Post #500: How to speed up "breeding-back"

Selective breeding with domestic cattle cannot, under any circumstances, revive the aurochs. What can be achieved is what I call the greatest similarity to the aurochs that is achievable using domestic cattle. I prefer to speak of reaching that instead of having “bred-back” the aurochs or having “completed” breeding back (a process that is actually never completed). The animals will remain domestic cattle, but with a high degree of morphological/phenotypical similarity and ecologic equivalence to the aurochs and with very similar if not identical social behaviour patterns. Some domestic traits, such as a reduced brain volume or sexual dimorphism, or a not quite as athletic bodily morphology et cetera will remain, but an identical colour scheme with a well-marked sexual dichromatism (which is not the same but part of the overall sexual dimorphism), the same body size range, a very similar if not identical horn shape and size, aurochs-like proportions, a well-expressed hump, an at least roughly similar skull shape and of course the ecologic and behavioural similarities can be achieved by breeding with domestic cattle. These cattle would be the prime option for replacing the aurochs ecologically in the wilderness. 

As readers of my blog will know, breeding for the greatest achievable similarity to the aurochs is a long-term endeavour. That is because cattle are a comparably slowly reproducing species (nine months of gestation, roughly two years until sexual maturity, litter size of only one individual) and most breeding projects do not want to sacrifice genetic diversity by using a high degree of inbreeding (which would speed up the process but has its downsides to health and adaptability). How could this long-term process be sped up? 

Concerning the greatest achievable similarity to the aurochs, there are many ways to the goal. Many combinations of cattle breeds might deliver all the desired traits (morphologically as much as ecologically), several projects are running at the moment and one can always start from scratch. But is there a most efficient breed combination, one that includes all desired traits but has the least amount of undesired traits? How to breed more efficiently than the current breeding methods employed by the projects that are running at the moment? I see three possible scenarios: 

 

-) Starting from anew with the most efficient breed combination. I have been puzzling about what might be the most efficient breed combination, and I think it would be a set of five breeds: Lidia (body morphology, sometimes also horn shape, pelage/forelocks), Chianina (body size, sometimes horn orientation and shape and sometimes leg length and morphology), Maronesa (perfect wildtype colour, sexual dichromatism, useful elements of horn curvature), Watussi (horn volume), indicine breed like Deoni (very short trunk and long legs, very small udder). The most efficient breeding scheme would be to start with a herd of Chianina cows that are covered by a good Maronesa bull, and producing a herd of F2 of that combination, and parallel to that a F2 of Lidia x Watussi and Lidia x Deoni. Ideally, there would be three lineages: one that is large, has the right colour + dichromatism, aurochs-like horn curvature and a good morphology; one that has the Lidia-like morphology with an aurochs-like horn volume and possibly shape; and one that has the Lidia-like morphology with a very short trunk and long legs. In the next step (third generation), I would create F3 of the Maronesa-Chianina lineage to stabilize the good traits plus F1 of the Lidia-Watussi and Lidia-Deoni F2. F1 will not be stable in inheritance, so creating an F2 from this new combination would be required, and only the resulting F2 with a Lidia-like morphology, short trunk and long legs, and aurochs-like horn volume with a curvature that is useful should be kept for further breeding. These F2 should then be bred to the F3s of the Maronesa-Chianina lineage, and the resulting F1 should be used to create F2 of that combination. If some of the F2s of this combination has all the desired traits, they can be used for further breeding with less strict selection. 

Minimum generations required: 6 generations (roughly 15-20 years)

Advantages: the result could be very aurochs-like 

Disadvantages: requires a large number of parental individuals to avoid too much inbreeding and relying too much on luck. Deoni would probably have to be imported from Asia, which might be impossible for practical reasons. 

 

-) Strong selection within the most aurochs-like currently available “breeding-back” population. The most aurochs-like currently available “breeding-back” population would be, in my opinion, the Lippeaue Taurus cattle population. What is lacking, to a certain degree, is horn volume and short trunk length (the latter is a problem that most taurine cattle have). Because of that, an ideal combination would be a herd of large Lippeaue cows (like Bionade, Larissa, Linea) plus a Watussi-influenced bull from Hortobagyi or from the Auerrind project that has a truly large horn volume. The resulting F1 offspring from this combination would then be selected – as the P generation is less genetically homogeneous than purebred P, the resulting F1 would not be homogeneous either, so selection is necessary. With the good F1, F2 would be created and so forth, and the animals of each generation are selected and only those that are as good or better than their parents are used for continuing the breeding. 

