bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of forage preservation method and proportion of concentrate on digestion of cell wall carbohydrates and rumen digesta pool size in cattle
Authors: HUHTANEN P. , JAAKKOLA S.
Published: April 2006

Six bulls with ruminal and duodenal cannulae were used in a 6 × 6 Latin square design with a 2 × 3 factorial arrangement of treatments. Barn‐dried grass (G) and direct‐cut silage (S) from the same sward were fed together with 250 (L), 500 (M) and 750 (H) g kg‐1 total dry matter (DM) of a barley‐based concentrate (barley 875 and rape‐seed meal 125 g kg‐1) at the level of 80 g DM kg‐1 live weight0·75. Rumen and total digestibility of cell wall constituents were measured by a double marker and total collection method. Rumen pool sizes of dietary constituents were estimated by emptying the rumen. Particle‐associated enzyme activities were measured from rumen particulate material and feed particles incubated in nylon bags in the rumen.

Neutral detergent fibre (NDF) and hemicellulose digestibility were higher (P<0·05) for G diets than for S diets while no differences were observed between the forages in acid detergent fibre (ADF) and cellulose digestibility. Both rumen and total digestibility of cell wall constituents decreased with increasing level of concentrate. The proportion of total cell wall digestion in the rumen was unaffected by the forage preservation method and the proportion of concentrate. NDF, and especially cellulose digestibility, declined quadratically with increasing level of concentrate. Dietary effects on particle‐associated carboxymethylcellulase and xylanase activity were consistent with those observed in cell wall digestion. There were no differences between the forages in rumen pool size of total ingesta or any dietary constituent. Rumen pool size of total ingesta decreased with increasing level of concentrate. On the other hand, DM content of ingesta increased with the level of concentrate, while the pool size of DM, NDF and ADF declined quadratically reaching a minimum on M level of concentrate. The differences in rumen NDF pool size were mainly in the digestible fraction. Calculation of digestion kinetic parameters showed that both the rate of passage and especially the rate of digestion were markedly depressed in animals fed on the highest level of concentrate. The results suggest that a reduced fate of digestion of NDF with high concentrate diets can be partially compensated for by an increased NDF retention time in the rumen of animals fed at a restricted level of feeding.
Influence of growth stage and season on the energy value of fresh herbage. 2. Relationships between digestibility and metabolizable energy content and various laboratory measurements
Authors: GIVENS D. I. , MOSS ANGELA R. , ADAMSON A. H.
Published: April 2006

This paper gives details of a study which has examined the effect of herbage growth type and season on the relationships of digestible organic matter in the dry matter (DOMD) and metabolizable energy (ME) contents measured in vivo to various laboratory measurements including three in vitro estimates of DOMD based on rumen fluid pepsin (RFP), pepsin cellulase (PC) or neutral detergent cellulase (NCD). Seventy herbages harvested over two years and comprising 32 spring primary growths, 14 summer regrowths and 24 autumn growths were used.

For DOMD in vivo, significantly different regression relationships were required for spring and autumn‐harvested herbage. Equations based on PC were:

Spring herbage: DOMD (g kg‐1 DM) = 436 + 0·501 PC (g kg‐1 DM) 2= 76·7%; r.s.d. = 25·4

Autumn herbage: DOMD (g kg‐1 DM) = 594 + 0·195 PC (g kg‐1 DM) 2= 15·5%; r.s.d. = 23·1

For autumn herbages there were no significant relationships with ME. As with DOMD in vivo the PC method was shown to provide the most accurate relationship with ME concentration of spring herbage. The relationship was:

ME (MJ kg‐1 DM) = 6·16 + 0·0094 PC (g kg‐1 DM) 2= 69·8%; r.s.d. = 0·57

For both DOMD and ME the relationships for spring herbage based on PC were the only ones which did not differ significantly from those of an earlier study.

It is concluded that even where significant relationships for summer and autumn herbages were developed, the predictors accounted for substantially less of the variability than in spring herbages. This appeared to be largely due to reduced range in the DOMD and ME content in summer and autumn herbages.
Seed development and seed yield potential of Italian ryegrass (Lolium multiflorum Lam.) populations
Authors: HIDES D. H. , KUTE C. A. , MARSHALL A. H.
Published: April 2006

Greenhouse and field experiments were carried out to study the seed development and seed yield potential of three populations of Italian ryegrass (Lolium multiflorum Lam.). These included an ecotype (Bb 1276) collected in the Lombardy Plain region of northern Italy, cv. Tribune, which was derived from this ecotype, and cv. Lemtal, a widely used cultivar from Belgium. Artificial seed shedding techniques in the green‐house study showed that Bb 1276 began shedding seed at a higher moisture content than cv. Tribune which in turn was higher than cv. Lemtal. The pattern and rate of shedding was similar for all three populations and generally Bb 1276 and cv. Tribune gave a greater proportion of shed seed than cv. Lemtal. Although the pattern of decline in seed moisture content was similar for all three populations, generally cv. Lemtal had a higher moisture content than cv. Tribune with Bb 1276 the lowest. Cultivar Lemtal had the highest mean 1000 seed weight, and Bb 1276 the lowest, with cv. Tribune intermediate. The field study involving cv. Tribune and cv. Lemtal showed that with the exception of 1000 seed weight, which for cv. Tribune was some 6% lower than that of cv. Lemtal, all the seed yield components were similar. Seed yields taken every 3 days after the standing crop had reached 50% moisture content showed that both cultivars increased in yield until harvest 3. After this date the seed yield of cv. Lemtal remained stable up to harvest 5 while that of cv. Tribune declined. The maximum seed yield of cv. Tribune was achieved at a seed moisture content of 42·9% while that of cv. Lemtal remained stable from 42·3% to 37·5%. The seed moisture content of the two cultivars again showed a similar pattern of decline but it was not possible to show consistent differences between cv. Lemtal and cv. Tribune. The 1000 seed weight of cv. Tribune was lower than that of cv. Lemtal, and the maximum seed weight of cv. Tribune appeared to be achieved earlier. Germination counts taken after harvest showed both populations exhibiting a high level of post harvest dormancy. Later counts taken 3 months after harvest were significantly higher than those taken earlier and there were no differences between cultivars or harvests.

