on typical slurry analyses. Within the limits of application rates tested in these experiments, yield depression tended to increase with increasing rate of slurry applied above this threshold. Although the results suggest that the effects are more likely to occur following spring applications of slurry, earlier (autumn or winter) applications would increase the risk of losses of slurry nitrogen by leaching and denitrification. These results, therefore, confirm current advice in the UK that, where possible, cattle slurry is best applied to grassland in early spring according to the fertilizer needs of the crop. High rates of application should be avoided after early March for cutting areas and, more especially, for early grazing.
Animal production evaluation of herbage varieties.
Authors: DAVIES D. A. , FOTHERGILL M. , DANIEL G. J. , MORGAN C. T.
Published: April 2006

Perennial ryegrass/white clover (Lolium perennel Trifolium repens) pastures of three white clover varieties were compared at UK lowland (Plas Gogerddan, PG) and upland (Bronydd Mawr, BM) sites over three harvest years (1989–91) under continuous variable stocking (ewes and lambs until weaning and lambs thereafter). Mean annual lamb output from small‐leaved S 184 (1179 kg ha−1) was 29% greater than that from prostrate small‐leaved AberEndura at PG with medium‐leaved Huia also giving 19% more output than AberEndura. At BM, output from S 184 (863 kg ha−1) was 19 and 14% greater than that from AberEndura and Huia respectively. The differences in lamb output between the small‐leaved varieties owed to a combined effect of higher individual lamb growth rates and greater stock‐carrying capacity, both of which were more pronounced in the post‐weaning period. The higher output from S 184 relative to Huia at BM was attributed to higher stocking rate, particularly after weaning. Clover productivity and persistence were also studied under three cutting‐only managements at PG. Performance under a treatment cut at 2–3 cm every 10 d (T1), which is synonymous with assessment of persistence in UK National List testing, was poor with clover growing point number of only 498 m−2 compared with 4906 m−2 on the grazed sward in autumn 1991. Although productivity and clover content under T3 (cut at 3–4 cm every 42 d — similar to National List yield regime) gave the same varietal ranking as lamb production, there was an under‐estimation of the small‐leaved varieties, particularly AberEndura, relative to Huia. An intermediate treatment (T2), cut at 3–4 cm every 21 d, also over‐estimated the performance of the medium‐leaved variety. Herbage data from ground level sampling every 21 d using exclosure cages on the grazed swards were also poorly related to lamb performance. These results highlight the effect of clover variety on lamb production, which appeared to be independent of leaf size, and also confirm the existing problems associated with assessment of white clover varieties using a cutting regime.
The performance of summer‐calving cows grazing perennial ryegrass swards
Authors: FISHER G. E. J. , DOWDESWELL A. M.
Published: April 2006

The objectives of this experiment were to study the effects of different grazing managements in spring on herbage intake and performance of summer‐calving dairy cows and to examine the effects of regrowth in early June on herbage intake and cow performance. Four spring‐grazing treatments were applied to predominantly perennial ryegrass swards: Control (C), sward grazed by cows to 6–8 cm sward surface height (SSH); CG16, sward grazed by cows to 3–4 cm SSH in May and allowed to regrow to a target SSH of 16cm in early June; CG8, sward grazed by cows to 3–4 cm SSH in May and allowed to regrow to 8cm in early June; and SG8, sward grazed by sheep to 2–3 cm SSH in May and allowed to regrow to 8 cm in early June, All swards were continuously stocked by summer‐calving (May and July) primiparous and multiparous cows from 16 June to 7 September, to a target SSH of 8–10cm.

Spring treatments bad marked effects on herbage intakes and milk production. Estimated in July by n alkane analysis, the mean herbage intake ± s.e.d. of cows on each treatment were 1·8, 1·4, 1·4 and 3·0 ± 0·31 kg dry matter (DM) 100 kg live weight (LW)−1 d−1 (P < 0·01) for treatments C, CG16, CG8 and SG8 respectively. Measured in August, intakes were 1·8, 20, 2·1 and 2·4 ± O·33kg DM 100kg LW−1 d−1 respectively. Severe spring grazing led to increased milk yield and reduced milk fat content from summer‐calving cows fed 5·2 kg d−1 of a proprietary concentrate. Average milk yields for the eleven experimental cows on each treatment were 24·3, 23·4, 26·2 and 29·0 ± 1·20 kgd−1 (P < 0·01) for C, CG16, CG8 and SG8, and average milk fat contents were 45·4. 42·4, 43·9 and 40·9 ± 1·02gkg−1 (P<0·05) respectively.