Minimum generations required: Indeterminable, as it depends on how good the Fs from the respective generations are, which in turn depends on luck and the number of animals used. 

Advantages: Would be the least effortful variant as it would be based solely on cattle that are already used in the project or projects. 

Disadvantages: Using current “breeding-back” cattle only might go at the expense of certain traits, mainly short trunk length. A suitable indicine breed like Deoni might have to be crossed-in, what will require more generations.  

 

-) Using introgression from wild yaks and Java banteng on an already aurochs-like population. Wild yaks would add perfectly aurochs-like horns which are found only very rarely in domestic cattle, very large size (up to 205cm withers height in bulls), long snouts, large hump, cold tolerance and physiological fitness. Java banteng would add a well-marked sexual dichromatism that is very rare in domestic cattle, large body size (up 190 cm withers height in bulls) with a well-marked size dimorphism and a short trunk. So both species would help to achieve an aurochs-like extent in aurochs traits that are rarely found in domestic cattle. I would start with two herds of Lippeaue Taurus cows, which are suitable for two reasons: a) they are the most aurochs-like “breeding-back” cattle to date, b) their comparably large body size should lead to no problems during gestation and calving. I would inseminate one herd with wild yak semen, and one herd with Java banteng semen. Of the resulting hybrids, the males would be infertile. For the herds with the hybrid cows, good Taurus bulls would be chosen. The resulting backcrosses would be selected: those that have the desired traits added by Java banteng and wild yak would be kept for further breeding, those that do not would not. The B1 individuals would be backcrossed with the Taurus bulls once again. The resulting B2 would be selected like the B1 generation. The B2 bull with the most desirable (= the desired traits added by Java banteng/wild yak present, as few as possible other traits added by these species present) would be chosen as sire for the good B1 and B2 cows. The resulting fourth-generation animals would be selected after the same principle. The best (= those that have the least influence from wild yak and Java banteng but still have the desired traits) of these two lineages would be kept for further breeding. The fifth generation animals would be F1 from the banteng lineage x wild yak lineage. As you can guess by now, F2 from this combination would be created. Only those that have the desired traits added by banteng and yak, respectively, would be kept for further breeding. They can be backcrossed with Taurus endlessly to wash out the undesired influence from the two species, as long as those individuals that have the desired traits added by them are kept for further breeding. The result would be very aurochs-like in having “perfect” horns, being very large (possibly larger than un-hybridized “breeding-back” cattle) and a more well-marked dichromatism than would be possible without hybridization. Also, they would have long snout as in the aurochs and a well-developed hump, possibly more so than “breeding-back” cattle without hybridization. 

Minimum generations required: 6 to theoretically endless (20 years to endless) 

Advantages: some important traits might be achieved better and faster than without the hybridization from wild yak and Java banteng, that is body size, hump size, udder size (or lack thereof), snout length, horn curvature and sexual dimorphism. 

Disadvantages: the hybridization with another species is controversial, some of the traits added by them are invisible or behavioural but have an impact and can only be bred out by a practice of backcrossing and selecting as much as possible, which requires several generations at least. 

 

As you see, none of these methods is entirely unproblematic, and none is noticeably faster than the other. Does this mean we would have to wait at least for another 20 years until we see a “complete” result in “breeding-back”, an individual that has all the desired and achievable traits? Probably. Some individuals, like a 25% yak or banteng individual, or a 25% Watussi 75% Lippeaue Taurus might look quite satisfying in a much nearer future already, although they would be imperfect from the breeding perspective (not genetically stable yet, too many behavioural, morphological and ecological traits from the hybrid parents, lacking some traits et cetera). Highly ambitious “breeding-back” with cattle simply takes a while. However, to be honest, I think that some herds, like the Lippeaue herd (perhaps combined with Auerrind or Hungarian Taurus cattle for horn volume), are already aurochs-like enough to be released in the wild, basically in a dedomestication experiment (that is, releasing the cattle in a reserve and not interfere with the natural breeding of the cattle) and let natural selection do the rest while the cattle are doing their ecologic job in a rewilding area. It must be noted, however, that the dedomestication process takes even longer than artificial selection. Having made this list, I think that using small and wise doses of hybridization with wild yaks and Java banteng is the most tempting of the three scenarios, as it would result in the most impressing and perhaps most aurochs-like cattle. An upcoming post is going to examine if using hybridization is a crazy idea.