The results are discussed in relation to the potential for selecting for improved seed yield potential in Lolium multiflorum Lam. Populations from northern Italy and suggestions are made for maximizing the harvested seed yield of cv. Tribune.
Sodium fertilizer application to pasture. 1. Direct and residual effects on pasture production and composition
Authors: CHIY P. C. , PHILLIPS C. J. C.
Published: April 2006

Results are given on the effect of sodium (Na) fertilizer applied as NaNO3 in five application sat 0 (Nil), 32 (Low) or 64 (High) kg Na ha ‐1yr‐1 and the residual effect of sodium chloride(NaCl) fertilizer applied in the previous year on the growth rate and the chemical composition of herbage cut at fortnightly intervals over the grazing season.

Na fertilizer at Low and High rates increased herbage Na contents by 20 and 40% respectively. Magnesium (Mg) content in herbage was increased at Low Na fertilizer application rate but there was no difference between the Nil and the High Na treatments. Calcium (Ca) content was increased in proportion to Na fertilizer level. Potassium (K) content of Nil Na herbage exceeded that of Low and High, but there was no effect of treatment on total harvested K yields. The contents of phosphorus (P), sulphur (S), true protein (TP) and modified acid detergent fibre (MADF) in herbage were not affected, but the dry matter digestibility (DMD) was increased with increasing Na fertilizer level. Applying Na fertilizer at the Low and High levels gave similar increases in water‐soluble carbohydrates (WSC) and ash contents and decreased crude protein (CP) and non‐protein nitrogen (NPN) contents. Net herbage accumulation(fresh and dry weight) was increased by 15 and 26% at the Low and High Na fertilizer application rates respectively.

NaCl fertilizer residues from the previous year increased herbage Na, DM, DMD and WSC contents, reduced K contents and did not affect Ca, P, S, CP, TP and NPN contents. Residues from Na fertilizer decreased MADF and ash contents at the Low and High Na application rates.

The main and residual effects of Na fertilizer were generally maximal in early season and diminished as the season progressed, with many of the effects eliminated by late season. Proportionally 0·70 of Na applied was recovered in the first two grazing seasons after application. The effects of Na fertilizer on mineral ratios are also described, together with the implications for animal health.
A comparison of diploid and tetraploid perennial ryegrass and tetraploid ryegrass/white clover swards under continuous sheep stocking at controlled sward heights. 1. Sward characteristics
Authors: SWIFT G. , VIPOND J. E. , McCLELLAND T. H. , CLELAND A. T. , MILNE J. A. , HUNTER E. A.
Published: April 2006

Two 1·0 ha plots of a late‐heading diploid perennial ryegrass (var. Contender) and a late‐heading tetraploid ryegrass (var. Condesa), and two 1·4 ha plots of the tetraploid with Aberystwyth S184 small‐leaved white clover, were direct sown in May 1987. Over the three years 1988–90 they were continuously stocked by Mule ewes with Suffolk‐cross twin lambs, from early April to the end of August, at a target sward surface height (SSH) of 4–6 cm on one set of plots (constant swards) and, on the other set, al 4–6 cm rising after June to a target 6–8 cm (rising swards). The heights were achieved by variable stocking. Fertilizer N was applied only to the grass plots at the rate of 150‐ 180kgN ha‐1 annually.

SSH was mainly within the target 4–6 cm, after higher initial heights at turnout in 1988and 1990. Mean heights of the constant swards (April‐ August) averaged 5·53, 4·43 and 5·04cm in the three years. The rising swards (July‐August) increased in height over the constant swards by an average of 0·88, 0·48 and 0·55 cm, in successive years.

Clover content of the herbage mass dry matter in the grass/clover swards increased over each grazing season to average 13·0, 26·5 and 21·2% in the three years, with a high mean stolon density of 130 in m‐2 in August 1990. Ryegrass tiller densities in year 3 were 23% higher in the diploid than in the tetraploid swards, which had 43% more than the 10000 tillers m‐2 of the tetraploid ryegrass/clover swards.

