Sward Performance Research Articles

Sward type alters enteric methane emissions, nitrogen output and the relative abundance of the rumen microbial ecosystem in sheep.

Observed improvements in animal and sward performance, coupled with a desire for more sustainable pasture-based feeding systems, has triggered a surge in the implementation of more botanically diverse pastures. However, thus far, there has been limited research investigating the effects of botanically diverse sward types on enteric methane (CH4) or nitrogen (N) excretion, alongside the ruminal microbiota and fermentation profile, in sheep. Hence, this study investigates the effect of sward type on CH4 production and N excretion, in addition to assessing the rumen microbiome, volatile fatty acid proportions, and ammonia nitrogen (NH3-N) concentration in sheep. A 5 × 5 Latin square design experiment was implemented to investigate 5 dietary treatments; perennial ryegrass (Lolium perenne L.; PRG) only or PRG plus white clover (Trifolium repens L.; PRG + WC), red clover (Trifolium pratense L.; PRG + RC), chicory (Chicorium intybus L.; PRG + Chic) or plantain (Plantago lanceolata L.; PRG + Plan). Diets were mixed at a ratio of 75% PRG and 25% of the respective companion forage and 100% PRG for the PRG treatment, on a dry matter basis. Twenty castrated male sheep were housed in metabolism crates across 5 feeding periods. Methane measurements were acquired utilizing portable accumulation chambers. Rumen fluid was harvested using a transoesophageal sampling device. Microbial rumen DNA was extracted and subjected to 16S rRNA amplicon sequencing and fermentation analysis. Data were analyzed using PROC MIXED in SAS. Results show that animals consuming PRG + WC ranked lower for CH4 production (g/d) than sheep offered PRG, PRG + Chic or PRG + Plan (P < 0.01) while the addition of any companion forage ranked CH4 yield (g/kg dry matter intake (DMI)) lower (P < 0.001) than PRG. There was a moderate positive correlation between DMI and CH4 (g/d; r = 0.51). Ruminal NH3-N was lowest in animals consuming the PRG diet (P < 0.01). There was a greater abundance of Methanobrevibacter and reduced abundance of Methanosphaera (P < 0.001) in sheep offered PRG, compared with any binary sward. On average, herb diets (PRG + Chic or PRG + Plan) reduced the urinary nitrogenconcentration of sheep by 34% in comparison to legume diets (PRG + WC or PRG + RC) and 13% relative to the PRG diet (P < 0.001). Sheep offered PRG + Chic had a greater dietary nitrogen use efficiency than PRG + RC (P < 0.05). This study demonstrates the potential for sward type to influence rumen function and the microbial community, along with CH4 and N output from sheep.

Genetic correlations between switchgrass performance in sward conditions and surrogate measures

AbstractSwitchgrass (Panicum virgatum L.) breeders use spaced‐seedling plots for evaluations of biomass yield, but prior studies are ambiguous about the relationship between performance in spaced plots and commercial seeded sward performance. This study used a split‐plot incomplete block design to evaluate 52 half‐sib switchgrass families across two years to determine the correlations among four different plot types (including seeded swards) and four individual plant traits. Plots (1.62 m2) that contained 3, 6, and 18 plants had mean yields of 5.92, 8.04, and 11.06 Mg ha–1, respectively, while seeded‐sward plots had a mean of 5.37 Mg ha–1. In a mixed‐model analysis including family‐, year‐, and plot‐type interactions with a spatial‐spline correction, the largest proportion of family variance was accounted for by the main family effect (48%), while the plot type‐by‐family effect was only 17% of family variance. These results indicate that spaced‐plant plots are reasonable surrogates for biomass performance in sward conditions. Yield reliability was 0.50 across all plot types with a mean of 0.46 for individual plot types. Surrogates for sward yield varied due to genetic background of the families. Yield of families derived from the Liberty cultivar (n = 32) had genetic correlations with winter survivorship scores (0.66). Diverse lowland ecotype families (n = 20) had genetic correlations with plant height and heading date. This study highlighted a major difference in performance among the plot types, specifically that seeded swards have depressed yield due to high plant density. This should encourage further research for the mechanism behind this difference in performance.

