Research trials at University College Dublin (UCD) Lyons Estate research unit in Kildare have looked at the potential for incorporating herbs into grazing swards on Irish sheep farms.

Outlining the results at the NSA sheep event in Ballymena, Professor Tommy Boland from UCD said that the study used four farmlets, each carrying 30 ewes with twin lambs at a stocking rate of 12.5 ewes/ha on a five paddock rotation.

Block one had perennial ryegrass-only swards. Block two had ryegrass and white clover swards. The third block was sown out with six varieties of grass and herbs, such as chicory and plantain, along with ryegrass and clover. Block four had nine species sown out.

Lamb performance

Lambs were weighed at six weeks old. Those on the ryegrass-only swards averaged 18kg, with lambs on the six-species mix averaging 20kg, a 12% increase in liveweight.

Boland said the higher liveweight was due to improved milk production in ewes from grazing the herbal leys.

As ewes were suckling twins, this meant an additional output of almost 5kg/ewe, worth £20 or £250/ha at a lamb price of £4/kg

At weaning, weights were 2.4kg higher in lambs grazing the six-species ley over lambs on ryegrass-only swards.

As ewes were suckling twins, this meant an additional output of almost 5kg/ewe, worth £20 or £250/ha at a lamb price of £4/kg. Lambs on the six-species ley also reached a slaughter weight of 45kg around 14 days earlier than lambs on ryegrass-only swards.

Worm resistance

Herbs are known for their anthelmintic properties in sheep, and faecal egg counts were used to determine dosing protocol for lambs.

The first dose was given to all lambs on the four blocks on the same day. Faecal egg counts showed lambs on ryegrass swards required a second drench 40 days later, while lambs on the six-species swards required a second dose 50 days after the initial treatment.

Over the course of the trial, earlier finishing and longer dosing interval meant lambs on the six-species ley used 50% less worm drench compared with lambs on ryegrass swards.

Challenge

While the results were positive, the downside to the herbal leys is a lack of persistency in grazing swards, with a lifespan of less than five years.

Herbs are anywhere from five to 10 times the cost of ryegrass seed, which makes it expensive to keep rejuvenating swards with plants such as chicory or plantain.

No work has been carried out in an upland environment or on heavier soils where sheep more commonly graze.

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