A preface should perhaps be in the name of both the authors. That convention is broken here in order to provide me, the "foreign" co-author, with an opportunity to pay particular tribute to Professor Cai Li. He has dedicated an entire lifetime, helped by colleagues, students and co-workers, to observing, recording and trying to understand the yak and its characteristics and attributes and its role in the life, culture and economy of the mountainous regions of central Asia. Some of this study has involved personal hardship, which most young scientists nowadays would find hard to imagine.
The areas of the world in which yak are kept are in many cases, even now, isolated by distance and difficult terrain. Much of yak husbandry is still steeped in tradition and values, which may not be encountered by "animal improvers" elsewhere. It is no mean feat therefore to have gathered the information on which this book is based and it is no discredit to its value that some of the expectations of modern data recording and analysis could not always be observed. Numbers involved in comparisons are often fewer than the observers would have wished, and one of the recurring regrets is that some factors remain confounded - for example, between breeds or types of yak and the location where they are found. It is thus not often possible to say whether a particular type of animal is better, or whether it is the conditions under which it lives which is the deciding factor.
The backbone of this book is the work of Professor Cai Li, particularly in his home province of Sichuan. Much of his work has been quoted by direct reference to specific publications, but other information on yak, when not attributed to a specific source also derives from Professor Cai Li's studies. However, it is hoped that readers will also quickly note that this book is based on a large array of information and a mass of data from many different sources and places. It follows that this book differs in breadth and depth from the many popular and a few review articles on the yak, which represent the bulk of the information published in the English language. (In addition there is a growing number of scientific papers on specific topics concerned with yak, also in the English language - and some in French and German). The more general of these articles mostly set out to say how remarkable an animal the yak is, because it has adapted to life in an extraordinarily hostile environment, and then give just a taste of information on body size, reproductive rate, milk yield, and perhaps little else. Usually, this provides no clue to the wide range of variation in performance and habitat of the yak and to the potential of the yak for change. Such conclusions need to be based on a more detailed assessment of the yak and critical evaluation of the results. Nonetheless, taken together, these articles and specific studies provide an impressive addition to the literature in the traditional languages for yak publications (mostly Chinese, but also many in Russian), and they have been quoted here whenever appropriate.
It is hoped, therefore, that this book will fill a gap in knowledge and understanding, not only among those concerned with the science of animal production, but also those just interested in the yak and wishing to dig a bit deeper. To accommodate especially the more general reader, an overview has been provided at the beginning of each chapter.
In spite of the claim to breadth and depth for this book, it has to be acknowledged that not every possible piece of information published on the yak has been used. Much of the wealth of articles in scientific journals, reports and proceedings of technical meetings (mainly in the Chinese or Russian language) deals with specific detail under specific circumstances. While it is one of the aims of this book to demonstrate the range of variation found in the management and performance of yak in both practical and experimental situations, and to provide a clue to the underlying factors, it was not thought desirable to make the references exhaustive. To do so would also have required some means of interpreting the causes of the plethora of small differences in performance, or characteristics, of the yak that would emerge. Such interpretation is not possible in the absence of a level and scale of experimentation, which has not been undertaken with the yak (or indeed with other types of domestic livestock, if considered over the kind of vast area encompassed by yak territory). The separate chapter on yak husbandry in different countries should go some way towards widening the picture as far as possible.
The publication of this book was requested by the Regional Office for Asia and the Pacific of the Food and Agriculture Organisation of the United Nations to coincide with the 50th anniversary of FAO's foundation. Due to restrictions on time, it has not been possible, in every case, to obtain information for chapter 11, on yak husbandry in different countries, direct from those involved - as was originally hoped. Thus, some of the information for that chapter has had to be compiled from existing, published information.
This preface must end with an apology. The problem of transliterating Chinese, and to a much lesser extent Russian, into the English alphabet may mean that some of the names of authors and the titles of papers and sources given in the list of references may not be totally correct in every detail. Also, it is a matter of regret that some of the references listed will be found difficult to access, even in the form of abstracts, by those wishing to do so. It is hoped that the revolution in communication, in which we find ourselves at the end of the 20th century, will also, in the future, apply to publication across far distant national boundaries for subjects such as the yak.