bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of stocking rate on a lamb production system with February‐lambing ewes
Authors: ORR R. J. , NEWTON J. E.
Published: April 2006

Masham ewes were stocked at 12(L), 16(M) or 20 (H) ewes ha−1, with 1·8 lambs per ewe on average, on two blocks (A and B) in both 1976 and 1977. Silage was offered at pasture to the ewes in early lactation and as stocking rate increased from 12 to 16 and then 20 ewes ha−1, 47, 73 and 100 kg DM per ewe was consumed respectively. Silage was cut mainly in the autumn and 179, 100 and 9 kg per ewe was made for L, M and H respectively. More variation between treatments was measured in net herbage accumulation in summer than spring and 11·4, 10·0 and 9·7t DM ha −1 was grown over the whole season for L, M and H respectively as a mean of both years.

High intakes of herbage OM were measured with values up to 40 g per kg live weight for BL lambs in 1976. Rapid lamb growth was achieved. There were effects of stocking rate on lamb performance and for L, M and H the respective growth rates to 4 weeks were 266, 248 and 247 g d−1; growth rates to sale were 274, 263 and 252 g d−1; days to sale were 124, 126 and 129; mean carcass weights were 17·7, 17·1 and 16·7 kg. Most ewes lost weight in early lactation, especially AH and BH in 1976, but there were no stocking rate effects on ewe weight change in 1977.
A comparison of unwilted and wilted grass silages offered to beef cattle without and with monensin sodium
Authors: STEEN R. W. J.
Published: April 2006

A randomized block experiment was conducted to compare unwilted and wilted grass silages and the effects of the feed additive monensin sodium on the silage intake and performance of finishing beef cattle. Two regrowths from a predominantly perennial ryegrass (cv. S24) sward were ensiled either without wilting or after field wilting for 3 d (dry matter (DM) concentrations 161 and 266 g kg−1 respectively). Both silages were treated with formic acid (2·6 and 30 litre t−1 respectively) and were well preserved. The silages were offered ad libitum to forty‐eight Charolais‐cross cattle (thirty‐two steers and sixteen heifers, mean initial live weight 351 kg) for 145 d. All animals received 2·2 kg concentrates per head daily and half of those on each silage treatment received in addition 200 mg monensin sodium per head daily. Silage DM intake was 5.04, 504. 5·48, 5·63 ± 0.134 kg d−l; fasted liveweight gain was 0·69, 0·77. 0·64 and 0·73 ± 0.033 kg d−l and carcass gain was 0·47, 0·50, 0·40 and 0·45 ± 0·020 kg d−1 for the unwilted silage without and with monensin and the wilted silage without and with monensin respectively. It is concluded that wilting grass of low DM concentration for 3 d prior to ensiling reduced the performance of finishing beef cattle below that obtained from well‐preserved unwilted silage in spite of a higher DM intake being achieved with the wilted silage. The inclusion of monensin sodium in a silage‐based diet increased performance without significantly affecting feed intake.
The antimicrobial spectra of organic compounds with respect to their potential as hay preservatives
Authors: WOOLFORD M. K.
Published: April 2006

Formic acid, sodium diacetate, propionic acid and two of its ammonium salts, ammonium isobutyrate and tributyl phosphate, were examined for their antimicrobial effects with cultures of micro‐organisms typical of the microflora of moist hay. The assays, which were conducted at pH 5, 6, 7 and 8, revealed that all potential preservatives discriminated against actinomycetes in particular and were least effective against fungi. In addition, it was apparent that antimicrobial properties were enhanced under slightly acid conditions and for this reason the use of mixtures of organic acids and salts in commercial hay preservatives is justified. Tributyl phosphate not only had the strongest antimicrobial properties of the compounds tested but was also the least affected by pH.
The effects of change in herbage mass on rates of herbage growth and senescence in mixed swards
Authors: BIRCHAM J. S. , HODGSON J.
Published: April 2006

A study was conducted to determine the influence of a change in herbage mass on rates of herbage growth (G), senescence (S) and net production of green herbage (NP) in swards of Lolium perenne L., Poa annua L. and Trifolium repens L. under continuous stocking with sheep. Swards were maintained at either high (1700–1900 kg OM ha−1; H) or low (700–900 kg OM ha−1; L) herbage mass from April to 20 August. From 20 August to 13 September half of the L sward was permitted to grow until a herbage mass similar to that of the H sward was achieved (LH), and at the same time half of the H sward was grazed down until a herbage mass similar to that of the L sward was achieved (HL). The other half of each sward was held at constant mass (LL and HH). Estimates of G, S and NP were obtained for each plant species over a 2‐week period from 17 September to 1 October and estimates of species population densities were also made.

The combined species rates of G and S per unit area were highest in treatment LH and lowest in treatment HL, whilst the rates for the LL and HH swards were intermediate. The rate of NP was similar in the LL, HH and LH treatments (34.5, 29.3, 33.6 ± 6.2 kg DM ha−1d−1) but was lower in the HL sward (100 ± 6.2). The effects of alteration of herbage mass on individual tiller or stolon G and S rates were rapid but population density changes were slower.

