The effect of a high-magnesium perennial ryegrass variety on the magnesium status of sheep

An early-heading variety of perennial ryegrass (Ramore) bred for high magnesium (Mg) content was compared with an early control variety (Frances) for its ability to increase Mg intake, Mg utilization and blood Mg concentration in sheep, and so reduce the incidence of hypomagnesaemic tetany. Swards of the two varieties were established and each was grazed by ewes suckling twin lambs from turn-out to weaning and thereafter by dry ewes. In early and late season herbage from a proportion of each sward was cut daily and fed fresh to ewes housed indoors in metabolism crates. Under grazing conditions herbage from Ramore swards had, over the 1992 and 1993 grazing seasons, a higher Mg concentration than Frances (2.35 g kg^?1 vs. 2.18 g kg^?1; s.e.m. 0.019, P< 0.001). During the spring period there was a higher (P 0.001, s.e.m. 0.0074) Mg concentration in the blood of ewes grazing Ramore (0.854 m mol 1^?l) swards compared with those grazing Frances (0.793 m mol 1 ^?1) whereas during the autumn period blood Mg concentrations were higher in ewes grazing Frances. Ewe and lamb liveweight gains, recorded in 1992 only, were higher on Ramore swards than on Frances swards, although the difference was not significant. Indoor feeding studies showed that Mg intake was significantly higher (P< 0.001, s.e.m. 0.026) in ewes offered Ramore (1.98 g d^?1) herbage compared with those offered Frances (1.74 g d^?1) herbage with no significant difference in dry-matter intake between the two varieties. Apparent availability and retention of Mg were higher for animals fed Ramore during the spring feeding periods than those fed Frances, but during the autumn feeding periods the reverse was true. Under indoor feeding conditions, variety had no significant effect on blood Mg concentrations. It was concluded that under grazing conditions a high Mg variety could provide an effective means of reducing the incidence of hypomagnesaemic tetany.     

Effect of a stay-green locus on the dry-matter yield, nitrogen yield and shoot density of perennial ryegrass

A rare stay‐green allele transferred from meadow fescue (Festuca pratensis L.) to perennial ryegrass (Lolium perenne L.) has improved both the colour of turf and the nutritive value of herbage. In this study its effect on shoot density and forage yield was assessed. Equivalent populations of perennial ryegrass were constructed with and without the stay‐green allele, following eight generations of backcrossing to perennial ryegrass. The stay‐green population, the normal population and the cv. AberStar were compared over two harvest years (2005 and 2006) in a field experiment with six application rates of N fertilizer (100, 200, 300, 400, 500 and 600 kg ha^?1 annually). There were no significant interactions between level of N fertilizer and population in any of the traits measured. The mean annual dry‐matter (DM) yield over all populations and fertilizer levels was 6·45 t ha^?1 lower in the second harvest year. Mean annual DM yields over all fertilizer levels of the normal population were higher than, or equal to, AberStar while those of the stay‐green population were significantly (proportionately 0·10–0·13) lower than the normal population. In 2005, the mean total yield of N in the herbage of the stay‐green population was 0·09 lower than that of the normal population and the mean concentration of N over all harvests was 1·5 g kg^?1 DM higher. The shoot density of the stay‐green population after the last harvest in November 2006 was 0·18 lower than that of the normal population (3689 and 4478 shoots m^?2 respectively).     

The effects of Rumex obtusifolius on the seasonal yield of two mainly perennial ryegrass swards

A preliminary field experiment on a sward cut six times during 1978 indicated that total grass herbage harvested was negatively related to the number of Rumex obtusifolius plants present; densities of five to ten plants m⁻² resulted in reductions of up to 30%, although the total quantity of herbage harvested (including Rumex ) may have remained constant. However, R. obtusifolius densities did not significantly affect grass yield during the first half of the growing season. A negative relationship between R. obtusifolius ground cover and grass yield, particularly from late July onwards, was shown in a second field experiment during 1979 and 1980 using a 3-cut management. It was estimated that to produce a 20% reduction in grass growth in July-August and October, R. obtusifolius ground covers of 30% and 20% respectively were needed. Sixty per cent of the total herbage harvested in 1980 consisted of R. obtusifolius. These results indicate the damage that can be caused by this species and suggest that control measures should be taken before early summer.     

