Tuesday, 15 August 2017

New photos from the Watussi x Maremmana crosses

Today, a couple of new photos of the two Watussi x Maremmana crosses have been published on Facebook: 
Cross bull "Apollo" © Claus Kropp
© Claus Kropp
It is clearly visible that the young cow is of a lighter colour than his half-brother. I am very much looking forward to see what they are going to look like fully grown. Watussi obviously contributes alleles enabling the production of red pigment, so breeding out the Agouti dilutions in the second generation might already result in a very aurochs-like colour scheme. 

Monday, 14 August 2017

The Murnau-Werdenfelser

One might wonder why this breed is particularly interesting so that it deserves an own post, except that its name sounds like a beer. Well, it is interesting mainly for two reasons. First, its colour scheme considering it is a rather derived Central European breed. Secondly, it was a more or less important founding breed of Heck cattle.

Murnau-Werdenfelser is of Bavarian-Austrian origin, descending from Gelbvieh, Braunvieh and other local breeds according to Wikipedia. Gelbvieh are, as their name suggests, rather light in colour – particularly, eumelanin is lacking. Braunvieh and other breeds might have contributed alleles producing more eumelanin. In any case, Murnau-Werdenfelser have the right colour scheme besides the Gelbvieh-like diluted ones. However, sexual dichromatism is reduced and variable. Some bulls are completely black in an aurochs-like manner, others show the colour of the cows. Most bulls seem to be somewhere in between. 

I do not know to which extent this breed was used in Heinz Heck's experiment as the literature is not precise. Cis van Vuure (2005) writes: "Heinz also used Werdenfelser cattle in his experiments, but Heinz himself makes no mention of this". He might have overlooked a remark from Heinz Hecks extensive article "Der neue Auerochse" ["The new aurochs"] published in 1980 in the international Heck cattle herd book stating: "For that I crossed Hungarian Steppe cattle, Scottish Highland cattle, Allgäuer, Werdenfelser, Angler, further also blackpied Lowland and Upland cattle, Podolian Steppe cattle and Corsican mountain cattle" (translated from German). However, he still gives no precise information to which extent the breed was used (in how many crossbred individuals, for example). 

Nevertheless many Heck cattle still bear a striking resemblance to individuals of this breed. I give some examples now that I found on google that could easily be mistaken for Heck cattle (in some cases especially if they had larger horns, but there are also many small-horned Heck cattle): 
All of these colour variants are still found among modern Heck cattle

Heck cattle is often regarded or claimed as a mix of "exotic" breeds such as the Spanish fighting bull (which is very likely not the case) and others. A closer look at Heck cattle's breeding history shows that actually Heck cattle also descends from a number of Central European breeds that left a clear mark in its phenotype, as the example with the Murnau-Werdenfelser shows. 

Saturday, 12 August 2017

The African aurochs

I finally get to making a post on the African subspecies of the aurochs, Bos primigenius africanus. I actually planned to do this post two years ago, but never found the time to do an appropriate artwork on its putative life appearance. This week I finally finished one, so I am going to sum up what is known about the life appearance, phylogeny and ecology of this subspecies.

Phylogeography: The aurochs probably originated in Africa

Previously, it was assumed in the literature that aurochs descended from the Asiatic species Bos acutifrons which lived in Asia 2 million years ago (van Vuure, 2005). However, the oldest remains of aurochs have not been found in Asia but in Africa. The remains include a huge-horned skull from Tunisia dated back to 700.000 years (Martinez-Navarro et al. 2014). Aurochs appeared in Spain shortly after this individual died, perhaps migrating directly from North Africa (my personal guess, but I do not know if they would have been able to cross the Gibraltar street via island hopping or something similar). This could mean that aurochs reached Europe twice from two different populations, and genetics indeed showed that Southern European and Northern European aurochs differed genetically (Mona et al. 2010). My suspicion is endorsed by the fact that the basalmost African aurochs skull also shows the largest horns known to date and that Pleistocen Italian aurochs have also been described having particularly large horns (Frisch, 2010). What is important to note is that there are no noteworthy osteologic differences between later B. p. africanus and B. p. primigenius, so that the differentiation of both subspecies might be based on solely geographic basis (van Vuure, 2005), especially if my suspicion is correct that European aurochs populations could be polyphyletic. What is interesting now is that the osteologically different B. p. namadicus seems to have diverged from the primigenius/africanus clade much earlier, somewhere 1,7-2.0 million years. Probably the progenitors of the namadicus clade migrated from Africa to India rather early. This supports the view that namadicus and therefore also zebuine cattle are a separate species, but that is only paperwork that does not alter the animals themselves therefore it does not really change my conceptions. More on the Indian aurochs in a separate post coming up. For previous posts and artworks on the Indian subspecies, see the 2015 post and the 2013 post (I consider the latter outdated). 