Within the limited conditions of this trial it was not possible to increase NP by manipulation of herbage mass under continuous stocking management but the results indicate that NP can be reduced in the short term if a sward of high herbage mass and low population density is grazed hard.
Silage and milk production: a comparison between unwilted and wilted grass silages
Authors: CASTLE M. E. , WATSON J. N.
Published: April 2006

Three grass silages made in sunny weather in early July from second‐harvest perennial ryegrass were compared in a 16‐week feeding experiment with twelve Ayrshire cows. The silages were either unwilted or wilted with and without conditioning, and had mean dry matter (DM) concentrations of 201, 261 and 272 g kg−1, and in vitro DOMD concentrations of 650, 669 and 672 g kg−1 DM respectively. All the silages had formic acid (‘Add‐F’) applied at a rate of 2.6 litres t−1 and were offered ad libitum plus 6 kg concentrates per cow per d. The daily intakes of silage DM were 905 kg per cow on the unwilted treatment and 9.86 and 9.65 kg on the wilted treatments with and without conditioning respectively. Daily milk yields were 171, 17.6 and 17.4 kg per cow on the unwilted, and wilted with and without conditioning treatments respectively and were not significantly different. Fat concentrations in the milk were not affected significantly by treatment, whereas the crude protein and solids‐not‐fat concentrations were significantly higher on the wilted than on the unwilted treatment. The efficiency of utilization of metabolizable energy for lactation was 6–7% lower with the wilted than with the unwilted silages and it is concluded that the unwilted silage was superior to the wilted silages as a feed for dairy cows.
A system for rapid freezing of pasture samples in the field
Authors: COLEBROOK W. F. , JAMES K. J. , HAMILTON W. J.
Published: April 2006

A system for rapid freezing and containment of pasture and forage samples in the field is described. Core temperatures of pasture samples of 2–5 kg mass can be reduced to below 0°C in a few minutes using liquified carbon dioxide in the ratio of 1 to 2 kg carbon dioxide to 1 kg of green plant material. Changes in the pH of the plant extract were very small (ca. 0 1 pH unit). The system is especially suitable for use in areas remote from normal laboratory facilities, where rapid freezing of herbage samples is essential.
The utilization of sown and indigenous plant species by sheep and goats grazing hill pastures
Authors: GRANT SHEILA A. , BOLTON G. R. , RUSSEL A. J. F.
Published: April 2006

The utilization of sown and indigenous plant species was studied in three experiments in which plots were stocked with similar live weights of sheep and goats. In the first experiment the animals grazed plots containing 0–5 ha of rush (Juncus effusus)‐ infested reseeded pasture and 0–5 ha of unimproved blanket bog. The second and third experiments took place on old rush‐infested improved pasture; in one experiment two levels of herbage mass of grass were provided while in the other the rushes were cut in spring or remained uncut.

The goats grazed the rushes readily in all three experiments. Reduction in herbage mass of grass increased utilization of rushes by goats although these animals still grazed rushes when grass supply was plentiful. Sheep scarcely grazed J. effusus even when hard‐pressed by shortage of grass. Both sheep and goats grazed J. acutiflorus.

In Experiment I sheep utilized reseeded pasture more heavily than did goats. Sheep grazed similar proportions of the leaves of grass and clover while goats grazed a lower proportion of clover leaves as compared with grass. Among the grasses sheep discriminated in favour of Lolium perenne whereas goats did not. On the blanket bog vegetation, Eriophorum vaginatum and Calluna vulgaris were grazed both earlier in the season and more heavily by goats than by sheep.

The relationships between sward structure and grazing height in accounting for differences in species selection by sheep and goats are briefly discussed. The possibility of using goals to control coarse weeds in hill pasture and for strategic grazing to manipulate floristic composition is outlined.
Growth rate, senescence and photosynthesis of ryegrass swards cut to maintain a range of values for leaf area index
Authors: KING J. , GRANT S. A. , TORVELL L. , SIM E. M.
Published: April 2006

An experiment was carried out in which simulated swards of ryegrass (cv. S23) were grown in boxes. In the first instance the swards were cut at weekly intervals to maintain five levels of leaf area index (LAI) from LAI 1 to 4–5 in simulation of continuous grazing. Measurements were made of growth, senescence and net growth rate and of net canopy photosynthesis at constant irradiance. The results showed that the swards adapted to the defoliation regimes mainly by changes in tiller population density and pseudostem length. When the swards had equilibrated to the cutting regime growth rate increased with LAI but, since tiller density and the partitioning of growth between herbage harvested and that lost by sensecence also changed with LAI, net growth rate was constant over the LAI range 2–4·5. Maximum weight of herbage harvested was obtained between LAI 2 and 3.

After 10 weeks of weekly cutting all the swards were cut back to LAI 1 and allowed to regrow. Growth rate showed almost no response to the previous culling treatments. The relationship of net canopy photosynthesis to LAI was linear for the frequently defoliated swards and curvilinear for regrowing swards. The reasons for this difference were examined.
The effect of cutting for conservation on a grazed perennial ryegrass‐white clover pasture
Authors: CURLL M. L. , WILKINS R. J.
Published: April 2006

Continuous stocking with sheep at high stocking rates may reduce the content of white clover (Trifolium repens) in mixed grass‐clover swards. The present experiment was carried out to investigate the effects on sward production and composition of resting a perennial ryegrass (Lolium perenne)‐ white clover sward from grazing and taking a cut for conservation.

