bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractThe 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

AbstractCattle 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

AbstractThe 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

AbstractA 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

AbstractIn 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

AbstractGrass (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

AbstractThe 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

AbstractA 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

AbstractAn 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

AbstractIntraspecific 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

AbstractPure 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

AbstractA 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

AbstractA 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.