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Thursday, 29 January 2015

Scoring cattle breeds for aurochs-likeness


Ever since I came to know of all those aurochs-like cattle, I tried to figure out a way how to objectively ascertain which breeds are closer to the aurochs than others. It turned out to be pretty difficult, or nearly impossible.

The reference for the comparison is the Near Eastern and European Aurochs that was the ancestor of taurine cattle and also the goal of the “breeding-back” projects.
The breeds to be compared are exclusively those currently used in these projects because otherwise I could include a pretty large range of breeds. But mind that those breeds included in “breeding-back” are by far not necessarily more aurochs-like than certain other primitive breeds.
I did not even try to include Heck and Taurus cattle. The reason why is explained down below.

The first question is the level on which the breeds should be compared. Basically there are four such levels: morphology/visible traits, behaviour, genetic level, ecologic level. The social and ecological behaviour of all cattle seems to be very similar. As to their behaviour to humans, although breeds are known to differ more or less in temperament, it is a fact that the behaviour of cattle is very plastic and depends a lot on on environment and socialization. How easy cattle are to handle is actually a trivial anthropocentric question that is barely of biological relevance, and there are no aurochs to compare with anyway.
How to define and measure “ecologically aurochs-like”, including traits such as hardiness, heat/cold tolerance and food needs? There are no living aurochs that can be used as a model, and there are  regional differences in ecological requirements as well. The same as with genetics: there is simply not enough data (yet) to include genetics. It seems that the appearance and morphology of cattle is the only really quantifiable aspect for such a list. Furthermore, it is questionable if such a split would be useful at all, because most, if not all, of the optically aurochs-like breeds are very hardy and robust and would be on the other list as well.

So I decided to focus on external appearance and morphological traits only, as the only quantifiable aspect that is also comparable with tangible evidence from wild aurochs. But this is not easy either. At first I had to figure out how to set up the character criteria. This is arbitrary already because I had to decide what is “a trait” at all. For example, you could say “wild type colour” is one trait, or you could include all the (partly speculative) individual loci that have to be right for a correct aurochs colour to evolve. It becomes more difficult when it comes to quantitative traits, because these are often highly polygenetic features. That’s the next problem: this schematized list assumes that all the characters are equal. But they obviously are not, because some traits are way more polygenic than others. Furthermore, traits may be connected to each other due to pleiotropy and developmental cascades. The question is if we can ascertain where this is the case (which I think is difficult) and if we should count them as one. Another question is which traits are regulated by “original aurochs alleles”, such as colour traits, and which mimic original traits as an artefact of selection; f.e. if cattle are large because they were selected for increased size, is this truly aurochs-like as well? Is this relevant at all? We surely can hardly answer this question in a useful way. I don’t know how to usefully consider the influence of the environment because it is rarely apparent if a difference between two breeds is influenced by environment or not.
Another problem is that many traits are more or less continuous, but to score the breeds I need to categorize them somehow. This forces me to make yet more subjective decisions: how precise should I do this? I decided to make a scale from 1 to 3, with 1 being equal or nearly equal to the wild-type trait and 3 being not or hardly similar at all, and 2 is the intermediate trait. So the cattle with the lowest number is the most aurochs like, and that with the highest number the least aurochs like of those chosen for this comparison. At first I started with 1-5, but the more precise the more complicated and subjective it becomes. So 1-3 is probably easier and more effective.

It gets even more problematic and subjective when considering that the breeds are not uniform and stable. Most breeds differ from herd to herd regarding their resemblance to the aurochs. Should we look at the most aurochs-like only, or simply exclude the ugliest, or try to find an average? The aurochs-likeness is not distributed among closed lines that can be differentiated, but usually distributed among the whole breed (also more concentrated in some herds than others) what makes it, again, more or less imprecise and arbitrary. I chose to I tried to find a kind of average but not to include those very ugly individuals that obviously were crossed with very domesticated breeds or strongly selected.  If a certain trait in a breed always has a mediocre resemblance to the aurochs, it gets a 2. If such a trait resembles the aurochs authentically in some individuals of the breed but in others not at all, it gets a 2. If some have mediocre resemblance but others a very good one it gets 1,5 and so on. And there you have the reason why I don’t include Heck and Taurus cattle here. It would be pointless because they are way too heterogeneous. In both of them you find a large variety of coat colours and horn shapes and horn sizes, proportions, size of appendages and so on. While it is clear that un-crossed Heck cattle lack some aurochs traits in general (like a size above 150 cm, or an elongated snout), Taurus cattle would have nearly all the desired traits but also a lot of undesired ones, so they would get a 2 for most of the characters. A more uniform but generally mediocre breed would give the same result, what would not appreciate the fact that Taurus cattle have a lot of aurochs-like traits but that these are never present all at the same time within one individual, and that Taurus cattle can differ significantly from individual to individual. I also wondered if it would be useful to integrate Lidia then, because they are very heterogeneous as well. But I decided to do so because they are not as heterogeneous as Taurus and Heck cattle.

So you see, the scheme that I worked out is quite subjective and simplified, although I did tried to do my best. I would say this scheme is in the end still an intuitive approach, but a systematic one.
Perhaps it is not possible to compare the breeds in a really objective and not too simplified way. I am open for suggestions!