As a remark, I do not consider the 700.000 year old aurochs skull a member of Bos primigenius africanus, even though it is from Africa. I consider aurochs from that time the most basal members of the clade before any subspeciation took place. 

Paleoecology of B. primigenius africanus

The African aurochs was neither an animal of the savannah nor the Sahara. Rather, it was present along the northern rim of the African continent from Morocco to Egypt and along the Nile delta where it was abundant (van Vuure, 2005). These North African ecosystems where the overlap zone of both the African and European biome, where European megafaunal species such as wolves, brown bears, red deer and aurochs lived along African megafaunal species such as African elephants, rhinos or hartebeest. Certainly the African aurochs was adapted to the way more arid climate of this region than aurochs from Central or Northern Europe.

Life appearance of the African aurochs

As mentioned above, the literature says there were no noteworthy osteologic differences between later B. primigenius africanus and European aurochs. Genetics would further have to show whether there was a continuum to the Middle east or not.
However, there are at least three prehistoric stone carvings from Libya that suggest the African aurochs had a distinct trait that distinguished it from the European populations. While there are good reasons to believe that so-called colour saddles did not appear in wild European aurochs bulls, it was seemingly the case in at least some north African wild bulls.

The two pictures are scanned from Frisch 2010 and © by Rüdiger Lutz. For the third one, go here. They show two engravings that definitely show grown, male aurochs with a colour saddle that is clearly indicated and extends till the hips. It can be ruled out that they show domestic bulls as they date back to 12.000 years ago, and are probably fully grown as the huge size is implemented by the small hunters surrounding them. The uppermost carving is from Hadarin in Lybia, other one probably too. The uppermost not only shows the colour saddle but also nicely the white muzzle ring and the light colour of the horns. The third picture is less anatomically precise and is from the flickR stream of archeofan and from Lybia as well. The upper scan actually shows another individual with a colour saddle (right side down below in the picture) but the sex is not visible on the photo. They are all stylistically very similar so probably from the same culture. It is also possible that one artist copied from the other, which is why artworks are imperfect evidence, but in this case we would have evidence for at least one African aurochs bull with a saddle. 

So while there are many literature and art references that support black bulls for European aurochs and absolutely none that suggest bulls with a colour saddle for Europe, there are at least three artworks supportive of this trait in North African aurochs. It could be a coincidence and maybe both European and North African aurochs showed saddles on occasion, but I think the chances for that being a coincidence are way lower than for the conclusion that European bulls usually were of a black colour and North African bulls seemingly had a colour saddle.

This is actually not unlikely. The aurochs had a large distribution area, and we often find that subspecies of wild bovines may vary in colour. Actually, the fact that North African aurochs bulls might have had a colour saddle would simply imply that the sexual dichromatism was not as strongly expressed as in the European subspecies. Other wild bovine species show geographic variation in this respect as well. For example, the Java banteng (Bos javanicus javanicus) shows the same colour dimorphism as European aurochs: black bulls, reddish brown cows. The Burma banteng (B. j. birmanicus) has a very reduced sexual dichromatism, both sexes are of a light brown colour. The Borneo subspecies is intermediate. Also Gaurs vary in sexual dichromatism, some populations having virtually none while it is more or less visible in others. The African forest buffalo also differs in its colour from all the other African buffalo subspecies (which is one of the reasons why some regard it as a separate species).
So it is absolutely plausible that the African aurochs, as a result of genetic drift and living in a different habitat/climatic zone might have displayed a slightly different colour as the European subspecies. It would also be possible that the African aurochs had a longer dewlap, since bovids in tropical or subtropical climates tend to have longer dewlaps for display and thermoregulations, while those in more temperate climates have furry ornaments like beards or manes instead. 

