Friday, 25 May 2012

Lecture : Dung Beetles and Drugs

The latest in the University of Nottingham’s most excellent sciency lectures saw Dr Helen West giving a presentation entitled 'Dung Beetles and Their Battle Against Drugs'.

Dr West is Associate Professor in Environmental Biology at the University of Nottingham’s Faculty of Science.

Dr West’s talk began by pointing out that there were some 10 million cows in the UK. Collectively, they produce 146million tons of manure per year. If it were not degraded by the environment, this would be enough to cover Cornwall ( NSB suspects the residents there would presumably have something to say about that, possibly starting with the phrase “Ooo-aarr”).


Dr West continued by explaining that, actually, a good quality cowpat can be quite an enticing environment for insects and the like as it provides nutrition, moisture and a protective environment.

Indeed, it can house a very wide range of flora and fauna, with many of the creatures feeding on each other, as can be seen in the schematic below.

Cowpats - There is a whole other world of activity within them. . .

Incidentally, when Dr West talks about a “good quality cowpat” what she means is one that is not too dry, has some fibrous content and is not a sloppy mess.

Moving on to talk about specific species, Dr West mentioned that those of the audience who partook of walks in the countryside will have seen cowpats with holes in them. These have been created by dung beetles (such as Geotrupes Stercorarius) that have burrowed in and, if one has patience, one can see them scurrying out from one hole and back into another. One way in which dung beetles break up the cowpat is to take balls of dung into underground tunnels and chambers, often as food for their young.

A British Dung Beetle (Geotrupes Stercorarius)

One of the first insects on the scene, as it were, of a fresh cow pat is the yellow dung fly. These eat the nuisance flies that annoy cows and people, so it is in a farmer’s interest to encourage these wee creatures. According to Dr West, a freshly laid cowpat can attract so many dung flies that they pretty much cover the entire surface. The flies prey on other insects and also lay their eggs on the surface of the cowpat.

A Yellow Dung Fly

Effects of Worming A large part of the talk covered the effects of drugs given to de-worm cows because a significant amount of the does passes right through the cow and is present in its cowpats, where it can significantly affect the amount and creatures present.

“avermectins” - a group which includes Ivermectin and are large molecules. These chemicals are toxic to the environment, indeed the National Trust advises against the use of these chemicals due to environmental concerns. In addition, this class of drugs cannot be used to worm cattle in coastal areas where the Chough live as this bird digs around in cowpats for insects to eat

Chemical Structure of Ivermectin

“milbemycins” - a group which includes Moxidectin and are large molecules similar to the avermectins but are much less toxic to the environmnent

Chemical structure of Moxidectin

“benzimadazoles” - a group which includes Oxfendazole and are small molecules.
Chemical structure of Oxfendazole
These drugs are administered either by injection or by pouring along the back of the animal. Dosage can vary from each animal in a herd being dosed 2-3 times a year down to just a proportion of the herd being dosed once a year. A survey by Stafford and Coles in 1998 found that 92% of farmers surveyed treated their animals more than once a year, with 43% treating their animals more than 3 times a year.

To assess the effect of worming on cowpats, Dr West and her team took cowpats that had been . . .er.. . “dumped” by cows that had (or had not) been wormed, placed them in buckets covered with flypaper and observed how many flies stuck to the paper.

“unwormed” cowpat sample : about 40 large flies

“wormed” cowpat sample : about 6 small flies

And the reduction in the number of flies and other insects in the cowpats results in a slowdown in the rate at which the cowpats are degraded, as shown in the following experiment. . .

The research team again took samples of “wormed” and “unwormed” cowpats and then buried them in sealed bags for various lengths of time. Initially, the cowpats were found to be about 80% organic matter. After a period of some 6 weeks it was found that the amount of organic matter was:

“unwormed” cowpat sample : 40% organic matter
“wormed” cowpat sample : 80% organic matter

Clearly, the “unwormed” cowpat sample was being broken down at a much faster rate than the “wormed” cowpat samples.

Current Research
The research team has been funded by the Esmee Fairbain Foundation to study around 80 farms in the midlands and aims to “evaluate the impact of treating livestock with anti-parasitic drugs on faunal diversity of lowland grasslands and to produce an accessible advice system for farmers”.

Dr West explained that the “advice system” would, ideally, be able to advise farmers on the most efficient and eco-friendly way of worming their cattle, as well as which drugs would be most appropriate for them, based on their farm type and local environment.

Why does it matter?
Rounding up the lecture, Dr West explained why she felt that it was important to maintain the biodiversity present in cowpats and other dung for reasons such as :

i) Better pasture quality due ot quick cowpat breakdown

ii) More sustainable agriculture

iii) More complete overall ecosystem

iv) We have a moral duty to maintain biodiversity

Image Sources:
Dung Beetle, Fly, Ivermectin, Oxfendazole, Moxidectin

1 comment:

  1. Hi,

    Just to say that the the dung beetle in the photo is Anoplotrupes stercorosus not Geotrupes stercorarius!