Swards were set‐stocked with 25 and 45 yearling wethers ha−1 either throughout a grazing season, or on swards that were rested for a 6‐week period and then cut in early, mid‐ or late season. In an additional treatment swards were cut only and not grazed.

Net herbage accumulation was higher at the lower of the two stocking rates and was marginally increased by the inclusion of a rest period at the high but not the low stocking rate. Clover content was higher at the lower stocking rate and was increased by the inclusion of a rest period by 30% at 45 sheep ha−1and by 11% at 25 sheep ha−1 The effect was most marked at the end of the rest period before cutting. When rested from grazing the tiller density of ryegrass decreased although tiller length increased, and clover stolon length, petiole length and leaflet diameter increased though leaf and node number per unit length of stolon decreased; the reverse applied when the sward was returned to grazing after cutting.

At the high stocking rate, rest periods in mid‐season or later maintained the greatest clover content and marginally increased total net herbage accumulation. At the low stocking rate the timing of the rest period had no significant effect on total net herbage accumulation or on clover content.

These results show that the combination of grazing and cutting is of benefit where the stocking rate is high enough to threaten clover survival and limit sheep performance. However, at such a stocking rate, feed reserves are at a minimum throughout the grazing season and so opportunities for resting the sward are probably low.
Variation among pregnant, non‐lactating dairy cows in eating and ruminating behaviour, digestibility and voluntary intake of hay
Authors: Harb M. Y. , Campling R. C.
Published: April 2006

The variation between non‐lactating British Friesian cows in eating and ruminating pattern, digestibility and voluntary intake of hay were measured about 4 weeks before calving. Among fourteen of the cows the daily duration of eating ranged from 214 to 462 min and rumination from 410 to 599 min with CV of 20 and 14 respectively. Daily hay intake varied between cows from 5.93 to 11.18 kg dry matter (DM) with a CV of 14. The mean digestibility coefficient of organic matter measured in nineteen cows was 0.57 ± 0.014 s.d. and of cellulose 0.70 ± 0.013 s.d. Intake of hay and cellulose digestibility were correlated (r = 0.51, P<0.05). There was a positive correlation between hay intake and duration of eating (r=0.64, P<0.01) but not between intake of hay and rate of eating. Daily time spent ruminating per kg hay DM eaten was negatively correlated with hay intake (r = 0.66, P<0.01). It is concluded that variation between cows in chewing time and in digestibility of cellulose may be important factors related to variation between cows in voluntary intake of hay.
A comparison of faba beans and peas as whole‐crop forages
Authors: FAULKNER J. S.
Published: April 2006

Faba beans and peas were compared as spring sown whole‐crop forages in two trials at Lough‐gall. No herbicide, insecticide or N fertilizer was used. Harvesting took place at the end of July. As pure stands, tic beans (cv. Blaze) yielded up to 10 t of dry matter (DM) ha−1. Lower yields were obtained at lower seed rates, or with horse beans (cv. Stella Spring), broad beans (cv. Polar) or peas (cvs Minerva and Krupp). Tic and horse bean forage had a mean DM concentration of 166 g kg−1, which was higher than those of broad bean and peas. Crude protein (CP) concentration at a mean of 159 g kg−1 was similar in tic beans and peas. Faba beans mixed with cereals yielded less than beans alone, but peas with cereals yielded slightly more than peas alone. The inclusion of a cereal raised forage DM contents but lowered CP contents. Perennial ryegrass‐white clover mixtures undersown in faba beans established well, but poorer swards were obtained in some of the pure pea stands which lodged severely. It is concluded that, as pure stands, tic beans have advantages over peas. Some of the disadvantages of peas can be overcome by growing a mixture of peas with cereals.
Supplementary feeding of forage to grazing dairy cows
Authors: PHILLIPS C. J. C. , LEAVER J. D.
Published: April 2006

Grass silage was offered to continuously stocked dairy cows in two experiments. In the first 12 weeks of the grazing season (Experiment 1) 32 cows were offered grazed herbage only (G), or grazed herbage with a silage supplement offered for 45 min after morning milking (GMS), overnight at a restricted level (GRS) or overnight ad libitum (GAS). The two overnight treatments involved housing the cows between afternoon and morning milking. In late season (Experiment 2) 18 cows were used in a similar experiment lasting 9 weeks to compare treatments G, GMS and GAS. Within experiments the same level of herbage was available to all treatments (mean sward height 9.6 and 7.2 cm in Experiments 1 and 2 respectively).

In Experiment 1, offering silage depressed herbage dry matter (DM) intake but had no significant effect on total DM intake. Silage (GMS, GRS, GAS) reduced milk yield but increased milk fat content and fat yield compared with G. In Experiment 2 offering silage depressed herbage DM intake but increased total DM and ME intakes. This led to increased milk yields, fat and lactose contents and liveweight gains, with the greatest benefit obtained when silage was available overnight.