I actually made a drawing of an African aurochs bull and cow, but that did not work out as well as I wished. So I took the photo manipulation of the Taurus bull Londo with the head of a Lidia bull (I was unable to find out the name of the copyright owner of the picture; if it is you and you want me to remove it from the manipulation, please leave a comment) and partly painted horns that shows what I imagine an aurochs bull to look like, and copied the saddle of this Pajuna bull on its back. I also gave it the light forelocks that often correlate with bulls having a saddle, probably as a result of reduced sexual dichromatism, although there is no direct evidence for it. Then I inserted it in a semi-desert landscape from the Mojave desert (I know, wrong continent; I had to remove a lot of Joshua trees. It is just a symbolic background) using a photo from Wikimedia Commons by Alen Istokovic. I am pretty happy with the result. Please do not use without permission, as I do not have the OK of the owner of the Lidia photo and the Pajuna photo.

“Breeding-back” the looks of the African aurochs?

A “breeding-back” project for the African subspecies is tempting. While it seems likely that many of the Iberian breeds are influenced from African domestic cattle, there is no solid proof yet that any cattle directly descend from wild African aurochs, which disappeared in antiquity. EDIT: Decker et al. 2014 (go here) find African taurine cattle to be the most divergent taurine cattle and therefore speculate that this was caused by introgression of B. p. africanus. The portion of African aurochs ancestry in African taurine cattle might be as high as 26%, although they do not have African aurochs aDNA to prove that directly (as far as I understand). However, I don’t consider it that dramatic, as the European and African subspecies probably were more or less closely related. A “breeding-back” project for the traits of the African subspecies would have to focus on the same objectives as those for B. p. primigenius, with the exception that colour saddles in bulls are appreciated and should be bred for. Lowering the mean degree of eumelanisation for bulls will probably result in some bulls displaying a reddish brown cow colour scheme (like this Pajuna, for example), just as bulls with a colour saddle are not uncommon in the projects focusing on the European traits.
A possible set of breeds to optically restore the North African subspecies could be:
- Maronesa (horn shape)
- Alistana-Sanabresa (similar to Sayaguesa but less eumelanised, bulls have a saddle)
- Pajuna (slender and many bulls have a saddle)
- Watussi (horn size, used only with caution)
- Maltese/Chianina (size, proportions, body shape)

All those breeds are from a more or less subtropical climate, so they should be suited to the North African ecosystems, especially Watussi. As for the use of Maltese vs. Chianina, it would depend on whether semen of Maltese bulls would be available (to avoid the annoying dilution genes of Chianina), if not, one would have to rely on Chianina. The African aurochs was probably not as large as Northern European aurochs, but one has to compensate the comparably small size of breeds like Pajuna or Maronesa. And you achieve good proportions and body shape with those large breeds.

Such a look-alike for the African aurochs that is suited to the local ecosystems could be reintroduced somewhere in North Africa along other megafauna. I suggest a “North African Kruger National park” just like I did it for Europe, inhabited by megafaunal species such as African elephants, rhinos, hartebeest, red deer, cattle, brown bears, wolves and others. However, the political situation in the North African states makes it unfortunately very unlikely that a megafaunal reserve of that kind will be realized in the near future.

Literature

- Cis van Vuure, 2005: Retracing the aurochs: history, morphology and ecology of an extinct wild ox.
- Walter Frisch, 2010: Der Auerochs: das Europäische Rind.
-  Martínez-Navarro, B., Karoui-Yaakoub., N., Oms, O. et al., "The early Middle Pleistocene archeopaleontological site of Wadi Sarrat (Tunisia) and the earliest record of Bos primigenius", Quaternary Science Reviews (2014).
- Mona et al. 2010: Population dynamic of the extinct European aurochs: genetic evidence of a north-south differentiation pattern and no evidence of post-glacial expansion.
- Hiendleder, Lewaski, Janke, 2008: Complete mitochondrial genomes of Bos taurus and Bos indicus provide new insights into intraspecies variation, taxonomy and domestication.



Wednesday, 9 August 2017

How good is the sexual dichromatism in the Lippeaue?

One of last week's posts was on sexual dichromatism in "breeding-back". Today's post will be on the same topic. I start with two pictures: 
The upper photo is from Hortobagy (© Istvan Sandor) and shows the breeding bull Rimu with a cow. The lower photo shows two Taurus individuals from the Lippeaue. Don't fall into the pitt concluding that these photos show good sexual dichromatism - it is not said that both individuals are closely related and inherit the sexual dichromatism that we want in these cattle. Their genotype is very heterogeneous and we cannot know for sure. That is why we should always look at the tendency in the total population, and I did this for the Lippeaue anno 2015. 

