There are a few things that might cause edge curling on cow skin rugs. A poor quality cow hide that has been unevenly split during the tanning process is the strongest likelihood.
Because the leather fibres in the thinner areas dry out faster than leather fibres in the thicker areas it can create uneven surface tension and make cowhides curl, especially at the front and back legs or cheek leather near the head.
Expect cheap cowhide to curl quickly - within months of purchase. This curling is sometimes the industry calls cigaring. However even a good quality cowhide can curl with the right environmental influences.
Again if the top surface fibres are drying and contracting faster than the underneath fibres due to heat exposure like strong direct sunlight or a heater blowing hot air over the cowhide over a long period of time. Or the reverse can be true for underfloor heating which dries out the underneath faster than the top surface.
They are most vulnerable to curling around the narrow leather parts like the front legs and the cheek leather near the head. Curling is simply something that low quality cowhide rugs can do, it should be considered the "nature of the beast".
There isn’t really a permanent cure but try to roll the leather back in the opposite direction to the curl and give it a squeeze massage.
A light misting of water can also help put a small controlled amount of moisture back into the leather. You can steam iron cowhide rugs on either the leather or hair side with a cloth between the iron and the cow skin.
If it really bothers you and continues to curl then the only other option is the trim off a slice of leather removing the curling area. The shorter the legs and cheeks are the less they will curl.
Use a sharp craft knife blade and cut from the underside (cowhide should be upside down) starting by wiggling the knife through the leather in the middle of the cutting path, then slowly draw the blade in a gentle curve mirroring the original shape of the cowhide rug and running the blade off the edge of the hide, repeat going in the other direction to complete the cut.
This technique cuts the leather but not the hair leaving a nice layer of hair still falling over the edge of the cowhide. I find it easiest if the cow skin rug is on the floor (upside down). I then stand on the cow skin rug to hold it down and lift the edge that I am cutting about 10cm away from the floor so the leather is taught. Be careful and watch out you don't cut your floor or your leg!
Of course it is very likely that curling will happen again if the cowhide is cheap and poor quality or the environmental factors are still happening. If cigaring is an ongoing annoyance then perhaps cowhide rugs are not the best flooring solution for you. Buy a sheep skin wool rug instead.
We have been selling beautiful top quality cowhide rugs in New Zealand for over ten years. It is interesting to note that in the last two years the NZ and Australian searches for cowhide trouble shooting and cowhide curling info has sky-rocketed after poor quality cowhide was introduced to New Zealand & Australia in bulk.
Cheap hides WILL fail so don't buy them!