The problem with fixing traits through conventional breeding

Today comes a rather theoretic post on the obstacles of breeding, which is relevant for “breeding-back”. One of the biggest challenges for “breeding-back” is to genetically fix the desired traits. By fixing traits I mean achieving that all the individuals of the population have the desired trait. For example, the E+ allele is fixed in Taurus cattle because all individuals are homozygous for this allele. Fixing a trait requires consequent selection and to consider the difference between genotype and phenotype. 

 

As an example: Heck cattle of the Wörth/Steinberg lineage have very large thick horns that match those of the aurochs in absolute and relative dimensions. However, their curvature does not curl inwards enough in most individuals (see this individual). Maronesa sometimes have a very narrow, aurochs-like horn curvature, but lack the desired volume (see this individual). Something intermediate would be ideal. And considering that those traits are very likely regulated by more than one gene, the results of crossing Wörth/Steinberg Heck cattle with Maronesa would likely be intermediate, and hence show the desired phenotype: horns with the right volume and right curvature. Is the work done with that? Not even nearly – the desired phenotype would have to be genetically stabilized in the individual and to be fixed in the population. Simply backcrossing the offspring with the individual with the desired phenotype again and again will not be able to do that, and here is why: 

The cross individual might have the desired phenotype, but that phenotype is the result of maximum heterozygosity between the parental breeds. It has the alleles for the horns that are not curled enough and the alleles for the narrowly curled horns on the same loci, and it has the alleles for the very large horns and the not so large horns on the same loci, resulting in a phenotype that is intermediate and hence “perfect”. When the animal produces offspring it either passes on the alleles for the very large horns, the not so large horns, the not very curved horns or the narrowly curled horns, but it will never pass on the desired phenotype because it is the result of a heterozygous state. Thus backcrossing with the F1 individual with the desired phenotype will be pointless because it is genetically unable to stabilize the phenotype. By stabilizing in this case I mean that the individual always passes on the desired phenotype to its offspring, which is the case when the alleles producing the desired phenotype are present homozygous. When the phenotype is the result of heterozygosity, stabilizing it is impossible. However, since both horn volume and perhaps (or: hopefully, for this example) horn curvature are quantitative traits that are regulated by more than one locus, there is the chance to genetically stabilize the desired phenotype. As a simplified example, let us assume that horn size is controlled by only two loci, A and B, (unlikely, but only an example) and that Wörth/Steinberg Hecks are homozygous for alleles producing very large horns on both locus A and B, and that Maronesa are homozygous for alleles producing not so large horns on A and B. Thus, they only pass on very large horns or not so large horns, it is stabilized in their genome. What we want is a stabilized intermediate phenotype by crossing those breeds. The F1 individual will have the right phenotype because it is heterozygous for both very large horn alleles and not so large horn alleles, producing the intermediary phenotype desired. But, as mentioned above, it is impossible to stabilize this phenotype with this genotype, the genotype is not right yet. The right phenotype in this individual is actually only an “illusion”. The only way to stabilize the intermediary phenotype is to produce offspring that is homozygous for alleles producing very large horns on either locus A or B, and that is homozygous for not so large horns on the other locus. This way, the intermediate (= desired) phenotype can be passed on in a stable fashion. If horn curvature is a polygenic trait too, it works the same with horn curvature. It is impossible to have that in a first-generation hybrid. Breeding this F1 individual to another breed or one of the parental breeds will not stabilize the desired phenotype, even if you backcross it with the F1 again and again and again. This is why “breeding-back” herds are still heterogeneous and not genetically stable even if the same breeding bull has been used for multiple generations. The most efficient way to stabilize the desired phenotype is to breed the F1 individual to another F1 individual of the same combination (if you have only breeds A and B, in this example Wörth/Steinberg Heck and Maronesa). This way it is possible that an individual is born that has only alleles from Heck on one locus and only alleles from Maronesa on the other locus, if the goal is to stabilize the intermediary phenotype of a quantitative trait (f.e. body size or horn size). If you have such a true F2 individual with the right genotype (the more individual of this combinations you produce the less luck you need, the less individuals the more lucky you have to get for that), it is possible to fixate the trait in the population by backcrossing its offspring with it. 

Summa summarum: If you cross two breeds because a phenotype intermediary between both breeds is the phenotype you desire, the F1 individual will not have the right genotype for stabilizing the trait in the population, no matter how long you use it as a sire. If you produce a true F2 of this combination, the offspring has at least the chance to have the right genotype. 