In my post on the genetic and developmental background of morphological traits, I outlined that it might be very difficult to impossible to achieve an authentic aurochs-like sexual dimorphism, in particular sexual dichromatism (the colour difference between the sexes), based on conventional phenotypic selection:

Always simply choosing red cows and dark bulls, or small cows and large bulls, or whatever sexually dimorphic trait, probably will work not here. You would actually have to choose individuals where the sexual dimorphism is laid down in the genome. A phenotypically red cow might either have a more or less strong sexual dichromatism (s. dimorphism in colour), or simply be red and have no sexual dichromatism at all, depending on the bulls that she would produce. The same is the case with dark bulls. How to know that? Well, at first the genetic background of the dimorphic trait has to be resolved, and then the individuals would have to be tested.

So not only would the auto- and gonosomal genes and alleles involved in sexual dichromatism have to be identified, each individual would have to be genetically tested. This would be very expensive and requires research. Therefore I concluded:

I think there are only two possibilities regarding breeding a good sexual dimorphism: either relying heavily on a breed where a well-marked sexual dimorphism is still retained […], or putting up with the fact that there will always be a certain number of cow-coloured bulls and bull-coloured cows

Nevertheless, this does not have to mean that the extent of sexual dichromatism cannot reach a satisfying level. I am going to have a brief look at some cases of breeding-back populations with a satisfying level of sexual dichromatism, and go deeper into my usual case-study herd of Taurus cattle at the Lippeaue in Germany.

As a brief reminder: standard “aurochs bull colour” is to be considered black with the exception of a dorsal stripe and a muzzle ring, the area on the back can also have a slight brownish tint but it is unlikely that European aurochs bulls possessed a so-called colour saddle. The full colour spectrum of the forelocks is unknown. “Cow colour” probably includes all shades of reddish brown to darker until black with a colour saddle or completely “bull coloured”. But those black cows were, according to written sources, very rare. For details, have a look at my previous post.

Sexual dichromatism in existing breeding-back populations

For the case of the Tauros and Auerrind Project, the time is surely to early now to judge sexual dichromatism yet – the gene pool is not mixed enough yet in the case of the Tauros Project, and the Auerrind Project is just getting started. For Taurus cattle, I pick the Lippeaue as an example but serve that for later. So what is left is Heck cattle for now.
Heck cattle are very heterogeneous in regards to sexual dichromatism, as they are in regards to all traits. In some herds, one has to conclude that there is little to no dichromatism at all (many bull-coloured cows, many bulls with a colour saddle). In many herds, there is a tendency of the cows being coloured lighter than the bulls but still contain many variations. In some Heck herds and lineages, however, a quite satisfying level of sexual dichromatism has been achieved. One good example is the herd at Hellabrunn zoo, Munich, at least when I visited it in 2011.
The Hellabrunn Zoo Heck herd has a really good colour and dimorphism
The Neandertal lineage has a satisfying level of sexual dichromatism as well. Many cows show the reddish-brown colour I we see in cave paintings. There are black ones too, of course. Both the Hellabrunn herd and the Neandertal lineage have a very good colour, very intense and seemingly cleared of dilution alleles (there have been no diluted individuals from these lineages for quite some time). Another herd with a good amount of sexual dichromatism that I know of is the one at the Lainzer Tiergarten at Vienna. But in a different way: there are no cows that can be considered “of a reddish-brown colour”, but the type with the dark base colour and the light colour saddle/back is prevalent instead. There were almost no black cows in the herd and no bulls with saddles when I last had a look at the herd in 2014.  Another Heck herd that I visited that also had a quite good colour is the herd at Tierpark Haag, Lower Austria, but the number of the individuals was so small that the gene pool cannot really be judged properly with only a handful of individuals.
The dimorphism in the Lainzer Tiergarten herd is good as well
So where did those Heck herds get their good dichromatism from? Of the founding breeds of Heck cattle, Corsican cattle is best in regards to colour in general and sexual dichromatism. The breed left a strong mark in Heck cattle’s phenotype, which is also not surprising since Heinz Heck relied heavily on crossed individuals with a high portion of Corsican cattle. And the comparably careful selection in both the Munich zoo and the Wildgehege Neandertal probably kept the genes responsible for good dichromatism abundant in those lineages compared to other Heck herds (which often turned into a bit of a “phenotypical mess”).

