Friday 13 July 2018

The Distaff, the Matriline, Epigenetics, and Mitochondria

In the Old Days when most people were farmers and before the industrial revolution, and even before the invention of the spinning wheel, a family's fabric all had to be made from scratch at home. The spinning equipment of the time was the drop spindle and distaff, and it was so time-consuming to make thread that most women and girls could spin and would carry their spinning paraphernalia about while watching their livestock or going up the lane to see their aunt, and spin any time their hands were not otherwise occupied.

The distaff is the thing that looks like a candyfloss

Whatever men and boys of yore occupied their hands with during idle moments doesn't seem to have passed into stockmanship parlance, or perhaps wasn't spoken of in polite conversation. Anyway, in modern times many people, men as well as women, do spinning as a hobby, and distaffs are uncommon in modern techniques, but the distaff remains as a slightly obscure piece of vocabulary to describe the mother's side of a pedigree.

Girly Girl
SirePaternal GrandsireGreat Grandsire -- patriline
Great Granddam
Paternal GranddamGreat Grandsire
Great Granddam
DamMaternal GrandsireDistaff Great Grandsire
Distaff Great Granddam
Maternal GranddamDistaff Great Grandsire
Distaff Great Granddam -- matriline
Example of a pedigree with the distaff indicated in red text

Often in stockmanship, when seeking advice from experienced persons, the wise old man or woman will say something way out there that sounds on face value silly and that seems to fly in the face of scientific understanding, and the younger more scientific enquirer thanks them for their advice and ignores it, until they later discover there does seem to be some truth in it and there is some scientific evidence to support it. Examples of these would include the belief that some animals tend to prefer to give birth under a full moon and that offspring that are very mildly linebred are fitter than both inbred animals and total outcrosses. Another aphorism you may hear from experienced breeders goes something like this: Faults and problems arising from the distaff are often harder to correct than issues coming from the sire's line.

According to the classic understanding of genetics, what the wise old stockman says would appear to be nonsense. All mammals and birds have diploid cells, that is, they have two copies of each chromosome, one from the sire, and one from the dam. Both the sire and the dam contribute equally to the genetic makeup of the offspring, and genes from either have equal chance of being passed on or lost. However, more modern developments in genetic understanding reveal a few things that might help to explain why the wise old stockman thinks this.

The first is that a tiny fraction of DNA is not found in the nucleus and thus isn't inherited in the conventional way. Mitochondria are structures that exist within the cytoplasm of the cells of nearly all plants and animals and are believed to have evolved from primitive bacteria-like cells. Although all domestic animals have mitochondria specific to their species, the DNA of mitochondria is very different to nuclear DNA, and the mitochondrion is always passed from a mother to her offspring, as she is the one who provides the ovum, and thus is the originator of the cytoplasm and mitochondria in every cell in the offspring. Male animals of course have mitochondria in their cells, but they cannot pass them on to the next generation through the sperm they produce.

It's known that mitochondrial diseases do occur, but it's not known if mitochondria contribute to other problems. Current thought is that mitochondria don't have a great deal of effect outside of a few specific conditions. However, if you are breeding to conserve a domestic breed or wild species, it can be difficult or impossible to recover mitochondrial diversity once it's been lost, so many breeders will pay attention to the matriline (the mother's mother's mother's mother...) in pedigrees in order to avoid losing matrilines. Mitochondria do change over time by mutation and the rate at which they change and how we can use that to understand evolution and other phenomena is something studied and debated by scientists, but this mutation rate is something that's unlikely to have much effect over human-timescale pedigrees.

Two matrilines: Bess and daughter Patience (left); Poppy and daughter Fleur (right)

Matrilines in domestic animals tend to be resilient as female offspring are usually retained for breeding programmes. However, sometimes matrilines can be lost because a female chances never to produce a female offspring, or occasionally because a female herself is so spectacular and useful to a programme that her male offspring are used widely on all the other females in the breeder's programme, to the extent that her female offspring end up not being useful to that programme on account of them being related to the best males and ultimately everyone else.

The second recently discovered way in which a dam may have undue influence on traits in her offspring is epigenetics. Every cell in a complicated organism such as a human, poodle, turkey, or alpaca, has the same DNA in the nucleus, and epigenetics controls how that DNA is used to construct a functioning organism and not a homogeneous pile of liver, brain, pancreas, blood, etc. cells by means of special proteins, structures, and chemical modifications to the DNA itself. Epigenetics is hugely important in not only the development, growth, and sustenance of life, but epigenetic errors are also implicated in many things that can go wrong, such as cancer. Although epigenetics is currently a hot research topic, there is still a great deal we don't understand about these mechanisms.