Combining targeted grass traits with red clover improves grassland performance and reduces need for nitrogen fertilisation

To increase ruminant production efficiency, the environmental impact of growing forage must be reduced, through lowering system inputs and increasing crop resilience to extreme weather. Here we examined the role of red clover (cv. AberClaret) in minimising nitrogen (N) requirements, alongside two novel grass varieties, (1) a festulolium (cv. AberNiche), developed for drought tolerance, with potential for deep-rooting, and (2) a ryegrass hybrid (cv. AberEcho), developed for high-sugar content, which may enhance ruminant N-uptake in-vivo. Field trials were conducted at two UK sites, growing festulolium and ryegrass ± red clover (at 29% of the seed mix weight) at a range of N fertilisation rates (0 – 600 kg N ha−1) for 2 years (six harvests). We assessed sward performance (N offtake, herbage quality, and grass N use efficiency), rooting depth and N transfer from clover to grasses using 15N natural abundance. Across both sites and years, dry matter yield and herbage-N content were overall greater from the swards that included clover. Dry matter yields from festulolium were not greater than from ryegrass under the drought conditions experienced in 2018, despite its greater root mass. Agronomic efficiency of fertiliser N was similar between grasses (19 – 22%), however the festulolium more effectively used endogenous soil N than the ryegrass. Inclusion of clover in the sward affected forage quality, with increased crude protein and metabolisable energy content and reduced sugar and fibre (NDF) content. Among the grass types, metabolisable energy was greater and NDF content less for ryegrass than for festulolium. A strong reliance on biological N fixation (80 – 94%) for clover was observed, however, N transfer from clover to the neighbouring grass was not evident from the ẟ15N signatures. We conclude that red clover is a viable fertiliser-N replacement strategy in short-term leys, and that grass varieties with improved herbage quality may provide a better option for optimising sward performance than drought tolerant grass varieties.

Dry matter yield and the prevalence of barley yellow dwarf and ryegrass mosaic viruses in old and young perennial ryegrass

Abstract Modern pasture management of perennial ryegrass results in reduced reseeding and increased reliance on asexual tiller multiplication. This may exacerbate viral impact by providing longer-living hosts to exploit, thus the effect of ryegrass age on sward performance and viral load was investigated. Genetically similar 10 year old field plants and 10 year old seed were used to produce 'mini-swards' of 'old' (tiller derived) and 'young' (seed derived) ryegrass lines. Dry matter yield and viral load (ryegrass mosaic, and barley yellow dwarf) were assessed over 10 months. For all lines the old mini-swards produced less biomass (4-29%) and viral load was significantly greater at most time points. Cause and effect between viral load and yield were not proven as other factors such as genetic drift, epigenetics, or other latent pests or diseases could not be ruled out. Keywords: Lolium perenne, barley yellow dwarf virus, ryegrass mosaic virus

The effect of applying cattle slurry using the trailing‐shoe technique on dairy cow and sward performance in a rotational grazing system

AbstractThe effects of applying cattle slurry using the trailing‐shoe technique on dairy cow and sward performance were examined in two experiments in Northern Ireland. In Experiment 1, forty‐eight cows were allocated to two treatments, with or without slurry application. In Experiment 2, sixty cows were allocated to four treatments, a combination of high and normal grazing stocking rate, with or without slurry application. In Experiment 1, slurry was applied during the first and fourth rotations. In Experiment 2, slurry was applied prior to the first grazing rotation and during the second, fifth and sixth grazing rotations. In Experiments 1 and 2, the total inorganic fertilizer nitrogen (N) inputs applied within the slurry treatments were 200 and 133 kg N ha−1, with 280 and 285 kg N ha−1 used within the fertilizer‐only treatments in each experiment respectively. Varying responses of milk yield to slurry application were observed. In Experiment 1, with a normal stocking rate, no effect was observed. In Experiment 2 with two stocking rates, reduced milk yields were observed at both stocking rates. Although not significant, there were indications that this reduction in milk yield when slurry was applied was higher at higher stocking rates.