If you are looking at a monogenetic trait, and you want to stabilize the intermediary phenotype that is the result of a heterozygous state, you will never ever be able to stabilize the intermediary phenotype in the population. To use Wörth/Steinberg Heck cattle and Maronesa as an example again: the former have horns that often are too upright for what is average in the European aurochs, while the angle of the horns is too narrow in most Maronesa. Let’s say the parental individuals have horns of an angle of 90° (Heck, too upright) and 35° (Maronesa, too narrow angle) and you want something intermediary to produce phenotype like in the European aurochs. If horn orientation relative to the snout is a monogenetic (Mendelian) trait, and the heterozygous state produces something intermediary like 60° as in the aurochs, it is impossible to stabilize this in the population, because the F2 will either have the 90° phenotype, the 35° phenotype or the desired 60° phenotype. You may be happy about the individuals having the right phenotype, but will never be able to fixate this trait in the population using these two breeds if horn orientation was regulated only by one locus. You would have to find a breed that has the right allele, as long as the right allele was not lost during domestication. I do not think that horn orientation is a Mendelian trait, but just to illustrate what I am saying, it would be impossible to fix a desired phenotype using two parental breeds that are homozygous for a phenotype that is not the desired phenotype. 

It gets more complicated if there are more than two alleles, f.e. three: let us say we have only one locus with three alleles, allele A producing the right phenotype when homozygous (60°), allele B producing very upright horns (120°) when homozygous, and allele C producing a very narrow angle when present homozygous (20°). Now let us assume that we have two parental individuals, one with horns having a 90° orientation and a genotype A//B (intermediary between the phenotypes A//A, the desired one, and B//B, the very upright horns), and one with a horn orientation of 35° with a phenotype A//C. By crossing these two animals, which both do not have the right phenotype, you would produce the following genotypes and phenotypes: 50% would be A//A, the right phenotype of 60° and right genotype, B//C would have a phenotype intermediary between 120° and 20° so perhaps the desired 60° but the wrong genotype, A//B with 90° as in one of the parents and A//C with 35° as in the other parent. If you produce only one offspring individual, the genotype will come about by chance. Either you have an individual that has the wrong phenotype and will be discarded, or you have the right phenotype but do not know if the genotype is right (A//A) or wrong producing the same or a similar phenotype (B//C). You can only know by producing further cross generations and analysing the offspring, when it is already too late if you picked the wrong individual. Thus, either the genetic background of traits is resolved (the individual alleles and the phenotypes produced are known, which is currently only the case in colour traits), or you have to accept that you also need a lot of luck or in some cases, stabilizing the trait is impossible with the breeds chosen because it is the result of a heterozygous state in a monogenetic trait.

Summa summarum #2: In a monogenetic trait, you need to have the one right allele in order to stabilize the fix phenotype. If the allele has been lost during domestication, it is not possible to stabilize the desired phenotype. 

 

Another problem for fixing desired phenotypes is genetic linkage. It is very likely that some domestic (= undesired) alleles are genetically linked with wildtype alleles (= desired) on the same chromosome. This can be a problem for “breeding-back” in two ways. For once, it might be the case that some desired phenotypes are genetically linked with domestic phenotypes in some breeds, f.e. the right colour might be linked to a wrong horn shape or other examples. In this case, a breed would have to be found in which this is not the case or you must hope to get very lucky with recombination. Another problem could be if a number of wildtype alleles for wildtype traits that are not morphologically visible (f.e. physiological traits) are genetically linked with visible mutations such as “wrong” colour variants or deviant horn shapes, the selection for aurochs-like morphology or looks might eradicate other wildtype traits for physiology, genetic fitness or immunology. This would be a case of bad luck, but cannot be ruled out completely. 

 

This is why it is a huge pity that there is currently no project that is trying to execute “genetic breeding-back” (go here for a post on that issue). For “genetic breeding-back”, the resolved full genome of that one British aurochs bull could be used as a template in order to accumulate wildtype alleles responsible for all aspects of the organism (physiology, morphology and life appearance, immunology, development, genetic fitness etc.), and produce something that is as aurochs-like as possible with living animals (not only in morphology, but also all other organismic traits). This would require a lot of extra research that has not been done yet, and it is problematic that we only have the genome of only one aurochs, which bears the danger of selecting against other wildtype alleles not found in that one particular genome. 

 

 

 

Using wild yaks for "breeding-back"?

I already did a post on the question if it would be wise to use existing wild bovines for crossbreeding in “breeding-back” a few years ago. I came to the conclusion that it is not recommendable to use hybridization with other wild bovines for “breeding-back” for a number of reasons. For once, while cattle are probably ecologically and ethologically identical with the aurochs and are derivations of the same species, other bovine species differ in behaviour (f.e. banteng fight less than domestic cattle, yak have a different display behaviour by using their tail tuft) and also ecology (banteng are a tropical species and eat more tree fruits than cattle do, yaks are more adapted mountainous habitat while the aurochs was a lowland species that preferred plain habitat). Therefore, the argument that “breeding-back” results are ethologically and ecologically identical with the aurochs as they are derivations of the same species would be gone. Furthermore, the acceptance for a species hybrid in the European wilderness would be lower than for “just” feral cattle. 

 

However, I am starting to believe that using careful, small doses of hybridization with wild yaks could be worth a try. 