The results suggest that severe grazing of swards in early season could improve herbage intake and milk yield of summer‐calving cows in mid‐ and late season. The most favourable spring treatment in this respect was severe grazing by sheep. However, this advantage could be negated in midseason by lax grazing at that time.
The nitrogen value of anaerobically digested sewage sludge applied to grassland during winter
Authors: EDGAR K. F. , KLESSA D. A. , FRAME J. , HARKESS R. D.
Published: April 2006

The manurial value of liquid anaerobically digested sewage sludge (LAS), surface applied once at four different times during winter to contrasting swards, was assessed over each of three growing seasons by comparison with fertilizer N. Four nominal rates of N (0, 18, 36 and 54 kg ha−1) were used based on the inorganic N content of LAS. Herbage dry matter (DM) and N uptake responses were measured by cutting three times per year.

Application of LAS in late winter compared with early winter led generally to greater N uptake and DM production. Herbage production response from LAS ranged from 5·4 to 30·1 kg DM kg−1 N; within this range, larger responses were obtained from a sown sward than from permanent pasture. The apparent efficiency of LAS compared with fertilizer N ranged from 0·41 to 0·88 (permanent pasture) and 0·20 to 0·77 (sown sward) but occasionally mean apparent efficiencies of over 1·0 occurred because fertilizer N was poorly recovered. There was no residual effect on annual N uptake from applying sludge. It is concluded LAS is a useful nitrogenous manure when applied to grassland in late winter/early spring but more research is needed to elucidate the importance of pathways of N losses following the surface application of LAS, and to quantify these losses.
Effect of rainfall and temperature on yield of Vicia sativa under rainfed Mediterranean conditions
Authors: PAPASTYLIANOU I.
Published: April 2006

The productivity of Vicia sativa grown in rotation with barley under rainfed Mediterranean conditions was examined at two locations over several years (eighteen location × year situations). Rainfall during the growing season ranged from 200 to 500 mm. Vetch relied on indigenous rhizobia for nodulation and N fixation while for phosphorus it was fertilized with 20kgPha−1. Harvesting took place at the beginning of pod formation. The dry matter (DM) yield reached 6·6t ha−1 and the N offtake 215 kg ha−1. The highest yields were obtained when rainfall exceeded the 350 mm level. The N concentration of the forage was not influenced by rainfall or by the productivity of the plants. Yield of DM was related to the number of days of ground frost in January but not in February and March. Monthly minimum and maximum temperature was not related to the DM yield. The combination of monthly rainfall and temperature explained over 95% of the variation in yield.
The effects of stocking rate in spring, and topping on sward characteristics and dairy cow performance in a poor grass growing season
Authors: FISHER G.E.J. , ROBERTS D.J.
Published: April 2006

A comparison was made under continuous grazing between applying a high stocking rate in spring (H) to maintain the sward surface height (SSH) of a perennial ryegrass pasture at 5–6 cm and a low stocking rate (L) to maintain SSH at 10–12cm with mechanical topping in mid‐June. The experiment was carried out in the dry season of 1989 and a lack of rainfall markedly affected the treatments and consequently animals were offered supplementary concentrate and forage in July to compensate for reduced grass intake and low SSHs.

Treatment H maintained the density of live grass tillers and live: dead tiller ratio in mid‐and late season, compared with the L treatment. The measured interval between defoliation of individual grass tillers was significantly less in the L pasture in samplings taken between 2 May and 29 August. January/February calving cows on the L pasture produced significantly more milk cow−1 with higher concentrations of protein and lactose, but less milk ha−1 compared with cows on the H sward. The results indicate that topping of a laxly grazed sward in drought conditions has no positive effects on sward characteristics or milk production.
Opportunities for reducing the environmental impact of dairy farming managements: a systems approach
Authors: JARVIS S. C. , WILKINS R. J. , PAIN B. F.
Published: April 2006