Predicted Efficiency of Spaced‐Plant Selection to Indirectly Improve Tall Fescue Sward Yield and Quality

The validity of spaced‐plant evaluation to determine sward performance of forage grasses has been questioned. This experiment studied the efficiency of spaced‐plant evaluation to indirectly improve sward yield and nutritional quality in tall fescue (Festuca arundinacea Schreb.). Narrow‐sense heritabilities, genetic and rank correlations, and indirect selection efficiencies were estimated for a tall fescue population grown in spaced plant and seeded sward environments. Heritability for yield was similar between spaced plants and swards (0.43 and 0.44, respectively), but genetic correlation between the two was low (0.37 ± 0.38). Inconsistency (r = 0.30, P = 0.17) in family ranking further suggested that spaced plants were not predictive of sward yield. Heritability of crude protein from swards was low (0.27 ± 0.25) compared with 0.77 ± 0.08 from spaced plants, but there was no genetic relationship between the two (r = −0.13 ± 0.30). Moderate to high heritabilities and genetic correlations were observed for most fiber traits, but indirect selection efficiencies and rank correlations of &lt;1.0 suggested that evaluation in a sward environment would be best to select for improved nutritional quality. Spaced‐plant evaluation appears to be less effective, or ineffective, at improving sward yield and nutritional quality in tall fescue. New techniques are needed that maximize genetic expression but simulate actual sward production of forage grasses.

The productivity of irrigated legumes in northern Victoria. 1. Effect of irrigation interval

An experiment was undertaken to determine the production and water use of pure swards of white clover (Trifolium repens L. cv. Haifa), red clover (Trifolium pratense L. cv. Redquin) and lucerne (Medicago sativa L. cv. Validor) between December 1987 and December 1990. The experiment was a split plot design with 3 irrigation interval treatments, which were the main plots, and 3 legume species, which were the subplots, all of which were replicated 4 times. Irrigation frequency was determined by evaporation minus rainfall (E-R) and was scheduled to occur at intervals of about 40, 80 or 120 mm of cumulative E-R. Annual amounts of harvested dry matter (DM) ranged from 8 to 22 t/ha depending on irrigation and species treatment. There was an interaction (P&lt;0.05) between irrigation interval and species during each irrigation season. White clover DM harvested was reduced (P&lt;0.05) by an average of 23 and 41%, respectively, as irrigation intervals were extended beyond 40 mm E-R (where up to 12 t DM/ha was recorded in an irrigation season). The decline in white clover growth in the less frequently irrigated treatments, relative to the 40 mm E-R irrigation treatment, was most pronounced between December and February, the months of highest evaporative demand, when these swards were 30 and 52% less productive (80 and 120 mm E-R, respectively). This compared with reductions of 16 and 32%, respectively, for red clover and 1 and 4%, respectively, for lucerne during the same period. Red clover, a dense productive stand initially, lost vigour and density in the second summer of this experiment, and from February in the second year was not harvested. However, for the period during which it was harvested, red clover production was reduced (P&lt;0.05) by 21%, on average, when the irrigation interval was 120 mm E-R compared with the 40 and 80 mm E-R irrigation treatments. The production of lucerne was not affected (P&gt;0.05) by the range of irrigation frequencies used in this experiment, although its crown density in the most frequent irrigation treatment was 30% less than in the 2 less frequently irrigated treatments when measurements were terminated in December 1990. However, after the first year, the lucerne swards were all highly productive, producing up to 21 t DM/ha in an irrigation season. For white clover to be productive, frequent irrigation is essential. However, all the indices of plant and sward performance measured during intensive studies showed that frequent irrigation of white clover resulted in earlier onset of water stress relative to the less frequent irrigation intervals. Despite this earlier onset of water stress, the yield advantage of frequent irrigation was large. Red clover and lucerne were less reliant on frequent irrigations to maintain productivity than white clover. However, red clover may need to be re-sown on a regular basis in the northern Victorian environment because of its failure to persist beyond 2 years. It is suggested that lucerne should be considered in preference to white clover because of its greater water use efficiency and its less critical reliance on irrigation management to maintain productivity.