It is concluded that the combination of a densely stoloniferous small‐leaved clover with the open growth habit of a tetraploid ryegrass can achieve swards of high clover content under continuous sheep stocking.
Performance of morphologically diverse orchardgrass clones in spaced and sward plantings
Authors: BUXTON D. R. , LENTZ E. M.
Published: April 2006

This study was conducted to determine effects and interactions of plant density on digestibility and plant morphology of diverse orchardgrass (Dactylis glomerata L.) clones. Propagules of ten orchardgrass clones with contrasting morphology from two maturity groups (inflorescence emergence differed by 8d) were evaluated in sward (0·15‐m centres) and spaced (0·60‐m centres) plantings. Plants were harvested from spring growth on a common date near anthesis and from summer growth when about 5 weeks of forage growth had accumulated. The plants were separated into morphological parts before measuring their size and in vitro digestible dry matter (IVDDM). There were few plant density × orchardgrass clone interactions, and correlation coefficients of clones grown at the two plant densities generally were high (e.g. 0·87 in spring and 0·67 in summer for IVDDM of total herbage). Plant density had little effect on morphology of leaf blades from reproductive tillers, but leaf blades of vegetative tillers were 12% (spring) and 22% (summer) longer from sward than from spaced plantings. Moreover, reproductive tillers were 26% taller in sward than in spaced plantings. Also, leaf blades of vegetative tillers in spring growth were more than twice as long, of similar width and 65% thicker than leaf blades from reproductive tillers. Because divergent genotypes respond similarly to plant density, it is concluded that observations taken in spaced plantings of orchardgrass can be used to make inferences about relative differences in sward plantings for the traits studied.
Response of permanent and reseeded grassland to fertilizer nitrogen. 2. Effects on concentrations of Ca, Mg, K, Na, S, P, Mn, Zn, Cu, Co and Mo in herbage at a range of sites
Authors: HOPKINS A. , ADAMSON A. H. , BOWLING P. J.
Published: April 2006

The concentration of mineral elements in herbage from permanent swards of mixed species composition (predominantly Agrostis spp., Holcus lanatus, Festuca rubra, Lolium perenne, Poa spp., etc.) was compared with that from sown perennial ryegrass (Lolium perenne) at two fertilizer rates (0 and 300kg N ha−1 year−1, both with P and K) and with L. perennel Trifolium repens (at 0 N with P and K). The investigation was conducted over four years at sixteen contrasting sites in England and Wales. Herbage samples for mineral analysis were taken at first and fourth harvests (May and August) each year from plots under 4‐weekly cutting. There was a wide degree of variation between sites, particularly for concentrations of Ca, Mg, Na and all trace elements analysed. Herbage from L. perenne reseeds had significantly higher concentrations of Ca, Mg, Na, Co and S, but K, Mo, Zn, Cu and P were generally lower than in the permanent swards. L. perennel T. repens swards had the highest concentration of major cations, but trace element levels were generally intermediate between those for 0 N permanent and L. perenne swards. Fertilizer N reduced concentrations of Ca, Mn, Mo and S, and increased Mg, Na and Zn, with no consistent effects on K, Co and Cu. Herbage at harvest 4, compared with harvest 1, had higher Ca, Mg, Na, Mn, Zn and S. Permanent and L. perenne swards responded similarly to fertilizer N and between harvest dates. Results are discussed in relation to previous reports of botanical and fertilizer effects on mineral concentrations, and the mineral requirements of livestock. Changes in mineral concentration resulting from reseeding permanent swards are considered unlikely to increase mineral‐related livestock disorders, and in many cases could be beneficial, though problems might arise on sites where some elements, e.g. Cu and Mg, are low.
The implications of controlling grazed sward height for the operation and productivity of upland sheep systems in the UK. 1. Effects of two annual stocking rates in combination with two sward height profiles
Authors: MAXWELL T. J. , SIBBALD A. R. , DALZIEL A. J. I. , AGNEW R. D. M. , ELSTON D. A.
Published: April 2006

The consequences of controlling sward height at two levels, around 5 cm (HS) and around 3·5 cm (LS), during spring and summer by adjusting weekly the proportion of the areas grazed in response to changes in rate of herbage production and utilizing the surplus pasture areas to conserve winter fodder were studied over three complete years for Greyface ewes with their lambs at 15ha−1 (SR15) and 10ha−1 (SR10). The rules used to control grazed sward height resulted in acceptable sward height control in three of four treatments and, by providing supplementary feed when sward height was below target, gave rise to similar levels of individual animal performance. Total output of lamb weaned was greater for the SR15 than for the SR10 flocks (607 vs 477 kg live weight ha−1; P<0·001). Amounts of winter fodder produced were less for the SR15 than for the SR10 flocks [39 vs 213kg dry matter (DM) per ewe; P < 0·001]. Significantly more supplementary feed (10·0 vs 4·4kg DM per ewe; P < 0·01) and hay (13·7 vs 4·0kg DM per ewe; P7lt;0·05) were offered around mating to SR15 flocks than to SR10 flocks. It is concluded that, provided that sward height can be controlled between 3·5 and 5·0cm during the spring and summer and that supplementation is offered when the grazed sward is below 3·5 cm, flock performance will fall within acceptable and predictable limits.
The effect of nitrogen fertilization upon the herbage production of tall fescue swards continuously grazed with sheep. 1. Herbage growth dynamics
Authors: MAZZANTI A. , LEMAIRE G. , GASTAL F.
Published: April 2006