Usually, epigenetics works as intended, which is why chickens lay chicken eggs that hatch into chicks and grow into normal-looking pullets and cockerels, but it's recently been discovered that sometimes the environment can interfere with this process. The picture of the young duck above was taken today. If you look closely at the duck's wings, they are not right. The carpal joints have in fact developed incorrectly and the tips of the wings are twisted into an abnormal position. The wings can't function and can't be closed normally to fit flush with the body. This deformity has been seen in both wild and domestic waterfowl since time immemorial, and it used to be assumed that it was a genetic disease, but we now know it's actually caused by an inappropriate diet. What happened was, the shop we bought duck crumbs from shut down, and the other shop couldn't get the duck crumbs in on time, so the ducklings had to be fed non-medicated chick crumbs when they hatched. The ducklings looked normal, but when their adult plumage developed, the duck in the picture developed this fault. Fortunately, domestic ducks don't fly, and the duck's welfare will not be compromised by this problem, but wild waterfowl might be put at particular risk of this problem from people throwing bread and other unsuitable food in watercourses. How, exactly, the inappropriate diet causes the wings to form improperly is not understood, but it may well be an epigenetic effect is involved.

So how does this relate to our female animals and the distaff? Of course, the mother mammal is the entire environment of her offspring throughout all the most crucial points of its development into a new individual! Anything that affects her also has the potential to affect the young she is carrying. It's also the case in most mammals that female foetuses develop ovaries and ova while in the uterus; indeed all the eggs a female will ever have she is born with. This leads to something epigeneticists call the grandmother effect, whereby an event that affects a female's pregnancy can affect both her daughter and her grand-daughter.

Eggs is eggs

How do I identify if an issue might not be genetic, and what do I do to fix it?

Most genetic issues are either autosomal dominant or autosomal recessive. With an autosomal dominant condition, approximately half of all an animal's offspring will have the condition. With a recessive condition, one quarter of the offspring will have the condition only if both parents are carriers (who don't express the condition) whereas one affected parent will produce half affected if bred to a carrier, 100% if bred to another affected, but none affected if bred to an animal without the gene. There are also some conditions that seem to be genetically influenced, but we don't understand how the genetics work and what other factors are involved, and in these instances affected individuals can turn up occasionally every few generations. These numbers are approximates and tend to vary in real life, so it can be hard to observe patterns, particularly in animals who only have one offspring at a time.

Therefore, what should serve as alarm signals that something is going wrong in the environment, is unrelated animals living in the same conditions having or producing the same problems, a female whose young all or nearly all have the same problem regardless of using different sires on her, and any problem that doesn't go away in the first generation when a relative not expressing the condition is bred to a mate who is established through careful pedigree research to be unrelated to her through around ten generations.

When deciding what to do, the urgency of the situation depends on the effect the problem is having on the animals. Problems that can occur cover a whole spectrum, from harmless cosmetic faults that don't impact the animal's welfare and ability to express its normal behaviour or prevent it living happily as a pet, or being kept on until big enough to be humanely slaughtered and eaten, depending on the species, to painful, fatal, and heartbreaking diseases on the other end. In the middle are problems that might be a nuisance to the owner but are manageable, and problems that can quickly be fixed by a vet with a local anaesthetic. If an issue in your bloodline is seriously compromising the welfare of the animals, whether it is genetic or not, you should cease your programme until you have a good idea how you can remedy it, as the animals themselves need to come first.

The first thing to investigate is what the animals are eating. If they are grazing, is there anything growing in the paddock they should not have? Is their food/concentrate in date, not mouldy or contaminated, and is it specifically suitable for pregnant animals of this species in terms of its nutrient profile?

Have the animals been given any medicine during the pregnancy? It's best to avoid using medicines at all on pregnant animals unless they are absolutely necessary, even ones claimed to be safe in pregnancy. The tests to ascertain safety tend to be conducted in controlled conditions and they might behave differently in real-life situations in combination with other factors.

Are there any environmental exposures? Don't allow people to smoke near pregnant animals. Don't use smelly cleaning products, joss sticks, 'odourifiers' etc. in the house where domestic pets live. Don't burn rubbish upwind of your livestock or spray pesticides or herbicides on or near areas they use. Keep animals out of recently painted/redecorated rooms and consider not painting and redecorating close to when you plan to have pregnant animals.

Remember that you may have fallen afoul of the grandmother effect. People might often struggle for years with an animal who has trouble getting pregnant to succeed with a much-welcomed daughter, only to find the daughter has the same problems when they try to breed her. Rather than throwing their hands in the air and giving up, they might find that another generation was all it needed. If a problem of this sort is really difficult to work with or won't go away, it can be an easier solution to work through a male offspring, i.e. to break the distaff. Remember, though, that when you break the distaff, you lose the matriline. You can return the pedigree to the distaff by keeping a daughter of the son, but the mothers' mother's... line will have been broken. Unless you happen to mate the son to a female of the same matriline. This isn't always as difficult as it might sound, and largely unrelated animals can turn out to be of the same matriline if you look deep enough into the pedigree. Adhara and Indi (and therefore Pandora and Saffi) are both from the same matriline, but you have to go back 30 generations to 1905 before you find the mother's mother's mother's... whom they share. A century and 30 generations means little to a germ-line mitochondrion.

And if you are fortunate enough to have a female animal who is fantastic in nearly every way and a dream come true to your programme, you might pass her traits on more successfully if you keep her daughters for breeding and not just her sons.

Also, always pay attention to what old people tell you, even if it doesn't seem to make sense at the time. :-)


  1. This is a wonderful combination of old wisdom and science. Thank you.