Silage was therefore beneficial in maintaining high DM intakes. Also, the substitution of silage for grazed herbage, particularly in Experiment 2, indicated that high stocking rates on grazing land can be maintained throughout the season, when silage is available ad libitum.
A quantitative model of the ensilage process in lactate silages
Authors: PITT R. E. , MUCK R. E. , LEIBENSPERGER R. Y.
Published: April 2006

A model of the ensilage process is presented which can be used to predict silage quality in lactate silages. The model simulates the major microbial and biochemical processes during ensilage, including aerobic respiration, hydrolysis of hemicellulose. growth and death of lactic acid bacteria and their production of lactic and acetic acids, reduction in pH, change in soluble sugar content, increase in osmotic potential, and proteolysis. The model is designed to operate on mixtures of grasses, legumes, or whole‐plant corn. Parameters for the model are developed from published silage experiments and pure‐culture bacterial studies. The model gives reasonably accurate predictions of key silage quality parameters, but further experimental work is needed on growth of lactic acid bacteria and on plant‐enzyme proteolysis. Predicted final pH depends primarily on the pH at which bacterial growth and death rates are equal. Initial bacterial concentration affects the time to rapid pH change, while maximum bacterial growth rate affects the rate of decline thereafter.
Evaluation of faecal indices for predicting phosphorus status of cattle
Authors: HOLECHEK J. L. , GALYEAN M. L. , WALLACE J. D. , WOFFORD H.
Published: April 2006

An experiment examining the relationships between dietary and faecal phosphorus (P) concentration and intake and faecal output of P by steers is described. Six forages with a wide range of chemical properties were fed to six steers in a Latin square design. Dietary P concentration was highly associated with faecal P concentration in simple linear regression equations including (r2= 0.91) and excluding (r2= 0.94) animal variation. The regression slopes were similar to those in an Australian study involving dairy cows. However, the intercept values for the two studies differed. Phosphorus intake was well associated with daily faecal P output. Another study in Australia with steers showed similar results. However, the linear regression equation in the present study differed from that in the Australian study. Therefore, the application of a generalized equation to predict P intake from faecal P output is not advocated until the reliability of the equation in this study is confirmed with other forages.
The control of leatherjackets, Tipula paludosa Meig., in grassland by early application of insecticide
Authors: MOWAT D. J. , JESS S.
Published: April 2006

To determine whether leatherjackets might be controlled by application of a pesticide in summer, before oviposition by crane flies, chlorpyrifos was applied to perennial ryegrass (Lolium perenne) swards on dates from July to September in anticipation of leatherjacket infestation. Subsequent winter population estimates showed that leatherjacket numbers had been reduced by at least 85% by 0·72 kg chlorpyrifos ha‐1 applied on 13 July, and by 0·60 kg ha‐1 applied on 3 August or later.

The significance of leatherjacket control by pesticide application on these dates is discussed in relation to previously recorded effects of pesticide treatment on other known pests. It is concluded that control of all common arthropod pests of proven significance in established grassland may be achieved with one application of pesticide.
The effect of herbage allowance on intake and performance of ewes suckling twin lambs
Authors: PENNING P. D. , HOOPER G. E. , TREACHER T. T.
Published: April 2006

The effect of herbage allowance on the herbage intake and performance of ewes and their twin lambs at pasture was investigated. Daily herbage allowances of 40,80.120 and 160 g organic matter (OM) kg‐1 ewe live weight, based on herbage mass measured to ground level, were offered during the first 12 weeks of lactation.

The sheep were grazed rotationally around four paddocks of a perennial ryegrass pasture for 7‐day periods and herbage mass, extended tiller length and digestibility of the herbage consumed by the animals were estimated. Herbage intake by the ewes was estimated during weeks two to twelve and live weights were recorded weekly: during the last two weeks of the experiment grazing behaviour of one ewe on each treatment was recorded continuously.

Herbage intakes by the ewes (164, 1–81, 2–42 and 268 ± 0153 kg d‐1) and live weight gains of the lambs (202, 245, 274 and 300 ± 7–3 g d‐1) increased with increasing herbage allowances. Herbage intakes by the ewes and growth rates of their lambs increased up to a herbage allowance which was over five times the amount of herbage eaten by the ewes.

As the animals reduced herbage mass and sward height, biting rates by the ewes during grazing increased by 4 (± 0·08) bites min‐1 cm‐1 and masticating rates decreased. Mastications reached a maximum of 90 (± 3·5) min‐1 at a sward surface height of 9 cm.
The fitting of frequency distributions to height measurements on grazed swards
Authors: GIBB M. J. , RIDOUT M. S.
Published: April 2006

Herbage height was measured in ryegrass/white clover (Lolium perenne/Trifolium repens) swards grazed by cattle using the rising plate meter or the sward stick. Ordinary single normal and double normal distributions were fitted to the data obtained. After the first 6 weeks of continuous grazing the double normal distributions fitted data for the taller swards better than the single normal distribution did, but for a short sward there was no improvement. There was no improvement due to the use of the double normal distribution with data for swards grazed by sheep.
Persistence of seeds of some grass species in cultivated soil
Authors: Roberts H. A.
Published: April 2006

