L. Tshering, D.B. Rai, M.R. Gurung and Chungsila
National AI Program and Semen Processing Centre, Thimphu, Bhutan
Yak play a significant role in the economy and social life of the people of Bhutan. The Department of Agriculture and Livestock Support Services supported the yak herders by distributing yak bulls procured from places in other breeding regions within Bhutan with the aim to mitigate the level and effects of inbreeding. To improve the productivity of Bhutanese yak, about 1000 doses of Chinese yak semen were obtained under Helvetas funding through Food and Agriculture Organization of the United Nations (FAO). The artificial insemination (AI) in yak was carried out from 1990 to 1997. A total of 82 inseminations were implemented and 45 progenies recorded. The phenotypic characters of the AI progenies are summarised in this paper as well as some discussions on breeding habits of yak in their natural habitat. The trial also highlights the practical difficulties faced by the field veterinarians and livestock extension workers to undertake such tasks that affect the success rate and AI coverage. From the experiences gained from the trial, the implementation of yak AI on a full scale is not recommended until concrete results are obtained.
Keywords: Artificial insemination, Bhutan, yak
Yak play a very important role in the economy and social life of the people of Bhutan. They are an integral component of the pastoral system in Bhutan. Yak are multi-purpose animals and provide milk, butter, cheese and meat for family consumption as well as for sale or barter in exchange for food grains and goods. They also provide hide, hair and wool, which are used for making clothes, tents, blankets, ropes and many other household items. Yak husbandry is an age-old practice and the only means of livelihood for many people living in high altitude areas.
Bhutan's Department of Agriculture and Livestock Support Services (previously Animal Husbandry Department) supported the yak herders by distributing yak bulls procured from places in other breeding regions with the aim to mitigate the level and effects of inbreeding (Gyamtsho 1996). To improve the productivity of Bhutanese yak, 1000 doses of Chinese yak semen were obtained under Helvetas funding through FAO.
The trial on yak AI was carried out in different regions on a limited scale from 1990 to 1997. As there is no motorable road to reach the yak herds, the frozen semen using medium sized storage containers that could last for a month was carried by porters requiring a minimum of two days walk to reach the yak herds. Oestrus in yak is seasonal with most of the females coming to heat during the month of July and August. The trial was carried out during this period to cover maximum females. The hind parts of the inseminated females were covered with locally made raincoat (Chaleb) to prevent natural service by breeding bulls. A total of 82 inseminations were carried out including pure yak semen as well as Tarentaise semen. Tarentaise semen was used in the trial to produce Zo and Zom and to confirm the success of AI in yak. All the progenies were ear tagged and each progeny was physically examined to determine phenotypic difference from the existing yak population.
A total of 82 inseminations were carried out and 45 progenies were recorded. The phenotypic differences observed and yak herders view on yak ´ yak AI progenies were as follows:
The Tarentaise progenies did not look to be typical Zo and Zom. However, the phenotypic differences observed in yak ´ Tarentaise progenies were as follows:
Usually the breeding season lasts from June to September with most of the females coming to heat during the months of July and August (Tshering et al. 1996). The seasonal oestrus may be due to improved nutritional status during summer months or may be due to increased day length. During the breeding season female yak are seen in heat in the morning and evening or on cloudy days after rain. Detection of heat without a yak bull is quite difficult.
The local method of restraining yak i.e. tying the fore limbs is very effective. Under this method of restraint, yak do not kick, although they make jumping movements. During the breeding season the breeding bulls become ferocious and it was quite difficult to separate the inseminated female yak from the bulls. Although, majority of the herders were of the view that the Chaleb was very effective in preventing mating by breeding bulls, there were few herders questioning the efficacy of this method as some breeding bulls were able to remove it by use of their horns.
The experience gained from the AI trial in yak indicate that the technology should not be implemented on a full scale due to the following reasons; i) as there is no motorable road to reach the yak herds, transportation of frozen semen and liquid nitrogen is very difficult, and ii) separation of breeding bulls from the herd/tying of the inseminated female yak till oestrus is over is not at all possible. Under such circumstances one cannot be completely sure that the progenies born are from AI.
the performance of AI progenies in terms of milk production needs to be studied in future. As the scope for AI in yak is limited by practical constraints, the other countries seem to be a viable option to improve yak productivity in Bhutan.
The authors would like to acknowledge Helvetas-Bhutan for financial support for obtaining the frozen semen and FAO for other logistic supports. The contributions of the district animal husbandry officers and extension agents are gratefully acknowledged.
Gyamtsho P. 1996. Assessment of the condition and potential from improvement of high altitude rangelands of Bhutan. PhD thesis, Swiss Federal Institute of Technology, Zurich, Switzerland. pp. 34–35.
Tshering L., Gyamtsho P. and Gyeltshen T. 1996. Yak in Bhutan. In: Miller D.G., Craig S.R. and Rana G.M. (eds), Proceedings of a workshop on conservation and management of yak genetic diversity held at ICIMOD, Kathmandu, Nepal, 29–31 October 1996. ICIMOD (International Centre for Integrated Mountain Development), Kathmandu, Nepal. pp. 13–28.