Variability in establishing white clover in pastures on farms

Reported problems with inconsistent white clover establishment in pastures prompted a MAF SFF project to investigate the causes. The establishment of white clover in 32 new and renovated paddocks on 16 farms in the Wanganui-Manawatu-Southern Hawke's Bay region was monitored and the inconsistency confirmed in the f irst year. Seedling emergence at 44% (range 22 to 84) for ryegrass and 35% (range 9 to 73) for white clover was low (expected 70%+) and inappropriate grazing management inhibited subsequent plant growth and sward performance to 20% of potential. There were a few good performances, but the 'grass to grass' technique was particularly hard on clover. These problems have arisen as a result of modern methods (e.g. direct drilling and fertiliser N) that are less 'clover friendly', and have moved away from the older proven techniques. Minimal seedbed preparation and method of sowing, combined with lack of knowledge of white clover growth strategies and management requirements are seen as the main causes. Change is inescapable and while modern farming techniques and expectations may have currently placed clover at a disadvantage, the challenge now is how to balance the requirements of the pasture species with the expectations of the farming production system in the future. Keywords: emergence, establishment, farmer knowledge, grazing management, life cycle, sowing conditions, white clover.

Genetic advance estimates for red clover (Trifolium pratense) grown under spaced plant and sward conditions

A spaced plant experiment and a sward experiment were conducted at INIA La Estanzuela, Uruguay in 1996 with six red clover (Trifolium pratense L.) populations, to study the efficacy of selecting genotypes for sward performance in a spaced plant nursery. This was examined through: (a) the ranking of the best linear unbiased predictors (BLUP) of populations and (b) the ratio of the correlated genetic advance in swards by selecting under spaced plant conditions to the direct genetic advance of selecting under sward conditions. From the eight characters analysed, only the rankings of BLUPs for leaf size and flowering were significantly the same between populations. The other six characters performed differently according to the level of competition imposed. Post-grazing leafiness and the difference between pre- and post-grazing leafiness (the two most important characters to measure preferential grazing) achieved greater genetic advance when selection was done as spaced plants: while for pre- and post-grazing height genetic advance was greatest by selecting under sward conditions. For other characters, the best conditions to select depended on the selection intensity achievable.

Estimate of N 2-fixation in waste-derived compost after treatment with glucose

It has been shown previously that treatment of grass swards cultured in waste-derived compost and treated with 8–24 g (5–15 g·L −1) glucose over 8 weeks resulted in a substantial increase of shoot dry matter and total nitrogen content, while a growth inhibiting effect was observed in unamended field soil. The improved sward performance in compost was associated with a significant expansion of the aerobic, diazotrophic bacterial population in the growth medium. The purpose of the present experiment was to measure the contribution of N 2-fixation to the improved growth. Glucose treatment resulted in the fixation of at least 128 mg total nitrogen per pot (equivalent to 14.5 mg N fixed per g C respired; 104 kg·ha −1), with 32 % made available to shoots for growth over the following 6 months. There was no evidence of accelerated soil organic matter decomposition that could account for the increased N availability.

THE EFFECT OF NURSERY CONDITIONS ON THE IN VITRO DIGESTIBILITY OF TIMOTHY (Phleum pratense L.)