Freshly collected ripe caryopses of twenty‐five indigenous grasses were mixed with the top 7–5 cm of sterilized soil confined in cylinders sunk in the ground and cultivated three times yearly. There was a flush of seedlings of most species shortly after sowing, but species differed in the persistence of viable seeds. About one third, including Bromus sterilis, B. hordeaceus, Lolium perenne ssp. perenne, Arrhenatherum elatius and Alopecurus pratensis, produced few seedlings after the initial flush. Others such as Deschampsia cespitosa, Holcus lanatus and Poa trivialis, recognized as forming persistent seed banks in grassland soils, produced appreciable numbers of seedlings in the second year after sowing. Most persistent were species that occur as arable weeds (Avena fatua, Poa annua) or in wetlands (Glyceria plicata, G. maxima, Alopecurus geniculatus). Emergence from the seed bank generally followed soil disturbance but some species (Aira praecox, Avena fatua, A. sterilis ssp. ludoviciana, Danthonia decumbens) exhibited consistent seasonal patterns which may be associated with cyclic changes in germination requirements of the buried seeds.
Growth and production of a Cortaderia ptlosa (Gramineae) community in the Falkland Islands
Authors: McADAM J. H.
Published: April 2006

Above ground production of a typical Cortaderia pilosa dominant sward in the Falkland Islands was estimated over one growing season by summing significant positive increments in DM production of various sward components and by sequential cutting to ground level. The standing crop was characterized by a high proportion of standing dead matter at all times of the year. Net herbage production was estimated as 2200 kg ha‐1 and 1440 kg ha‐1 by the ‘difference’ and “sequential culling” techniques, respectively. The pattern of leaf growth was determined on another site by regular linear measurements of a population of physiologically similar C. pilosa leaves. There was very little early season growth and most of the DM was produced in a short period in the middle part of the growing season. The poor early season growth was attributed to adverse climatic conditions. A significant increase in green matter digestibility in October and November was masked by the low digestibility and high contribution to the overall DM by the standing dead component of the herbage.

The implications of these findings are briefly discussed in relation to the increased utilization of C. pilosa by improved pasture management, including burning and possibly reseeding areas with improved species. Tissue turnover studies combined with more knowledge of sheep nutrition cycles would enable grazing systems to be developed on a sounder basis than previously.
Effects of vernalization on the subsequent rates of leaf extension and photosynthesis of perennial ryegrass (Lolium perenne L.)
Authors: Stapleton J. , Jones M. B.
Published: April 2006

Temperature and daylength treatments have been used to investigate the apparent link between the potential for rapid leaf extension in spring and floral initiation and development in Lolium perenne (cv. Vigor). After growth at 5°C for 10 weeks (vernalization treatment) the leaves which developed at 15°C expanded significantly faster than non‐vernalized controls under both long and short days. Under long days floral development was initiated in vernalized plants but under short days it was not. Specific leaf area was higher in vernalized than non‐vernalized plants under long days.

The photosynthetic capacity of leaves which developed on plants which had been previously vernalized and then grown at 15°C under long days was higher than non‐vernalized controls when expressed on a leaf area and dry weight basis, but not on the basis of chlorophyll content. Vernalization followed by short days resulted in a smaller and non‐significant increase in the photosynthetic capacity of leaves.

Application of gibberellic acid (GA) as a spray to non‐vernalized plants did not affect floral development but did increase the rate of leaf extension. The application of GA did not affect specific leaf area or photosynthetic capacity expressed on an area basis.
A comparison of two cultivars of Holcus lanatus with Lolium perenne, under cutting
Authors: WATT T. A.
Published: April 2006

This work examined whether or not Holcus lanatus, cv. Massey Basyn, is an improvement on plants from German Commercial seed of this species and whether either could outyield Lolium perenne cv. Aberystwyth S23. The three grasses were sown in monoculture in a field near Oxford and received a total of either 250 or 500 kg N ha‐1 over two years. They were also sown with Tri‐folium repens cv. Blanca. The plots were cut 11 times over the 2‐year period at a height of 50 mm from ground level.

At the high rate of nitrogen Lolium perenne always gave the highest yields of DM and DOM. In the second year, both types of H. lanatus gave higher yields than L. perenne at the low level of N. The L. perenne and T. repens mixture yielded more than that with H. lanatus and T. repens. H. lanatus depressed the yield of T. repens more than did L. perenne. H. lanatus h lanatus; Massey Basyn was affected less by rust infection than was German Commercial H. lanatus. At the final harvest, plots with r. repens contained more unsown grass than did N‐fertilized plots sown to grasses only.
The invertebrate fauna of grassland and its influence on productivity. 1. The composition of the fauna
Authors: CURRY J. P.
Published: April 2006

The invertebrate groups which are of most significance in grassland are briefly reviewed. Factors influencing the abundance and composition of the fauna are considered together with the types of damage caused in grassland, the economic importance of such damage and beneficial effects on soil fertility.
The effect of lodging on 14C‐assimilate distribution after anthesis in Lolium perenne, CV. S24, grown for seed
Authors: HAMPTON J. G. , CLEMENCE T. G. A. , HEBBLETHWAITE P. D.
Published: April 2006

Field experiments in 1981 and 1981 examined assimilate distribution in lodged and non‐lodged plots of perennial ryegrass (Lolium perenne), cv. S24, grown for seed. Lodging was prevented either mechanically (1982 only) or chemically, by application of paclobutrazol (PP333) at 2 0 kg a.i. ha‐1. For each treatment, main‐tiller ears, stems and leaves and subtending vegetative tillers were fed with 14CO2 at 24 and 17 days after anthesis in 1981 and 1982, respectively, and the pattern of 14C‐assimilate export from each fed part was determined.