The effect of nitrogen and length of primary growth period on yield of leaf and stem components of perennial ryegrass

The influence of length of first growth period of the season and level of nitrogen application on yields of leaf and stem components of perennial ryegrass was estimated. Three primary growth periods of 21, 42 and 70 d were used in combination with nitrogen treatments allowing 0, 1.43, 2.86 and 429 kg N per ha per d of growth applied as a single dressing at the beginning of the growth period. Increases in level of nitrogen application and in growth time produced higher yields of both components, but particularly of stem. Mean leaf yield per tiller reached a maximum with a 42-d growth period. Whilst the ratio of leaf: stem was altered markedly by longer growth periods it was apparently unaffected by nitrogen application.     

Relationships and influence of yield components on spaced-plant and sward seed yield in perennial ryegrass

Adequate seed production is essential for cultivar success in perennial ryegrass turf and forage industries, but improvement is limited by the complexity of yield components and low-rank correlations between selection and production environments. This study examined seed yield components among 20 perennial ryegrass entries in both spaced plantings (selection environment) and swards (production environment) at two locations in Minnesota. Competitive (23 plants/m²) and non-competitive (3 plants/m²) spaced-plant nurseries were tested. Competitive spaced-plant total yield was highly correlated with sward yield (r_s = 0.64 and 0.66, p < 0.01) at both locations, whereas the non-competitive environment showed no correlation. Structural equation modelling (SEM) was used to explore the indirect and direct relationship of fall vegetative growth, winterkill, and yield components on total seed yield in all environments. Fertile tiller number (spikes plant⁻¹/m⁻²) exhibited both strong direct and indirect influence on total seed yield in all environments. However, the importance of fertile tiller number in the SEM was reduced with increased plant competition. The SEM showed that both weight per spike and seed yield per spike influenced total yield in spaced plants; however, neither consistently predicted total sward yield. The ratio of these two traits (g seed spike⁻¹/g spike⁻¹) gave an index of fertility that was easy to measure and had a superior correlation with sward yield at two locations (r_s = 0.81 and 0.54, p < 0.05) when spaced plants were under competition. Results suggest that increasing competition in spaced plantings and selecting for spike fertility may more accurately identify superior plant material compared to lower competition environments.     

The effect of delayed autumn harvest on the survival of varieties of perennial ryegrass

The reactions of five early and five late varieties of perennial ryegrass to stimulation of bulky autumn growth and deferment of harvesting were compared in terms of spring growth and subsequent recovery during three winters. Winterkill was marked in 1971–72, particularly when harvesting was deferred to late November, in early varieties S24 and Presto Pajbjerg and in the late variety S23. Least affected among early varieties were Premo and Barvestra (tetraploid) and among late varieties, Perma and Barpastra (tetraploid). All varieties showed rapid recovery. The results are discussed in terms of the significance of winterkill, and the effects of age of sward, variety susceptibility and deferment of autumn defoliation. It is concluded that the form of winterkill which occurs in the west of Scotland can have serious consequences to farm productivity in severe winters. Autumn growth left standing into November can also lead to winterkill. Under good management, varietal differences are unimportant. In a severe winter, no varieties of perennial ryegrass are reliable.     

The effect of cutting on the proportions of perennial ryegrass and white clover in mixtures

In two experiments with ryegrass/white clover mixtures, the proportion of clover was measured before and after cuts which removed 8-75% of above-ground biomass. Cutting was found to reduce the proportion of clover leaf area in the crop in both experiments, sometimes by as much as two-thirds, and the proportion of clover dry weight, by up to half, in one of them. That is, the harvested material contained a greater proportion of clover than did the sward before the cut. This disproportionate removal of clover was due to clover having a greater proportion of its leaf near the top of the canopy than grass. It showed that preferential removal of clover occurs as a result of the purely passive selection by a mower, not only as a result of grazing by animals which may be capable of active as well as passive selection.
Despite the disadvantage to clover of losing more of its leaf area than grass, and in some cases more of its dry weight also, when the mixture was cut, the clover content of the sward did not decrease during the growing season as a whole. This was because, where no nitrogen fertilizer was applied, clover had a greater relative growth rate (RGR) than its companion grass during the growth periods between cuts and this increased its percentage of the mixture. Even where nitrogen was applied, clover equalled the RGR of grass and maintained its proportion of the crop, except in one instance.     