Fifteen timothy (Phleum pratense L.) genotypes of similar maturity were grown in simulated sward (100 plants m−2), spaced-plant (1 plants m−2) and growth room nurseries for 2 yr or harvests. The whole plant in vitro digestibility (IVD) was determined at early heading. IVD values were strongly influenced by growing conditions and highly significant [Formula: see text] year × genotype and harvest × genotype interactions were found. The precision of IVD determination was similar in all nurseries. Correlation between genotype means of simulated sward and other nurseries, although significant [Formula: see text] is some cases, was too low to be of predictive value. Some genotypes tended to rank relatively high in all nurseries, but the relative performance of most genotypes was inconsistent. It is concluded that the choice of nursery techniques used to predict the sward performance of timothy genotypes is more critical than is generally assumed.Key words: Timothy, Phleum pratense L., in vitro digestibility, IVD, nursery competition

The comparative effects of defoliation, treading and excreta on a Lolium perenne-Trifolium repens pasture grazed by sheep

SUMMARYThe effects of treading and the return of excreta on a Lolium perenne-Trifolium repens sward defoliated by sheep set-stccked at high and low stocking rates were examined. Sward performance was measured inside ‘graze-through’ cages which allowed defoliation without treading and excreta return, and outside where sheep grazed either fitted with harness to prevent the return of excreta or unharnessed to allow the normal return of excreta. Live-weight gain was measured from excreta return and non-return swards. The treatments imposed had large effects on herbage growth and botanical composition.At a stocking rate of 25 yearling wethers/ha, sheep excreted about 1·1 kg N/ha/day, which increased soil N and led to an increase in herbage growth of about 26 %. The return of excreta increased ryegrass tiller density and this was partly responsible for a 26% reduction in the proportion of clover in the sward; the weight of clover was 13% loss where excreta were returned, and on this treatment stolon length at the end of the experiment was similar to that at the beginning. Doubling the stocking rate increased the N returned via excreta to about 1·3 kg N/ha/day, and this increased herbage growth by 53% but suppressed the proportion of clover by 21%, though not the weight of clover. Clover stolon length decreased during the experiment at this stocking rate, both with and without the return of excreta. Sheep live-weight change benefited from the stimulus to herbage growth where excreta were returned at the high stocking rate, but not at the low stocking rate.Treading by 25 sheep/ha increased soil compaction but had no significant (P &gt; 0·05) overall effect on herbage growth and botanical composition. However, treading by double the number of grazing animals significantly reduced herbage growth by 10%, plant root weight by 47% and the proportion of clover in the sward by 11%.Differences in sward performance between stocking rates were due more to the difference in defoliation intensity between these stocking rates than to either treading or the return of excreta.

A comparison of diploid and tetraploid Lolium perenne L. sown alone and in mixtures with particular reference to the effect of treading

SUMMARYDiploid and tetraploid perennial ryegrass (Lolium perenne L.) cultivars were compared sown alone and in mixtures, with and without cattle treading for 4 years after the year of sowing. Data were also obtained on the survival of tetraploid ryegrass in mixtures under farm conditions.The overall effect of treading was not large but annual yield of dry matter was reduced by cattle treading every year (mean 9%). Sheep grazing and treading also reduced yield below that of cut plots. The reduction depended on the sampling date and varied from 40% to nil. In two instances treading increased yield.Interactions between cultivars/mixtures and treading occurred in 22% of the occasions when treading influenced yield. In the first harvest year the tetraploid Reveille was more resistant to treading than the diploid S. 24. In older swards (3rd and 4th harvest year) the situation was reversed. The occurrence of cultivar/mixtures × treading interactions and the effect of mixing diploid and tetraploid ryegrass on resistance to treading were unpredictable.The evidence from the main trial and the farm survey showed that tetraploid ryegrass could persist for at least 3 years after the seeding year when exposed to periods of high stock density. In addition, in mixtures there was no initial domination of the sward by either component when cut or when subjected to severe treading. In the third harvest year of the experiment the proportion of tetraploid ryegrass decreased considerably. Total yield of the mixtures was not significantly different from that of pure swards of the components though seasonal distribution of yield could be modified. The contribution of tetraploid ryegrass to swards up to 4 years old was in proportion to the percentage of tetraploid in the seeds mixture. Evidence from both the experiment and farm survey demonstrates that it is possible to exploit advantages claimed for tetraploids in mixtures for three harvest years without detrimental effect on sward performance.