Prevention of lodging increased assimilate movement to the ear from the flag leaf, although movement from main‐tiller leaves was primarily downwards to vegetative tillers. Assimilate movement to the stem was also increased because the cessation of stem elongation was delayed, especially where lodging was prevented by PP333. Both increases were at the expense of the tillers, although their number was not reduced in non‐lodged plots. Possible reasons for these changes in assimilate distribution are discussed.
Control of sward conditions and apparent utilization of energy in the buffer grazing system
Authors: ILLIUS A. W. , LOWMAN B. G. , HUNTER E. A.
Published: April 2006

Experiments were carried out over four years to develop a system of buffer grazing. Groups of 16 cattle were set stocked with or without buffer areas formed by withholding a proportion of the grazing area by electric fence. It was found that buffers should be grazed if sward height, measured by rising plate meter, was reduced below 5 cm, or otherwise cut for silage. Increasing the area of the buffer reduced cattle gains but increased silage yield and sward quality, and the best compromise over 4 years was a buffer area of 25‐30% of the initial grazing area. Buffer treatments gave higher UME and financial output than controls, due to the value of silage from the buffers and to the higher nitrogen inputs which were successfully managed under buffer grazing. The higher outputs over 4 years were also associated with lower viability and therefore lower levels of risk, resulting from a number of compensating processes at sward and animal level. There was no indication that grazed UME was higher on buffer treatments at a given level of nitrogen, suggesting that any increased grazing efficiency must be offset by other disadvantages when comparing intensive with lax defoliation regimes. The results suggest that there is considerable stability in grazing systems which may frustrate attempts to improve their biological efficiency, although there is some scope for manipulating the seasonal pattern of land use and animal performance.
Effect of sample drying on the determination of fibre and water‐soluble carbohydrates of maize silage
Authors: PICCAGLIA ROBERTA , GALLETTI GUIDO C.
Published: April 2006

Neutral detergent fibre (NDF), acid detergent fibre and water‐soluble carbohydrates (WSC) were assayed in wet and dry samples of maize silage, either treated with NaOH or untreated (control), before and after ensiling.

Statistically significant effects of drying at 60°C were observed in WSC, NDF and cellulose estimations expressed on the basis of 105°C dry matter.

It could therefore be preferable to analyse wet samples, as these are not altered by the degradations induced by oven‐drying and are more representative of the original condition of the forage.
The invertebrate fauna of grassland and its influence on productivity. III. Effects on soil fertility and plant growth
Authors: CURRY J. p.
Published: April 2006

The effects of grassland invertebrates on organic matter decomposition, soil fertility and plant growth are reviewed. Their role as primary decomposers is limited because of relatively low rates of metabolic and enzymatic activity compared with microorganisms. However, they greatly facilitate decomposition by fragmenting and incorporating litter into the soil and by stimulating microbial activity. Earthworms are the main litter consumers in productive temperate grasslands and termites in the tropics, while the activities of dung beetles, dipterous larvae and earthworms are essential for efficient dung decomposition. Earthworms and microbial‐feeding invertebrates facilitate mineralization and release into the soil solution of plant nutrients. Earthworms have a major influence on soil structure through burrowing, soil ingestion and mixing and they significantly increase plant growth.

Herbivorous invertebrates at non‐outbreak densities normally consume less than 10% of net primary production in grassland, but consumption bears little relationship to overall effects on productivity. These depend on factors such as the nature of the damage caused and regrowth potential, tolerance for damage and effects on animal production at the time of attack. Sap feeding insects may cause wilting and reduced growth and selective feeding on preferred species can alter botanical composition, while aphid‐transmitted virus disease can depress yield. On the positive side, low levels of herbivory can stimulate growth, weed feeding insects may limit the distribution of pasture weeds, while the role of flower‐visiting insects can be important in the pollination of legume seed crops. Pest management approaches incorporating biological control, alteration of botanical composition, adjustment of stocking densities and accurately timed insecticidal applications offer prospects for the control of recurring pests such as grass grub and porina in New Zealand.
Interactions between fertilizer use and leatherjacket control in grassland
Authors: BLACKSHAW R. P. , NEWBOLD J. W.
Published: April 2006

A coordinated experiment was set up in eight fields of established grass; four In Northern Ireland and four in the West of Scotland. At each site one of three different fertilizer rates (0, 75 and 150 kg N ha‐1) were applied to plots that had previously either received a 0.72 kg ha‐1 chlorpyrifos treatment to control leatherjackets or no spray. Both fertilizer and insecticide applications increased herbage yields. Yield increases in response to chlorpyrifos treatments were equivalent to that obtained from 75 kg N but were not linearly related to leatherjacket numbers. A curvilinear function relating loss per leatherjacket to population size was derived and its validity is discussed. It is concluded that herbage yield increases resulting from chlorpyrifos and nitrogen applications were independent and cumulative.
Application of double normal frequency distributions fitted to measurements of sward height
Authors: GIBB M. J. , RIDOUT M. S.
Published: April 2006