Dairy farming systems are important sources for the emission of a number of materials that include various forms of nitrogen (NO3−, N2O and NH3) with potential environmental impact. The present paper is a systems synthesis study and assesses the likely impact of changes in management on N flows and losses. These include tactical fertilizer adjustment, slurry injection, maize silage production and the use of white clover as an alternative to fertilizer N. Implications for greenhouse gases (N2O and CH4) and support energy have also been considered. Substantial reductions in inputs and total and proportional losses by all die options considered were predicted by this study. Thus, using a tactical approach to fertilizer application and injecting slurry or using 50% maize silage reduced overall N losses from 160 (under conventional management) to 86 and 109kg Nha−1 respectively. Combining both possibilities reduced losses further to 69 kg ha−1. Although use of white clover, especially at low contents in the sward, was the most effective regime to reduce losses, this was at some cost to production so that losses per livestock unit (LU) did not always differ from those under other managements. Changing the N management had consequences for greenhouse gas emission with an estimated maximum 70% reduction in N2O release. The effects on CH4 emissions were relatively small. Substantial reductions in support energy costs were also obtained: these arose mainly from the reduction in fertilizer N use, which represented 66% of the total support energy in the original system.
The effect of timing of slurry application on the microflora of grass, and changes occurring during silage fermentation
Authors: DAVIES D. R. , MERRY R. J. , BAKEWELL E. L.
Published: April 2006

Cattle slurry (50 m3 ha−1 equivalent to 68 kg N ha−1) was applied to grassland plots 70 d (early application) and 34 d (late application) before ensiling and the retention and survival of slurry and epiphytic micro‐organisms on the growing herbage were examined and compared with those on herbage from corresponding fertilizer‐treated plots. The populations of lactic acid bacteria, enterococci and enterobacteria on herbage increased dramatically after slurry application. Thereafter, numbers of lactic acid bacteria declined, although they were always higher than on untreated herbage. Number of enterobacteria also declined but were higher on chopped grasses at ensiling [106 colony‐forming units (CFU) g−1 fresh matter (FM)] than they were on hand‐cut. unchopped herbages at all previous sampling times. Clostridia numbers were lowest on untreated and highest on slurry‐treated herbage, particularly after the late application (>103 CFU g−1 FM). Herbage was harvested 70 d and 34 d after slurry application, chopped and ensiled in laboratory silos. All herbages, irrespective of treatment, had low dry matter (DM) values (ranging from 149 to 170 g kg−1 FM) and fairly low water‐soluble carbohydrate (WSC) concentrations (130 g kg−1 DM or less). The initial rate of pH decline up to 4 d was most rapid in slurry‐treated herbages, with all pH values falling to < 4. 5 by day 4 and remaining there until day 21. However, after 90 days the pH values of all silages had risen to > 4. 5. accompanied by a marked decline in lactic acid concentration. Lactic acid‐fermenting Clostridia increased in numbers, reaching peak values of 107 CFU g−1 FM by day 21, remaining high until opening, and were probably responsible for increases in butyric acid levels in all silages, with the highest concentrations occurring in those prepared from slurry‐treated herbages. The results suggest that, although some faecal lactic acid bacteria may have beneficial effects in the early stages of fermentation, Clostridia from slurry can survive on herbage for extended periods. The results indicate that the potential for growth of Clostridia in silage may be independent of source or size of the initial population even at tow pH, if other conditions are favourable.
Effects of interval between harvests and application of fertilizer N in spring on the growth of perennial ryegrass in a grass/white clover sward
Authors: WILMAN D. , FISHER A.
Published: April 2006

A perennial ryegrass/white clover sward, which had been grazed for over 2 years, was cut at 1‐, 2‐, 3‐ or 6‐week intervals from 18 April to 28 November 1986. Two rates of fertilizer N application in spring, 0 and 66 kg N ha−1, were compared. Perennial ryegrass growth was studied in three 6‐week periods, beginning on 18 April, 18 July and 17 October. Clover growth was studied in the same three periods and described by Fisher and Wilman (1995) Grass and Forage Science, 50, 162–171.

