GRASSLAND farms in Pembrokeshire could improve pasture quality and increase available grazing acreage by increasing dung beetle populations.

The dung beetle’s role in agriculture is to break down dung, moving nutrients and organic matter into the soil. Changes in pasture management and overuse of some livestock wormers have reduced populations in the UK and elsewhere, meaning that dung is slower to break down.

According to St David’s-based dung beetle expert Dr Sarah Beynon, the sharp decline is creating a production constraint in UK livestock farming.

“We have evidence to show that when there are no beetles to break down a pat, the dung may sit there for a year. It just does not decompose,’’ said Dr Beynon, who has established a dung beetle breeding centre in St David’s.

“The dung from five cattle can cover an acre a year. It’s not just the area where the pat sits that is affected, animals won’t graze around it either so farmers are losing large proportions of their grazing land.’’

In rotationally grazed, intensive dairy systems, the first rotation can be fully grazed but the area available for grazing will diminish with each subsequent rotation. “If you don’t have an active dung beetle population on your farm, less and less land can be grazed as the season progresses, as dung sits on the surface taking up grazing area,’’ said Dr Beynon.

Beetle tunneling increases soil aeration and this, together with the burial of dung, can promote growth of palatable grass and stimulate biological activity in the soil.

Dung beetles thrive in unimproved, permanent pasture. What they like less is improved land with short-term leys. However, with more than 40 species of dung beetle native to the UK some will thrive in these systems too. Overuse of certain wormers and ectoparasiticides impact on numbers too. Chemicals contained in these are often excreted in dung.

In order to help replenish populations, Dr Beynon advises farmers to first question the necessity of every treatment. “Farmers need to ask themselves “do I really need to treat, or am I just doing it as part of an established routine?’’ By carrying out faecal egg counts and blood tests, treating with a chemical need only be done if it is necessary.

“Mature cattle often don’t need to be wormed, as they have developed their own immunity to worms.’’

During the grazing season, Dr Beynon recommends, where possible, switching to chemical groups less toxic to dung beetles, such as products containing chemicals ending ‘-azole’, as well as pyrantel, closantel, morantel, monepantel or moxidectin. She suggests trying to avoid products containing doramectin, eprinomectin, abamectin, ivermectin, closuron and synthetic pyrethroids when animals are at pasture.

“If you do need to use these chemical groups, ideally animals should be kept off pasture for 72 hours after treatment. Although evidence is sparse, tapeworm treatments containing praziquantel do not appear to adversely affect dung beetles.’’

Dr Beynon said overuse may cause localised extinctions of some species. “If a livestock farm that is surrounded by arable land overuses certain chemicals and kills its dung beetles, the chances are that the population won’t be replenished because there are no livestock farms in close proximity to draw dung beetles from.’’

The length of time it takes for the dung pats to disappear indicates whether a farm has a healthy dung beetle population. If pats remain intact for more than a few weeks, depending on the time of year, the population is likely to be low