Genome-wide markers for seed yield and disease resistance in perennial ryegrass

The market success of perennial ryegrass(Lolium perenne L.) cultivars depends on sufficient seed production, as they are propagated by seed. However, breeding for high quality forage production reduces seed yield, and breaking the negative correlation would help to overcome the problem. The foliar disease crown rust is another factor affecting reproductive capacity and thereby seed yield. We evaluated seed yield-related traits and resistance to crown rust in a collection of commercial cultivars and ecotypes of perennial ryegrass and identified genome-wide markers associated with the traits. The study revealed high variation between the ecotype and cultivar groups as well as between years. A genome-wide association study identified 17 DNA single-nucleotide polymorphisms(SNPs) of which eight were associated with crown rust and nine with flag-leaf length. The SNP markers were located within or near predicted genes functioning in defense against pathogens. The identified genes are strong candidates for a further in-depth functional study to continue unravel determination of leaf architecture and crown rust resistance in perennial ryegrass.     

The effect of temperature on the spring growth of perennial ryegrass at three contrasting sites

The effect of temperature on the spring growth of perennial ryegrass swards was studied at three contrasting sites. Two of these were situated on land restored after opencast coal mining, one of which had been drained. The third was on undisturbed land of the same soil type. Rates of leaf extension were measured in an attempt to give an early indication of differences in plant growth in the spring of 1982.
Spring growth started earliest on undisturbed land. On the restored land drainage proved beneficial, for although the onset of growth was delayed compared to the undisturbed site the subsequent rates of growth were similar. Both the onset and the rate of growth were slower on the undrained site. Highly significant relationships existed between leaf extension rate and soil temperature at each site. However, when sites were compared, differences in soil temperature could only partly explain observed differences in growth rate between sites.
It was concluded that some factor other than soil temperature was responsible for the difference in spring growth between the undisturbed site and the undrained opencast site in this experiment.     

Independence of dry matter yield and leaf yield among perennial ryegrass varieties differing in seasonal yield distribution

Four varieties of perennial ryegrass ( Lolium perenne L.), (Ba11316, Merlinda, Morgana and Talbot), with similar ear emergence dates but differing in seasonal yield distribution were compared over two harvest years (1992 and 1993) in a small plot trial employing six levels of fertilizer N (100 to 600kg Nha⁻¹ year⁻¹ applied monthly as split dressings). In each year, a conservation cut in May was followed by five further harvests at monthly intervals. Herbage samples from each of the twelve harvests were separated into leaf lamina and other tissues, and the yield of leaf lamina calculated. The percentage of flowering tillers was determined in May and July of each year, Ba11316 produced significantly more dry matter (DM) than the other three varieties at six of the twelve harvests, but its total DM yield over all twelve harvests was 5% less than Merlinda and 3% less than Morgana, owing to lower yields of reproductive growth in May of both years. Varieties also varied in mean leaf content of the herbage over all harvests, Ba11316 being 69 g kg⁻¹ higher than that of Merlinda. Differences among the varieties in leaf content were primarily because of difference in proportion of flowering tillers, Ba 11316 having a lower proportion of flowering tillers than the other three varieties. However, the mean leaf content of the tetraploid Merlinda was significantly lower than that of Morgana although these two varieties had a similar mean percentage of flowering tillers. Despite its lower total DM yield, Bal 1316 produced 16% and 14% more leaf over the two harvest years than Merlinda and Morgana respectively. Total leaf yield of Talbot was significantly higher than that of Merlinda and Morgana, although Talbot had been developed twelve years earlier than the other two varieties.     

The effects of spring closing date on the yield and quality of perennial ryegrass and cocksfoot cut for conservation

This second paper concerned with effects of prolonged spring defoliations on two early perennial ryegrass varieties (Cropper and RvP Hay Pasture), an intermediate perennial ryegrass (Talbot) and an early cocksfoot (Roskilde) examines the effects of different closing dates on ear emergence, weekly DOMD ( in vitro ) and conservation yields. The grasses were mown fortnightly to simulate sheep grazing from January until three closing dates, 19 April, 3 May or 17 May, in 1978 and 1979. A set of plots was left undefoliated. All plots were sampled weekly from 2 or 3 weeks after 17 May until the end of June or early July.
Prolonged mowing resulted in a small delaying effect on 50% ear emergence of the ryegrasses. The maximum delay was 3 d with the latest closing date. Under this treatment, ear emergence of the cocksfoot was delayed by an average of 12 d but by only 0–4 d under the earlier closing dates. Delay in date of closing caused a significant delay in the time to reach a given DOMD but the effect was largely confined to the latest closing date and was greatest for the cocksfoot. The time when 670 g kg⁻¹ DOMD was reached was delayed in the ryegrasses by no more than 5 d, except for a 12-d delay in the intermediate ryegrass in 1978 following the late closing date. Under this treatment the delay for the cocksfoot was 8 d in both years. The early ryegrasses produced stemmy regrowths.     