Herbage heights were measured with a rising plate meter in mixed perennial ryegrass/white clover (Lolium perenne/Trifolium repens) swards maintained under five different systems of management. Double normal distributions fitted to the height frequencies were used to interpret changes over the grazing season in the mean heights of the shorter ‘frequently’ and the taller ‘infrequently’ grazed components of the sward, the variability of height within the two components, and the proportions of the two components in the sward. An attempt was also made to demonstrate that the overlap of these components, implicit in fitting double normal distributions, is a true reflection of the height distributions of frequently and infrequently grazed areas of the sward, and that the fitting of such a distribution provides a useful estimate of the proportion of a sward which is infrequently grazed.
The effects of a flexible grazing management strategy and leader/follower grazing on the milk production of grazing dairy cows and on sward characteristics
Authors: MAYNE C. S. , NEWBERRY R. D. , WOODCOCK S. C. F.
Published: April 2006

An experiment was carried out during 1984 to examine the effects of three alternative grazing strategies for January/February calved British Friesian dairy eows on sward and animal production. Cows were rotationally grazed across 1 d paddocks without concentrate supplementation from 30 April to 1 October. A flexible grazing (EG) treatment involved manipulating residual herbage height, as assessed by a rising‐plate sward stick, with cows initially grazing to 80 mm, reducing to 60 mm when milk yield declined below 20 kg d−1 and finally to 50 mm when milk yield declined below 15 kgd−1. Control (C) cows grazed to a constant residual herbage height of 60 mm throughout the season (a 60‐inm rising‐plate sward stick height is equivalent to a sward surface height of approximately 80 mm). On a further treatment a leader/follower (LF) approach was used, with cows paired for calving date and parity and within pairs allocated to either a high‐(leader) or a low‐yielding (follower) group, according to milk yield at turnout, with the leader group grazing 1 d ahead of the follower group. Overall stocking rates on C and LE treatments were identical but herbage allowances differed as a result of treatment effects.

Animal performance data for the FG, C and LE treatments, respectively, were: milk yield (kg d−1) 14·5, 14·7 and 16·0 (s.e. 0·59); milk fat yield (g d−1) 577, 571 and 637 (s.e. 29); milk protein yield (g d−1) 528, 527 and 576 (s.e. 19); and liveweight gain (kg d−1) 0·09, 0·20 and 0·14 (s.e. 0·04).

Overall, there was no benefit in animal production following lax grazing in spring even with high‐yielding cows, and this approach resulted in the accumulation of stem and senescent material in the sward in mid‐season. However, preferential treatment of high‐yielding cows by grazing as a leader group in a leader‐follower system resulted in higher milk production, particularly in late season, with an overall improvement in milk yield for the LF treatment of 9% relative to treatment C.
The effect of pesticide application on the establishment of white clover in a newly‐sown ryegrass/white clover sward
Authors: MOWAT D. J. , SHAKEEL M. A.
Published: April 2006

In plots of perennial ryegrass and white clover, regular treatment with chlorpyrifos and methiocarb more than trebled the clover content of the sward, compared with untreated plots, in just over 2 years from sowing. Chlorpyrifos alone accounted for most of the effect, which was attributed mainly to the control of Sitona lepidus. Combined treatment increased total herbage dry matter yield by 4·24 t ha−1 during this period but had little effect on grass‐only plots. Methiocarb appeared to have contributed by assisting earlier establishment of clover, but otherwise had little effect until slugs, which were initially uncommon, became more abundant in the later stages of the experiment. The effect of slug control was most noticeable in a cultivar of low cyanogenic potential. This factor did not influence the effect of chlorpyrifos.
Susceptibility to losses during mechanical silage and haymaking operations in relation to grass dry matter content
Authors: MCGECHAN M. B.
Published: April 2006

A series of laboratory experiments is described to investigate the susceptibility of grass forage to losses during mechanical field conservation operations in relation to dry matter content. Losses were measured during a simulated manual ‘tedding’ treatment carried out on grass samples being dried on a laboratory thin‐layer drying rig. Values of loss per successive treatment remained at a near constant low level at low dry matter (DM) contents, except for a somewhat higher loss level from the first treatment. As DM content rose above about 60%, the level of loss per treatment rose rapidly with increase in DM content. A relationship between loss per treatment and DM content was derived from the data by a bilinear regression analysis, and this will be incorporated into an Operational Research model of forage conservation systems.
The effect of some invertebrate species on the growth of white clover (Trifolium repens L.) in the lahoratory
Authors: MOWAT D. J. , SHAKEEL M. A.
Published: April 2006

In laboratory experiments to clarify earlier field observations, Sitona lepidus larvae caused significant damage to established clover plants at infestations of approximately 1–2 per plant. When eggs were placed on the soil, cultivars of differing cyanogenic capacity were damaged equally. The plants did not recover when larval feeding ended.

Leatherjackets, slugs and ‘lucerne flea’ fed most on the least cyanogenic cultivars, even where no choice was offered. Plants ultimately recovered from damage by leatherjackets. Deroceras reticulatum caused more damage than did Arion fasciatus. The proportion of leaves damaged by lucerne fiea was highest in the least cyanogenic eultivar but also tended to increase in the most cyanogenic cultivar, confirming a field observation. At high population densities lucerne flea was capable of killing some seedlings but was not tested against established plants.
The effects of simulated continuous grazing on development and senescence of white clover
Authors: JONES D. R. , DAVIES ALISON
Published: April 2006

Two experiments investigating the effects of simulated continuous defoliation on white clover development and senescence are described. Stolons growing in boxes in a glasshouse were defoliated repeatedly by hand to simulate different intensities of continuous grazing by sheep. The experiments continued in both instances until eleven leaves had been produced on stolons in the most favourable treatment.