My list of characters is:

a) Body size
b) Size dimorphism
c) Proportions
d) Body conformation
e) Tall processi spinosi at the shoulder area („hump“)
f) Skull shape
g) Wild-type colour *
h) Sexual dichromatism
i) Horn size (thickness as much as length)
j) Horn shape
k) Horn orientation
l) Appendages (Udder, dewlap, fleshy zebuine hump)
m) Fur not overly long

 * no dilutions, E+/E+, no white spots, no other deviant colours

A 1 for body size means 165+ cm at the withers for bulls, a 1,5 means 150-165 cm, a 2 means 150-140, and 3 means 140- cm. Size dimorphism is intuitive because there is no reliable and universally valid data for the respective breeds anyway. All breeds therefore received a 2, because none of them has a dimorphism that equals the hypothesized ratio of the aurochs, except Watussi which received a 2 because its dimorphism seems reduced even further. Bodily proportions refer to the ratio between leg length and trunk length. Body conformation refers to muscling, fat, and also the bulk of the trunk. The score for the processi spinosi is intuitive. Concerning horn size, a breed also gets a 2 if the length is right but the horns are too thin or vice versa (f.e. most, but not all, Highlands).  



a
b
c
d
e
f
g
h
i
j
k
l
m

Boskarin
1
2
1
1
1
2
2
2
2
2
2
1
1
20
Chianina
1
2
1,5
1
2
2
2
?
3
2,5
2
1
1
21
Highland
3
2
3
3
2
3
3
?
1,5
1,5
1
2
3
28
Holstein
1,5
2
2
3
2
1
3
3
3
2
1
3
1
27,5
Hungarian Grey
2
2
1,5
1
2,5
3
2
2,5
1
3
3
1
1
25,5
Lidia
3
2
1,5
1
1
2
2
2
2
1,5
1
1,5
1
21,5
Limia
2
2
1
1,5
2
2
1
1
2
2
1
2
1
20,5
Maremmana
1,5
2
2
2
2
2
2
2
1
3
3
2,5
1
26
Maronesa
3
2
1,5
1,5
1,5
3
1
1
1,5
1,5
1,5
1,5
1
20
Pajuna
3
2
1,5
1
1,5
1
1
2
2,5
2,5
1,5
2,5
1
23
Podolica
1
2
1
1
1
2
2
2
2
2
2
2
1
21
Sayaguesa
1,5
2
1
1,5
1,5
1
1
2,5
2
1,5
1
1,5
1
19,5
Tudanca
2
2
1,5
1,5
1,5
2,5
1
2
1,5
2,5
1
2,5
1
21
Watussi
2
2,5
1
3
3
3
1
2,5
2
2,5
2
3
1
28,5

There are Lidia herds which are almost perfectly wild-type coloured (except sexual dichromatism). But the breed as a whole has a lot of animals with the “black” mutation and, white spots are not uncommon, and certain other deviant colours can be found as well, f.e. roan and brindle. Watussi cattle have a lot of colours, but most of those in Europe have this whine red colour, which seemingly has E+ as a base. Highland and Chianina get a question mark for sexual dichromatism, because this trait is masked beneath diluting alleles, so it cannot be ascertained if it is present or not. Holsteiners sometimes have the E+ allele, which reveals that the sexual dichromatism is very reduced or absent in this breed. The sexual dimorphism is very reduced in Sayaguesa as well, but there are still plenty of cows that have brown shadings in their coat, so they get a 2,5. The colour in Watussi is very similar in tone in both sexes, but there are cases where the bulls are definitely slightly darker than the cows, so they get a 2,5.

Adding all numbers, this is the result:

Sayaguesa
Boskarin/Maronesa
Limia
Podolica/Chianina/Tudanca
Lidia
Pajuna
Hungarian Grey
Maremmana
Holstein
Highland
Watussi

This fits my expectations very well (perhaps this is not surprising, because I did this comparison). As I outlined, this was just an attempt to figure out how to better compare the level of resemblance to the aurochs between different cattle breeds.

Such a comparison not only tries to be informational but could also be helpful for “breeding-back”. But beware that this rating scores all traits defined here as equal. This is OK in such a schematised table, but should be taken with caution for breeding. Some traits are definitely more difficult to breed for than others. Coat colour, for example, is much easier to achieve than other features because the colours are controlled only by few loci. Body size is very difficult to breed for, as its response to selection is weak. So a breed with very large body size is worth a lot. Another aspect is the frequency of such traits. There are only a few Iberian breeds with an authentic aurochs-like horn curvature, and even in those breeds these kind of horns are not always present (f.e. Maronesa, Lidia, Sayaguesa). So the right horns are very desirable as well. I don’t know about the heritability of skull shape, but there are not many breeds with an aurochs-like elongated skull (at least not many primitive breeds).
All in all I think that good-looking Sayaguesa are the most useful cattle currently used in “breeding-back”. They have the large size, elongated skull, the right proportions, well-shaped humps and some have an authentic curvature, so you get many traits that are difficult to acquire at once. Furthermore, they don’t have the annoying recessive dilution factors that Steppe-type cattle, Chianina or Heck cattle have. Their sexual dichromatism is nearly absent. I have no definitive clue on the exact genetic background of that trait in cattle, or how easy it is to breed for it, but most Sayaguesa crosses have the desired dichromatism when crossed with the right cattle. Luckily, Sayaguesa is the common breed of all three current crossbreeding projects (Taurus, Tauros and Uruz), and its influence in usual Heck cattle is getting consistently larger thanks to mixing with Taurus cattle.

Surely there is much room for subjectivity and different opinions in this scheme and my conclusion.

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