G. Wiener
Roslin Institute (Edinburgh), Roslin, Midlothian EH25 9PS, UK, and Edinburgh University, Centre for Tropical Veterinary Medicine, Roslin, Midlothian EH25 9RG, UK
Yak have generally been described as particularly well adapted, anatomically and physiologically, to cold climates and high elevations. It has also been widely inferred that yak will not perform well, or even survive, in environments, which are markedly different from the traditional, noting especially an intolerance to high ambient temperatures. This view may need revision in the light of the successful spread of yak to a wide variety of environmental conditions in several parts of the world and most especially in North America over the past decade, albeit in still relatively small numbers and small herds. There are around 90 commercial breeders of yak in the USA and Canada with herds varying in number from less than ten breeding females to in excess of 400. Yak are bred pure, but yak bulls are also used to cross with other cattle. The primary aim is lean meat production, but fibre is also prized. In some areas, yak are also trained for packing. Yak in North America are not restricted to the cooler mountainous regions, although these predominate and include some of the larger herds. Some herds are in coastal regions and in relatively low-lying areas with climates that are temperate or warm for much of the year. Birth weights of calves are said to vary from 13 to 27 kg. Under good conditions, calves weaned at 4–5 months old can weigh 70 kg. Females on the best farms are first mated at 18 months of age, though 2 to 2.5 years is more common. Most of the cows calve every year. The adult weights of females vary from 240 to 360 kg and bulls from 550 to 680 kg.
Keywords: Adaptation, North America, performance, yak
Six yak were imported to Canada in 1909 though only 1 male and 3 females survived to the following year. The yak did not initially reproduce but after being moved to different, colder locations, a small population of yak was built up. Two centres commenced breeding experiments: at Buffalo Park, Wainwright, where the main emphasis was on hybridisation experiments with American bison and domestic cattle, and at Fairbanks Experiment Station in Alaska where the aim also included crossing with domestic cattle. The various trials were suspended by 1930 (Deakin et al. 1935; White et al. 1946). Yak, however, survived in National Parks and zoos. It is likely that the present population of yak in Canada and the USA are derived from this foundation-although there are also unconfirmed reports of yak derived from an importation to Bronx Zoo in 1890 and possibly elsewhere.
Yak are also known to exist in a number of zoos around the world outside their main areas, and a successful small herd has been at Whipsnade Wild Animal Park in England since the 1940's from whence small satellite herds have been set up (Cai and Wiener 1995). Small numbers of yak are also kept in a commercial setting in New Zealand. This may not be a complete list.
The existence and relative success of yak in environments, which must be regarded as non-traditional for yak suggests an adaptability of yak to a wide variety of climatic and environmental conditions.
The purpose of this report is to draw attention to the present status of yak in commercial herds in the USA and Canada and to provide some very limited and preliminary records of performance.
About 70 owners of yak herds in North America are members of a yak breed association-the International Yak Association (IYAK). In addition, there are some other herds not affiliated to the Association. The latter are likely to be fewer in numbers and with relatively few animals. Sixteen of these non-affiliated herds have been located and are included in Table 1, which shows their distribution by State, but, in addition, there could be other herds. The total number of yak in these various herds has been estimated at around 2000, of which about half are breeding females and there are said to be an approximately equal number of crossbreds (yak × various breeds of cattle). However, the numbers are not precisely known.
About two-thirds of all the herds affiliated to IYAK were contacted by mail, but only a small proportion responded. Apart from the geographical distribution of the herds, as shown in Table 1, other information is restricted to those herd owners. Information was sought on the origin and size of each herd, its management, farm environment, breeding policy, and any available information on performance and marketing. Not each response was complete in every respect.
One herd owner in New Zealand was also contacted and provided information.
Table 1 shows the distribution of yak herds by country and State. It can be seen that the distribution stretches from British Columbia and Alberta (Canada) in the north to Arkansas (USA) in the south, and from the Oregon coast in the west to New Hampshire in the east. One correspondent referred to a herd in Alabama, but this was not verified.
Table 1. Location of yak herds in the USA and Canada, by State.1
Location |
Number of herds |
No. Providing data |
USA |
||
Arkansas |
3 |
|
California |
2 |
|
Colorado |
10 |
5 |
Idaho |
4 |
1 |
Indiana |
1 |
|
Iowa |
1 |
|
Kansas |
1 |
|
Kentucky |
1 |
|
Massachusetts |
1 |
1 |
Michigan |
5 |
|
Minnesota |
1 |
1 |
Montana |
3 |
|
Nebraska |
5 |
12 |
Nevada |
1 |
|
New Hampshire |
1 |
1 |
New Jersey |
1 |
|
New York |
3 |
|
North Dakota |
1 |
|
Oregon |
10 |
1 |
South Dakota |
1 |
|
Virginia |
2 |
|
Washington |
9 |
1 |
Wyoming |
1 |
|
Canada |
||
Alberta |
13 |
2 |
British Columbia |
5 |
2 |
Many of the herds in States adjacent to the Rocky Mountain range are on ranches at elevations up to around 2600 metres above sea level (masl), typified by cool summers and cold winters but the majority of herds, even in the mountainous regions, are at lower elevations with hotter summers. In other States, it is common to have yak in hill areas up to perhaps 700 masl, but a few are located at little above sea level, as well as coastal areas-including a small island off Vancouver Island. The herds in coastal areas will experience few if any frosts in winter with little or no snow and a fairly high rainfall spread throughout the year.
