Barbed wire originated in the USA and has been around since the late 19th Century. It is made from strands of galvanised steel wire through which sharpened wires or barbs protrude. The intention of barbed wire is to provide a stock-proof fence to contain farm animals and keep unwanted visitors out. It is a relatively cheap fencing material and is quick and easy to construct; all that is needed are wooden stakes and some staples.
So popular was it with the US cattle ranchers that within 25 years of its invention much of the previously open land over which cattle were grazed was fenced and managed under private ownership, changing the face of the great plains of America within a short space of time.
In 1999 a EU funded survey found that the amount of scratch damage on hides varied significantly from country to country; in Germany only 6% of hides were reported to be affected, in the UK this figure rose to 90%1.
Damage to leather
As the animal brushes against the wire, the barbs cut into the skin surface and the harder the animal presses against it or the more it moves whilst in contact with it, the greater the damage to the hide.
As soon as the skin is cut, it begins to make temporary repairs; a blood clot forms to plug the wound to prevent further blood loss and infections entering the skin. Inflammatory cells migrate into the wound and begin to draw the edges together. This is what we describe as a ‘scab’.
The cells that produce the fibrous protein collagen, the fibroblasts, produce collagen fibres to knit the wound together. If the cut extends right through the grain layer, the hair roots are damaged and the hair will not grow back again. In normal skin, the collagen fibres are woven together in a three-dimensional manner, rather like a basket weave, but in scar tissue the collagen fibres are laid down in parallel layers and are very dense. It is this very dense structure that is responsible for the high visibility of barbed wire scars on leather. Process chemicals, eg dyes, find it difficult to penetrate the very dense structure of scar tissue and so they often appear paler in colour.
If the animal is slaughtered soon after scratching itself on barbed wire, the skin will not have had sufficient time to heal. Consequently, the cut remains open at the grain surface of the leather. These are known as ‘open scratches’. Where scar tissue has formed to knit the wound back together they are known as ‘healed scars’ or ‘closed scars’.
Many people think that barbed wire scars are a weak point in the leather. This may be true to a certain extent if the cuts are deep and have not yet healed. But if they have healed, theoretically, they should actually be stronger than the original skin tissue.
Scar tissue comprises of densely packed collagen fibres and elastin (an elastic fibrous protein) both of which are inherently strong. Therefore, the scar should be stronger, not weaker. In fact, as discussed in an earlier article in this series2, deliberately induced scars have been used to strengthen weak tendons in racehorses’ legs for many years.
Whilst the typical healed barbed wire scar may not necessarily have an adverse effect on the strength of the leather, there is no doubt that they are unsightly and, if present in abundance, no use for premium aniline leather. The lighter scratches and scars can be removed by correcting the grain and finishing, but the deeper injuries can be more difficult to conceal. After correcting or buffing the grain, stucco can be applied to fill the gaps before finishing, but this is labour intensive and is often messy; residues of stucco are often seen sticking to the back of the leather.
In an ideal world, the tanner would like to see the end of barbed wire, but it has served the farmer well for more than 150 years, so its demise is far from imminent. Farmers could use it more considerately and minimise the risk of damage to hides. If barbed wire was replaced with an alternative fencing material, or the barbs covered with rubber hose, in those areas where cattle tend to congregate or get crushed together (water troughs, gates etc) a significant amount of damage would be prevented.
Barbed wire is not only a problem for tanners; it is also a serious threat to wildlife. Wild animals frequently become entangled and suffer serious injury or death. In Australia3, a project funded by the World Wildlife Fund for Nature has been launched to offer farmers guidelines on how to make barbed wire safer or, preferably, replace it with an alternative fencing material.
Electric fencing is a viable alternative to barbed wire. Like barbed wire, it is easy to install and is relatively cheap. The original electric fence was a bare wire through which a regular electric pulse was sent from one terminal. The other terminal went to ground. Anything conductive, eg cow or human etc, that touched the wire and the ground at the same time would complete the circuit and receive a painful electric shock.
Modern ‘low impedance’ electric fences only release an electric shock when touched, by means of a solid state switching device rather than a continuous pulse. Once animals have touched the electric fence, they soon learn to avoid it. However, electric fencing is rather more problematic for the farmer than barbed wire since its performance can be affected by soil type, weather conditions and vegetation.