Strategies for controlling the breeding of livestock are extremely variable in pastoral societies across the world. By its very nature, pastoralism makes it difficult to control which animals breed, unless poor-quality males are excluded, either by mechanical means or by castration. Pastoralists are better at ensuring that their herds do not mix with other herds than they are at controlling breeding within their own herds. Nonetheless, different societies seem to have taken very different attitudes, for reasons that are not always evident.
There is also great variety from species to species; camel pastoralists are much more likely to take an interest in breeding than are sheep and goat producers. Musil (1928) describes the Arabian Bedu's complex ideas about breeding. In contrast, Black-Michaud (1986) attributes extreme indifference to the Luri small ruminant herders of the Islamic Republic of Iran. The Incas had a highly effective system for recording the details of llama bloodlines, using quipu cords and a selection process to ensure that the strongest and fittest animals were used for breeding (Brotherston, 1989: 244). Mongolian herders make a very clear association between human and animal bloodlines; human ancestry is closely recorded and there is a sense that the same should be true for livestock, although this process was interrupted by the collectivization of herds and the partial introduction of "scientific" breeding practices. Many pastoral peoples in West Africa seem relatively indifferent to the control of breeding, even among cattle, although they are well aware of the need to introduce new cattle races if their herds begin to exploit a different environmental niche (Blench, 1999a).
The notions that pastoralists should ensure that they are breeding from high-quality males and that exotic stock would increase output have a long history in pastoral development. Horse pastoralism is replete with semi-mythological narratives of kings searching for stallions with near-magical attributes. In the real world, however, such introductions have not had the same success. In some ways, the reason is evident; pastoralists breed their animals to survive and produce under extremely harsh conditions, including climatic and environmental extremes. Animal breeders concentrate on marketable attributes, and frequently focus on individual traits such as milk or meat production. Research stations are not ideal places to test livestock for extreme drought and disease stress. The result is that the improved animals do not generally have the qualities that pastoralists really need, although they are pleased with the increased milk or meat output. As a consequence, the features of the introduced stock that make it attractive in the first place are rapidly eliminated and the overall herd output remains static.
Nonetheless, since pastoralists do engage in their own introductions, it must be possible to do so; a more effective programme would work with animals that are genetically closer to those in the pastoral herds and under conditions that are more similar to those experienced by a real herd. Some progress in this direction has recently been made through "open-nucleus" breeding schemes, where the pastoralist exchanges animals with those in an improved herd. More success in this area will come with a greater understanding of the conflict between pastoralists' and animal breeders' goals.
The castration of male animals is a common strategy among pastoralists in many systems. It has the advantages that animals may become fatter and are very often less aggressive, thereby becoming easier to manage. The disadvantage is that incorrect decisions about the genetic attributes of those left entire, or accidents to male animals, may leave a herd breeding from poor-quality animals. One counter-strategy is the use of mechanical means to prevent animals reproducing; genital covers for sheep and goats are quite widespread in Western Asia. Castration was probably rarely practised in sub-Saharan Africa in pre-modern times because of the risk it poses to the stock of males; however, the gradual spread of better health care has made it more widespread as a strategy. In the Andes, castration seems to have been widespread across all species (Göbel, 1997: 42). Castration also depends on social institutions for the effective circulation of males; in some ways it has structural similarities to the effects of droughts and blizzards. If there are too few potent high-quality males, when one dies it is only possible to recover by borrowing animals from beyond the household or community. This works more effectively when the community is more cohesive, but can lead communities to take substantial risks in reducing the numbers of males.
Pastoralism is not well adapted for ex situ strategies because of the lack of infrastructure in pastoral areas and the difficulties of access. As was suggested in Controlling bloodlines, some societies take great care over bloodlines and controlled mating while others allow unrestricted access to females. The concept of introducing unknown semen or embryos into the intricate breeding mosaic seems unlikely to be easily accepted by the former group. It may be introduced for the latter, but the consequences will probably be the same as they are for more conventional introductions of improved breeding stock; the elements in the introduced line that make it attractive will rapidly be eliminated by the harsh conditions of pastoralism.
Nonetheless, pastoralists are also the owners and managers of rare livestock breeds and there is now increasing concern that these could be lost or progressively eliminated by genetic introgression. The loss of such breeds would lead to a corresponding loss of genetic traits that have, in some cases, built up over millennia, for example the resistance to extreme cold of Yakut cattle, the resistance to extreme water heights of Criollo and Kuri cattle, and trypanotolerance. Recent scientific advances have made more intricate possibilities available for conservation and monitoring. Cloning is carried out to reproduce improved phenotypes at present, since the goal is not breed conservation, but the same technology could be adapted to clone extremely rare breeds or individuals containing valuable genes. Nonetheless, cloning technology is subject to the same objections as conventional cryopreservation: it does not reproduce the evolving responses of a live population.
The mitochondrial DNA of cattle is now routinely extracted through polymerase chain reactions (PCRs) and can be used not only to establish the evolutionary history of breeds and species but also for routine monitoring of genetic variability within populations. DNA can be used to measure, directly, the levels of homozygosity and, thus, the degree of inbreeding, thereby forming the basis for planning conservation programmes. The International Livestock Research Institute (ILRI) has taken the lead in this area and is at present engaged in DNA characterization of African cattle breeds.
At present, all of these techniques are concentrated in the developed world and within the scientific establishment of a few countries. Some are controlled by patents that are owned by large agricultural companies that will only license the technologies for their own profit. As with transgenic crops, the technology will probably spread quickly to parts of the developing world where there is a sophisticated science infrastructure, but will completely bypass many other countries. The whole area is too new to make any secure predictions possible, but access to information, as is the case in many other areas, may perpetuate inequity, although not along conventional developed-developing world dichotomies.