The effect of level of nitrogen application upon the dynamics of herbage growth in a continuously grazed sward of tall fescue was investigated during two successive years. In order to obtain a large range of sward structural conditions, the experiments were carried out with two contrasting cultivars: cv. Clarìne and cv. Barcel, and, in Year 2, with two different sward heights or leaf area indices (LAIs). During each of five experimental periods (2‐3 weeks), swards received either optimum (N2) or deficient (N1) N applications, were maintained at their target LAI, and leaf growth was measured on labelled tillers. With continuously defoliated tillers, N‐shortage had only a small effect on the leaf elongation rate compared with tillers protected by cages. The leaf production per tiller was only slightly reduced by N shortage, and it was mainly by the means of a reduction in tiller density that the N deficiency resulted in reduced herbage growth per hectare. These results indicate that, in continuously grazed swards, in contrast with results previously found in intermittently defoliated swards, leaf elongation is not the only important component of difference in herbage growth and that the promotion of tillering rate is an additional pathway for N response in such management regimes.
Effects of nitrification inhibitor and acid addition to cattle slurry on nitrogen losses and herbage yields
Authors: PAIN B. F. , MISSELBROOK T. H. , REES Y. J.
Published: April 2006

Cattle slurry was applied to grassland on two contrasting soils in autumn and spring between 1987 and 1990. Slurry was applied with or without the addition of acid, to lower the pH to 5·5, and, in autumn only, with or without a nitrification inhibitor. Ammonia volatilization, denitrification and apparent recovery of N by the cut herbage accounted for 61–86% of the ammonium nitrogen (NH4+‐N) applied in slurry. Estimates from lysimeter experiments indicated that nitrate leaching from autumn application may have accounted for an additional 1–2% only. Acidifying slurry reduced volatilization losses to 1–12% of the NH4+‐N applied, and the nitrification inhibitor halved denitrification losses from autumn applications. Reductions in nitrogen losses were reflected in significant increases in first‐cut herbage yields which, for slurry applied in the autumn with acid and the nitrification inhibitor, were generally greater than those from 120 kg ha−1 N as ammonium nitrate applied in the spring. There were no significant differences between treatments at subsequent cuts in each season but, owing to the large increases at first cut, total yields were significantly higher for autumn‐applied slurry with acid and nitrification inhibitor.
An evaluation of the drop‐disc technique for measurements of herbage production in ryegrass for silage
Authors: DOUGLAS J. T. , CRAWFORD C. E.
Published: April 2006

The drop‐disc method of estimating herbage dry‐matter production was evaluated for ryegrass from growth commencement to the silage stage; the latter typically corresponded to a maximum dry matter (DM) mass of almost 7 t ha−1. A close linear relationship (r2= 0·829) was found between disc settlement height and DM mass up to 4–5 t ha−1 for the period when growth was mainly vegetative rather than reproductive. During the latter stage, the presence of stems and the occurrence of lodging had a detrimental effect on the quality of disc calibration data. The technique was demonstrably useful in experiments as a cheap, rapid and trouble‐free method for monitoring the initiation of grass production and rate of production during the vegetative stage.
Intake and behaviour responses by sheep to changes in sward characteristics under rotational grazing
Authors: PENNING P. D. , PARSONS A. J. , ORR R. J. , HOOPER G. E.
Published: April 2006

A 10‐week grazing experiment was conducted on a perennial ryegrass sward with lactating ewes and their twin lambs. Three paddocks were rotationally grazed with rest periods of from 4 to 5 weeks. Sward surface heights at the start of each grazing were 145, 259 and 250mni for treatments RG1, RG2 and RG3. A further four paddocks were maintained by continuous variable stocking (CS) at sward surface heights (SSHs) of about 30, 60, 90 and 120mm. Sward and animal measurements were made on the two different grazing managements as the RG swards were grazed down, giving measurements at similar sward heights for treatments RG and CS.

There was less green leaf and the total herbage mass present under RG was less than on CS swards at the same sward heights, demonstrating the differences in structure between rotationally and continuously grazed swards.

Regression analysis of animal factors on sward factors showed that grazing behaviour was more highly correlated with green leaf mass than SSH or any of the other sward measurements. On the RG swards, maximum intake per animal was reached at about 1500 kg green leaf mass ha−1. A SSH of 60mm allowed the CS ewes to achieve the highest intake rate, but at this height the ewes on treatments RG2 and RG3 were restricted to approximately half this rate. The results suggest that green leaf mass or leaf area index, rather than sward surface height, could be used as a rational basis to relate intake of herbage to sward state for swards changing rapidly in leaf to stem ratio.
Seasonal variation in growth characteristics of Lolium perenne and Trifolium repens in swards under different managements
Authors: BARTHRAM G. T. , GRANT S. A.
Published: April 2006

In a range of perennial ryegrass/white clover swards, variation in the surface heights of the grass and clover components, the rates of increase of these surface heights and the specific leaf areas (SLAs) of ryegrass and white clover were described for 1 year. The swards were of an early‐ or late‐flowering (Aurora or Melle respectively) perennial ryegrass variety growing with either a small‐ or a medium‐leaved (Kent or Milkanova) white clover and were either continuously stocked by sheep or continuously stocked apart from a rest period in April‐May (Aurora) or May‐June (Melle).

The surface heights of grass and clover were not affected by the variety of their companion species, and the surface heights of the two clover varieties were similar. The grass was always taller than the clover, although the magnitude of the difference between the species varied with time of year and the timing of the rest period.

Before the summer solstice the rate of increase in height of grass was greater than that of clover except at cool temperatures (5°C) and warm temperatures (16°C), and in the unrested Melle sward. After the solstice the rates of increase in height, particularly of clover, were lower than the rates seen at similar temperatures before the solstice.

Overall, the SLAs of both clover varieties were greater than those of ryegrass when grown with Aurora but not when grown with Melle, and the SLAs of both species increased during the year. By October the SLAs of both grass varieties were less than those of their companion clovers.

