Incorporating a mixed sward on to sheep farms can result in earlier slaughter weights for lambs and improvements in ewe condition, according to new research.
With diverse sward mixtures becoming a feature on more farms in recent years, the inclusion of clover and herbs can improve sward quality and increase animal intakes leading to significant improvements in animal performance.
These findings were provided by Teagasc, and determined that lambs grazing mixed swards reached their slaughter weight 16-28 days earlier.
By introducing clover, the protein content in the sward will be increased, and will fix nitrogen, lessening the need for an artificial nitrogen application.
Herbs such as plantain and chicory are drought-tolerant and can uptake minerals from deeper in the soil, giving a high mineral content in the sward.
Experiment
An experiment was established at Teagasc Athenry and ran from 2018 to 2021, investigating a range of mixed swards and their impacts on both sward and animal performance under a pasture-based sheep production system.
The sward types included in the study were:
- Perennial ryegrass (PRG);
- Perennial ryegrass and white clover (PRG+WC);
- Perennial ryegrass and red clover (PRG+RC);
- Perennial ryegrass and plantain (PRG+Plan);
- Perennial ryegrass and chicory (PRG+Chic).
The swards were stocked at 11.5 ewes/ha, managed in a rotational grazing system and received 130kg N/ha/yr.
Research officer at Teagasc, Philip Creighton said: “Results from this study found that all swards produced similar annual herbage yields of 10.5-11.5t DM/ha.
“However, lamb performance was significantly affected by sward type.”
This was seen when lambs that had grazed on the PRG sward were compared with those that had grazed on “any of the mixed swards,” showing those that were on the mixed sward had achieved the appropriate slaughter weight between 16 and 28 days earlier.
This improvement in lamb condition was seen during the post-weaning period, which Creighton said saw the lambs grazing the mixed sward types gain between “22-43g/day more than the PRG lambs”.
This also caused less concentrates to be fed to the lambs on the mixed swards to finish them.
The highest performing lambs were those grazing PRG+RC and PRG+Chic, followed by those grazing PRG+WC and PRG+Plan, all of which were performing significantly better than those grazing PRG.
Creighton added that ewe performance was largely similar across sward types, with some improvements in ewe body weight and body condition score (BCS) occurring from six weeks post-lambing until the following mating period.
Sowing a mixed sward
A series of plot trials were conducted by Teagasc to investigate the effects of establishment method, seeding rate and perennial ryegrass ploidy, post-grazing sward height (PGSH) on the mixed sward types (PRG+WC, PRG+RC, PRG+Plan and PRG+Chic).
Preliminary results show that the establishment method had no effect on the establishment of white clover, red clover or chicory.
The direct drill method aided the establishment of plantain in a PRG+Plan sward, relative to the conventional method (plough, till, sow).
Lisa McGrane of Teagasc said: “Within a set total seeding rate of 25kg/ha clover and herbs were included at a low, medium or high level.
“Clover seed was included at a rate of 2.5, 5.0 or 7.5 kg/ha and herb seed was included at a rate of 2.0, 3.5 or 5 kg/ha for the low-, medium- and high seeding rate treatments respectively.”
Results show that seeding rate had a significant effect on forage content in all of the mixed swards.
“The low inclusion rate of 2.5kg clover/ha was sufficient to establish white clover, whilst the medium inclusion rate of 3.5kg herb/ha was sufficient to establish chicory,” she added.
“For the PRG+RC and PRG+Plan sward types, high inclusion rates of 7.5kg clover/ha and 5kg herb/ha respectively were beneficial and led to higher red clover and plantain contents in the sward,” added McGrane.
“When the mixed sward types were sown using a diploid or a tetraploid perennial ryegrass, these were higher contents of white clover and plantain when sown with a tetraploid perennial ryegrass.
The results showed there were similar levels of red clover and chicory when sown with a diploid or tetraploid perennial ryegrass.
Following the successful establishment of a diverse sward, grazing management can also have significant impacts, particularly on sward persistency, McGrane explained.
In a plot trial, three target PGSHs of 4.0, 4.75 and 5.5cm were implemented over a three-year period.
Over a three-year period, it was found that red clover persistence was poor under severe grazing to 4.0cm PGSH, the lax grazing to 5.5cm PGSH had a negative impact on plantain and chicory persistence, while white clover persistence was similar under all three PGSHs applied.
The study found that across all sward types, the intermediate 4.75cm PGSH was most suitable.
Results
Concluding the research findings, Creighton said the mixed swards in this study provided a significant improvement in animal performance while producing similar levels of herbage production relative to that of a perennial ryegrass monoculture.
“Issues around forage persistency exist. However more detailed agronomy work will help to identify appropriate management advice for the use of mixed swards under sheep grazing,” he said.
Researchers at Teagasc are confident that implementing appropriate management advice can maximise sward persistence without negatively affecting animal performance and sward quality, by supporting the successful incorporation of mixed swards on commercial sheep farms.