The single largest herd of yak in the USA, numbering in excess of 800 head, and an equal number of yak crosses with domestic cattle, is situated in Nebraska east of the Rocky Mountain range at an elevation of 1280 masl and with an annual precipitation of 420 mm.
A small herd of yak (but one of several) in New Zealand, for which contact was made with the owner, is located at the northern end of the South Island. It is only a short distance from the sea, 40 masl, and has a summer temperature that can exceed 30°C and mild winters. Annual precipitation is 2500 mm.
Four coat colour types are described-all black, black with some white markings (called trim) which predominates, black and white (described as 'royal') and a 'gold' colour, said to be recessive to black, which is present in small numbers.
Birth weights of yak calves are typically quoted as varying from 13–27 kg. Weaning weights generally at 4–5 months of age, were quoted as 65–70 kg for some farms presumed to be providing above average rearing conditions. Adult weights of yak cows were given in the range 240–360 kg and yak bulls 550–680 kg, though one yak bull in Canada was reported to weigh 820 kg.
Some females were mated for the first time at 18 months of age but 2–2.5 years is more typical. Calving annually is the norm, but one of the herd owners noted that half his yak cows had only 2 calves in 3 years. Bulls are not generally used for mating until 3 years old, although some younger ages were reported.
Few health problems were encountered but the need for routine vaccinations and deworming, especially in humid conditions, was referred to by several of the herd owners.
Most of the herd owners stressed that natural grazing in summer and hay in winter represented most of the feed. Some gave small supplements of grain. All provided mineral blocks and some mentioned a need for an adequate amount of copper in the block to promote health and the breeding of the yak (Cai and Wiener 1995).
Reference was made by many of the herd owners to the feed efficiency of their yak relative to other cattle and hence to the relatively small quantities of feed and pasture required per kg live weight of animal.
For the most part, yak were kept out-of-doors the year round. One of the owners of a small herd referred to the provision of winter housing, but with only moderate success. In general, yak were regarded as reasonably tame and, with few exceptions, easily handled and easily confined by fencing.
Possible heat stress for yak was mentioned but did not amount to a problem. The animals sought some shade and water-cooling in periods of high heat in summer but reference was made to one farm (not contacted) where even this was not found necessary.
Most of the yak were kept for breeding and the sale of breeding stock. Bulls were also sold for this purpose and for crossbreeding to other cattle. The leanness of yak meat and the efficiency of feed conversion of both pure and crossbred yak are stressed in the promotion literature. Crossbred males are all sold for meat.
A few yak are trained for packing and trekking, particularly in the vicinity of the Rocky Mountains. Some specialist attention is given in some of the small herds to the yak wool and hair for weaving-the undercoat wool fetching a high price. Milk is mentioned in the promotional literature but there were no reports of currently successful milking and milk processing. A few of the yak are sold as farm 'pets'. A few `collectors' value hides, heads and horns.
The performance data provided were not extensive and are unexceptional. Since strict averages of performance data are not available, it is difficult to compare the results from the USA with corresponding published data from, say, China. On the face of it, the range of birth weights of yak calves provided suggests that they might be a little above those expected in traditional yak areas. Also, the inferred growth rate of calves to weaning, perhaps exceeding 400 g per day, is also higher than the gains of around 300 g previously quoted (Cai and Wiener 1995). However, the calves here are reared under what should be regarded as good conditions and with access to all the maternal milk, whilst traditionally the herders took some milk for domestic consumption-thus restricting the intake by the calf. In one comparison made by Zhang (1985), yak calves given access to all their dams' milk gained 439 g per day over 159 days, compared with 395 g and 195 g for calves which had dams that were also milked either once or twice a day, respectively. Some of the adult weights, particularly of breeding bulls, appear slightly higher than usually reported for domestic yak (Joshi 1982; Cai and Wiener 1995; Lensch et al. 1996). The herds' surveyed reported higher reproductive rates for their yak than are common in the more traditional circumstances.
Two matters of genetic interest arise from the spread of yak in North America and elsewhere. They concern the numerical size and nature of the genetic base for these populations and their adaptation to new environments.