The effect of cutting frequency and applied nitrogen on production and digestibility of perennial ryegrass

Grass swards were cut at intervals of 2, 3, 4, 5, 6 and 8 weeks and received 336 or 673 kg ha^?1 nitrogen the higher level being applied as a single or as split dressings. Reducing cutting interval from 8 to 2 weeks reduced mean DM yield by 37% from 14·2 to 9·0 t ha^?1 and digestible DM yield by 24% from 9·4 to 7·2 t ha^?1. The response to the extra N at the highest level of application was greatest under the most frequent cutting regimes. Application of N did not affect the digestibility of DM. Results are discussed in relation to the comparative effects of frequency of cutting at different seasons of the year and at different levels of N.     

The effect of additives on the ensilage of forage of differing perennial ryegrass and white clover content

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 strategic nitrogen application and defoliation systems on the productivity of a perennial ryegrass/white clover sward

The productivity of a mixed sward comprising perennial ryegrass cv. Fantoom and white clover cv. Aran was measured under eight defoliation management systems and two fertilizer N rates (0 and 75 kg ha^-1) applied in spring. The defoliations involved a basic six-harvest simulated grazing system together with the interposition of silage cuts once or twice at varying times during the growing season; evaluation was made over three harvest years, 1983-85. Mean annual production of total herbage DM over the three years was 8.351 tha^-1 without N and 9.49 tha^-1 with 75 kg N ha^-1, a mean response of 15.2 kg DM per kg applied N. The responses for individual treatments occurred mainly at the first cuts, whether for simulated grazing (a mean of 12 9 kg DM) or for silage (a mean of 259 kg DM); however, this influence of spring N was not sustained at other cuts over the season. Mean annual white clover DM production was 4.19 t ha^-1 with no N and 3.32 t ha^-1 with 75 kg ha^-1 N, but the reduction due to N was not significant in any year. The mean amount of clover stolon DM present post harvest over all management systems was 1.33 t ha^-1 with no N and 1.03 t ha^-1 with 75 kg ha^-1 N. Mean annual DM production of total herbage from the six-harvest system was 8.11 t ha^-1 Compared with 8 88 t ha^-1 (a 9% increase) from the systems with one silage cut and 9.241 ha^-1 (a 14% increase) from the systems with two silage cuts. Corresponding white clover DM production was 4.02, 3 87 and 3 53 t ha^-1, respectively, and mean stolon DM amounts post harvest, 1 12,1.15 and 1-23 t ha^-1, respectively. It is concluded that grass/white clover swards are suitable for management systems which involve cutting for conservation. Spring N application did not greatly reduce white clover production in this experiment where white clover was at higher levels than are likely in farming practice and the swards were not grazed. More knowledge of spring N rates, and indeed of N application rates generally, would be advantageous in future assessment of silage cutting systems.     

The effect of insecticide treatment on the establishment and growth of Italian ryegrass under different sowing conditions

Italian ryegrass, Lolium multiflorum Lam., cv. RvP., was broadcast in spring on to fine and coarse seedbeds at seed rates of either 2 or 20 kg ha^-1. Each of the four combinations of sowing condition was either left untreated or treated with fungicide or insecticide. The establishment of the sown species and of weeds under each regime was measured and their relative contribution to dry matter assessed in four cuts during the sowing year. Seed rate affected weed invasion and yield more than seedbed condition. Insecticide treatment increased the establishment and yield of ryegrass and its contribution to total herbage yield under all four sowing conditions. The fungicide treatment had no effect. The improvements caused by insecticide treatment were associated with a reduction in the level of infestation by shoot flies, Oscinella spp. (Diptera: Chloropidae): the effect of a single treatment in April was still detectable in October.     