 

I am mainly thinking about this because of the horns of wild yaks. If you want to see an animal that has horns exactly looking like those of an aurochs, look at wild yaks. It is fascinating how the horns are really identical in both species. See here, here or here. The curvature matches that of the aurochs’ horns as much as the relative and absolute size. Horn tips that truly curl inwards as much as in the aurochs is rare in “breeding-back”, and also rare in primitive taurine cattle, which is why I consider this trait one of the challenges for “breeding-back”. Strict selection would be necessary to produce this kind of horn shape, which would take its time and selection also has to care about other traits as well, while crossbreeding with wild yaks could produce that horn shape quite fast. 

Another reason is the morphology of the wild yak. A hairless wild yak superficially resembles an aurochs. They have a large hump in both sexes and usually a very long snout. Also, they have a comparably short trunk in both sexes. As the right horn shape, these traits are comparably rare in “breeding-back” and primitive taurine cattle. Most “breeding-back” cattle have a hump that is smaller than in the aurochs, and a truly large hump is mainly restricted to Spanish fighting cattle. The very long snouts of many aurochs bulls has not yet been reproduced by “breeding-back”. Wild yaks would thus also be beneficial for morphological traits. 

Also, the body size fits European aurochs. Wild yak bulls reach 170 to 205 cm withers height [1,2], which is the upper size class of European aurochs bulls. This very large size would be very useful for breeding for large size, especially as it compensates the small sizes of breeds used like Heck cattle (in Hungarian Taurus cattle), Watussi (in Auerrind and Hungarian Taurus cattle), Pajuna (Tauros cattle and Auerrind) or Highland (Tauros cattle). 

 

Thus, using wild yaks would speed up the process of achieving aurochs horns, body size and morphology considerably. Another advantage is that wild yaks are very cold-adapted and have a very dense undercoat. This would compensate the use of Watussi, which is adapted to a subtropical climate. Also, the yak is predominantly a grass eater, and thus ecologically overlaps with cattle. Crossbreeding with wild yaks would also lead to an increase in physiological fitness: wild yaks have a higher endurance than domestic yaks (and possibly domestic cattle), a more efficient respiratory metabolism as domestic yaks (and possibly domestic cattle), a more efficient digestion (the weight of wild yaks increases during winter, whereas that of domestic yaks and cattle decreases) and a lower death rate during winter [3,4]. 

 

To sum up the benefits of crossbreeding with wild yaks in “breeding-back”: 

- Wild yaks have horns identical to those of the European aurochs. 

- Wild yaks have large humps, a short trunk and a long snout

- The body size of wild yaks matches that of large aurochs and would compensate the use of small breeds 

- Wild yaks are very cold-adapted with a dense undercoat what would compensate the use of Watussi 

- The wild yak has a higher physiological fitness than domestic yaks and possibly domestic cattle 

 

However, there are some problems. Of course typical yak traits, behavioural (f.e. presenting their tail tuft when threatened) and optical (f.e. the long hair on the ventral body side), would have to be selected out just as all other undesired traits. But some traits are not visible in the living animal:  

- Yaks have 14-15 rib pairs, while cattle/aurochs have 13 

- Yaks have a larger lung than cattle, an adaption for living in high altitudes 

- Yaks are adapted to a mountainous habitat, while cattle/aurochs prefer flat lowlands 

- Yak have less and barely functional sweat glands as an adaption to cold, which could be problematic in hot regions 

- Yak have a slightly different skull anatomy: in cattle/aurochs, the premaxilla reaches the nasal bone, while in yaks the premaxilla only reaches the maxilla and not the nasal bone 

 

As these traits are not visible, they can barely be actively eradicated by breeding. One possibility to get rid of them in the population is diluting the yak influence as greatly as possible, while at the same time taking care that the horns, snout length, body morphology and size remain in the population. 

I would take a herd of aurochs-like “breeding-back” cows and inseminate them with wild yak semen (obtaining a wild yak bull for breeding would be very difficult as they are barely kept in zoos). The F1 bulls would be infertile. Thus, I would take an aurochs-like “breeding-back” bull to cover all the F1 cows. The resulting B1 bulls might be fertile, but reduced. If they are not able to breed, I would cross the B1 cows with the “breeding-back” bull again. The resulting B2 bulls would be fertile in any case, and would be 12,5% wild yak. The B2 bull could be bred to the 25% wild yak cows, and then a F2 of that combination by crossbreeding the results could be produced. When crossbreeding, one must pay attention to only breed with the hybrids that have the desired horn shape, size and body shape. Hopefully this results in a bull that is about one third yak (strictly genealogically) but only has the horns, body size and large hump that reveals its wild yak ancestry, while obvious yak traits like the long ventral body hair would be gone. This bull, being an F2 individual of the new combination, might be stable for at least some of its traits and can be used for backcrossing with the pure “breeding-back” cows. I would remove the other yak hybrids then. This way, the resulting animals would be taurine cattle with merely introgression from wild yaks and the yak influence would be further diluted in future generations while the aurochs-like horns, body size and morphology would remain in the population. 

This plan would take five generations to produce the aurochs-like result using careful wild yak introgression. Very strict selective breeding using the best of the best “breeding-back” cattle could be successful in five generations too, on the other hand. 

