Wednesday, 5 November 2014

Sheep of the month - November 2014

Crossbred sheep on salt marsh pasture. Image: Jessica Winder

Breed notes
Many modern sheep are a mixture of breeds, combining the desired qualities of each. Here, Beulah Speckled-Face ewes (hill type: hardy, good mothers) have been bred to Blue-Faced Leicester rams (high milk production, high rates of multiple births, good conformation for easy lambing). Resulting ewes (called Mules) are then bred to meat rams, such as Suffolks, which are fast growing with a high meat yield.

Isotope notes
Coastal wetlands are an important pasture resource, either by direct grazing or production of hay. Because of the high salinity and regular flooding of these areas, only specialised plants can grow here. They have different isotopic composition (carbon, nitrogen and sulfur) to dryland and freshwater plants.

Animals which have been pastured on salt marsh will therefore be isotopically distinct from those pastured elsewhere. The progressive embankment of salt marshes in Europe has reduced the availability of this pasture type. Lamb produced on salt marsh pasture is considered to have a distinctive taste, and is highly prized as a delicacy in some regions of Europe. 

Friday, 19 September 2014

Sheep of the month - September 2014

Tarascons on high-altitude summer pasture. Image: Vincent Gleyses

Breed notes
The Tarascon is a middle-sized, horned sheep breed, developed in the 19th century in the Central Pyrenees, France. It is kept for meat. Tarascon sheep are hardy and strong-limbed, adapted to thrive on poor mountain pastures (1200 m above sea level) and seasonal transhumance. Unusually, they can lamb year-round, instead of only in spring. The fleece is white and very curly, with no kemps or guard hairs.

Isotope notes
The practice of regularly moving livestock between specific grazing grounds to take advantage of differences in growing season (transhumance) has been practiced by pastoralists worldwide. In mountainous areas, it typically means extensive grazing at higher altitude in summer, and more intensive grazing in lower valleys in winter. 

Differences in altitude affect the isotopic composition of graze. Firstly, different mixes of species grow at different altitudes. Secondly, plant isotopic composition is affected by differences in temperature, rainfall, hours of sunshine, and soil quality. The tissues of transhumant livestock will reflect these differences, but seasonal cycles of isotopic change will be obscured.

Monday, 18 August 2014

Sheep of the month - August 2014

Awassi sheep grazing on stubble. Image: Ferrell Jenkins

Breed notes
Awassi sheep are hardy, with a red head and legs, convex face and drooping ears. They are a fat-tailed sheep breed, having the characteristically heavy tail and hindquarters with fat storage deposits. Males are horned and females mostly polled. Awassi fleeces are double-coated with plenty of kemps, in a range of colours from white to brown. Ewes produce relatively large quantities of milk compared to other breeds. Awassi are the most numerous and widespread sheep breed in the Middle East.

Isotope notes
The image shows livestock grazing on the remains of a crop after the grain has been harvested. This manures the field as well as providing late summer/early autumn nutrition for the grazers. This practice will be isotopically visible only if the harvested crops are isotopically distinct from the plants the animals normally eat. Potential examples include: peas or beans in areas with little clover in the pasture (as legumes and non-legumes are isotopically distinct); C4 crops such as maize, millet, sorghum or sugarcane in predominantly C3 plant areas; or if the field crop has been heavily manured. 

Monday, 4 August 2014

What happens to wool samples in the lab? Part 3

After washing and grinding, the sample needs to be got ready for the analysis itself. When being loaded into the mass spectrometer, the powder is contained in capsules made of pressed metal foil:
Unbelievably tiny capsules
These are both 3.5 mm across by 5 mm high. The one on the left is made of tin (for carbon and nitrogen isotope value analysis) and the one on the right is made of silver (for hydrogen and oxygen isotope value analysis). As you can imagine, loading sub-microgram amounts of highly static hair powder into these is a recipe for madness... especially if you've got to do scores of them in triplicate....

Microbalance plus tools
We weigh exactly how much sample is in each capsule. We do this on a very sensitive balance. The object to be weighed is placed on the small round platform you can see inside the perspex cylinder. This is then closed so that no air movements can disturb the weight. I am loading pinches of hair powder with the very fine tweezers you can see. I clean these between each sample using methanol, which is in the orange-labelled squeezy bottle.

Lab book with weights and trays with samples
Storage tray close-up
Once we've got the right amount of powder in the capsule, we fold it tightly to stop it falling out again. Then we put the folded capsule in a storage tray. These have 96 little wells, so one sample goes into each. The weight of the sample in each well is recorded. We can then take (or send) the samples to the lab where the actual analysis will be done.

Next: running the analysis. This next post will have to wait for a bit, as I won't be doing this for a few months...