The only documented evidence available to the author concerning the origin of yak in North America, suggests the possibility that all are descended from three of the yak cows and one of the two yak bulls imported to Canada in 1909. In numerical terms, over a period of 90 years, the expansion to the present population is entirely feasible, given the expectations for reproductive rate and generation interval. This would suggest, however, a close relationship among the animals existing. In addition, however, there is rumour of other, independent sources of yak blood entering the population; but these will need to be investigated and confirmed. It is also highly likely that some of the crossbreeding of yak with other cattle has led to the introduction of some B. taurus genes into the American yak gene pool. DNA analysis should be able to provide evidence for or against such infusion.
Some of the yak in North America are kept in environments, which, on a traditional view, could be regarded as alien for yak, most especially those near the Pacific coast. It has to be borne in mind that the yak is regarded as particularly well adapted to cold, relatively dry climates at high elevations and with relatively poor, highly seasonal feed supply. Many of the herds in North America are in mountainous areas. A better supply of feed even in these areas, especially in the winter, than is common in the traditional yak lands adjacent to, and to the north of, the Himalayas, can be taken to account for the higher reproductive rate and better early growth rate.
It is the herds in coastal areas, including the herd reported in New Zealand, and those in low-lying temperate or warm environments, which call for comment. Even in these situations, the yak appear to perform and reproduce well, without suffering debilitating stress. Cai and Wiener (1995) reported that the situation correspond to the yak herd at Whipsnade in England and for the apparent success of yak in zoos and wild animal reserves in various parts of the world. It needs to be asked, therefore, whether such yak differ genetically from domestic yak in, for example, China, or whether the special adaptive characteristics of the yak to cold and harsh conditions do not inhibit life in warmer and gentler environments.
There is, of course, a possibility that genes that may have been introduced from crossbreeding with other cattle may include genes for adaptation to the new environments. In the case of yak, any such introduction of genes must come through crossbred females, as the crossbred males are sterile. The process of crossing, however, seems too random, too varied and selectively non-deliberate to provide a satisfactory explanation for adaptation, without much further evidence. Moreover, in the short period of 90 years or so under consideration, even if genes for adaptation to new environments had been introduced, they would have required strong positive selection pressure to spread throughout the population. Future DNA analysis should provide an answer at least to the extent of any introgression, but is less likely to resolve the nature of the genes introduced in relation to adaptive characteristics.
It would be altogether simpler to hypothesise that yak are not intrinsically unable to survive and reproduce in a wide variety of environments. It would then be necessary to explain why in the principal areas for yak production in China and adjacent countries, the yak, the cattle and the crossbreds generally occupy different strata of territory. Yak are generally predominant, even exclusive, at the highest elevations where intrinsic adaptation to the harsh environment is of paramount importance. Cattle are at the lower altitudes where they are capable of expressing their higher potential for productivity. The crosses in the intermediate locations benefit from both adaptation and production characteristics of their respective yak and cattle parents, as well as benefiting from any hybrid vigour that may be generated. In the present context of yak in North America and other `new' environments, however, it seems that yak are not by nature inhibited from thriving in 'cattle country'. The converse, however, of the adaptation of cattle to traditional `yak country' is unlikely, as B. taurus and B. indicus cattle are absent from the regions which require the ability to withstand the greatest extremes of cold and oxygen deprivation and of feed shortage in winter and early spring.
Professor Jack Rutledge, Department of Animal Sciences, University of Wisconsin, provided initial encouragement and contacts for this survey and made helpful comments. The following kindly provided the information about their herds and about yak in the USA: Edward and Jody Cothey, Jim Delaney, Bob Hasse, Gene Herrley, John Hooper, Harlan and Saundra Lear, Jerry McRoberts, Tad and Kristen Puckett, Dane Smith, Daniel and Karen Tee, Phil Wykle, Mary Yatsevitch; from Canada: Erik Dahinden (who also located other Canadian herds), Ken Jones and Robert Owen; and from New Zealand: Matthew Benge.
Cai L. and Wiener G. 1995. The yak. FAO (Food and Agricultural Organization of the United Nations) Regional Office for Asia and the Pacific, Bangkok, Thailand. 237 pp.
Deakin A., Muir G.W. and Smith A.G. 1935. Hybridization of domestic cattle, bison and yak. Publication 479, Technical Bulletin 2, November 1935, Department of Agriculture, Dominion of Canada, Canada. 29 pp.
Joshi D.D. 1982. Yak and chauri husbandry in Nepal. His Majesty's Government Press, Kathmandu, Nepal. 145 pp.
Lensch J., Sley P. and Zhang Rong-Chang. 1996. Der yak (Bos grunniens) in Zentralasien. Duncker & Humblot, Berlin, Germany. 269 pp.
White W.T., Phillips R.W. and Elting E.C. 1946. Yak and yak-cattle hybrids in Alaska. Journal of Heredity 37:355–358.
Zhang Yinsong. 1985. Observation and analysis on milk production of yak in Qilian area. Journal of China Yak 1:51–56.