The results are discussed in relation to their implications for the species composition of the swards.
Influences of enterobacteria on the fermentation and aerobic stability of grass silages
Authors: ÖSTLING C. , LINDGREN S.
Published: April 2006

Grass (220 g DM kg−1 was ensiled after adding 106 and 108 enterobacteria (90%Rahnella aquatilis, 9·9%Hafnia alvei and 0·1%Escherichia coli g−1 fresh mutter. The silages were exposed to aerobic conditions alter 125 d of storage. In all treatments H. alvei rapidly superseded the initial high number of Enterobacter agglomerans (naturally present) and R. aquatilis. The maximum number of enterobacteria was detected about I d after initiation of fermentation. After 4 d of fermentation, when concentrations of undissociated lactic and acetic acids ranged from 52 to 36 mM and 41 to 51 mM respectively, no enterobacteria were detectable. Inoculating the crop with enterobacteria restilted in a temporarily retarded rate of production of lactic and acetic acids and a 50% increase in the concentration of ammonia‐N. The concentration of endotoxin in the silages was 6–7 μg g−1 fresh matter. There was no change in the level of endotoxin during ensiling. High numbers of enterobacteria at the beginning of the fermentation improved the aerobic stability of the silages. There was a lag in the decrease in concentrations of acids and delays in the increase in pH, respiration rate and numbers of yeast and Bacillus spores, in uninoculated silages the pH increased from 4·1 to 5·0 after 8 d of aerobic storage, whereas in inoculated silages a pH of 5·0 was not reached until after 16 d of storage.
Influence of seed quality on seedling growth of white clover (Trifolium repens L.)
Authors: PASUMARTY S. V. , HIGUCHI S. , MURATA T. , MATSUMURA T.
Published: April 2006

The influence of seed quality on seedling growth of white clover cv Makibashiro plants was examined in a controlled environment. The average dry matter (DM) yield of 70‐day‐old seedlings from a poor‐quality seed lot was significantly less than that from a high‐quality seed lot. In both seed lots, a linear relationship between the DM yield and time from sowing was observed. The slope of regression of DM yield against time from sowing for the poor‐quality seed lot was less than the equivalent slope of the high‐quality seed lot, suggesting that possible avenues for increased DM accumulation in a high‐quality seed lot are somewhat indirect (time of emergence, uniform emergence etc.); a direct effect of seed quality on the photosynthetic ability of plant tissue seems less likely to occur. The root: shoot ratios declined in both groups of plants with increasing age. Seedlings from the high‐quality seed lot reached a stable root:shoot ratio (equilibrium state) much earlier than those from the poor quality seed lot. The seed quality had no influence on the proportion of DM partitioned to various organs. The results of this study are discussed in relation to field establishment.
A mathematical model of the aerobic deterioration of silage
Authors: WILLIAMS A. G. , CRITTEN D. L. , REYNOLDS A. M.
Published: April 2006

A mathematical model of the aerobic deterioration of silage is described that includes the physical processes of gas and heat Rows, as well as an established model of microbial growth and the associated chemical changes. Yeasts and acetic acid bacteria are included in the growth model. The version of the model described relates to a cylinder of silage subject to forced aeration, a common experimental configuration. The model was very sensitive to variations in insulation thickness and yeast growth rate, and to initial pH, especially when maize was the forage. Great care is needed when selecting input data for use in the model to be sure that the physical and chemical properties are accurate. The model solution was sensitive to grid size, but with 361 cells, the maximum grid resolution that could be used on a 486 series PC, solutions were achieved with an acceptably small loss of accuracy. The model predicted the results of an experiment on silage deterioration quite accurately. However, the model also predicted that considerable spatial gradients of parameters, such as temperature, pH, and lactic acid, would occur. This indicates the need for care when taking samples or making temperature measurements in deterioration experiments. The model is potentially a useful tool in predicting the optimal time and position to take samples for analysis in a time‐course experiment.
Lactation performance of spring‐calving dairy cows grazing mixed perennial ryegrass/white clover swards of differing composition and height
Authors: WILKINS R. J. , GIBB M. J. , HUCKLE C. A.
Published: April 2006

An experiment was designed to examine the changes in clover content of three mixed perennial ryegrass/white cover swards of differing initial clover contents subjected to different grazing height management regimes and their effect on lactation performance of 48 Friesian dairy cows and heifers. Two paddocks were established for each treatment and grazed on alternate days. Treatments T17 and Tl3 consisted of swards with initial clover contents of 0·17 and 0·13 of the dry matter (DM) mass, respectively, grazed to maintain compressed sward heights of 6 cm throughout the season. A third treatment, SI5, consisted of a sward with an initial clover content of 0·15 grazed to maintain a compressed sward height of 4·5 cm for the first 78 days of the grazing season (period 1). Throughout period 1, half the animals on each treatment each received 4 kg of a concentrate supplement daily, while the others remained unsupplemented. From days 79 to 90, the cattle on treatment S15 grazed a similar sward, while the compressed sward height of the S15 paddocks was allowed to increase to 6 cm before re introduction of the animals. The three swards were then grazed for a further 47 days (period 2) before the animals were housed and milk yield recorded for a further 63 days (period 3). While sward T17 showed little change in clover content over the first 29 days of grazing, remaining at just below 0·18 of DM mass, swards T13 and S15 showed a marked decline in clover content to 0·05 and 0·07 of DM mass respectively. However, by the end of period 1 the clover content of all three swards had increased markedly (0·25, 0·15 and 0·15 of DM mass respectively). By the end of period 2, clover proportions were slightly higher than initial values (0·19. 0·15 and 0·15 of DM mass for treatments T17, T13 and S15, respectively). Owing to the relatively small differences in clover content of swards TI7 and T13, there were no significant effects of these two treatments on milk yield or composition in any period. Supplementation had no effect on milk composition and had little effect on milk yield, except when sward height was maintained at 4·5 cm. There was no carryover effect of supplementation on milk yield or composition in periods 2 or 3.
Evidence from the use of isozyme markers of competition in swards between short‐leaved and long‐leaved perennial ryegrass
Authors: HAZARD L. , GHESQUIÈRE M.
Published: April 2006

