transhumant that live in the high altitudes (International Conference on Nomadism .... Cattle and small stock play a critical role in the agro-pastoralist ...

http://www.google.com.ar/url?sa=t&source=web&cd=10&ved=0CFwQ...

Answers.com - What is nomadic herding - [ Traducir esta página ]Ancient History question: What is nomadic herding? when farmers constantly move place to place because more feed is available or for other reasons that ...
wiki.answers.com/.../What_is_nomadic_herding - En memoria caché - SimilarNomadic pastoralism - Wikipedia, the free encyclopedia - [ Traducir esta página ]Historically nomadic herder lifestyles has led to warrior-based cultures, that have made them fearsome enemies of settled people. ...
en.wikipedia.org/.../Nomadic_pastoralism - En memoria caché - SimilarSands shifting for Africa's nomadic herders | Environment | The ... - [ Traducir esta página ]7 Feb 2010 ... Millions of hectares of land used by pastoralists have been lost to sedentary farming and conservation.
www.guardian.co.uk/.../sands-shifting-africa-nomadic-herder... - En memoria caché - SimilarNOMADIC HERDING REGIONS XOMADIC herding is the dom- - [ Traducir esta página ]the regions of nomadic herding is further emphasized by a tabulation of ... Nomadic herding occupies the broad belt of dry lands that extends from the ...
www.jstor.org/stable/140368 - SimilarAsia :: Nomadic herding -- Kids Encyclopedia | Online Encyclopedia ... - [ Traducir esta página ]Asia, Nomadic herding: In the drier parts of Asia, especially Southwest Asia, most rural people make a living by raising livestock. Many are nomads who move ...
kids.britannica.com/comptons/.../Asia - En memoria caché - SimilarNOMADIC HERDING « Agriculture Science - [ Traducir esta página ]1 Apr 2010 ... NOMADIC HERDING An extensive form of animal grazing on natural pasturage, entailing constant or seasonal migration of the nomads alongwith ...
scienceofagriculture.wordpress.com/.../nomadic-herding/ - En memoria caché

This may not be the most elegant translation. Technically, the term is transhumant shepherds/herders/drovers. In Spain it refers to the practice of moving herds of sheep and cows from the lowland pastures, which become parched in summer, to highland pastures. Spain has 4,000 km of drovers' routes that were maintained specifically to allow livestock to move from one area of the country to another.

Or, if they are the owners, farmers grazing their herds seasonally - which I think would work in your sentence.

"The patterns of seasonal grazing, often involving transhumance, have
been largely unchanged since the early days of agriculture."
http://www.birdlife.org/eu/pdfs/BCEurope_CAPreformpaperFeb08...

Although I also favour "transhumant (livestock) farmers"!

The World Gathering of Nomads and Transhumant Herders is meeting in Segovia this September, 8th - 16th.
http://www.iberianatureforum.com/index.php?topic=532.0;wap2



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Note added at 20 hrs (2011-03-19 14:53:33 GMT)
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Here an interesting article: http://libro.uca.edu/vassberg/land1.htm
in this paragraph you have both transhumant herding and seasonal migrations:
"...The derrota, of course, was not created by jurists rationally manipulating legal principles of ownership. Rather, it had its origins in the needs of the rural community at a certain time in history. There were several broad economic factors explaining the adoption of the custom. The basic justification for the derrota was the need to maintain an adequate supply of accessible pasture resources for the important pastoral sector of the rural economy. The celebrated development of transhumant herding was one solution to the problem. But it was not possible to send all animals on seasonal migrations across the peninsula in search of green pastures. Most of Spain's animals, in fact, did not participate in the periodic transpeninsular migrations, but instead remained near the villages of their owners. It was essential to devise a way to feed them...."