Applied N increased the number of ryegrass tillers m−2, the rate of leaf extension and the weight of new leaf produced tiller−1 and m−2per week. Increasing the interval between cuts reduced the number of ryegrass tillers m−2 and increased the rate of leaf extension, weight tiller−1and the weight of new leaf produced tiller−1week−1. Increasing the interval between cuts increased the weight of new ryegrass leaf produced m−2 where N had recently been applied, but otherwise had little effect on the weight of new leaf produced m−2. Applying N favoured the grass in competition with the clover in every respect, whereas increasing the interval between cuts only favoured the grass, compared with clover, where N had recently been applied; where N had not been applied, the ratio of ryegrass tillers to clover growing points in the sward was very little affected by the interval between cuts.
Use of bovine somatotropin for milk production: the effect of time of treatment initiation on milk production of Holstein/Friesian dairy cows placed on a high‐forage, low‐concentrate feeding system
Authors: PHIPPS R. H. , ADRIAENS F. , HARD D. L. , DE KERCHOVE G. , WELLER R. F.
Published: April 2006

Sixty multiparous Holstein/Friesian cows were used in a 2 × 2 factorial design trial to determine the effect of the administration of bovine somatotropin (BST), at either 60 or 120 ± 3 d post partum, on milk production. All cows were offered ad libitum a forage mixture containing, on a dry‐mailer (DM) basis, grass and maize silage in a 1:1 ratio and 4 kg d−1 fresh weight of concentrate, which contained 115 and 495 g kg−1 DM of neutral detergent fibre (NDF) and crude protein (CP), respectively, and 13–5 MJ kg−1 DM metabolizable energy (ME). BST‐treated cows received subcutaneous injections of a prolonged‐release formulation of BST (sometribove). Injections were administered into the ischiorectal fossa at 14‐d intervals for the remainder of the lactation. This schedule resulted in sixteen and twelve injections cow−1 when treatment w as in it rate d at 60 and 120 + 3 d post partum respectively. This corresponded to treatment periods of 32 and 24 weeks, in which the production responses were measured. When compared with control cows, the administration of BST from 60 and 120 ± 3 d post partum increased mean milk yield by 1–2 and 3.3 kg day−1 respectively, although only the latter milk‐yield response was significant (P <0.001). The administration of BST produced a small nonsignificant increase in DM intake, no effect on milk composition and a small but significant reduction in body condition In conclusion a significant milk‐yield response can be obtained from the use of BST in high‐forage, low‐concentrate feeding systems if forage quality is high and treatment initiation is delayed until mid‐lactation. This is illustrated by the fact that the lactation yield increased from 6054 to 6842 kg. and was obtained when using only 1.2 t of concentrate.
The use of repeated‐measurements analysis to describe the overwintering of white clover cultivars
Authors: COLLINS R. P. , FOTHERGILL M. , POTTER J. F. , RHODES I.
Published: April 2006

An experiment was set up to investigate the morphological and physiological changes occurring in two white clover (Trifolium repens) (clover) varieties, AberHerald and Huia, growing in binary mixture with two perennial ryegrass (Lolium perenne) (grass) varieties, Preference and Ba 10761. Measurements were made on four occasions during winter/spring 1993–94. The statistical procedure of antedependence analysis was used to check for the existence of serial correlations among data from the different sampling dates. Evidence of antedependence was found in only three of the seventeen variables measured, and an order of antedependence for each of these was estimated. The antedependence structure providing the best fit to the data was then used in an analysis of covariance on the data set for that variable. The rest of the seventeen variables could be safely analysed by a split‐plot analysis of variance for each sampling date separately. This result validated the sampling protocol used in the experiment.
The effects of sward characteristics and supplement type on the herbage intake and milk production of summer‐calving cows
Authors: FISHER G. E. J. , DOWDESWELL A. M. , PERROTT G.
Published: April 2006

High (H; 27 350 m−1:) or low (L. 13 300 m‐1) tiller density perennial ryegrass swards were created in the mid‐ and late grazing season by imposing different sward heights in the spring. Summer‐calving cows then grazed these swards from 6 June to 2 September 1992 and were offered 5 kg fresh weight hd−1 d−1 of either a barley (S) or a molassed sugar beet pulp (F) based supplement. The factorial combination of sward and supplement types resulted in four experimental swards being grazed by thirteen Holstein/Friesian cows each.

Supplement F contained more crude fibre (110 vs. 58 g kg−1) and less metabolizable energy [12–5 vs. 13–2 MJ kg−1 dry matter (DM)] than supplement S. Herbage on the H sward contained more metabolizable energy (11–9 vs. 104 MJ kg−1 DM) and crude protein (232 vs. 205 g kg−1 DM), had fewer rejected areas f 16–5 vs. 26–9%) and a higher live‐dead tiller ratio (4–6 vs. 2–1) than that on the L sward.

