A brief history of sheep: Survival of the wooliest

The development of the modern sheep from feral animals is one of mankind's major achievements, writes Gordon Levet.

Sheep marooned on Arapawa Is in the Marlborough Sounds a century or more ago have reverted to a feral state.

Sheep marooned on Arapawa Is in the Marlborough Sounds a century or more ago have reverted to a feral state.

ANALYSIS: In most aspects of human endeavour, an understanding of history will give a better understanding of current events and an insight into future possibilities.  This is certainly the case in sheep breeding. 

We need to understand three aspects in the history of sheep breeding, as they all have an impact on our breeding programmes.

First, sheep in their natural state before man's intervention.  Secondly, how man reprogrammed the genetic balances to suit his own requirements, and thirdly how performance recording and computer technology has affected genetic factors over the past five decades.

Gordon Levet.
Supplied

Gordon Levet.

Now first let us examine how sheep evolved and  adapted to their environment over thousands of generations, and how the genes of these feral sheep still impact on our breeding programmes.

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The sole purpose of sheep in nature – like all other living species – is to survive and ensure the survival of their species.  They evolved, via their genetic development, to withstand extremes in weather conditions, including ice ages, and to overcome challenges from parasites and diseases with their immune systems.  They also had to develop a range of skills as a defence against many predators.

So what are these traits that ensured their survival?

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.   A coat of mainly two fibres.  Hair, the long dominant primary fibre, and wool, the shorter secondary fibre.  Hair protected the body and ensured a waterproof thatching. Wool provided insulation from heat and cold.  This principle is common in nature with many birds, especially water fowl, having feathers and down.  Husky dogs also have an undercoat which protects them from extreme cold.

. Coats were shed annually in spring, not only to ensure heat control but also to aid mobility.

Multi-coloured coats, mainly shades of grey, provided an effective camouflage in their habitat of the arid, mountainous regions of Southern Europe, Asia Minor and North Africa, ensuring a degree of protection from their predators.

Mobility and agility were essential for survival so they evolved to have goat-like bodies – light boned and sinewy, with a minimum of muscling.

Horns provided protection from smaller predators as well as ensuring the dominance of the strongest male.

All these survival genes are dominant and although temporarily suppressed by man's endeavours, they are ever ready to reassert their dominance at the first opportunity.  We need to understand that nature has its own selection and culling systems aimed at ensuring the survival of the species.  Those that are weak, lack constitution, or are physically unsound will be removed by predators, disease or parasites.  Only the strongest male will earn the right to sire the next generation.  On the female side, the ewes with the strongest constitutions coupled with longevity will contribute the largest number of daughters.

The second event in the history of sheep began when man started to domesticate animals and farm, about 13,000 years ago.  The characteristics of feral sheep did not meet man's needs so, the process of re-designing them started. 

This required a breeding programme that suppressed the survival genes and developed the desired genes.  Progress to breed such sheep would have been painfully slow as there were only feral sheep and there was no knowledge of genetics.  Over time, these early farmers learned to understand their animals and stockmanship skills were learned.

By the Middle Ages much had been learned and achieved.  Wool was spun, woven, dyed and turned into fabric and traded across Europe and sent East on the caravan silk roads.

In the 17th and 18th centuries, different breeds were developed to suit local needs in the counties of England.  Some of these breeds were named after their home counties, eg Suffolk, Dorset and Romney Marsh. 

The development of sheep from feral animals needs to be acknowledged as one of the major achievements in the history of agriculture.  This success was attributable to top stockmen who became stud masters through trial and error, careful observation, an understanding of structural soundness and what was meant by a strong constitution. 

They were in fact practicing geneticists.  Through fairs and shows, they would have shared knowledge and experiences and exchanged top sires.  But things were about to change.

The third era in the history of sheep development has occurred over the last 100 years.  The early part of the 1900s saw the development of agricultural universities, agricultural research institutions, veterinary faculties and the training of geneticists and other scientists.  The boom in prices in the New Zealand livestock industry after World War II resulted in an increase in farm consultants employed by the Ministry of Agriculture, and the Dairy and Wool Boards.  All of these changes coincided with the development of computer technology.

A combination of all these factors posed a challenge for the stud breeding industry and the conventional practice of only using eye appraisal as a basis of selection.  However, these conventional methods were dismissed as irrelevant and at times ridiculed by many academics. 

A new age of performance recording had dawned, hailed as the only criteria for selection.  Measuring productive traits and using the computer to transform raw data into breeding values (BV) became possible, and seen as the way to obtain genetic improvement. 

It was argued that to include selection for immeasurable traits like structural soundness, constitution etc, would only reduce progress in the productivity traits.  And of course this is correct. 

This new thinking was based on the theory that "if a perceived fault or any other trait did not adversely affect productivity it should be ignored and that if productivity was affected the animal would be culled".  Sounds a good theory and in the short term, works a treat. 

However, it has serious flaws.  This theory does not take into account two other breeding principles.  First, "if a trait is not selected for, it will be lost" or conversely "if a fault is not culled for, it will eventually become endemic in a flock". 

Secondly, the theory ignores the fact that "all animals possess powerful survival genes which seek to returns their species back to their origins".  Like gorse plants, once established, they are very difficult to eliminate.

Over the last 50 or so years, ram breeders have fallen into two groups following different breeding philosophies.

First, there are those who are conservative.  They still believe that such traits as structural soundness - including feet and jaws – constitution and wool quality are essential in breeding good productive sheep.  In addition, these breeders also consider computer generated figures and rankings are an essential part of the selection process.

The second group of breeders had what would be considered a more modern approach to breeding, having accepted the theories advanced by knowledgeable professionals.  These breeders make their selections based mainly – or solely – on computer figures and rankings for productive traits and perhaps FE tolerance. 

The progress they have made in these areas is impressive and credit for this is well deserved. 

However, some have paid a heavy price for these gains in the form of physical faults that have developed. 

In some ram breeding flocks shearers report that they are no longer required to call "black wool" as this fault has become so common.  Serious problems with feet have become endemic in some flocks and it is also reported that legs have been broken in the normal process of shearing through inadequate bone. 

Sadly, the clients of these ram breeders will be plagued with the same problems.  Many of these problems can be traced back to the powerful survival genes and to reverse these trends will require radical action and take many generations.

The genetic engine we are trying to breed into our sheep must be matched by a chassis and infrastructure that can support it.  This principle is understood in the motor industry, but is not always recognised by those engaged in animal breeding.

Gordon Levet is a life-long romney breeder renowned for developing a worm-resistant strain of sheep. He received the Royal Agricultural Award in 2008 and the Sheep Industry Innovation Award in the 2016 Sheep Industry Awards.

 - Stuff

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