Intraspecific competition in Lolium perenne was studied using a replacement series of a short‐leaved and a long‐leaved genotype that was managed under different cutting frequencies and nitrogen supplies. Leaf length, tiller density and yield were recorded 6 months after sowing. Since the two competitors were labelled at the PG1/2 locus, it was possible to identify unambiguously the origin of tillers in the mixtures and to estimate the average length of lamina of each genotype. The difference in leaf length between the two competitors was maintained under particular types of management and generated contrasting competitive abilities leading to evolution of the genotypic composition of the mixtures. Thus, under infrequent cutting, competition for light resulted in the domination of the long‐leaved genotype and in a concomitant intragenotypic selection for leaf length. Supplying nitrogen fertilizer emphasized the phenotypic plasticity of the genotypes, particularly of the dominated one. Frequent cutting reduced competition for light and the change towards the short‐leaved genotype was far less rapid. The yielding and competitive abilities of ryegrass genotypes and the implications for breeding are briefly discussed.
The effect of additives on the ensilage of forage of differing perennial ryegrass and white clover content
Authors: CUSSEN R. F. , MERRY R. J. , WILLIAMS A. P. , TWEED J. K. S.
Published: April 2006

Pure perennial ryegrass or perennial ryegrass/white clover mixtures (70:30 and 40:60 on a fresh‐matter basis) were ensiled in laboratory silos either untreated or alter treatment with freshly cultured Lactobacillus (Lb.) plantarun or freshly cultured Lb. plantarum plus Lactococcus (Lc.) lactis. freeze‐dried Lb. plantarum or freeze‐dried Lb. Plantarum plus sodium formate, sodium formate or formic acid. The effect of these additives on silage fermentation characteristics and quality of the resultant silages was examined. There were significant interactions between treatments and herbages for all silage quality parameters measured, except for acetic acid concentration. The influence of additives on the final pH of all silages was small but statistically significant. Lactic acid concentration was not directly related to herbage mixture, overall mean values ranging from 118 to 120 ± 1.5 g kg−1 dry matter (DM), but wider variation was seen between treatments for individual herbage mixtures. Acetic acid concentrations were significantly (P<0·001) affected by herbage mixture ensiled, increasing linearly as clover content increased from zero to 60%. Untreated control and formic acid‐treated silages contained significantly (p<0·001) higher acetic acid concentrations than those treated with other additives. Silage ammonia N concentrations were significantly (p<0 001) influenced by herbage mixture. Lowest ammonia N concentrations (< 50 g kg−1 DM) were observed in silages that had been treated with formic acid, freshly cultured Lb. plantarum or Lb. plantarum plus Lc. lactis. The fraction 1 leaf protein (FILP) contents of silages were significantly (P <0·001) affected by both treatment and herbage mixture, with consistently and significantly higher values found in freshly cultured inoculant‐treated silages. A poor correlation (r2= 0·12) existed between ammonia N and FILP in all silages. The inclusion of up to 60% white clover in the ensiled herbage did not adversely affect final silage quality. However, additive treatment markedly influenced the residual FILP content of silages, those treated with freshly cultured inoculants having the highest values.
The effect of calving date and stocking rate on the performance of spring‐calving dairy cows
Authors: DILLON P. , CROSSE S. , STAKELUM G. , FLYNN F.
Published: April 2006

A 3‐year experiment on milk production systems was set up in 1989 to investigate the effect of calving date and stocking rate on the performance of spring‐calving dairy cows. An early‐calving herd (System A) with a mean calving date of 23 January and stocked at 2·9 cows per hectare was compared with two later calving herds (Systems B and C) with a mean calving date of 15 March. System B had a similar stocking rate to System A (2·9 cows ha−1), while System C had a stocking rate of 2·6 cows ha−1. The average lactation yields (kg) over the three years were as follows: 5872, 5444 and 5584 (milk)210, 204 and 215 (fat), 187, 184 and 189 (protein) and 261, 245 and 250 (lactose) for Systems A, B and C respectively. The average milk composition (gkg−1) was: 36·0, 37·6 and 38·7 (fat), 31·9, 33·7 and 33·8 (protein) and 44·5. 45·1 and 44·8 (lactose) for Systems A, B and C respectively. Delaying calving date to coincide with the beginning of the grass‐growing season (System B compared with System A) reduced milk yield per cow significantly (P < 0·05) in all three years of the experiment. However, fat and protein concentration were increased, resulting in no significant difference in the yield of fat or protein per cow. Reducing the stocking rate from 2·9 cows per hectare to 2·6 cows per hectare for cows calving in mid‐March (System C compared with System B) increased milk yield per cow significantly (P < 0·05) in only one of the three years (1990). Milk fat content was increased significantly in 1990. Stocking rate had no other
A comparison of quadrat, capacitance meter, HFRO sward stick, and rising plate for estimating herbage mass in a smooth‐stalked, meadowgrass‐dominant white clover sward
Authors: MURPHY W. M. , SILMAN J. P. , BARRETO A. D. MENA
Published: April 2006

