One of the main topics at last week’s Agricultural Science Association sheep masterclass held in UCD Lyon’s Research Farm was the results of a two-year trial assessing the merits of multispecies swards in sheep production system.

The results of the research undertaken by Cornelia Grace were presented by Tommy Boland, associate professor with the School of Agriculture and Food Science.

The results showed potential improvements in lamb performance when grazing six- and nine-species swards over perennial ryegrass swards, with standout performance variables of lambs grazing the six-species sward being 2.4kg heavier at weaning than lambs grazing the perennial ryegrass-only swards and drafted for slaughter over 12 days earlier on average.

The trial

The research was carried out on hill paddocks in the Lyons Research Farm, with four treatments used. The first was a perennial ryegrass sward receiving an allocation of 163kg nitrogen/ha/year, while the second was a ryegrass and white clover sward with a lower nitrogen allocation of 90kg N/ha/year.

The multispecies swards were a six-species mix containing perennial rye grass, timothy, white clover, red clover, plantain and chicory, while the nine-species mix had the above, along with cocksfoot, birdsfoot trefoil and yarrow.

Tommy explained that the rationale behind incorporating multispecies swards is that they work in a complementary manner, with the merits of each individual plant delivering advantages at different stages throughout the grazing season.

For example, Tommy said that multispecies swards are regularly used in New Zealand in areas prone to drought, with the deep rooting nature of some species accessing moisture during periods of low rainfall and ensuring that a source of herbage is available at all times.

The four treatments were grazed over two seasons (2015 and 2016) with 30 twin-suckling ewes at a stocking rate of 12.5 ewes/ha. Each group had access to five paddocks and all groups were standardised in terms of lamb birth dates, starting weight, etc. The perennial ryegrass-only sward sustained the lowest six-week and weaning weight.

“Any time we added any species into a perennial ryegrass sward, we got a lift in performance. The benefit was greatest in the six-species mix, with lambs gaining over 345g daily up to their six-week weight.

“We are not sure if this was due to changes in ewe milk yield or composition and further research is needed in this area to find exactly what is driving the higher performance.”

Lambs grazing the nine-species mix averaged just over 330g daily, while lambs on the perennial ryegrass and white clover (PWC) gained over 310g daily, followed by the perennial rye grass (PRG) sward, which sustained a growth rate of about 295g/day.

The differential in six-week weights carried through to weaning and is reflected in Figure 1. Lambs grazing the six-species mix were 2.4kg heavier than lambs grazing the PRG swards. These lambs achieved an average daily gain (ADG) of over 280g, slightly ahead of lambs on the PWC sward which gained about 278g daily, while lambs grazing the nine-species mix gained approximately 273g daily, followed by the PRG group, which achieved an ADG of 268g.

The effect of sward type on the number of days it took lambs to reach a target slaughter weight of 45kg was less pronounced between the mixed species swards and the PWC sward. All three were pretty similar and were over 12 days shorter than the PRG-only sward.

Table 1 details the effect of sward type on slaughter performance in more detail. Tommy says that the higher kill-out performance of the six-species sward is likely to be influenced by the younger age at which lambs are drafted for slaughter rather than solely attributable to the type of sward lambs are grazing.

Ewe condition

The multispecies swards also delivered significant benefits in terms of ewe liveweight and body condition score, with ewes heavier and achieving a better body condition score at six weeks into lactation, at weaning and at mating.

It also delivered a boost in scanned litter size, with ewes grazing the six-species mix scanning nearly 2.35 lambs per ewe, followed by the PWC group at approximately 2.25 lambs, while there was little difference between the other two groups at about 1.8 lambs per ewe.

Lower parasite burden

The final component of the analysis and one that Tommy believes could give the greatest potential given the increasing prevalence of anthelmintic resistance is the effect of sward type on worm burdens.

Lambs grazing the mixed-species swards had a much lower worm burden than lambs grazing both the PRG and PWC swards.

The results showed the length of time between the first and second anthelmintic treatment for lambs grazing the nine-species swards as the longest at 58 days.

This was ahead of the six-species sward at about 51 days, the PWC swards at 41 days and the PRG sward having the shortest interval at 36 days.

However, the six-species group required the lowest number of anthelmintic treatments at less than 1.5 treatments per lamb by means of possessing a lower days-to-slaughter figure.

More research needed

There was not too much variation between the annual herbage dry matter production, with the six-species highest at just over 10t DM/ha, slightly ahead of the PRG and nine-species swards, which produced just shy of 10t, while the volume of herbage produced was significantly lower in the PWC sward at just over 9t DM/ha.

Tommy’s advice to those attending the event is that while the two-year trial showed definite benefits in incorporating multispecies swards into the farm’s production system, further research is needed to establish the potential of multispecies swards.

“The results show very positive benefits in lamb performance, but this is only one component. There are still big question marks about persistency of the sward – we had the crop growing for just two years and there were some issues with the persistency of yarrow and birdsfoot trefoil in the nine-species mix.

“There is also much more work needed around weed control, as, essentially, any herbicide used to control weeds will also kill the multispecies swards.

“There is also much more to learn around management of the crops. New Zealand farmers are grazing crops to a post-grazing sward height of 9cm to 11cm, the height that we are typically going into crops at here. I would say to any farmer thinking about growing crops to grow a small area and see how it performs.

“For now, perennial ryegrass swards will remain the mainstay in sheep production, but there is definitely a place for these crops, particularly in a world where there is a growing focus on using less anthelmintics and inputs.”