Sward, but not supplement type, significantly affected the intake of grazed herbage (P<0–001). On average, the herbage intakes of cows grazing II swards were higher than for L swards (14–5 vs. 11 6kg DM d−1) and those of cows on the S and F supplements were 12–6 and 13–5 kg DM d−1 respectively. Averaged over the grazing period, sward and supplement had no significant effects on milk yield, milk composition or yield of constituents. When expressed on an average weekly basis, cows grazing an L sward and offered the F supplement on occasions had significantly lower milk yields and higher milk fat contents (P<005) than those grazing an H sward and offered the S supplement. There were no significant effects on cow live weight or condition score change. The results suggested that grazing swards with a high density of live tillers increased herbage intakes and on occasions milk yield, relative to low density swards. However, small increases in energy intake from sward and supplement effects were used primarily to ameliorate liveweight loss.
The effect of age of the sward on the relationship between water‐soluble carbohydrate accumulation and drought survival in two contrasted populations of cocksfoot (Dactylis glomerata L.)
Authors: VOLAIRE F. , GANDOIN J. M.
Published: April 2006

In Mediterranean drylands, drought survival is a major factor of persistence of perennial forage grasses. In the island of Corsica, plant survival and changes in water‐soluble carbohydrate (WSC) content were investigated in first‐ and second‐year swards of two populations of cocksfoot: Lutetia, a drought‐sensitive cultivar, and KM2, a drought‐resistant Mediterranean population. When subjected to a moderate drought under a rain‐shelter. Lutetia died whereas KM2 recovered with low mortality. The sensitivity of survival to the date of defoliation is emphasized. In first‐year swards, WSC content in entire tiller bases at the end of the drought was four times greater in KM2 than in Lutetia and was correlated with differential recovery in the two populations. Conversely in second‐year swards, no relationship between WSC content in entire tiller bases and recovery was found. However, WSC content in the youngest living enclosed leaves of KM2 accumulated to reach 63% of dry matter (DM) whereas in Lutetia WSC fell below 30% of DM; this factor might be associated with its survival. In both tiller bases and enclosed leaves, sucrose content and the content of large fructans tended to increase over the summer, whereas monosaccharide content declined. Enclosed leaves are the main survival organs: their role as a sink for translocated material (sucrose) and as a site of fructan accumulation is discussed.
Grass silage as a basic feed for store lambs. 3. Effect of barley supplementation of silages varying in chop length on silage intake and lamb performance
Authors: FITZGERALD J. J.
Published: April 2006

An experiment was carried out to study the effect of silage chop length and barley supplementation on silage intake and the performance of store lambs. The silages were cut from a perennial ryegrass regrowth at a relatively mature stage of growth in early July. Different types of harvester were used to produce a long silage (L), single‐chopped (S), double‐chopped (D), medium precision‐chopped (MP) or a short precision‐chopped (SP) silage. The chop length of the silages averaged 37.4, 12.4, 8.4, 7.0 and 2.9 cm respectively. All silages were treated with formic acid at 2.51 t−1grass. They were well preserved and of a good quality with a dry‐matter (DM) digestibility of 720–760 g kg−1 DM. The silages were fed ad libitum to Suffolk crossbred store lambs over a period of 10 weeks. Each silage was fed either alone or was supplemented with whole barley at 400 g lamb−1 d−1.

When offered silage alone, intakes were 738, 679, 773, 980 and 910 (± 30) g DM d−1 for silages L, S, D, MP and SP respectively. Similar relative differences in intakes between the silages were evident when supplemented with barley. Liveweight gain on silage alone was higher on the precision‐chopped silages (85–93 g d−1) than the long or flail‐chopped silages (28–49 g d−1). Liveweight gain on the precision‐chopped silages was also better when supplemented with barley (150 vs. 90–112 (± 90) g d−1). Silage intake and lamb performance were similar for the MP and SP silages, despite the difference in chop length.

Barley supplementation reduced silage intake to a similar extent for all silages (‐9%) and increased total DM intake (+ 30%) and metabolizable energy intake (+ 37%). The substitution rates of silage for barley were similar for all silages and averaged 0.24 g silage DM g−l barley DM. The response in weight gain per 100g of barley fed was similar for all silages and averaged 20.0 g liveweight gain and 13.4 g carcass gain. Feed conversion efficiency of the total diet was similar for the Mail‐chopped and precision‐chopped silages but was less for the long silage.