It was found that leaf dry matter production was reduced in proportion to the leaf complement of the stolon. Reduction of the leaf complement from two leaves to one leaf led to a reduction in subsidiary branch production of about 25% and an increase in percentage dead stolon from 33 to 44%, If no fully expanded leaves were retained branch production fell to 40% or less of that observed when two leaves were retained.

Stolons growing in swards continuously grazed by sheep usually have a green leaf complement varying between zero and two leaves per growing point. The consequences of maintaining different leaf complements in this range are discussed in the light of the current experiments.
Use of the in situ technique in the study of degradation of lucerne and smooth bromegrass genotypes
Authors: MATHISON G. W. , JAHN H. G. , WALTON P. D. , MILLIGAN L. P.
Published: April 2006

Six lucerne (Medicago sativa) genotypes (Beaver, Vernal and four other strains being developed at the University of Alberta) and five smooth bromegrass (Bromus inermis) genotypes (Carlton, Magna and three genotypes being developed) were examined in terms of forage dry matter (DM) yield and degradability, as determined by the rate and amount of material which disappeared from bags suspended in the rumen of cattle. Dry matter yield did not differ (p > 0·05) between lucerne genotypes at first cut. The smooth bromegrass strain 517 had a proportionately Oil higher (P < 0·05) DM yield than did the Magna strain. No differences (P < 0·05) were detected within either smooth bromegrass or lucerne genotypes for 48 or 60 h in situ DM degradability. The 416E smooth bromegrass genotype, however, had a significantly higher (P < 0·05) rate of DM degradation in the rumen than the other genotypes and also exhibited a longer (P < 0·05) lag period before a significant amount of DM degradability occurred. In the in situ technique, approximately eighteen bags would have been needed to obtain DM degradability measurements with a confidence interval of 0·04 for DM degradability of a probability of 0·95. Further in vivo studies with the bromegrass genotypes are warranted to ascertain if the differences in digestion rates and lag times are related to meaningful differences in animal intake and digestibility.
The nutritional evaluation of Italian ryegrass cultivars fed as silage to sheep and cattle
Authors: MOSELEY G. , JONES E. L. , RAMANATHAN V.
Published: April 2006

Three feeding trials with big bale silage were carried out to determine whether previously established intake differences between artificially dried Italian ryegrass cultivars could be repeated under differing conditions of food preparation and presentation. The silage was prepared in 2 consecutive years from the same field crop and fed to groups of cattle in both years. The second year silage was also fed to sheep indoors. All animals were fed ad libitum and the voluntary intakes recorded for groups of cattle and individual sheep. Chewing activity was also recorded on all groups of sheep.

The chemical composition of the two cultivars as fresh grass was similar in 1984 but there were small differences in 1983 with Tarquin showing slightly higher organic matter digestibility (DOMD) and lower dry matter and water‐soluble carbohydrate compared to RvP. The only consistent differences in silage composition between cultivars was a slightly higher level of modified acid detergent (MAD) fibre in RvP compared to Tarquin. Despite these small differences the voluntary intake of cattle fed Tarquin was 19% higher than RvP in the first year and 35% in the second, while sheep showed a similar difference of 40% with the second year silage.

Recording of jaw activity with sheep showed that animals spent 40% more time eating and 27% more time ruminating RvP than Tarquin per unit of food eaten. This suggested that the intake differences, which were independent of digestibility, were related to the physical resistance of the feed to breakdown by chewing. These differences depend on the structural characteristics of the plants and were associated with differences in leaf/stem ratios and MAD‐fibre content. These are less likely to be affected by the method of conservation or feed presentation and, although the degree of difference between the cultivars changed with the different procedures, the inherently higher intake of Tarquin persisted.
Effect of plant density on stolon growth and development of contrasting white clover (Trifolium repens) varieties and its influence on the components of seed yield
Authors: MARSHALL A. H. , JAMES I. R.
Published: April 2006

Plants of two contrasting white clover varieties (cv. Aberystwyth S184 and Olwen) were planted in the field in spring in each of 2 years at four densities (9, 25, 49 and 100 plants m−2) in 1‐m2 plots. The effect of plant density on stolon growth and development and the components of seed yield was subsequently measured.

Stolon growth and development was influenced by plant density, variety and year. At low plant densities both white clover varieties produced longer primary stolons than at higher densities. Plant density, however, had no significant effect on the number of inflorescences at harvest. At the high stolon densities there were significantly fewer reproductive nodes per primary stolon than at the lower plant densities. Plant density did not significantly affect any other seed yield components, but the number of inflorescences at harvest, florets per inflorescence, seed set per floret and 1000‐seed weight were all significantly influenced by both variety and year.

The relationship between the vegetative and reproductive growth of white clover is discussed in relation to plant density, variety and climate and the possible role of defoliation managements on inflorescence development.