The sexual dichromatism in the Lippeaue

Taurus cattle is, just like Heck cattle, a mosaic population that is heterogeneous in appearance and instable in inheritance yet. This is not surprising as there are still some first-generation crosses in the herd, the youngest individuals are of the 7th generation already. Taurus cattle is heterogeneous, but one could still determine whether there is a tendency to sexes having different colours or whether the inheritance of colours is independent from sex. In order to determine that tendency, I decided to count the individuals and note their colour, and distribution among the sexes. I made two categories for the sexes respectively: for bulls, “bull colour” as defined above and anything that is less eumelanisized than that (so either a prominent colour saddle or reddish brown colour overall) and for cows either “bull colour” (or black, if you will; except for the light markings of course) and anything lighter coloured than that (so either black with a saddle, or the various shades of reddish brown). Some individuals show diluted colours where the red pigment is reduced. However, the amount of sexual dichromatism is determined by black pigment, so I counted those diluted animals with reduced red pigment but not the half-Chianina individuals (neither bulls nor cows) which have a semi-dominant dilution that reduces black pigment, what makes them not comparable. I counted the individuals in their summer coat, as the winter coat is often darker than the summer coat and a saddle might disappear that is otherwise present.
I used a photo archive I was provided by Matthias Scharf that showed all individuals present in the herd in the year 2015 on several clear photos. I counted only individuals that already had their adult colour, so no calves. Usually it would be problematic that only the breeding bulls are kept till full age, but luckily they kept a lot of young bulls with their adult colour until fall 2015 when they were either sold or slaughtered.
These are the results:

Total number: 71

Bulls total : 25
Bulls black: 22 à 88%
Bulls with a saddle*: 3 à 0,12%

* There where no reddish-brown bulls, and from what I know usually such bulls do not appear in the Lippeaue, except for half-Chianina individuals.

Cows total: 46
Cows “cow coloured”: 39 à 85%
Cows black: 7 à 15%

We should expect those numbers to fluctuate slightly with each year, and are of course dependent on the "selection policy" in the Lippeaue. But this should be a number that can be worked with. In my opinion, this is a quite satisfying degree of sexual dichromatism. In the past, I have been wondering what would be the minimum point from which on the sexual dichromatism can be considered satisfying, and I concluded that no bulls with saddles and only 5-10% black cows would be satisfying to me. The amount of dichromatism in the Lippeaue comes comparably close. The question is if phenotypic selection could increase it any further in this case. I think it would be difficult. But to me, the level of dichromatism in the Lippeaue is satisfying. It would be interesting to do the same evaluation for other herds, such as Heck herds with good dimorphism (f.e. Neandertal or Hellabrunn) and such with very low dimorphism. Perhaps this level of sexual dichromatism would also be found in a lot of other herds of Taurus and Heck cattle. It will be very interesting to compare it with future herds of the Tauros Project and Auerrind project that work with different breeds.

Where did the Lippeaue population get its good dichromatism from? Sayaguesa has almost no sexual dichromatism, so probably not that breed. Most likely it is thanks to the Heck cattle from the Neandertal lineage that were the base of the herd in the 1990s. It is also plausible that Chianina inherits some degree of sexual dichromatism masked beneath their colour dilutions, as Sayaguesa x Chianina cows tend to be of a much lighter colour than bulls of the same combination.
  

Tuesday, 8 August 2017

Some interesting bulls from Oostvaardersplassen

I have many articles in preparation at the moment, but today I have a short post for you - browsing around on youtube I discovered a recent video that shows some bulls from Oostvaardersplassen. In the past, I made a number of posts on how the OVP population is getting slowly more aurochs-like in many respects; body shape and skeleton as well as the horn shape seems to adjust in a way that moves the population to a more aurochs-like appearance. In the posts linked below I show many examples for that, and also give explanations why the wild-type traits seems to have a selective advantage for the very heterogeneous start population, and also supported it with a lot of photos. 

- Aurochs-like features at Oostvaardersplassen
- New aurochs head reconstruction and new photo from Oostvaardersplassen 
- Heck cattle at Oostvaardersplassen - A special population 
- Dedomestication Series 

Unfortunately, many of the linked photos are not displayed anymore because the html seem to have changed or because of an error by Blogger. That happens all the time and I cannot fix it. I apologize. 