 

I think executing this plan in an experimental herd would do no harm. Unfortunately this will probably never happen, as wild yaks are very difficult to obtain. They are rarely kept in zoos. As far as I know, the only wild yaks in captivity are found in two Chinese zoos and one in Chicago. 

I think it would be vital for the preservation of the wild yak to build up a solid population in captivity, ideally with a herd book in order to secure the purity of the animals (there is the danger of hybridization with domestic yaks). 

 

Literature 

 

[1] Castello: Bovids of the World. 2016. 

[2] Jianlin et al.: Ecology, Evolution and Behaviour of Wild cattle: Implications for conservation. 2014. 

[3] Zhonglin: Development of a new yak breed through utilization of wild yak genetic resource – serial technologies of the development of the Datong yak breed. 2004. 

[4] Lanzhou Institute of husbandry and pharmaceutical sciences: the 5^th international conference on yak. 2015. 

 

 

New photos and videos of the Taurus cattle at Hortobagyi

The National park Hortobagyi in Eastern Hungary is the largest Taurus cattle breeding site. They have about 400 individuals. I intended to visit the population and to analyse it as I did with the Lippeaue Taurus cattle, but my contact person doesn't work there anymore unfortunately. 

The Hortobagyi Taurus cattle started with Heck x Hungarian Grey animals, to which Taurus individuals from the Lippeaue, a Holstein x Hungarian Grey, Watussi and later also a breeding bull from the Wörth/Steinberg lineage (named Anno) were added. They have some very interesting animals there. 

Here are some recent photos, published by the Hortobagyi National Park on facebook: 

#1  © Csoban Peter

#2 © Csoban Peter

#3 Csoban Peter

#4 © Csoban Peter

#5 © Csoban Peter

Photo # 1 shows bulls and steers. They definitely have Steinberg/Wörth influence, as well as the cow on #3. The cow on photo #2 could have Watussi and Grey cattle influence. Watussi influence is also very likely for the cows on photo #4. Of all the individuals on the photos, they have the most aurochs-like horn curvature. The cow on #5 also has interesting horns, although perhaps too upright. 

I also found two youtube videos featuring bulls: 

The second video also shows steers among the bull groups. I like the horn curvature of the bull at 3:28 in the second video. 

In general it can be said that the Lippeaue Taurus cattle have the better overall morphology (proportions, body shape etc.), while the Hortobagyi Taurus cattle have more horn volume and also the curvature is not bad in many individuals. 

Challenges for "breeding-back"

Some traits are relatively easy to achieve in “breeding-back” projects, while others are more challenging. The most important characteristic, the ecologic capacity to sustain themselves in nature, is at the same time one of the easiest to achieve, because “breeding-back” exclusively works with healthy, robust landraces. Also comparably easy to achieve are colour traits. Of all the “breeding-back” herds known to me, the Hellabrunn zoo Heck cattle herd and perhaps also the Wildgehege Neandertal Heck cattle are the only herds in which the aurochs colour scheme has been stabilized and deviant colour variants have been eliminated. This is comparably easy, as colour – being a qualitative trait – is regulated by only a few genes (the Maronesa breed is also an example for a flawless wildtype colour also with a well-marked sexual dichromatism). Other “breeding-back” herds, like the Taurus cattle, Tauros cattle and Auerrind cattle herds have not yet stabilized the aurochs colour in their gene pool, which is only due to the fact that their history is not as long as that of these two particular Heck herds. I am confident that with the right selection policy they will achieve the same “correct” aurochs colour. 

Colour is an easy fix. Other traits are not as easy, f.e. quantitative traits such as body size. Taurus cattle already have a satisfying body size, with cows over 150 cm and bulls possibly between 155 and 170 cm withers height. But to fully match Holocene aurochs, bulls with 180 cm withers or more height should be desired to be present in the population. This is achievable, as large Chianina are of that size. 

 

But there are traits that are actually quite a challenge for “breeding-back” because they are either not found in domestic cattle, or only very rarely. There are several challenges for “breeding-back”. 

 

Inwards-curling horn tips 

Perfectly aurochs-like horns in the Sayaguesa cow Dona-Urraca in the Lippeaue

 

The horns of the aurochs had a pronounced inwards curve and the horn tips of many individuals probably curled inwards (as seen in this wild yak), which is suggested by the shape of the bony core. This horn shape is not very common even among primitive landraces. The ABU, who breed the Taurus cattle in the Lippeaue, got lucky because they found a Sayaguesa individual with a perfectly aurochs-like horn curvature named Dona-Urraca. Many Taurus cattle with inwards-curving horns have them because of her. Other Sayaguesa individuals often have horn tips curling outwards or at least not inwards that strongly. Regarding other breeds, one would have to find the right Maronesa individuals, which can have a perfectly aurochs-like horn curvature, or some Lidia which also can have inwards-curving horns. In any case, because a very aurochs-like horn curvature is not common even among primitive cattle, selection has to be very strict if inwards-curling horns are to be fixated in the whole population. 

