Crossbreeding or not crossbreeding? That is not the question

The Domestic Animal Diversity Network (DAD-Net) has an email-based forum to which you can subscribe. The latest issue has a contribution from Saverio Krätli (freelance researcher and consultant specialising in pastoralism, and editor of the journal Nomadic Peoples) and Fred Provenza (Professor Emeritus of Behavioral Ecology in the Department of Wildland Resources at Utah State University, US) that we thought might be of wider interest. The authors kindly agreed for it to be reposted here. Many thanks to them, and to DAD-Net.

On 16 October 2020, ILRI geneticist Olivier Hanotte posted on the DAD-Net forum an announcement about a paper in Nature Genetics he had co-authored: The mosaic genome of indigenous African cattle as a unique genetic resource for African pastoralism (Kim et al. 2020). The paper finds that “a major taurine × indicine cattle admixture event dated to circa 750–1,050 yr ago … shaped the genome of today’s cattle in the Horn of Africa;” infers that the combination of genetic resources derived from such admixture “is at the root of the present success of African pastoralism;” and concludes recommending “further crossbreeding of indigenous African cattle with exotic cattle … as one of the pathways for the continent’s food security.”

However, in 2015, a paper by an ILRI team including Olivier Hanotte had raised concerns that “African indigenous cattle are endangered of extinction due to rash crossbreeding with exotic breeds” (Mwai et al. 2015).

And in 2000, another paper by an ILRI team led by Olivier Hanotte, upon finding widespread combination of taurine and indicine origins in African cattle, concluded that “the integration of … these results should … provide a rational basis needed for the conservation of the genetic diversity found in indigenous African cattle population” (Hanotte et al. 2000).

This tension between favouring crossbreeding and warning against it seems also reflected in the reactions to the posting of 16 October, for example by FAO animal-production officer Paul Boettcher: “the study does demonstrate that mixing of breeds is not inherently detrimental.”

We agree that “crossbreeding is not inherently detrimental” but with a qualification: it depends on what is meant by crossbreeding, as there is more than one crossbreeding tradition on the planet and differences are not simply in degree along a scale of sophistication. They are differences in kind, as between apples and oranges.

Thus, the debate on crossbreeding might be focussing on the wrong question. What matters is not whether or not to use crossbreeding with pastoral systems or indigenous breeds, but rather what kind of crossbreeding and why.

Livestock keepers in Africa have exchanged animals and crossbred for centuries as part of the processes of developing and maintaining the so-called indigenous breeds. Crossbreeding is also practiced amongst contemporary pastoralists, if only sparingly documented — for example the work on cattle breeding amongst nomadic FulBe (Fulani) in Niger (Krätli 2008) and Cameroon (Boutrais 2007), and camel husbandry amongst the Rendille in Kenya (Kaufmann 2007).

Pastoral breeds are constantly in the making, as they are developed to interface the livelihood/production system with landscapes that are also constantly in the making. The primary objective of breeding in pastoralism thus is not to maximise a trait or set of traits towards some ideal optimum animal-object with the right combination of genes, but rather to keep as high as possible the capacity of a given herd to function as a matching interface with ever-changing landscapes. The same logic also drives the use of crossbreeding.

This kind of breeding and crossbreeding is aimed at embedding variability into the herd so as to match the variability in the environment. This includes not just genetic resources but also epigenetic gene expression that complements complex learned behaviours functional to interfacing with the environment. Examples are feeding competence, social organisation, knowledge of the territory, attachment to herders, experience in managing difficult terrains or high temperatures, and so forth, all of which create animals adapted to the multiple landscapes they inhabit (Provenza 2008). These kinds of complex behaviours are part of what animal behaviour scientists call “animal culture” (Landau and Provenza 2020).

Animals create relationships with what they deem to be relevant facets of the social and biophysical environments they inhabit. Mothers and social group are crucial transgenerational linkages to landscapes. Mother’s influence begins in the womb (through flavors of foods she eats in her amniotic fluid), continues after birth (through flavors of foods in her milk), and she is a model for what and what not to eat and where and where not to go when her offspring begin to forage. Learned behaviors and abilities involve anatomical and physiological changes in organ systems, including the microbiome, as genes expressed epigenetically facilitate ongoing co-creation in ever-changing environments. While these behaviours are not innate, they are transmissible, thus still inheritable although in a non-genetic way (Krätli 2007, Provenza 2018).

Social and cultural linkages with landscapes are outside the field of vision of classical genetics and mainstream animal science. For a more representative view of what matters here, we need to turn to conceptual frameworks that are more aware of the relationship between organism and environment, such as developmental biology (Lewontin 2000, Oyama et al. 2001) and epigenetics, especially the work of Eva Jablonka (Jablonka and Lamb 2006). This is also not so far from the marriage between animal sciences and agroecology proposed for example by Bertrand Dumont and his colleagues at INRAE as a path for redesigning animal production for the 21st century (Dumont et al. 2014). Following an approach that is closer to breeding in pastoral systems than to conventional gene-based breeding, scientists are training livestock to eat invasive plants thought to be unpalatable; or training them not to eat otherwise palatable plants, for example to allow the use of sheep to manage vineyards (Provenza 2003;

Breeding and crossbreeding for embedding variability into the herd increases domestic animal diversity. It is a functional, contingent and continuous honing the capacities of a herd to interact with the landscape. Crossbreeding towards some “ideal” optimum, on the other hand, reduces the variability within the breeding population and reduces domestic animal diversity. One approach does not exclude the other, and some pastoralists today may at times use both, if with different sections of their herds.

This fundamental difference in approaching breeding and crossbreeding reflects fundamentally different traditions of livestock keeping. In pastoral systems, the operational logic is to work with nature, engaging with its variability as an opportunity. In animal production systems following the tradition of mainstream animal science, the aim is to “emancipate” production from the environment, focussing on the animal’s metabolism.

In short, there is crossbreeding and crossbreeding, and the presence of one tradition is not a licence for the other. We propose that the debate on crossbreeding in pastoral systems would benefit from taking onboard the existence of an alternative tradition based on a different way of representing the natural environment and relating to it. With climate change now on our door step, an approach to breeding, and ultimately to livestock keeping, centred on interacting with a changing landscape seems increasingly relevant even beyond pastoral development.

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