tly varying altitude, the use of hybrid livestock is likely to be more efficient, in biological terms, than the use of yaks or cattle. By judiciously selecting cattle, yaks, or hybrids all altitudes from sea level to above 5,000 m can be utilized with best efficiency.
The hybrid's milk is intermediate in composition between that of its parents. However, hybrids yield up to 7 kg of milk per day against the yak's 3 kg. (It seems that the hybrid derived from cattle bull and female yak produces considerably more milk, with a higher fat content than that derived from yak bull x cattle female.) Also the female hybrids produce larger quantities of milk than Nepalese zebu cows on the same hill pastures. They also produce a calf each year, while under normal herd management yaks tend to produce a calf every 2 years.
Hybrids do not tolerate extremes of altitude or cold as well as purebred yaks.
The normal gestation period for yaks is about 1 month shorter than that of cattle, and the gestation period for a hybrid is intermediate between that of the parents - hence there may be problems at calving when a female yak is sired by a bull from a large cattle breed.
Research and Conservation Needs
Research is needed to identify differences in altitude tolerance between various hybrids. This should include measurements of hemoglobin count, respiration rate, and pulse rates at different altitudes.
Studies are also needed on all production characteristics, particularly on the meat and milk production potentials.
Cataloging the breeding strategies of different areas where hybrids occur would be useful, along with a historical perspective.
Research to determine the most productive hybrids by crossing different yak and cattle "breeds" in areas with different environmental conditions could be extremely useful.