Monday, 1 February 2016

Pigs: East meets West

I have never worked on or with pigs, other than trying to prepare tissue slices from a piece of fresh mammary tissue which was as tough as old boots. I do though recall the scheme in Hong Kong to cross the local Chinese breed with imported British breeds in order to eliminate the swayback condition and increase the rate of growth. I was, therefore, interested to see what lay behind the title of a paper in Proc. Roy. Soc, Artificial selection on introduced Asian haplotypes shaped the genetic architecture in European commercial pigs1, written by a group using genomics at Wageningen University in the the Netherlands, a famous centre for pig research.

I discovered from that paper that Chinese pigs had been imported into Europe about 1700 in order to cross them with the then existing European breeds. The introgressed genes of the Chinese pigs are still present because now as then, the improvements they introduced were desirable commercially. Artificial selection has ensured their survival because they are associated with more backfat.

A view of Macau with swayback pigs in front of the Sampan
George Chinnery (1774-1852)
The whole story of the domestication of the pig from the wild boar (Sus scrofa) is fascinating, linked as it is to the migration of human populations. To cut a long story short, pigs were domesticated independently about 10,000 years ago leading to two main genetic lines, one in Europe, the other in the Far East. In Europe, pigs were not kept in sties; they were fattened in woods on acorns and beechmast—the pannage system. As forests were felled and populations increased, the pig became a farm animal living in sties; a shift, in other words, from an extensive system to an intensive one. The change from pannage to intensive production occurred at different rates in different areas. An example given is that well into the 1600s, the best pigs were said to come from the best woods of oak and beech, notably the New Forest in southern England.

I read that the initial improvements to pigs by selective were made in the English midland counties of Leicestershire and Northamptonshire. As global trade increased, it was with these early breeds that the Chinese imports were crossed. There were, apparently, two separate introductions, each from a different Chinese breed, one being ancestral to the Large White and Berkshire; the other to the later Swedish Landrace, Duroc and Welsh. The historians have found reference as early as 1720 to the presence of small black pigs which appear to match the appearance of those described at the time by travellers in China and south-east Asia.

During the 18th Century, cross-breeding was in full swing, as this quote from Beilbys’s General History of Quadrupeds in 1800 illustrates:

By a mixture of the Chinese black Swine with others of the larger British breed, a kind has been produced which possesses many qualities superior to either of the original flocks. They are very prolific, are sooner made fat than the larger kind, upon less provisions, and cut up, when killed, to more useful and convenient portions.

I did find it interesting, in the light of later developments in Hong Kong, was that an increase in the rate of growth (and, therefore, age at which they could be slaughtered) was also ascribed by writers in the 19th Century as a character introduced by the Chinese pigs.

History, archaeology and genomics have all contributed to knowledge of how modern industrial pig production came about4. But the story is incomplete if the move in the opposite direction is not also considered. During the 1950s, In an effort to improve pig-farming in Hong Kong, the government’s Department of Agriculture and Fisheries acting in concert with the Kadoorie* brothers (Lawrence, Lord Kadoorie, 1899-9993, and Sir Horace Kadoorie, 1902-1995, founders of the Kadoorie Agricultural Aid Association) imported breeds from UK in order to cross them with the local Fa Yuen breed and thereby increase productivity as well as eliminate swayback, the inherited condition in which the spine is depressed to such an extent that the abdomen is dragged along the ground. The Kadoories initiated a major philanthropic scheme of self-help to the refugee farmers of the New Territories. Grants were made, interest-loans were made for the construction of proper sties, and pigs of the improved crosses were donated, co-operatives were organised while government extension and advisory services educated and informed. The story of all this effort is given in a recent article3. However, reading it does come with a health warning. As well as being written in social ‘science’-speak, the writers interpret the activity as a scheme to prevent the rise of communist sympathies in the farmers of the New Territories. While that may have been the case in isolated cases, and the ‘morale’ of the farmers was raised, the dual aim of increasing the efficiency and productivity of food production in Hong Kong to achieve a degree of self-sufficiency as mainland China was in political turmoil and food exports from China were controlled by a capricious regime, while at the same time helping the local and refugee farmers to raise their standard of living, seemed to those of us in Hong Kong while all this was going on the predominant purpose, and one that had begun with Geoffrey Herklots’s work in university and in government to improve the lot of the farmers and fisherfolk by setting up marketing schemes in the immediate aftermath of the liberation from Japanese occupation in 1945. It echoed, of course, successive British government’s policies—now abandoned—in the middle decades of the 20th Century to achieve a greater degree of self-sufficiency within Britain, as summed up by the title of a 1975 government White Paper, Food from our own resources.

Crossing the Fa Yuen pig with the standard British breeds eliminated the problem of swayback. Rate of growth and body weight were improved while the females were prolific. From the efforts of the Kadoories and the then new government department of agriculture, the industry grew to a level of about 400,000 locally-produced pigs per annum. That success itself brought the problem of pollution of water courses from the effluent, one that was tackled successfully by my old colleague and friend, Professor Daniel Chan of the Department of Zoology of the University of Hong Kong (who could range successfully from his major research interest in comparative endocrinology to the practical problems of ‘red tides’ and establishing a gene bank for local breeds of chicken);he instigated a dry sawdust litter system which also eliminated the powerful odour so characteristic of pig sties2. But the days of major production of pork production in Hong Kong were numbered. An agreement with China in 1978 for the import of fresh produce from the mainland, together with the construction of entire new cities on the flatter lands of the New Territories and the regulation of effluent production, have had a dramatic effect on pig farming. From 1114 pig farms in 1989, there were just 43 in 2014. In the meantime, successful pig breeds have spread throughout the world all carrying, as a result of incessant artificial selection, the results of those independent domestications of the wild boar.

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*The Kadoorie family funded the Kadoorie Building at the University of Hong Kong which houses the School of Biological Sciences.

1 Bosse M, Lopes MS, Madsen O, Megens H-J, Crooijmans RPMA, Frantz LAF, Harlizius B, Bastiaansen JWM, Groenen MAM. 2016. Artificial selection on introduced haplotypes shaped the genetic architecture in European commercial pigs. Proceedings of the Royal Society B doi.org/10.1098/rspb.2015.2019 
2 Chan DKO, Chaw D, Lo CYY. 1994. Management of the sawdust litter in the “pig on litter” system of pig waste treatment. Resources, Conservation and Recycling 11, 51-72.
3 Chan, WC, Miller B. 2015. Capitalist pigs: Governability, subjectivities, and the regulation of pig farming on colonial Hong Kong (1950-70). Environment and Planning D: Society and Space DOI: 10.1177/0263775815598154 
4 White S. 2011. From globalized pig breeds to capitalist pigs: a study in animal cultures and evolutionary history. Environmental History 16, 94-120.