After about 35 years of natural selection, the morphology of the bulls in particular noticeably changed. The steppe cattle-like bulls you see on old photos from 1983 (see Frisch, 2010) vanished. On this video, you see a bull (0:37) with a morphology that matches perfectly that of many very aurochs-like Lidia bulls or accurate aurochs reconstructions. This individual still has the diluted colour that is the vestige of steppe cattle descendants, but there are many examples without colour dilutions. In a number of individuals, you see horns with an inwards-curve starting to resemble that of the aurochs you find nowhere else in uncrossed Heck cattle (see the linked posts above). But those individuals are, surprisingly, cows exclusively. 
Today, I found this video: 
Have a look at the bulls at 2:33. They are of a lean stature, have a flawless aurochs bull colour and the horns are big and curved - surely not curved very strongly, but especially if you pause at 2:34 you see that the so-called "primigenius spiral" is starting to develop. And the horns are comparably large as well. It is not impossible that such bulls were found in the reserve ten or even twenty years ago as well, but one would have to have look to find five of them next to each other. It is evident when you look at older photos from OVP easily available on the net. From 4:29 onwards you see some more footage (they might be the same bulls or even more individuals of this interesting morphology and appearance). Their build is definitely no comparison to what Heck cattle of zoos look like, and phenotypic plasticity is not the sole cause for these differences as many of the bulls at OVP also tended to look very domestic for a long time. 
This video and many recent photos show in my opinion that the Heck cattle population at Oostvaardersplassen is definitely evolving on a genetic basis, and in a direction that approaches the aurochs in many respects, which is probably not a coincidence. That makes it a very valuable population that should be protected in any case, and not be removed for whatever blind reasons (not just because of horn shapes. Examining if the decades of natural selection also led to metabolic and behavioural changes could be very insightful). 
Unfortunately, it is not legally possible to take a bull from the reserve and use it for breeding because of veterinary reasons. However, perhaps it is possible to get semen from one of these interesting aurochs-like bulls at the start of becoming dedomesticated. 

It is also apparent that the bulls are not very large. I would not be surprised if Heck cattle actually become smaller at OVP due to limited size and food availability (island effect). It would be interesting to measure some of these individuals, many bulls might actually be below the 140cm mark already (personal guess). It is also suspected that Chillingham cattle, living semi-feral in the Chillingham park for centuries now, also got smaller with time (for my post on Chillingham cattle, go here). 

Sunday, 6 August 2017

Colour saddles in bulls: good, bad or neutral?

The life appearance of living European aurochs is pretty well resolved. We have numerous well-preserved bone material, related species and descendants to compare with, and contemporaneous references in art and literature that provide us a clue on what the European aurochs looked like. However, it is not as precise as if someone would have taken coloured photographs or made taxidermies of a sufficient number of individuals back the time when they were still around and well, and therefore not all aspects of its external appearance are known with certainty, or the degree of regional and individual variation of traits that are not indicated by the bones. I made a post about traits where we have no certain clues for, such as the colour of the forelocks in bulls and if there was variation, or which colour shade was prevalent in cows.

Two further questions rise up in “breeding-back” concerning the colour of the bulls. Where there European aurochs bulls that showed a so-called colour saddle? And if not, should we still permit it in “breeding-back” bulls, especially breeding bulls?
At first I want to explain what a colour saddle is. In wild-type coloured cattle (phenotypically E+), both sexes are born with a chestnut-brown colour and eumelanisation (eumelanin is the black pigment, pheomelanin the red pigment) with black pigment starts from the head, neck, feat, pelvis and tail tip. The degree of eumelanisation is dependent on testosterone level (and, I hypothesize, perhaps also other signal molecules). In wildtype coloured cattle displaying sexual dichromatism, the melanisation of cows stops earlier than in bulls, leaving them lighter coloured. The “standard” aurochs bull colour that is suggested by the evidence involves full eumelanisation of the coat of the bulls with the exception of the muzzle ring and dorsal stripe (of course in domestic cattle, where selective breeding greatly altered the phenotypic traits and sexual dimorphism, you find a lot of  “bull-coloured cows” and “cow-coloured bulls”). In cases where the melanisation does not run until this maximum point but stops earlier, a light area on the dorsal and – depending on degree – also pelvic area remains. This is called a colour saddle. You find that in many wildtype coloured cows and bulls. For cows, it is universally desired. For bulls, there are diverging opinions. The photos down below show a fully melanised wildtype coloured bull (Churro, a Sayaguesa bull, photo by Matthias Scharf) and a wildtype coloured bull with a saddle (its son Linnet, a Taurus bull, photo taken by myself).