 

The right trunk length 

 

This is a very tricky one because taurine cattle only very rarely have the right trunk length. The trunk of most taurine cattle is longer than in the aurochs. Only some Chianina bulls, some Junqueira bulls and very rarely sometimes also Lidia bulls have a trunk as short as in the aurochs. In cows, the trunk should be a little bit shorter than the shoulder height, which I have not seen in any taurine cows yet that have a trunk as short as in the Sassenberg cow skeleton, the only definitive European aurochs cow skeleton that is mounted and on display: 

 

The Sassenberg aurochs cow. All rights reserved please don't use without permission. 

Since the right trunk length is very rare in taurine cattle (at least in the breeds commonly known, there might be some landraces in the Near and Middle East where the situation is different), all “breeding-back” results to far have a trunk that is longer than in the aurochs, even in the best Taurus cattle individuals (which, in my opinion, represent the current top level of “breeding-back”). Achieving the right trunk length will be very difficult when it is not found in at least some individuals. That is why I suggested using primitive zebu landraces, which sometimes have a very short trunk and thus proportions matching the aurochs, in order to achieve the right trunk length. Zebus of course have many undesired traits, which is why, again, strict selection would be required. 

 

The right snout length 

 

Regarding the snout length we have a similar situation. The snout of most “breeding-back” results are not quite as long as in long-snouted aurochs individuals. As outlined in a previous post, the aurochs was variable in snout length. While the Torsac dirac aurochs, and possibly also the Cambridge specimen, have snout lengths comparable to primitive breeds, many aurochs specimen have a longer snout. Some Holstein have long snouts as well, but the skull anatomy seems to be different from the aurochs. While this photo of a Holstein skeleton shows that the snout is long because the diastema is particularly long, in aurochs skulls it is the whole snout (including the toothed part) is longer than in most domestic cattle. These Maltese cattle also have a rather long snout which might match the aurochs, but I have not seen skulls of that breed yet in order to see if the anatomy is indeed identical or only superficially identical as in the case of Holstein. 

In any case, as in most cattle the snout is shorter than in most aurochs, achieving the right snout length will be difficult. The snout is actually an important trait, as a shortened snout is typical of all domestic mammals – thus, achieving the right snout length would be restoring a typical wildtype trait. 

 

The right body morphology 

 

This is another trait that is very difficult to breed for because only some taurine cattle, mainly some individuals of the Lidia breed, have the right body shape. By that I mean a slender waist, a not too bulky intestinum and a muscular body. Only some Lidia individual have a body shape that is plausible for a wild bovine when you compare them with wisents or banteng. Old Lidia bulls, however, may grow quite hefty. Even the best “breeding-back” individuals have a body shape that still looks domestic. It will be very difficult to breed for the right morphology. 

 

Udder size 

 

The aurochs had an udder that was invisible from the side, as cave paintings and comparisons with living wild bovines tell us. Probably it was nonexistent when cows did not have suckling calves. A large udder is a typical trait of domestic cattle, and probably costs a lot of energy and heat during winter. Thus achieving the small to nonexistent udder of the aurochs is desirable for “breeding-back”. The udder is enlarged in all modern domestic cattle breeds, even in Lidia which are not bred for milk. Some Lidia have a virtually invisible udder, on the other hand. Chianina cows also have a comparably small udder as much as primitive zebu breeds. Strict selection would be required to achieve the very small udder that is desired. So far, most “breeding-back” results have udders considerably larger than in the aurochs. 

 

Achieving the right phenotype but maintaining genetic diversity at the same time 

 

The goal of “breeding-back” is to create a more or less homogeneously aurochs-like population. For that to be realized, strict selection is required for all of these traits mentioned above. This, on the other hand, reduces the genetic diversity. By stabilizing the desired traits, the genetic diversity becomes increasingly narrow. This is problematic because a healthy population that is self-sustaining and able to a adapt needs genetic diversity. Therefore, achieving the goal is a balancing act between fixating the desired traits and maintaining genetic diversity at the same time. This is another challenge for “breeding-back” . 

 

As you see, there are several challenges for the breeding of aurochs-like cattle. Achieving “perfect” results that have all the desired traits will therefore take its time. Another approach would be to breed to a certain level of quality and than let natural selection do all the rest. Natural selection will “refine” the horn shape, proportions, body morphology and udder size over a sufficient amount of generations. Therefore, it is actually not necessary to breed for “perfection”. If you follow the approach of letting natural selection do the rest, “breeding-back” is actually already ready. One would have to pick the best individuals that are available so far, release them into a wilderness area and let natural selection do the work. For that approach, actually taking f.e. Lidia, the probably most primitive taurine breed, and releasing herds of them together with some Chianina cows for body size, Watussi cows for horn size, Maronesa for horn curvature and colour and Sayaguesa cows for overall appearance, would be enough and after perhaps already after 30-40 years of natural selection, very aurochs-like animals would have been produced. 