Testing perennial ryegrass (Lolium perenne L.) as spaced plants in swards

A method of testing spaced plants in swards of another grass crop is described. The procedure provides information on sward performance at each stage of the breeding scheme. A large number of entries may be included, together with whatever cutting frequency.

Some factors affecting the establishment and early production of oversown grasses

The effects of rate of sowing, herbicide, and superphosphate on seedling establishment of two oversown improved grass species, their sward performance, and the resultant soil phosphate levels were studied in two experiments at Glen Innes, New South Wales in 1973. The experimental area had received 1250 kg ha-1 superphosphate prior to sowing and was carrying native grasses and white clover (Trifolium repens). In the first experiment, treatments applied were combinations of: four sowing rates (5.5, 11, 22, 44 kg ha-1) ; three herbicide rates (0 + 0, 8.3 + 0.55, 49.5 + 3.3 kg a.i. ha-1 2,2-DPA 4- amitrole) and two superphosphate rates (0, 250 kg ha-1). In the second experiment, three rates each of herbicide (0 + 0, 8.3 + 0.55, 16.6 + 1.1 kg a.i. ha-1 2,2-DPA + amitrole) and superphosphate (0, 125, 250 kg ha-1) were applied in a factorial design. Both experiments were sown with Phalaris aquatica and Festuca arundinacea. For both species, seedling numbers increased as herbicide and sowing rates increased but declined with superphosphate application. These main effects were more pronounced during the earlier samplings. Seedling numbers of both species, particularly phalaris declined with time. As herbicide rates increased, total dry matter production was progressively reduced, but production of fescue increased from 19 to 232 and phalaris from 0.5 to 60 kg dry matter ha-1. The addition of superphosphate eliminated the adverse effect of herbicide on the legume component. Superphosphate increased fescue dry matter production but decreased that of phalaris. Prior application of herbicide at the heaviest rate and superphosphate applied at 125 kg ha-1, both increased soil phosphate by approximately the same amount (7.5 and 8.2 p.p.m. respectively).

Sward tests of some morphological-agronomic groups of Stylosanthes accessions in dry tropical environments

An experiment is described in which 33 accessions of Stylosanthes, comprising 12 morphological–agronomic groups of six species, were grown with an associated grass Urochloa mosambicensis for 3 years in small mown swards at nine different dry tropical environments in northern Australia. Pattern analysis was used to elucidate the major differences in sward performance between accessions and sites and to classify the 33 accessions defined by 54 sward attributes (6 measurements x 9 sites) over 3 years. There was a close relation between the classification of the accessions defined by sward data with a previous morphological-agronomic classification based on spaced-plant data. Among the morphological-agronomic groups tested, S. hamata M–A 28 was outstanding at most sites. However, at the extreme ranges of adaptability, S. scabra M–A 18 was more productive at sites with a growing season of 24–30 weeks, and S. scabra M–A 17 was more productive at sites with one of less than 10 weeks.

PASTURE SEEDS MIXTURES, COMPETITION AND PRODUCTIVITY

THE PRINCIPLES involved in making up a pasture seeds mixture are many and complicated, and while considerable attention was paid to these principles in the period between 1910-30 (e.g., Cockayne, 1914, 1917; Levy, 1923, 1936; Stapledon and Davies, 1927, 1928) development of other areas of investigation of sward performance have in recent years tended to overshadow the importance of the species mixture in determining the productivity of a sward.