Margret Bunzel-Drüke from the ABU also pointed me to the possibility that a saddle in bulls might just be a very broad dorsal stripe, but I have to say I am not convinced of that. Colour saddles are usually not that sharp-edged, and usually show some sort of colour gradient. Dorsal stripes, on the other hand, are always sharp-edged and the colour is more or less homogeneous. And more importantly, even in the colour saddle itself you can usually discern the dorsal stripe, unless the colour of the saddle is very light.
Now I am going to have a look at the questions above.

Where colour saddles present in wild European aurochs bulls? When we discussed about bulls with colour saddles this year, Margret Bunzel-Drüke told me that the colour variant we want in “breeding-back” is called “castania” by Spanish breeders (and considered wildtype by us), and therefore cattle displaying this variant should simply display the colour of the aurochs. This is also the same case in horses, dogs, cats and budgerigars – when the genes are the same, they display the colour of their wildtype. However, there is a difference in the case of cattle. Not only the colour genes themselves determine what the final colour will be, but as outlined above, it is also dependent on the level of at least one signal molecule – testosterone – and therefore linked to sexual dimorphism. As an example, I think it is pretty plausible that Sayaguesa and Cachena have the same colour alleles (wildtype+ on each loci as I see no divergent colours). In both breeds, the sexual dichromatism is very reduced, Cachena being on the less eumelanised end of the spectrum, and Sayaguesa obviously on the strongly eumelanized end of the spectrum.
As a consequence, the question is not just which colour alleles were present in the aurochs but also how strongly marked the sexual dichromatism was in the case of the aurochs. For that, we have to look at the historical evidence we have.

Cis van Vuure, who intensively studied tons of contemporaneous literature and artworks featuring aurochs, is convinced that European aurochs bulls at least did not have a colour saddle. The famous cave paintings (Lauscaux, Chauvet et cetera) give us a clue about the colour of living aurochs at that region and time (Pleistocene, Southern Europe). They show aurochs cows of really all colour shades we find in living wildtype coloured cows, also a “bull coloured” one, but the bulls are shown always black. There are also some line drawings of bulls, but a saddle is not indicated (yet there are some small spots on the head and neck area – I assume these are meant to indicate curly hair but there are also other possibilities). Anton Schneeberger, who delivered the most precise verbal description of living aurochs in Gesner 1602, described the bulls being completely black except for the light dorsal stripe, and cows being of a chestnut colour, and only very rarely turning black as well. In the Holy Roman Empire of the Middle Ages, hunters categorized the aurochs as part of the “Schwarzwild”. In German, hunters like to categorize game after their colours (roughly): “Schwarzwild” means “black game”, and nowadays only includes wild boar as the aurochs died out 400 years ago. “Rotwild”, meaning “red game”, is a hunter’s term for Red deer. So it seems that a black or very dark colour must have been prevalent in the perception of an aurochs for the contemporaneous people (this, of course, neglects lightly-coloured cows; bulls probably got more intention as they made way more impressive trophies). The Carta Marina by Olaus Magnus shows a rider being attacked by a dark brown aurochs, from the year 1539. However, the drawing is very stylized. Sigismund von Herberstein was in possession of a stuffed aurochs coat, and it showed a black colour with a faint dorsal stripe. Plinius quotes an earlier source that describes the aurochs as the “black forest ox”. Romanian folk tales also speak of the “black aurochs”. Russian and Polish stories and expressions, however, speak of red or reddish brown aurochs. But it is unclear in these cases which sex is to be meant. The social system of cattle includes cow herds with calves and young bulls, where the prevalent colour would be reddish-brown, and solitary bulls. If one witnesses a cow-calf herd, he would most likely describe “the aurochs” as reddish brown. If one witnesses a lone bull, it would depend on the colour of the individual bull. For the references of these historical accounts, see van Vuure 2005.
So what to make of this? It is not only that there is no evidence for colour saddles in bulls. It is interesting that Schneeberger notes the presence of such a minor detail as the narrow dorsal stripe, but not a colour saddle. If some of the bulls he witnessed had one he might have mentioned it as well, especially since he mentions the very rare black cows. One could criticize that he does not mention the muzzle ring as well yet it is considered a universal trait of the aurochs, but old bulls often have a very reduced muzzle ring (see Churro) and perhaps not all aurochs had this trait; Bantengs and Gaurs are variable in this respect as well.
Even more interesting is that at least two North African prehistoric stone carvings that I am aware of show aurochs bulls being hunted (I am not confusing them with the tomb paintings that show domestic cattle) that definitely have an extensive colour saddle (one of them also shows the muzzle ring). These are line drawings and the saddle is indicated. Is it a coincidence that for Europe, although there are many artistic and written references to the colour of aurochs bulls, there is no evidence for a colour saddle and in North Africa at least in two cases? Of course this is possible, and we have no direct way to prove that, but I think not. I consider it more likely to say that European aurochs bulls probably lacked a colour saddle while the African subspecies either showed it on occasion or universally. Would not a shiny red colour saddle extending on the whole back of the bull be a rather prominent trait that is worth mentioning? And if there were indeed European aurochs bulls with such a trait, why do all the sources always support black bulls only (in the cases where bulls are definitely referred to)? Apart from that, the contrast between the reddish-brown saddle and the black surrounding colour was that striking that eyewitnesses would have barely simply described such an individual as being of a “brown”, “black” or whatever colour but probably refer to the saddle in particular (would you when taking a look at a bull like Linnet on the photo above?).
So it seems more likely that European aurochs bulls never, or in very rare cases (twin births, after injuries of the gonads) ever had a saddle and that they were universally black, while there were black cows on occasion.