The results of this study show that the benefit in weight gain due to the higher intake of precision‐chopped silage was maintained when the silage was supplemented with a moderate level of barley. Such silage required supplementation with barley (400 g d−l) to achieve a rate of liveweight gain of 150g d−1.
Response of perennial ryegrass varieties to annual changes in sward management
Authors: GILLILAND T. J.
Published: April 2006

The effect of annually switching sward management between cutting regimes that simulated rotational grazing and those for forage conservation vs. maintaining a constant management regime was studied by testing for ranking‐order changes between six perennial ryegrass varieties.

Total dry‐matter (DM) yields were found to change in response to an annual switch in management. When under a conservation management and switched in the next year to simulated grazing, all six varieties yielded more in that year than when they were maintained constantly under simulated grazing. Similarly, when under a simulated grazing management and switched in the next year to conservation, all six varieties yielded less than when maintained constantly under a conservation management. These yield differences were largely expressed in spring of the year following the management switch.

Differences in the ranking order of varieties were observed between the constant sward management treatments and the alternating managements. However, in these changes in variety ranking, no variety was consistently favoured or disadvartaged by the annual switch in management. Therefore, no clear evidence was produced that an alternating management system had any consistent effect on variety ranking and the observed changes were possibly due to the normal year‐to‐year variation frequently recorded in variety performance trials.
The effects of regrowth and maintenance height on a grass sward with a high density of tillers
Authors: FISHER G. E. J. , DOWDESWELL A. M.
Published: April 2006

A perennial ryegrass sward was grazed by sheep in April 1993 to a target sward surface height (SSH) of 3 cm to create a high density of grass tillers. From 3 May, the sheep were removed and small plots were established on the sward, when the average tiller density (± s.e.) was 35 900 ± 420 live tillers m−2. Different regrowth treatments were then imposed by allowing plots to regrow to target SSHs of 6 cm (18 g dry matter (DM) M−2), 9 cm (78 g DM m−2), 12 cm (132 g DM m−2) or 15 cm (197 g DM m−2). The plots were then maintained by cutting at either 6 or 9 cm SSH until the end of the experiment on 30 September. Live tiller density was reduced by regrowth beyond 8.9 cm (78 g DM m−2, P<0.001) and leaf‐stem ratio and in vitro organic matter digestibility were reduced by regrowth beyond 6.1 cm (18 g DM m−2, P < 0.05). The effect on live tiller density was sustained through the remainder of the season. From the beginning of June to the end of September, maintenance of SSH at an average of 9.1 cm compared with 6.4 cm also resulted in lower live tiller density, live‐dead tiller ratio and leaf‐stem ratio and higher herbage mass (at least P< 0. 05). There were significant interactions between regrowth SSH and maintenance SSH, so that leaf‐stem ratio, live‐dead tiller ratio and live tiller density were reduced by regrowth to a SSH of 16–4 cm followed by maintenance at 9.1 cm, compared with regrowth to 6.1 cm and maintenance at 6.4 cm.
Soil compaction effects on second‐harvest yields of perennial ryegrass for silage
Authors: Douglas J. T.
Published: April 2006

Variation in dry‐matter yield at second harvests was studied in a long‐term comparison of wheel traffic systems and soil compaction in grassland for silage in Scotland. Yields were obtained from compacted soil subjected to conventional traffic (C), from less compacted soil in a reduced ground‐pressure traffic system (R) and from non‐compacted soil in a zero‐traffic system (Z). Relationships between the ratios of second‐harvest yields, C2/Z2 and C2/R2, and a number of soil, rainfall and crop parameters were tested by correlation analysis. The yield ratios increased significantly with the number of days after mowing before 2 mm of rain fell in 1 d (r= 0·923*** and 0·715*, for C2/Z2 and C2/R2 respectively), and C2/Z2, but not C2/R2, decreased with increasing amount of rainfall in the 14 d after first mowing (r= 0·787*). It was concluded that yield from compacted soil was greater than that from non‐compacted soil because the former depended less on rainfall in the weeks after first mowing. The degree of soil compaction in the reduced ground‐pressure traffic system, although maintaining first‐harvest yield benefit, reduced the risk of significantly diminished yield at second harvest in dry summers.