Therefore, it is not really necessary to breed for perfection. Nature will do that for us after a sufficient amount of time. 

 

Is our picture of the aurochs idealized?

Let us recapitulate the morphology and life appearance of the aurochs: it was large, had a short trunk and long legs, a long snout and horns facing forwards in a 60° angle relative to the snout. Right? 

Yes and no. In fact, there might have been more variation on some aspects of the aurochs’ morphology than we usually expect. There is the danger of idealizing the aurochs’ life appearance by assuming that the typical or average morphology was universal. 

Variation did not concern the aurochs’ body morphology and proportions. All aurochs specimen have a short trunk and long legs, resulting in a trunk length that equals the shoulder height in bulls and is a little bit shorter in cows, and all individuals, male and female, had a hump. But there was variation in the skull anatomy. Generally speaking, the skull of the aurochs had a longer snout than in most domestic cattle and a larger brain volume (go here for a post on the brain volume of the aurochs), which is not surprising, as a reduction in brain volume and a shortening of the skull are typical traits of domestic animals. However, the snout length apparently varied between the individual aurochs. While some skulls, such as that of the old Friemersdorf skeletal mount or that of the Sassenberg bull, have a really long snout, longer than in any domestic cattle heads I have seen so far, the Torsac dirac bull skeleton has a comparably short-snouted skull. The snout length of that specimen is actually similar to that of many domestic bulls. Male aurochs skulls usually also have very prominent eye sockets, more so than domestic cattle – but this was not the case in all male specimen. The Vig bull has a comparably slender skull, with less prominent eye sockets. 

There also was considerable variation concerning the horns within the European subspecies. Wild yaks have very aurochs-like horns. They match those of the aurochs both in dimensions and curvature as well as colour. Go here. This horn shape and size displayed by wild yaks is the “standard” when we imagine the horns of the aurochs. However, there was more variation in terms of horn shape and size in the European aurochs compared to the current wild yak population. The basic curvature was always the same – the so-called primigenius spiral. But it was present in numerous variations. Some horns were quite wide-ranging with a comparably weak curvature (such as in the Vig bull), others had a strongly-expressed curvature (such as the Prejlerup bull). The 60° orientation relative to the snout is the arithmetic mean of what Cis van Vuure found to be the average horn orientation in European aurochs (50 to 70°). The variation, however, was larger. The Vig bull has horns in a 80° angle, a skull at the museum of Horsholm has a possibly even larger angle (the narrowest angle I have seen so far is that of the oldest aurochs skull with 40°, but that skull was found in Africa and therefore likely not of the primigenius subspecies). Since those skulls with more upright horns are from the Northern half of Europe, while those skulls with a sharper angle tend to be from Southern Europe, it could be that there was a north-south gradient regarding horn orientation. Horn length also varies not inconsiderably. The skull with the smallest horns I have seen so far is that of the Himmelev bull, while very large-horned specimen are f.e. the Sassenberg bull. 

 

My latest aurochs reconstructions illustrate some the variation found in the European aurochs. The Torsac dirac bull has a snout comparable in length to many domestic bulls, the Kiew aurochs has comparably upright and weakly curved horns, similar to the Vig bull. The horns of some good Heck cattle, f.e. of the Wörth/Steinberg lineage, are not totally dissimilar to this horn shape. 

Life reconstruction of the Torsac dirac bull (left, photo © by Claude Guintard) and the Kiev bull (right, photo © by Andrzej Zieleniak)

 

The variability of the European aurochs’ horns and also snout length suggests to me that this subspecies was genetically quite diverse. Time is not such a big factor here as most of the specimen I mentioned in the text are from the early Holocene. 

 

What implications does this have for “breeding-back”? I think that “breeding-back” should be able to reflect the variability found in the European aurochs in its breeding results. Considering that some good Heck cattle, f.e. the bull Aretto from the Wörth/Steinberg lineage, have horns coming close to those of the Kiew or Horsholm specimen, and that some Taurus cattle, f.e. the bull Linnet, have horns resembling those of the Preljerup specimen, the variation spectrum for aurochs-like horn shapes is already present in the total “breeding-back” gene pool. Also the horn size spectrum of the aurochs, with some Wörth/Steinberg Heck cattle having horns matching the absolute and relative dimensions of very large-horned aurochs specimen. Now the challenge is to get rid of deviant (domestic) horn shapes and let natural selection do the rest (as the Oostvaardersplassen population shows, the primigenius spiral evolves after a certain amount of time in a variable population, go here for example). Breeding has yet to produce a snout length as long as in long-snouted aurochs specimen, which is not easy and as challenging as achieving the right trunk : leg length ratio. 

 

Exmoor x Konik crosses

The Exmoor pony and the Konik pony are the two horse breeds most frequently used for rewilding, and are often associated with the European wild horse by their advocates (go here). Both breeds are more or less uniform in colour: most Koniks are of a black dun colour (although sorrel dun and black individuals can appear), and Exmoor ponies are either of a bay colour or a seal brown colour with the wildtype non-dun allele (nondun1) EDIT: Exmoor ponies have been found to have the d2 allele, hence the domestic non-dun variant. Thus, another breed for introducing wildtype non-dun would have to be found. 