A single‐probe capacitance meter (Pasture Probe), the Hill Farm Research Organization (HFRO) sward stick, a rising‐plate meter, and cut quadrats were used to estimate herbage mass of swards that were rotationally grazed by cattle, cattle followed by topping, cattle followed by sheep, or sheep alone during 1989 and 1990 grazing seasons. Mean target pre‐ and post‐grazing herbage masses were 2200 and 1100 kg dry matter (DM) ha−1 respectively. Linear regressions, correlations and scatterplots were calculated relating meter and sward stick readings to herbage mass on an ash‐free organic matter basis measured by cutting quadrats of herbage at ground level.

Mean coefficients of variation for quadrat, capacitance meter, sward stick and rising plate were 28·8, 15·5, 27·2 and 27·9% respectively for pre‐grazing herbage mass measurements, and 20·2, 10·1, 21·4, and 18·4% respectively for post‐grazing measurements. These coefficients indicate that the capacitance meter varied less in estimating pre‐ and postgrazing herbage mass than the other three methods.

Correlation coefficients relating cut quadrats to capacitance meter, sward stick and rising plate readings were 0·65, 0·70 and 0·72 for pre‐grazing, and 0·36, 0·31 and 0·05 for post‐grazing herbage mass measurements respectively.

The non‐destructive methods provided quick herbage mass estimates at a level of precision adequate for making day‐to‐day grazing management decisions on farms.
The effect of tractor wheel passes on herbage production from diploid and tetraploid ryegrass swards
Authors: FRAME J. , MERRILEES D. W.
Published: April 2006

Diploid and tetraploid perennial ryegrass swards were managed under an intensive silage system over 3 years. The swards were subjected to five tractor wheel pass treatments to simulate combinations of silage operations in the field from cutting, tedding, lifting and fertilizing. Wheel tracking was applied uniformly over the swards after June, July, August and October cuts each year.

Tractor wheel passes caused mean reductions in herbage dry matter (DM) yield during successive years of 14%, 6% and 9% compared with their absence, and frequent or delayed wheel passes affected yield more adversely than infrequent or undelayed wheel passes. Nitrogen and mineral concentrations in herbage and nutrient offtakes were also generally reduced but organic matter digestibility (OMD) was unaffected. Soil assessments each autumn showed that soil bulk density increased in the wheel‐pass treatments, particularly when frequently applied. The two sward types responded in a similar manner to the wheel‐tracking treatments, probably because they had similar cushioning capability, the disadvantage of the tetraploid in terms of fewer tillers in relation to the diploid being compensated for by larger tiller size. Soil compaction, with its adverse effect on sward growth vigour, and direct wheel damage to young regrowth will be lessened by minimizing wheel traffic on silage swards and undertaking operations over short rather than long periods.
The effect of partial replacement of grass silage with fresh grass on rumen fermentation characteristics and rumen outflow rates in cattle
Authors: MCKEE C. A. , CUSHNAHAN A. , MAYNE C. S. , UNSWORTH E. F.
Published: April 2006

An experiment was designed to examine the effects of partially replacing extensively fermented grass silage with varying proportions of fresh grass (0, 0–33, 0–67 and 100) on rumen fermentation, degradation of dry matter (DM) and rate of outflow of liquid and particulate phases from the rumen with four mature Limousin steers. The fresh grass had a higher pH and water‐soluble carbohydrate and lower ammonia‐N and lactic acid concentrations than the silage. Partial replacement of silage with fresh grass resulted in a reduction in rumen ammonia concentration, and in the proportion of rumen propionate, i‐butyrate and n‐valerate and an increase in the proportion of rumen acetate and in both die particulate and liquid outflow rates from the rumen. These changes in rumen fermentation parameters could account for increases in animal performance in situations in which grass silage is partially replaced with fresh grass.
Influence of irradiance on branch growth of white clover stolons in rejected areas within grazed swards
Authors: TEUBER N. , LAIDLAW A. S.
Published: April 2006

Development of white clover stolons (Trifolium repens) was compared when grown in rejected areas and in adjacent defoliated areas over 28 days in May ‐ June in continuously stocked grass/white clover swards. In the cut areas more branches were borne on stolons with more but shorter internodes and shorter petioles than in the rejected areas. Red (R)/far red (FR) ratio at the base of the cut sward was significantly higher than in the rejected sward.

Five experiments were carried out in which red light‐emitting diodes (LEDs) supplied supplementary irradiation at the node of the youngest fully expanded leaf on white clover stolons growing in association with dense canopies of perennial ryegrass. Axillary bud/branch length was the only significantly affected aspect of development that was measured, irradiation enrichment increasing length by about three‐fold over a 2–4 week period. One of the experiments involved identification of the site of perception of the R/FR effect. Natural and supplementary light were excluded from the stolon (by covering with a 2‐cm layer of black beads), petiole (by wrapping in aluminium foil), both or neither and showed that exposure of the stolon/ petiole base to supplementary light was necessary to stimulate axillary bud growth.