What happens to wool samples in the lab? Part 2

Once the samples have been washed, they are dried and ground. Grinding hair samples is tricky, as they're very elastic. To do this, we use a machine called a ball mill.
Loading wool into a ball mill cartridge
The wool fibres, which are 5-20cm long in the fleece, are cut into ~1cm lengths. Then they are loaded into the steel cartridge with a grinding ball. The machine shakes the cartridge so that the ball crushes the other contents. Note that I'm handing the samples with tweezers: this is partly to make sure they're kept as clean as possible, but mostly because the fibres are very static and stick to my gloves...

Milled wool 
And here's the result after a minute or so: wool powder. Like the whole fibres, this is usually static as anything, so it needs really careful handling to stop it jumping about!

Next: weighing into unbelievably tiny capsules in Part 3.

Thursday, 10 July 2014

What happens to wool samples in the lab? Part 1

This year I have continued collecting sheep wool samples from Scandinavia and the Baltic region. I am very grateful to the farmers who have sent me samples from their sheep, which are all from heritage breeds. These sheep have eaten grass and hay but no concentrates. 

I thought I would show you what happens to the samples once they get to the laboratory:

Sample logging
First the sample is logged. Sample logging is boring but essential. Each sample is allocated a number in our central database, and that number is also written on the sample bag, so we can always find out what it is and where it came from.

Preparation for washing
A small section of each piece of fleece is transferred to a small glass vial. The sample number is also written on this vial. These samples are from Estonia: double coated fleeces in a variety of colours. The remainder of the sample is kept in a fridge.

Wash number 1
Each vial is filled with water, capped, and put into the machine on the right, which is a sonicator. This shakes its contents using ultrasonic waves, which helps dissolve the muck on the wool. I sonicate with water to remove dirt, and then with hydrocarbon solvents to remove grease from the fibres. I use 6 separate washes, which is more than most researchers use for cleaning hair for isotope analysis. I found that wool needs lots of cleaning (much more than, say, cattle or human hair) as the fine fibres trap much more muck between them than do coarser fibres.

Next: grinding the wool into powder in Part 2.

Friday, 27 June 2014

Sheep of the month - June 2014

Skudde ewe being shorn. Image:
Breed notes
Skudde sheep originate from the heather landscapes of the south-eastern coasts of the Baltic Sea. They have a typical fleece for an unimproved breed, with fine under-wool interspersed with coarser hairs. They are small and slender, and grow slowly compared to most modern sheep breeds. Rams have impressive curling horns. Today this breed is mostly kept to maintain grassland. More info:

Isotope notes
Sheep grow wool continuously throughout the year, though usually more slowly in winter when the days are shorter. They need to be shorn at least once a year. Frequency of shearing depends on the rate of wool growth, and whether animals are stalled or outdoors over winter. The wool is cut so as to leave the fleece hanging together, as it is easier to handle.

The isotopic composition of a wool fibre reflects the total diet of a sheep between shearings. Analysing a series of samples down the fibre can therefore indicate pasture type, fodder type and water sources, and how these change over the farming and climatic year.

Thursday, 15 May 2014

Sheep of the month - May 2014

Suffolk ewe and lambs grazing. Image: Rancho Radiata

Breed notes
Suffolk sheep have white wool and black faces and legs. One of the largest breeds of sheep, they are kept mainly for lean meat production. Suffolk lambs grow faster than those of any other breed. The fleece is short, medium fine fibre, mostly white with some back hairs. The breed was developed in the early 19th century in East Anglia, GB. More info:
Isotope notes
Lambs start to consume pasture plants once they are 2-3 weeks old. If left with their mothers, they will continue to suckle for about 6 months. In modern commercial farming, lambs are typically weaned (separated from their mothers, so receiving no more milk) between 1 and 3 months old.
Once weaned, the isotopic composition of a lamb’s tissue will increasingly resemble that of an adult sheep. The speed at which this happens will depend on how fast the lamb grows. Many modern breeds, including Suffolks, have been developed to mature (put on weight) faster than more primitive breeds. The duration of the isotope signature of milk consumption will therefore be shorter in these animals (assuming the same weaning age).  

Wednesday, 30 April 2014

Sheep of the month - April 2014

Soay ewe and newborn lamb. Image: Woodland Creek Farm

Breed notes
The Soay breed is descended from a feral population of sheep on the island of the same name in the Western Isles of Scotland. They are about a third of the size of most modern sheep breeds, are very agile, and show a wide variety of coat colourings. Their fine wool is shed naturally every year and does not need to be sheared, but can be plucked (‘rooed’) instead. Soays are thought to resemble British prehistoric sheep breeds. More info:

Isotope notes
Lambs live on their mothers’ milk alone for at least the first two-three weeks after birth. Ewes produce an extra rich milk called colostrum for the first 24 hours or so after lambing. Adequate consumption of colostrum is very important for lamb survival as it is rich in both nutrients and antibodies. Ewe milk quality depends on the ewe’s nutrition in late pregnancy.

Suckling is detectable isotopically. For this period the lambs are consuming their mothers' tissue, and are effectively a trophic level higher than she is. All the tissue they grow in this period will show this signature, reflecting both the mother’s diet and the lamb’s consumption of milk.  