But the European wild horse was not homogenous in colour for the most time of its existence. I made a post on the colour phenotypes of the European wild horse this year. The most frequent phenotypes were bay or black (with the wildtype non-dun allele) and bay dun and black dun. The genetic background of seal brown is not resolved yet. 

While neither the Konik or the Exmoor pony comprise all the wildtype colour phenotypes found in the native European wild horse, it happens that crossing those breeds would result in a population that has all the colour phenotypes because the Konik contributes the alleles for black and dun, the Exmoor pony contributes the alleles for bay and wildtype non-dun. Thus, a mix population of those two breeds would be authentic in terms of wildtype colours. More than ten years ago, the Dutch foundation Stichting Taurus, which is also involved in the Tauros Programme, did exactly that: they produced Exmoor x Konik crosses. 

© Henri Kerkdijk-Otten

I was sent the photo by Henri Kerkdijk-Otten (dear Henri, if you are reading this and are not OK with me posting that picture, please let me know). 

Not only do these animals comprise all alleles for all the main colour phenotypes found in the European wild horse, also one individual had an upright mane (for reasons unknown to me). This makes this combination even more exciting, as I no longer consider a falling mane plausible for the European wild horse (go here). 

Sadly, the Konik x Exmoor ponies were all slaughtered by the Stichting Taurus. However, both breeds can still be combined in other locations or projects. 

The aurochs and insular dwarfism

Insular dwarfism is the evolutionary phenomenon that large species tend to decrease in size when confined to an area of limited space, most frequently an island. This is also called the island effect. The body size of large animals often adapts to the confined environment by shrinking down. The reason for that is that the island provides only limited space and limited resources, so that smaller individuals have a selective advantage over large ones due to the fact that they need less space and resources. Also, the smaller the individuals the higher is number of individuals that can survive on the given area, and the higher the number of individuals, the higher is the potential for genetic diversity and thus the chance of survival. Therefore, shrinking in size provides evolutionary advantages for large animals on islands, which is why there are plenty of examples for insular dwarfism in many vertebrate groups. 

The Mediterranean Sea has numerous islands, some of them large, such as Sicily, others small, such as Crete. And consequently, there were plenty of mammal species endemic to these islands that are examples for island dwarfism until the late Pleistocene. There were pygmy hippopotamuses on Crete, Sicily, Malta and Cyprus. Famous are also the dwarf elephant species Palaeoloxodon falconeri, P. cypriotes and Mammuthus creticus, to name a few. 

Sicily was home to several pygmy mammal species. Hippopotamuses, elephants, a dwarf deer (Cervus siciliae), a dwarf steppe bison (Bos priscus siciliae) and also a dwarf aurochs. It was already noted by van Vuure (2005) that aurochs on Sicily were 20% smaller than on the mainland. To be precise, the Sicilian dwarf aurochs had a withers height of only 130 cm [1]. This dwarf aurochs was described as a subspecies on its own that is barely recognized in the literature, Bos primigenius siciliae. There also was a dwarf aurochs on the small island of Pianosa, which had a shoulder height of only 100 to 120 cm and was described as Bos primigenius bubaloides [1]. Authors have suggested that this aurochs population evolved adaptions for moving on rocky uneven grounds [1], which would be unique for an aurochs.  

Both B. p. siciliae and B. p. bubaloides are barely recognized in the aurochs-related literature. The very small body size found in these populations seems to justify the subspecies status, and assuming that both taxa are not nomina nuda but have been described properly, they are valid. Thus, the aurochs actually was not divided into only three subspecies, but actually six: Bos primigenius primigenius (the European aurochs), Bos primigenius africanus (the North African aurochs), Bos primigenius namadicus (the Indian aurochs), Bos primigenius suxianensis (the East-Asian aurochs, go here for details), Bos primigenius siciliae (the Sicilian dwarf aurochs) and Bos primigenius bubaloides (the Pianosa dwarf aurochs). It would be interesting to see the osteologic material of these two subspecies. Island dwarfism often goes hand in hand with other morphological changes, such as paedomorphy and changes in proportions. Also, it would be relevant to know if the material assigned to the taxa was from males or females, because of the considerable sexual dimorphism we find in the aurochs. 

In contrast to other aurochs populations, the extinction of these insular forms does not necessarily have to be of anthropogenic cause. Small populations are particularly vulnerable to inbreeding and the resulting loss of genetic diversity, what makes them less able to adapt against abiotic and biotic factors. The Sicilian aurochs probably died out because it was outcompeted by the normal-sized aurochs when a land bridge between the Italian mainland and the island emerged about 20.000 years ago [2]. The same also happened to the other pygmy species [2]. In this case, human activities were not the cause of the extinction of the endemic mammal fauna. 