It is concluded that the relative content of red light, and possibly absolute level, in irradiance at the base of the canopy in rejected areas is implicated in the young branch growth and that release of the buds can be achieved by defoliation, presumably due to increasing the red light content; however, the effect of increased photosynthetically active radiation (PAR) reaching stolons and young leaves cannot be discounted as an additional factor.
The intake of grass and rush (Juncus effusus L.) by goats grazing rush‐infested grass pasture
Authors: MERCHANT M.
Published: April 2006

The intakes of rush and grass by goats grazing rush‐infested reseeded pasture (rush ground cover, 5.9%) were measured in three periods between July and September in one year, using n‐alkanes as dietary markers. Diet composition and intakes were measured at intertussock sward heights maintained at 3–4 cm and 5–6 cm and at an intertussock sward height maintained at 3–4 cm where the rushes had previously been grazed by goats to reduce rush green stem height to 0.75 of that of ungrazed tussocks.

There was no effect of intertussock sward height or initial rush green stem height on the dietary proportion (overall mean 0.51) or dry matter (DM) intake of rush but there was an effect of period, which was related to changes in sward conditions over the experiment. Rush intake was positively related to the amount and accessibility of green rush stems and grass intake to intertussock sward height. Digestibility of DM of the diet, measured using n‐alkanes, was high (overall mean 0.71), suggesting that the nutritive value of the rush is greater than previously estimated from in vitro digestibility measurements. Under these conditions, it appears that the goats select a mixed diet and the results are consistent with animals selecting food items to maximize their rate of nutrient intake.
The effect of grazed sward height and stocking rate on animal performance and output from beef cow systems
Authors: WRIGHT I. A. , MAXWELL T. J. , RUSSEL A. J. F. , HUNTER E. A. , SIBBALD A. R. , HETHERINGTON R. A. , WHYTE T. K.
Published: April 2006

During three consecutive summers, forty spring‐calving beef cows and their calves grazed perennial ryegrass‐dominant swards receiving 250 kg N ha−1 at one of two annual stocking rates [2.0 (SR 2.0) or 2.5 (SR 2.5) cows ha−1] and one of two sward heights [4–5 (LS) or 7–8 (HS) cm] in a 2 × 2‐factorial experiment, replicated twice. Sward heights were maintained from turn‐out in spring by weekly adjustment of the area grazed and herbage was cut for silage in June and again in August from the areas not grazed. After the second cut of silage there was no control of sward height. Calves were weaned in early October and cows removed from pasture and housed when sward heights fell to 4 cm in autumn. Cows were fed in groups a variable but measured quantity of silage during winter to achieve a body condition score of 2.0–2.25 at turn‐out the following spring.

During the period of sward height control the cows on the HS treatment gained more live weight than those on the LS treatment (0.841 vs. 0.496 kg day−1; P<0.01) as did the calves (1.167 vs. 1.105; P<0.05). but the stocking rate treatment had no effect. From the time of second‐cut silage to the time of weaning and housing respectively, calves and cows gained more live weight on the SR 2.0 treatment because sward heights were higher. Reproductive performance of cows was not affected by treatment.

The quantity of silage produced and consumed per cow was not affected by sward height treatment, but the SR 2.0 treatment produced significantly (P<0.001) more silage (1559 kg dry matter per cow) than the SR 2.5 treatment (833 kg dry matter per cow) and had higher winter silage requirements (1249 vs. 1153 kg dry matter per cow: P<0.05). The overall mean stocking rate at which winter fodder production and requirements would be in balance was calculated as 2.25 cows ha−1 but values were 1.86, 2.60 and 2.28 in each of the three years of the experiment.

The results showed that it was possible to control sward height in temperate beef cow systems by adjusting the area available for grazing. Body condition score can be used as a means of determining the feeding levels required to manipulate body condition of cows over winter to achieve prescribed levels of body condition. The experimental approach allows the identification of the stocking rate at which self‐sufficiency in winter fodder can be achieved and the year‐to‐year variation associated with that stocking rate. This approach could be generalized if information on herbage growth rate were available, either from direct measurement or from predictive models.
Growth and water relations of field‐grown tall fescue as influenced by drought and endophyte
Authors: ELBERSEN H. W. , WEST C. P.
Published: April 2006

Field plots were established in autumn 1992 in which endophyte [Neotyphodium coenophialum Glenn. Bacon, Price and Hanlin (formerly Acremonium coenophialum)]‐infected (E+) and endophyte‐free (E−) isolines of three tall fescue [Festuca arundinacea Schreb.) genotypes were planted. Plants were subjected to three water‐withholding periods in 1993 and one in 1994, or were kept well watered throughout the experiment. There were no consistent endophyte effects for leaf elongation, tiller density or dry weight per tiller. There were genotype X endophyte interactions (P<001) for tiller density and shoot dry weight per area and genotype X water X endophyte interactions (P<005) for cumulative leaf elongation in 1993. These interactions indicated the highly specific effect of host genotype‐endophyte association on the expression of plant growth. Leaf rolling in the stressed treatments was more severe in E− than in E+ plants in 1993, but there were no differences in 1994, and stomatal conductance tended to be lower in E− than in E+ plants in 1993. Fractional water content of the lower 3 cm of the youngest fully developed leaf sheath was usually greater, and never less, in E+ than in E− plants. The leaf rolling and stomatal conductance results suggest that E− plants were more severely stressed in the summer after planting. Thus, the endophyte may induce greater water retention in the leaf sheath and therefore better protect the internal growing zone from lethal desiccation.