Friday, 14 March 2014

Wool sampling spring/summer 2014

In my research, I study the composition of samples of archaeological sheep wool to find out where they come from. In order to be able to read the data from the past, I need to have equivalent data from now. That means I also analyse modern wool samples from the same regions. During my PhD, I worked on understanding textiles from the UK and Iceland. Now, as a postdoc, I am extending this approach to Scandinavia and the countries round the Baltic.

In 2013, I contacted sheep farmers' organisations in Norway, Denmark and Sweden. I asked them to put me in touch with farmers who wanted to send me wool for this project. One farmer in Denmark, two in Sweden and five in Norway very generously answered my request and sent me samples from their flocks. In total, almost a hundred samples, which is very good indeed - thank you VERY much!

Relief map of Scandinavia and the Baltic Sea region, with sampled farm locations indicated. Background image source
This year I am extending sampling towards the east, to get wool from Finland, Estonia, Latvia, Lithuania, Poland as well as from here in Germany. I am also keen to get samples from mountainous and inland areas of Norway and Sweden. Mountain environments are likely to be different from coastal ones, both in vegetation and in farming practice, so this would be isotopically very interesting. 

I have contacted sheep-farming organisations in all these countries again this year. I am looking for samples from sheep which are being kept in a 'traditional' manner, that is without concentrate feeds, on unfertilized pasture, and with hay supplementation from the local area only, with or without transhumance to altitude during the summer. Samples are taken at clipping to minimise work required. 

Can you help me with this project? I'd love to hear from you! Email

Sheep of the month - March 2014

Cattle and sheep in mixed grazing. Image: Susan Schoenian 
Species notes
Domesticated herbivores consume plants differently. Cattle predominantly eat grass, with some weeds and bush/shrub leaves. Sheep eat more weeds, and can be successfully kept on shorter, less mature grass than cows. Goats prefer to browse on leaves. This means that different species can be grazed in the same area (either all at once or at different times in the year) as they will not eat the same plants. This can reduce the chance of damaging the pasture by over-grazing. However farmers have to consider the potential for disease/parasite transmission between species. More info:

Isotope notes
Plants differ in isotope composition because of differences in their metabolism. The most important factors are their photosynthetic mechanism (C3/C4/CAM), nitrogen fixing ability (root microbe symbiosis type) and water-use efficiency (transpiration rate). This last can also differ strongly between different parts of the same plant, and between seasons as humidity and temperature change. Therefore, different domesticated herbivores grazing on the same pasture may consume diets which are different isotopically.

Monday, 17 February 2014

Sheep of the month - February 2014

Three pregnant Katahdin ewes in a field
Pregnant Katahdin ewes. Image: Suzanne Cox via

Breed notes
Katahdin are a breed of sheep developed in the 20th century in Maine, USA. They are a hair sheep, which means they do not produce a woolly fleece but instead have a coarser hairy coat which moults naturally every year. These types of breeds are more common in hot climates. They are becoming more popular in temperate climates because wool is not as profitable as in the past. More info:

Isotope notes
Pregnancy will affect the isotopic composition of ewes’ tissues because of two separate factors: (1) different routing of nutrients through the ewe’s body towards the growing lamb, and (2) changes in the ewe’s diet during pregnancy.

Farmers may choose to provide additional feed to pregnant ewes, especially during the last month of pregnancy when lambs are growing very quickly. Because sheep fertility varies with day-length, late pregnancy is likely to be in late winter/spring. Ewes’ tissues may therefore acquire more of a winter feeding signal (see January 2014) than other sheep which receive less supplementary feeding.

Wednesday, 15 January 2014

Sheep of the month - January 2014

This is the first in a new series of regular blog posts linking agricultural practice and isotopic composition. This relationship is the core of what we're working to understand at the ASIL in Kiel. 

Jacob sheep in a snow covered field eating hay
Jacob sheep eating hay during snow cover

Breed notes
Jacob sheep are piebald, with black-and-white faces and spotted bodies. Both males and females can have 2-6 horns. They are an unimproved (primitive) sheep breed of unknown origin and antiquity. They have a medium fine fleece and no outer hairy coat, unlike other primitive breeds which typically have a fine inner coat and hairy outer coat. More info:

Isotope notes
In cold climates, alternative fodder sources must be provided to grazing animals during periods of snow cover. In the past, this has typically been summer vegetation, cut and stored as hay, but it might include straw, chaff and spoiled grain. Additional 20th/21st century options are silage (fermented cut vegetation) and commercial ‘cake’.

Isotopically speaking, this means that animals are consuming summer vegetation in winter. This is likely to affect their tissues’ isotope values, because plant species availability and plant isotope values vary seasonally in response to temperature, humidity and growth rates. Mean tissue values for animals receiving fodder may therefore be shifted overall towards a summer signal when compared to other species which do not. 

Many thanks to Punkin's Patch for permission to use the photo!