 

The island effect is also relevant for rewilding and “breeding-back”. Reserves are of limited space and if the population is reproductively isolated, it is basically an island from an evolutionary perspective. This implicates that in order to avoid an inbreeding depression individuals have to be exchanged between the reserves (which is, as far as I know, common practise in African reserves), and to avoid the island effect. Chillingham cattle, which have been living reproductively isolated in the Chillingham park for several centuries, apparently decreased in body size over time (go here for my article on Chillingham cattle). Thus, while natural selection seems to replicate many of the wildtype aurochs traits in feral cattle, we cannot expect the Heck cattle at Oostvaardersplassen to become larger by natural selection – if anything, they will get smaller or already got smaller. In order to avoid this as much as an inbreeding depression in other semi-feral herds of aurochs-like cattle, individuals between the reserves would have to be exchanged on a regular basis.

 

Literature

 

[1] Masini, Palombo, Rozzi: A reappraisal of the Early to Middle Pleistocene Italian Bovidae. 2012. 

[2] Sondaar, van der Geer: Evolution and extinction of Plio-Pleistocene Island ungulates. 2005. 

 

 

 

Are Heck cattle aggressive?

Heck cattle are sometimes reputed as an aggressive breed, or even the “most aggressive cattle breed in the world”. Why is that? Well, mainly because of one incident. 

Everybody will be familiar with the story of the British farmer who purchased a herd of Heck cattle, and slaughtered several individuals because of their behaviour. They would have attacked people without a reason. Several tabloids have reported that story in the most lurid way possible. People who are only half-educated on Heck cattle often say this aggressive behaviour is because the breed was bred using the Spanish fighting bull, which is not true (go here for details). 

In the literature, however, Heck cattle are described as generally unproblematic in behaviour based on the experience of breeders [1]. And it has to be remembered that there are dozens of grazing projects using Heck cattle, where people handle the cattle and which are also open for visitors. The number of Heck cattle used in these projects in Germany alone is in the three-digit range. The majority of modern Heck cattle live in these projects. And yet there never has been an incident of an individual attacking or even injuring humans without a reason. I am not saying that there never was an attack, because there was one incident on the Isle of Wörth with the cow Arizona, which attacked because a woman approached her calf (go here). But cows attacking because they “defend” their calves is common among any cattle breed. People are killed or injured in the alps by ordinary farm cattle breeds every year, yet nobody considers Braunvieh or Fleckvieh aggressive breeds. Furthermore, Arizona is not an aggressive individual, I visited her herd in 2013. In general, the behaviour of Heck cattle in grazing projects is unproblematic. If Heck cattle were an aggressive breed, they would be difficult to handle and would not be that heavily used in grazing projects. Also there are many private keepers that have Heck cattle on farms, and there never was a case of aggressive individuals reported. 

I can confirm myself that Heck cattle are usually totally unproblematic in their behaviour towards humans. I have visited several Heck herds, and there never was even one individual that showed signs of aggression. Some of them even were that tame that I could stroke them. 

Why was that incident in Britain, then? It has to be noted that cattle behaviour also depends a lot on socialization. I do not know anything about the background of those Heck cattle which the British farmer purchased. If he got them from a grazing project, or any area with few human contact, it would not surprise me if he considered their behaviour too “wild” for a usual farm, because cattle redevelop wild behaviour quite quickly when living with few human contact [2]. We should not forget that cattle are prey animals that will defend themselves if they consider themselves threatened. Also, there is always variation in a breed. Even some Highland cattle individuals can have a grumpy temper on occasion. Maybe it was a combination of both factors, no socialization with humans previously and individual variation, maybe the farmer just had really bad luck with his individuals. 

It inevitably seems to be a case of bad luck as the overwhelming majority of Heck cattle are unproblematic in their behaviour. If they were an aggressive breed, there would be a lot of incidents of Heck cattle attacking without a reason, which is reportedly not the case. If that was the case, the breed would not be used that heavily in grazing projects, on farms and in zoos. 

Heck cattle are not an aggressive breed. Yet, that story from Britain gets repeated over and over and over because it seemingly is too entertaining for some people. But repeating that story over and over does not make Heck cattle any more aggressive than they are. 

 

Literature 

 

[1] Julia Poettinger, 2011: Vergleichende Studie zur Haltung und zum Verhalten des Wisents und des Heckrinds.

[2] Bunzel-Drüke et al.: Praxisleitfaden für Ganzjahresbeweidung in Naturschutz und Landschaftsentwicklung – “Wilde Weiden”. 2008.  

 

 

New Auerrind promo video

Recently a new promo video for the Auerrind project has been published on youtube: 

It shows the Sayaguesa x Chianina cows, the Grey x Sayaguesa cow and her (Sayaguesa x Watussi) x (Sayaguesa x Grey) bull calf, the Chianina x Watussi cow plus the new breeding bull Benito (Sayaguesa x Maremmana). 

Here is a recent photo of the Chianina x Watussi cow published by Claus Kropp on Facebook: 

© Claus Kropp