The influence of vernalization on response to nitrogen of perennial ryegrass

Vernalized and unvernalized perennial ryegrass (Lolium perenne cv. Gremie) tillers planted in microplots in a glasshouse in April 1974 and 1975 were exposed to natural daylength thus inducing vernalized plants to produce reproductive, and unvernalized plants vegetative growth. Nitrogen was applied at 0–30 g m^?2 (to 24 g m^?2 in 1975) to both types of herbage. At the first defoliation in each year yields from vernalized grass were greater than those from unvernalized grass; subsequently differences were minimal or reversed. Vernalization had no significant effect (P > 0.05) on total yields over four defoliations in either year. Apart from the first cut in 1974 nitrogen application increased dry matter yields of both types of herbage. Tiller numbers were usually increased by the lowest level of nitrogen application but at higher levels the effect was variable. There was no evidence of an interaction effect of level of nitrogen application and vernalization on dry matter yields.     

The effect of time of initial defoliation and height of defoliation on the productivity of perennial ryegrass swards

Over a 3-year period the productivity of perennial ryegrass ( Lolium perenne L., cv. S24) swards as influenced by variations in the time of initial defoliation and close (2·5 cm) and lax (8 cm) defoliation was studied. Treatments with initial defoliations in the early vegetative stage, stem elongation and flowering stages of growth gave higher annual yields than treatments in which the initial defoliation was taken at an intermediate stage of growth when the majority of the stem apices had just been elevated above the height of defoliation. Initial defoliation treatments which removed a high proportion of apical meristems while the yield at the initial defoliation was still low produced the lowest annual yield. Consistent lax defoliation reduced yield by 14·5% compared with continual close defoliation. However, taking an initial lax defoliation followed by subsequent close defoliations produced a slight yield advantage of 4·8% over consistent close defoliation. The results are discussed in relation to other research findings and the practical implications commented upon.     

The influence of climatic factors on physiological development in perennial ryegrass

Dates of initiation of reproductive development and of ear emergence were determined for four cultivars of perennial ryegrass (Lolium perenne) representing a range in maturity from early to late in a single trial in 1977. The influence of climatic factors upon the reproductive development was investigated and it was found that, while day-length largely influenced the dates of initiation, subsequent growth and development towards ear emergence was influenced mainly by temperature. The data indicated that cultivars may have similar requirements in terms of accumulated temperature between the physiological growth stage of initiation and the agronomically significant growth stage of ear emergence. The possibility of achieving greater accuracy in forecasting ear emergence dates by relating meteorological data to the physiological development of the individual cultivars is suggested.     

The performance of summer-calving cows grazing perennial ryegrass swards

The objectives of this experiment were to study the effects of different grazing managements in spring on herbage intake and performance of summer-calving dairy cows and to examine the effects of regrowth in early June on herbage intake and cow performance. Four spring-grazing treatments were applied to predominantly perennial ryegrass swards: Control (C), sward grazed by cows to 6–8 cm sward surface height (SSH); CG16, sward grazed by cows to 3–4 cm SSH in May and allowed to regrow to a target SSH of 16cm in early June; CG8, sward grazed by cows to 3–4 cm SSH in May and allowed to regrow to 8cm in early June; and SG8, sward grazed by sheep to 2–3 cm SSH in May and allowed to regrow to 8 cm in early June, All swards were continuously stocked by summer-calving (May and July) primiparous and multiparous cows from 16 June to 7 September, to a target SSH of 8–10cm. Spring treatments bad marked effects on herbage intakes and milk production. Estimated in July by n alkane analysis, the mean herbage intake ± s.e.d. of cows on each treatment were 1·8, 1·4, 1·4 and 3·0 ± 0·31 kg dry matter (DM) 100 kg live weight (LW)^?1 d^?1 (P < 0·01) for treatments C, CG16, CG8 and SG8 respectively. Measured in August, intakes were 1·8, 20, 2·1 and 2·4 ± O·33kg DM 100kg LW^?1 d^?1 respectively. Severe spring grazing led to increased milk yield and reduced milk fat content from summer-calving cows fed 5·2 kg d^?1 of a proprietary concentrate. Average milk yields for the eleven experimental cows on each treatment were 24·3, 23·4, 26·2 and 29·0 ± 1·20 kgd^?1 (P < 0·01) for C, CG16, CG8 and SG8, and average milk fat contents were 45·4. 42·4, 43·9 and 40·9 ± 1·02gkg^?1 (P<0·05) respectively. The results suggest that severe grazing of swards in early season could improve herbage intake and milk yield of summer-calving cows in mid- and late season. The most favourable spring treatment in this respect was severe grazing by sheep. However, this advantage could be negated in midseason by lax grazing at that time.