Should we permit bulls with a saddle for breeding then? Currently, all “breeding-back” projects permit a colour saddle in bulls more or less. I have always been against the use of bulls with a colour saddle as breeding bulls because of the risk of reducing the sexual dimorphism of the herd. In a previous post, I outlined that always picking black bulls and red cows for breeding probably will not result in the strongly marked sexual dimorphism of the European aurochs because one would have to consciously pick those individuals where sexual dimorphism is actually laid down in the genome. A black bull might just as well inherit black or very dark cows. Without knowing the exact genetic background of sexual dichromatism in cattle and without screening each individual for it, we can never know whether a black bull or a red cow inherit the sexual dichromatism we want. In the case of a bull with a saddle, however, we can be sure that the sexual dichromatism is reduced and since the sexual dichromatism is already less than in the aurochs, using such an individual for breeding might reduce it even further (the same goes for black cows of course, but black cows are confirmed to have existed in Europe while bulls with saddle probably did not). There is one possible example for that in the Lippeaue.
In the Hellinghauser Mersch herd, the Sayaguesa x (Heck x Chianina) bull 42 623 is currently used as a breeding bull. This bull has a colour saddle but does not display any colour dilutions. Some of its male offspring show a colour saddle as well, and I got the impression that they do that more often than the offspring of the black bull Lamarck. One of the young bulls I spotted in the field has a rather extensive saddle, or actually it is a brown back that gives it the colour of a cow. Using this individual for breeding might probably result in a number of wholly reddish-brown bulls appearing in the next generation. I would definitely not recommend using a bull with saddle or brown back for breeding if it itself descents from another bull that had a saddle as well. It might make this trait even more common in the population and lower the variation span towards more brownish bulls.

Nevertheless, the degree of sexual dichromatism is just one of many traits that “breeding-back” focuses on. Of the five breeding bulls at the Lippeaue, two have a colour saddle, but both of them are valuable for breeding. Linnet has a good horn curvature that shows the desired inwards-curve and 42 623 is a 170cm giant with a prominent shoulder hump. So the colour saddle can be permitted as both bulls contribute precious traits to the herds. It is like the fact that too small horns or such of insufficient curvature are not desired, but a bull might contribute other desired traits that are otherwise rare in a population, so that this deficit can be connived and corrected in later generations. There are also varying degrees of a colour saddle. For example, a saddle can either be very small or very faint (such as in the Taurus bull Luxus, which was used as a breeding bull for a short time about ten years ago). Also, subadult bulls might show a saddle but outgrow it as they age, such as Manolo Uno, the most famous Tauros bull to date. However, I would not use a saddled bull that itself descends from such a bull, as there is the danger of perpetuating this trait.

So a bull with a colour saddle does not always have to be selected out, but I recommend to avoid this trait for breeding bulls unless it has a number of otherwise valuable traits.

Literature 

Cis van Vuure: Retracing the aurochs: history, morphology and ecology of an extinct wild ox. Pensoft, 2005.